Synthesis and Characterisation of New Perfluoropropenyl Complexes of Gold, Platinum, Palladium, and Titanium Lulu M. Alluhaibi, Alan K. Brisdon*, Robin G. Pritchard

School of Chemistry, The University of Manchester, Manchester M13 9PL, UK

Corresponding author: alan.brisdon@manchester.ac.uk

Tel: +44 (0)161 306 4459

ABSTRACT:

The new stable perfluoropropenyl organometallic complexes [(Ph3P)Au(E-CF=CFCF3)], trans-

[(Ph3P)2Pt(Z-CF=CFCF3)Cl], trans-[(Ph3P)2Pd(E-CF=CFCF3)Cl], [(COD)Pt(E-CF=CFCF3)2] and

[Cp2Ti(E-CF=CFCF3)Cl] have been obtained from the reaction of LiCF=CFCF3 – derived from Z-

CFH=CFCF3 (HFC-1225ye) – with appropriate transition-metal starting materials. The complexes have

been characterized by multinuclear NMR studies (19F ,1H, 31P and 13C) and single-crystal structure

determinations. Based on the X-ray derived data a comparison is made between -bound

perfluoropropenyl and perfluorovinyl ligands; whilst they are found to be electronically quite similar on

the basis of their trans-influence the perfluoropropenyl group is significantly more sterically-

demanding, and it is suggested that this accounts for the predominance of mono-perfluoropropenyl-

substituted complexes with enhanced stabilities.

KEYWORDS: Perfluoropropenyl, Organometallic Complexes, Z-HFC-1225ye, X-ray structures.

Highlights

The formation of perfluoropropenyl transition metal complexes from HFC-1225ye The first structurally characterized examples of early TM and bis-substituted perfluoropropenyl

organometallic complexes An assessment of the electronic steric properties of the perfluoropropenyl ligand based on X-ray

diffraction data

Dedicated to Prof. Antonio Togni the winner of the ACS Prize in Fluorine Chemistry 2017.

1

1-INTRODUCTION

The first fluoro-organometallic compound, IHgCF3, was reported in 1949[1], since then a great many

more organometallic compounds containing fluorocarbon groups have been prepared, including those

containing small -bound fragments, such as CF3,[2] CF=CF2,[3] and in a few cases, CF=CFCF3.

However, perfluoropropenyl organometallic complexes are scarce in comparison with perfluorovinyl

organometallic complexes; with approximately six times as many perfluorovinyl organometallic

complexes having been published compared with the number of perfluoropropenyl complexes according

to SciFinder searches.[4] Table 1 lists the main-group and transition metal perfluoropropenyl complexes

that have been reported to date and their methods of synthesis.

Table 1 Perfluoropropenyl organometallic complexes reported and their method of synthesis.

Compound Reagents Year published Ref.

[(CO)5Re(Z-CF=CFCF3)] CF3CF=CF2 + Re2(CO)10 1965 5

[(CO)5Mn(Z-CF=CFCF3)] CF3CF=CF2 + Mn2(CO)10 1965 5

[Cp(CO)2Fe(E-CF=CFCF3)] CF3CF=CF2 + [Cp(CO)2Fe]2 1965 5

trans-[(PEt3)2PtCl(CF=CFCF3)] CF3CF=CF2 + trans-[(PEt3)2Pt(H)Cl] 1967 6

trans-[(PEt3)2PtCl(E-CF=CFCF3)] trans-[(PEt3)2Pt(2-CF2=CFCF3)] + SnCl4 1973 7

[Co(CO)4(Z-CF=CFCF3)] CF2=CFCF2I + Zn[Co(CO)4] 1975 8

cis- and trans-[Fe(CO)4I(Z-CF=CFCF3)] CF2=CFCF2I + Fe2(CO)9 1976 9

[Ag(CF(CF3)=CF2)] CF2=C=CF2 + AgF 1970 10

[ICd(E- & Z-CF=CFCF3)] E & Z-ICF=CFCF3 + Cd 1986 11,12

[Cd(E- & Z-CF=CFCF3)2] E & Z-ICF=CFCF3 + Cd 1986 11,12

[Cu(E- & Z-CF=CFCF3)] E & Z-ICF=CFCF3 + Cu 1986 12

[IZn(E- & Z-CF=CFCF3)] E & Z-CF3CF=CFI + Zn 1987 13

[Zn(E- & Z-CF=CFCF3)2] E & Z-CF3CF=CFI + Zn 1987 13

[Cp*Ir(PMe3)H(CF=CFCF3)] CF2=CFCF2I + [Cp*Ir(PMe3)HLi] 1999 14

[(Et3P)3Rh(E-CF=CFCF3)] CF3CF=CF2 + [(Et3P)3RhH] 2002/2003 15,16

[(Et3P)3Rh(E-CF=CFCF3)] CF3CF=CF2 + [(Et3P)3Rh(Bpin)] 2010 17

[(n-Bu)3Sn(CF=CFCF3)] CF3CF=CF2 + Zn + Bu3SnCl 2004/2005 18, 19

[ClZn(E-CF=CFCF3)] CF3CF2CH2F + LDA + ZnCl2 2006 20

[Hg(E-CF=CFCF3)2] Z-CF3CF=CFH + HgCl2 2012 21

[PhHg(E-CF=CFCF3)] Z-CF3CF=CFH + PhHgCl 2012 21

2

[Ph3Sn(E-CF=CFCF3)] Z-CF3CF=CFH + Ph3SnCl 2012 21

[Ph2Sn(E-CF=CFCF3)2] Z-CF3CF=CFH + Ph2SnCl2 2012 21

[PhSn(E-CF=CFCF3)3] Z-CF3CF=CFH + PhSnCl3 2012 21

[Sn(E-CF=CFCF3)4] Z-CF3CF=CFH + SnCl4 2012 21

[(n-Bu)3Sn(E-CF=CFCF3)] Z-CF3CF=CFH + n-Bu3SnCl 2012 21

[(n-Bu)2Sn(E-CF=CFCF3)2] Z-CF3CF=CFH + n-Bu2SnCl2 2012 21

[Ph3Ge(E-CF=CFCF3)] Z-CF3CF=CFH + Ph3GeBr 2012 21

[Ph3Pb(E-CF=CFCF3)] Z-CF3CF=CFH + Ph3PbCl 2012 21

trans-[CpCo(Z-CF=CFCF3)(PPh2Me)OTf] [CpCo(=CF2)(PPh2Me)] + C2F4 + Me3SiOTf 2013 22

[(PCy3)2Pd(BF4)(E- & Z-CF=CFCF3)] CF3CF=CF2 + [Pd(PCy3)2] + BF3.Et2O 2014 23

[(DPPE)Ni(OTf)(E- & Z-CF=CFCF3)] [(DPPE)Ni(C3F6)] + Me3SiOTf 2015 24

[Rh(E- & Z-CF=CFCF3)(PEt3)3] CF3CF=CF2 + [Rh(GePh3)(PEt3)3] 2016 25

For transition metal perfluoropropenyl complexes the preparative methods fall into three main classes;

(i) the reaction of hexafluoropropene (HFP) and organometallic complexes to form either -bound

perfluoropropenyl complexes directly, or via a -to- rearrangement, (ii) reactions of metal powders

with perfluoropropenyl halides to give mono- and bis-substituted perfluoropropenyl complexes and (iii)

C-F activation of hexafluoropropene by transition metal complexes. For main-group perfluoropropenyl-

containing organometallic complexes the majority of the known compounds come from either reaction

of a perfluoropropenyl halide with a metal powder, or the generation of CF3CF=CFLi, derived from Z-

CF3CF=CFH (HFC-1225ye), followed by transmetallation. Using this latter route a series of group 14

perfluoropropenyl complexes have been prepared, some of which, such as [Bu3Sn(E-CF=CFCF3)], have

been shown to be effective cross coupling partners under Stille-Liebeskind conditions for generating

perfluoropropenyl-containing aromatic compounds.[21].

Given that there are relatively few transition metal perfluoropropenyl organometallic compounds

known, and those that do exist are important intermediates in C-F bond activation studies, we have 3

investigated the HFC-derived method by which main-group perfluoropropenyl compounds can be

prepared for the synthesis of some new transition-metal complexes of the CF=CFCF3 ligand using HFC-

1225ye (Z-CF3CF=CFH) as the starting material, along with a suitable metal-halide. HFC-1225ye (also

denoted as HFO-1225ye, or R-1225ye) is a non-ozone-depleting CFC replacement with a low global

warming potential and short atmospheric lifetime,[26] that has been investigated as a possible

replacement for HFC-134a (CF3CH2F) in refrigeration and air-conditioning applications and so has the

potential to act as a convenient starting material.

2-RESULTS AND DISCUSSION

Based on the previously published method by Brisdon et al.[21] Z-HFC-1225ye was converted into the

perfluoropropenyl lithium compound Z-CF3CF=CFLi by reaction with one equivalent of base (typically

n-BuLi, or LDA) in dry diethyl ether or THF at temperatures between -73 and -80 °C. Subsequent

addition to the ethereal solution of CF3CF=CFLi of an appropriate transition metal halide [RnMXn] was

expected to result in the formation of the corresponding perfluoropropenyl organometallic compounds

of the type [RnM(CF=CFCF3)n], as outlined in Scheme 1.

Scheme 1 Outline synthetic method for the formation of perfluoropropenyl organometallic compounds

Work-up and isolation of the products was straightforward, typically involving the addition of hexane to

ensure complete precipitation of the metal halides, which were filtered off, followed by evaporation of

the solvents to leave a crude product. Subsequently purification could be effected by column

4

chromatography and initial characterization was achieved using multinuclear NMR spectroscopy. For

example, the reaction of [(Ph3P)AuCl] with Z-CF3CF=CFLi resulted, after purification by column

chromatography using diethyl ether and chloroform, in a white solid in good yield (77%), the 31P{1H}

NMR spectrum of which exhibited a singlet at ca. 40.9 ppm. This can be compared with (31P) = 14.3

ppm for the starting material, and 42.2 ppm for the analogous perfluorovinyl-containing complex,

[(Ph3P)Au(CF=CF2)].[27]

Table 2 Summary of 19F and 31P{1H} NMR data for the new transition-metal perfluoropropenyl complexes.

Compound δCF3 δFtrans δFgem δP[(Ph3P)Au(E-CF=CFCF3)] −66.5 ppm (d.d)

3JCF3 Ftrans =16.1Hz4JCF3 Fgem=10.6 Hz

−150.4 ppm (q)3JFtrans CF3 =16.1Hz

−119.9 ppm (q)4JFgem CF3 =10.6 Hz

40.9 ppm (s)

[(Ph3P)2Pd(E-CF=CFCF3)Cl] −66.7 ppm (d.d.t)3JCF3 Ftrans = 15.3 Hz4JCF3 Fgem= 8.5 Hz5JCF3 P = 5.2 Hz

−146.5 ppm (q.d)3JFtrans CF3 =15.3 Hz3JFtrans Fgem= 16.4 Hz

−87.0 ppm (q.t)4JFgem CF3 = 8.5 Hz3JFgem Ftrans = 16.4 Hz

22.8 ppm (q)5JP CF3= 5.2 Hz

[Cp2Ti(E-CF=CFCF3)Cl] −63.4 ppm(unresolved s)

−139.2 ppm (q.d)4JFtrans CF3 =12.2 Hz3JFtrans Fgem= 3.1 Hz

−82.8 ppm (unresolved s)

---

[(COD)Pt(E-CF=CFCF3)2] −66.3 ppm (d.d.d)3JCF3 Ftrans = 14.8 Hz4JCF3 Fgem= 3.3 HzJ = 2.2 Hz

−149.2 ppm (q.d)4JFtrans CF3 =14.8 Hz3JFtrans Fgem= 4.0 Hz3JFtrans Pt = 445 Hz

−102.4 ppm (m)4JFgem CF3 = 3.3 Hz3JFgem Ftrans = 4.0 Hz2JFgem Pt = 112 Hz

---

[(Ph3P)2Pt(Z-CF=CFCF3)Cl] −67.7 ppm (d.d.t)3JCF3 Fcis = 23.2 Hz4JCF3 Fgem= 13.5 HzvirJCF3 P = 2.1 Hz

−102.6 ppm (q.d)3JFcis CF3 = 23.2 Hz3JFcis Fgem = 123.2 Hz3JFcis Pt = 437 Hz

−173.0 ppm (d.q.t)4JFgem CF3 = 13.5 Hz3JFgem Fcis= 123.2 HzvirJFgem P = 3.6 Hz2JFgem Pt = 302 Hz

20.9 ppm (m)1JP Pt= 2781 Hz

The 19F{1H} NMR spectrum showed three signals at -66.5, -119.9 and -150.4 ppm with relative

intensities of 3:1:1, as expected, and consistent with previously reported data for main-group

perfluoropropenyl-containing compounds.[21,28] Assignment of the CF3 signal is trivial based on both

the chemical shift and integration values; the assignment of the two C-F signals, which both appear as

quartets due to coupling with the CF3 group, was made on the basis of previously reported data [21] and

the magnitude of the C-F coupling constants, which could be observed in both the 19F and 13C NMR

5

spectra. The largest magnitude fluorine-fluorine coupling of ca. 16 Hz, is observed on the signals for the

CF3 group and Ftrans (where Fgem and Ftrans are labeled with respect to the metal, M, see Scheme 1). The

4J(CF3-Fgem) coupling constant was found to be ca. 10 Hz, but interestingly, there was no measurable

Ftrans-Fgem coupling. Although it is surprising that this coupling is too small to be observed, it is not

unprecedented, in that the same effect is reported for both IZn(CF=CFCF3) and Zn(CF=CFCF3)2. [13,

20] The geometry of the bound perfluoropropenyl group can be determined as the E-isomer, with

mutually cis- fluorines, based on the magnitude of the 3J(FF) coupling constant since these are ca. 120

Hz for two fluorine nuclei that are mutually trans- across a C=C bond.[29] The NMR data is

summarized in Table 2.

We were able to grow single crystals suitable for X-ray diffraction studies of the product, and Table 3

lists the relevant crystal and refinement details of this and the other complexes studied. The gold

complex crystallizes in the Pna21 space group with two unique [(PPh3)Au(CF=CFCF3)] molecules

present in the unit cell, but with no particularly significant differences between the geometrical

parameters determined for either of them. The molecular structure of one of these molecules is shown in

Figure 1. As expected an essentially linear, (P-Au-Cl)av = 175.3(7) , two-coordinate gold complex is

found, with average Au-P and Au-C distances of 2.281(5) and 2.041(19) Å. These distances can be

compared with those previously reported for [(PPh3)Au(CF=CF2)] where d(Au-P) = 2.272(3) Å and

d(Au-C) = 2.028(9) Å; [27] the similarity in the Au-P distances suggest that there is little electronic

difference between the perfluorovinyl and perfluoropropenyl substitutents based on their trans-

influence, ie their ability to lengthen the Au-P bond trans to the fluorinated ligand. Confirmation of the

geometry of the perfluoropropenyl group proposed as the E-CF=CFCF3 isomer from the NMR data is

obtained from the X-ray structure. The average C=C bond distance is 1.32(3) Å, while the C-CF3

distance is 1.36(4) Å and there is no significant difference between the and - C-F distances. These

distances are consistent with expectations.[30] They are also similar to those reported previously for

6

perfluoropropenyl-containing compounds, of which there have been just six structural determinations to

date. Two of these are of main-group compounds, Ph3Sn(E-CF=CFCF3) and Ph3Ge(E-CF=CFCF3),[21]

while for transition-metal complexes there are two further structures of E-perfluoropropenyl complexes,

[Pd(PCy3)2(E-CF=CFCF3)(BF4)] and two polymorphs of [(PEt3)2(CF=CFCF3)Rh(-O)4Rh(PEt3)2(E-

CF=CFCF3)], [25] and two examples of Z-perfluoropropenyl-containing complexes, [CoCpBr(PPh2Me)

(Z-CF=CFCF3)][22] and [Rh(PEt3)3(Z-CF=CFCF3)].[15]

Figure 1 ORTEP representation of the structure of one molecule of [(Ph3P)Au(CF=CFCF3)], hydrogen atoms omitted for clarity and thermal ellipsoids are shown at 50%. [Selected bond lengths: d(Au1-P1) = 2.278(5), d(Au1-C1) = 2.043(18), d(C1-F1) = 1.38(2), d(C1-C2) = 1.34(3), d(C2-C3) = 1.42(3), d(C2-F2) = 1.36(2), d(C3-F3A) = 1.36(2), d(C3-F3B) = 1.37(3), d(C3-F3C) = 1.34(4) Å.]

7

Scheme 2 The synthesis of (cyclooctadiene)bis(perfluoropropenyl)platinum.

The reaction between [(COD)PtCl2] (COD = cyclooctadiene) and Li(CF=CFCF3) at low temperature in

THF was expected to give the complex [(COD)Pt(CF=CFCF3)2], Scheme 2. Analysis of the 19F NMR

spectrum showed the anticipated three signals in the ratio 3:1:1. Close examination of the splitting

pattern of the CF3 signal that occurred at −66.3 ppm showed, in addition to the doublet of doublet

coupling arising from coupling to both the Ftrans and Fgem nuclei, a further small doublet splitting was

present. Similar additional coupling has previously been reported in the tin compounds Ph(4-n)Sn(E-

CF=CFCF3)n when n>1[21] and since this arises only in compounds that possess more than one

perfluoropropenyl group it is believed to arise from coupling with a fluorine nucleus of another

perfluoropropenyl group, presumably through space, although it could also be an artifact of the complex

AA’MM’X3X3’spin-system. The NMR data therefore suggests that this complex is

[(COD)Pt(CF=CFCF3)2] and this is in agreement with elemental analysis figures (although analysis of

fluorinated compounds does result in higher uncertainties than in non-fluorinated systems), and

confirmation came from a single-crystal X-ray structure determination of the product, as shown in

Figure 2.

8

Figure 2 ORTEP representation of the molecular structure of [(COD)Pt(CF=CFCF3)2], hydrogen atoms omitted for clarity and thermal ellipsoids are shown at 50%. [Selected bond lengths: d(Pt1-C1) = 2.010(10), d(C1-F1) = 1.372(14), d(C1-C2) = 1.316(14), d(C2-C3) = 1.475(17), d(C2-F2) = 1.347(13), d(C3-F3A) = 1.321(15), d(C3-F3B) = 1.348(16), d(C3-F3C) = 1.356(15) Å.]

The complex crystallized in the orthorhombic space group Pbcn and Z = 8, with the platinum atom

located on a two-fold rotational axis. The complex adopts a pseudo-square planar geometry (C1-Pt1-C1i

= 90.8(4)°) with two mutually cis- symmetry-related E-CF=CFCF3 fragments, and as such represents

the first crystallographically-characterized example of a transition-metal organometallic complex that

has two bound perfluoropropenyl groups.

The C=C and C-F bond distances are similar to those found in the gold complex, and, as in that case,

there are no especially short intermolecular distances that might indicate the presence of any significant

intermolecular interactions.

To date nearly all the transition-metal perfluoropropenyl complexes prepared have been of mid- to late-

transition elements. We were therefore interested in trying to prepare a complex of an early transition

metal, and chose to study the reaction of [Cp2TiCl2] with LiCF=CFCF3. Following work-up, a red solid

9

was isolated, the 19F NMR spectrum of which displayed three signals at -63.4, -82.8 and -139.2 ppm in

the ratio 3:1:1; the two higher frequency signals were observed as broad signals from which no coupling

information could be obtained, however some coupling could be observed on the third peak.

Characterization of this complex therefore relied upon elemental analysis and ultimately a single-crystal

structure determination. Both of these pieces of data showed that the complex was mono- rather than

bis-substituted, ie [Cp2Ti(CF=CFCF3)Cl], scheme 3.

Scheme 3 Method used to prepare chlorobis(cyclopentadienyl)perfluoropropenyl titanium.

10

Figure 3 ORTEP representation of the molecular structure of [Cp2Ti(CF=CFCF3)Cl], hydrogen atoms and the alternate, disordered carbon atoms of the Cp rings are omitted for clarity, thermal ellipsoids are shown at 50%. [Selected bond lengths: d(Ti-Cl) = 2.320(2), d(Ti-C1) = 2.206(8), d(C1-F1) = 1.382(9), d(C1-C2) = 1.319(11), d(C2-C3) = 1.492(11), d(C2-F2) = 1.362(9), d(C3-F3A) = 1.315(10), d(C3-F3B) = 1.327(10), d(C3-F3C) = 1.300(11) Å.]

The single-crystal X-ray derived structure of the product is shown in Figure 3. The two

cyclopentadienyl rings were found to be disordered across two equally populated sites, however no such

disorder was observed in the perfluoropropenyl fragment. This structure represents the first example of

a -bound perfluoropropenyl group attached to an early transition metal, to date the other reported

structures feature cobalt,[22] rhodium [15,25] and palladium [23] metal centres. It is noteworthy that

this complex is sufficiently stable to allow crystals suitable for X-ray diffraction work to be obtained,

because previous work on the analogous perfluorovinyl-containing compounds found that

Cp2TiCl(CF=CF2) was the least stable of the compounds Cp2Ti(CF=CF2)2 and Cp2TiX(CF=CF2) (X = F,

Cl), all of which decomposed over a few hours in solution, which made any attempt to grow crystals for

single crystal X-ray diffraction work impractical.[31] However, it is reported that the related titanium

system possessing a more sterically-demanding cyclopentadienyl ligand set is more stable[32] and in the

11

case of cadmium compounds those containing the perfluoropropenyl group were found to be more

stable than their perfluorovinyl analogues.[11]

The X-ray determined C=C and C-C distances of the perfluoropropenyl group are similar to those

observed in the previous structures, and again the - and -C-F bond lengths are indistinguishable

within experimental limits. The Ti-Cl bond length, at 2.320(2) Å is similar to that reported for [(5-

C5Me4Et)2TiCl(CF=CF2)] where d(Ti-Cl) = 2.3462(6) Å.[32] The Ti-C bond length in the

aforementioned complex is 2.1739(15) Å, which is slightly shorter that that found for the

perfluoropropenyl-containing complex, where d(Ti-C) = 2.206(8) Å. The only other relevant data with

which comparisons might be made is from an EXAFS study of the perfluorovinyl-containing complexes

Cp2Ti(CF=CF2)2 and Cp2TiF(CF=CF2) which reported Ti-C distances of 2.033(12) and 2.050(18) Å

respectively.[31]

The observation of a slightly longer Ti-C bondlength in Cp2TiCl(CF=CFCF3) compared with the close

fluorovinyl analogues and the exclusive formation of the mono-substituted complex, even though an

excess of LiCF=CFCF3 was employed in the reaction, lead us to suspect that the steric demand of the

perfluoropropenyl group might be significantly greater than that of the perfluorovinyl group. In order to

investigate this we used the program G-solid[33] to determine the effective cone angle of the ligands

coordinated to the metal centres based on our crystallographic data. For the complexes

[(Ph3P)Au(CF=CFCF3)], [(COD)Pt(CF=CFCF3)2] and [Cp2TiCl(CF=CFCF3)] we obtained G2.28 values,

ie values where the M-L distance is set to 2.28 Å, as used in Tolman cone angle calculations, of 104,

103 and 102° respectively for the perfluoropropenyl ligand in the three complexes. This compares with

the value for the perfluorovinyl group of 93° calculated from the X-ray diffraction data for

[(Ph3P)Au(CF=CF2)],[27] 89° for the chloride ligand in [Cp2TiCl(CF=CFCF3)], 126° for the COD in

[(COD)Pt(CF=CFCF3)2] and 125° for PPh3. These values would suggest that substitution of one or more

chloride ligands of Cp2TiCl2 with either one or two perfluorovinyl groups is likely to have only a small 12

steric impact on the titanium centre [G2.28(Cl) = 89° and G2.28(CF=CF2) = 93°]. However, because the at-

metal steric demand of the perfluoropropenyl fragment is calculated to be 10° larger [G2.28(CF=CFCF3)

= 103°], the introduction of a perfluoropropenyl group results in a significant increase in steric crowding

compared with the perfluorovinyl group, and this may be the reason for the preferential observation of

the mono-substituted perfluoropropenyl complex. Furthermore, the additional degree of steric protection

of the metal centre provided by the perfluoropropenyl group may contribute to the enhanced stability of

the organometallic CF=CFCF3-containing compound over the CF=CF2-containing analogues.

However, in the case of the COD-containing complex, where the bidentate COD ligand has a G2.28 value

of only126° there is a much reduced steric demand around the metal centre and so the bis-substituted

perfluoropropenyl complex can be readily accommodated.

Scheme 4 Method used to prepare chlorobis(triphenylphosphine)perfluoropropenyl palladium.

In order to test these ideas further we chose to react trans-[(Ph3P)2PdCl2] with an excess of

perfluoropropenyl lithium generated from Z-HFC1225ye, since this could give either the mono- or bis-

substituted complex, scheme 4. Following the reaction and work-up, the fluorine NMR spectrum

demonstrated the presence of two perfluoropropenyl-containing species as evidenced by the observation

of two sets of peaks in an approximate 1:3 ratio. For the less abundant compound peaks were observed

at ca. -61, -124 and -155 ppm, while for the major species signal occurred at ca. -66, -87 and -146 ppm.

The 31P{1H} NMR spectrum also showed two signals, the weaker of which appeared as a broad singlet 13

at 29.7 ppm, while the signal for the more abundant complex appeared as a poorly-resolved quartet at

22.8 ppm. Following column chromatography the major species was isolated and spectra of this species

confirmed the NMR assignments. In particular, the observation of a quartet signal in the 31P{1H} NMR

spectrum suggests that the phosphorus nucleus couples to the three CF3 nuclei of a single CF=CFCF3

unit. It would also require that the two phosphines remain mutually trans- to each other in order to

remain equivalent. Confirmation of such an arrangement can be obtained from the 13C{1H} NMR

spectrum which shows virtual coupling between P and C nuclei for the carbon signals of the phenyl

rings.[34] This second-order effect arises because of strong coupling between the two phosphorus nuclei

when they are trans- to each other and results in the observation of triplet splitting patterns, as the

carbon nuclei appear to couple equally to both chemically-equivalent phosphorus nuclei.[35]

We were able to grow single crystals suitable for X-ray diffraction studies of this complex, and solution

of the data confirmed the product to be the square-planar Pd(II) complex trans-[(Ph3P)2PdCl(E-

CF=CFCF3)], as shown in Figure 4. The angles around the palladium centre lie in the range 86.54(4) –

91.53(4) °. The Pd-P distances of 2.3227(12) and 2.3398(12) Å (average 2.3313(12) Å) are comparable

with those found for the perfluorovinyl analogue, trans-[(Ph3P)2PdCl(CF=CF2)] ,[36] prepared from the

reaction of [Pd(PPh3)4] and CF2=CFCl , where d(Pd-P) = 2.3269(7) and 2.3318(7), average 2.3294(7) Å,

while the Pd-Cl distance of 2.3410(13) Å is a little shorter than that of the perfluorovinyl-containing

complex, d(Pd-Cl) = 2.3653(7) Å. The bond distances within the perfluoropropenyl fragment are very

similar to those found in the preceding structures and do not warrant any particular further discussion.

Unfortunately we were unsuccessful in isolating the minor species produced in this reaction, and

therefore it cannot be identified with certainty; however we consider that it is likely to be the bis-

substituted complex.

14

Figure 4 ORTEP representation of the molecular structure of trans-[(Ph3P)2Pd(CF=CFCF3)Cl], hydrogen atoms have been omitted for clarity and thermal ellipsoids are shown at 50%. [Selected bond distances: d(Pd-Cl) = 2.341(13), d(Pd-P1) = 2.3398(12), d(Pd-P2) = 2.3227(12), d(Pd-C1) = 2.005(5), d(C1-F1) = 1.369(8), d(C1-C2) = 1.309(10), d(C2-C3) = 1.427(15), d(C2-F2) = 1.378(6), d(C3-F3) = 1.338(13), d(C3-F4) = 1.354(13), d(C3-F5) = 1.322(11) Å.]

Finally, we investigated the analogous platinum system; following the reaction of an excess of

LiCF=CFCF3 with trans-[(Ph3P)2PtCl2] the NMR spectra of the crude product suggested the presence of

a number of different compounds, some of which we were able to separate by column chromatography,

but only in low yield. The 19F{1H} NMR spectrum displayed a set of three multiplets at ca. -65.4, -97.8

and -154.1 ppm in the relative intensity ratio 3:1:1, while a second, much more intense set of 3:1:1 ratio

peaks were observed at -67.7, -102.6 and -173.0 ppm. The first set of signals are consistent with those

observed in most of the complexes containing E-CF=CFCF3 fragments, with the two C-F resonances

possessing a small mutual coupling constant. However, the second set of signals show a number of

differences in both the chemical shifts and coupling constants in comparison with those previously

described. For example, one of the C-F resonances is detected at a considerably lower frequency, ca. -

173 ppm, and the mutual coupling constant between the two C-F signals is now 123 Hz, suggesting that

15

in this case the two fluorine nuclei are located trans to each other across the C=C bond,[29] indicating

that this complex contains a Z-CF=CFCF3 group.

The 31P{1H}NMR spectrum confirms the presence of two species, with an intense signal at 20.0 ppm

with 195Pt satellites (J = 2781 Hz) and a second resonance of approximately 10% relative intensity at

20.2 ppm with J(PtP) = 2626 Hz. The observation of single resonances and the value of the Pt-P

coupling constants indicate that these complexes adopts a square-planar geometry based on trans

phosphines, because much larger magnitude Pt-P coupling constants are usually observed in similar cis

geometry systems, such as cis-[PtCl2{PPh2(CF=CF2)}2] where J(PtP) = 3698 Hz.[37]

Confirmation of the identity of the major complex as trans-[(Ph3P)2Pt(Z-CF=CFCF3)Cl] was achieved

by growing crystals suitable for X-ray studies, the structure resulting from the X-ray determination is

shown in figure 5. As anticipated from the NMR data, the square-planar, d8, Pt(II) complex shows a

trans-disposition of the two phosphines; the P-Pt-P angle is 171.57(7) °, the Pt-P bond distances are

2.2958(17) and 2.3025(18) Å and the Pt-Cl distance is 2.349(2) Å. Unfortunately part of the

perfluoropropenyl fragment is disordered across two sites, with two alternative positions for the - and

-carbon atoms (which were modeled as isotropic centres in the relative ratio 68:32), however it is still

clear that the perfluoropropenyl group is present as the Z-isomer, in agreement with the 19F NMR data.

Furthermore, the complex, as was observed for the palladium analogue, is only mono-substituted and so

also possesses one chloride ligand.

16

Figure 5 ORTEP representation of the molecular structure of trans-[(Ph3P)2Pt(Z-CF=CFCF3)Cl], (hydrogen atoms and disorder in C=C omitted for clarity), thermal ellipsoids are shown at 50%. [Selected bond distances: d(Pt-Cl) = 2.349(2), d(Pt-P1) = 2.2958(17), d(Pt-P2) = 2.3025(17) Å.]

While the relative sizes of the perfluoropropenyl and chloride ligands may be involved in the formation

of mono- rather than bis-substituted complexes, it is not clear how the Z-CF=CFCF3 isomer arises in the

platinum complex, nor why there is no analogue in the palladium, or other, systems. We carefully

checked the NMR spectra of the starting HFC, and found no evidence of the other isomer being present.

It is unlikely that isomerization of the lithium reagent occurs, otherwise we would expect to observe

products containing the bound Z-isomer of –CF=CFCF3 in the other metal complexes. This leaves the

possibility that isomerization occurs after formation of the perfluoropropenyl platinum product.

Although E- to Z- isomerization of 1,2,3,3,3-pentafluoropropene is known to occur in the liquid phase

with SbF5,[38] and on solid alumina catalysts,[39] we are not aware of analogous systems where

isomerization has been reported before. However, since the isolated material is only obtained in very

17

low yields we are wary of speculating further at this stage, and so currently we are undertaking

additional studies of the formation and application of these complexes.

Table 3 X-ray structure determination data

Formula C21H15AuF5P[PPh3Au(CF=CFCF3)]

C7H6F5Pt0.5,[(COD)Pt(CF=CFCF3)2]

C13H10F5TiCp2TiCl(CF=CFCF3)

C39H30ClF5P2Pd[(PPh3)2PdCl(CF=CFCF3)]

C39H30ClF5P2Pt[(PPh3)2PtCl(CF=CFCF3)]

Formula Weight

590.27 271.71 344.56 797.48 886.14

Crystal System Orthorhombic Orthorhombic Monoclinic Monoclinic Monoclinic

Space group Pna21 (No. 33) Pbcn (No. 60) C2/c (No. 15) P21/c (No. 14) P21/c (No. 14)

a, b, c /Å 16.4976(4),10.0035(2),23.3621(13)

7.6010(8),14.5438(14)13.7859(12)

13.9279(9),7.3310(4),25.4212(14)

16.6616(11),11.7550(5),19.0635(12)

15.246(2),11.9952(14),20.013(3)

/° 90,90,90

90,90,90

9095.568(5),90

90,113.937(8),90

90,110.506(16),90

V/Å3 3855.5(2) 1524.0(3) 2583.4(3) 3412.6(4) 3428.0(9)

Z 8 8 8 4 4

D(calc) /gcm-3 2.0338 2.464 1.772 1.552 1.717

(MoK)/mm 17.764 9.272 0.914 0.772 4.319

F(000) 2240 1056 1376 1608 1736

Crystal size/mm

0.04 x 0.18 x 0.20 0.24 x 0.24 x 0.48 0.11 x 0.18 x 0.33 0.06 x 0.24 x 0.33 0.26 x 0.33 x 0.56

Temperature /K 100 150 150 100 100

Radiation/Å 0.71073 0.71073 0.71073 0.71073 0.71073

Theta Min-Max/°

2.4, 27.5 3.4, 26.0 3.3, 26.0 3.2, 26.0 3.4, 27.5

Dataset -21:21; -12:12; -30:29 -9:5; -15: 17; -13: 17; -17:12; -8:9; -28:31 -22:14; -13:14; -23: 22 -19:18; 0:15; 0:25

Total Reflections

37530 3851 8094 14170 19450

Data > 2 7022 1014 2155 4934 5100

Nref, Npar 8435, 506 1496, 115 2525, 136 6702, 433 7640, 432

R, wR2, S 0.0574, 0.1415a, 1.04 0.0683, 0.1867b, 1.04 0.0920, 0.1871e, 1.31 0.0573, 0.1214d, 1.05 0.0457, 0.1083c, 0.93

Min. Max Resd. Density [e/Å3]

-1.71, 1.75 -3.12, 3.59 -0.61. 0.73 -0.69, 1.35 -1.05, 1.42

a w = 1/[2(Fo2)+(0.0680P)2+53.1360P] where P=(Fo2+2Fc2)/3; b w = 1/[2(Fo2)+(0.0882P)2] where P=(Fo2+2Fc2)/3; c w = 1/[2(Fo2)+(0.0320)2+16.0230P] where P=(Fo2+2Fc2)/3; d w = 1/[2(Fo2)+(0.0305P)2+4.4549P] where P=(Fo2+2Fc2)/3; e w = 1/[2(Fo2)+41.2790P] where P=(Fo2+2Fc2)/3.

3-CONCLUSIONS

18

In conclusion, we report a one-pot, low-temperature method for the synthesis of a number of new

sigma-bound perfluoropropenyl organometallic complexes via the intermediate

perfluoropropenyllithiium formed from Z-CF3CF=CFH and butyllithium. The method is of general

utility and can be used to prepare examples of early and late transition metal complexes. These

complexes are stable and have been characterised based on their multinuclear NMR data and in most

cases by single crystal X-ray analysis. In each case these are the first crystallographically-characterised

examples of perfluoropropenyl organometallic complexes of the particular metals. For many of the

complexes, even when an excess of (CF3CF=CFLi) was used in the reaction, mono-substituted

perfluoropropenyl-containing complexes were observed as the major species, thus [(Ph3P)Au(E-

CF=CFCF3)], trans-[(Ph3P)2Pd(E-CF=CFCF3)Cl] and [Cp2Ti(E-CF=CFCF3)Cl] result from the reaction

of [(Ph3P)AuCl], [(Ph3P)2PdCl2] and [Cp2TiCl2] respectively with LiCF=CFCF3. However, reaction

with [(COD)PtCl2] under similar conditions gives rise to the first bis-substituted perfluoropropenyl

complex for any transition metal element that has been characterized. While the data from X-ray

diffraction studies suggest that -CF=CF2 and -CF=CFCF3 fragments exhibit similar electronic

properties, the greater steric demand of the pentafluoropropenyl ligand is proposed as the reason for the

observation of a lower degree of substitution and the greater stability of these complexes compared with

the analogous perfluorovinyl systems.

4-EXPERIMENTAL

4-1. General Methods

All reactions were carried out under anaerobic conditions in oven-dried glassware, with moisture-

sensitive reagents being handled under a nitrogen atmosphere. Non-chlorinated solvents were dried over

sodium wire for at least 24 h prior to use. HFC-1225ye was kindly donated by Mexichem Fluor. NMR

spectra were recorded at 20 °C on a Bruker Avance III 400 MHz spectrometer operating at 400.00,

19

100.61, 376.46, and 161.97 MHz for 1H, 13C, 19F, and 31P respectively using CDCl3 as solvent. Chemical

shift values are quoted relative to TMS, CFCl3 or 85% H3PO4 in parts per million (ppm) on the δ scale,

and coupling constant (J) values are reported in Hz. The splitting patterns are labelled as follows: s =

singlet, d = doublet, t = triplet, q = quartet and m = multiplet. Microanalyses were conducted by the

University of Manchester’s School of Chemistry Micro-Analytical service. IR spectra were recorded on

a Perkin-Elmer FT RX1 spectrometer, and intensities are labelled as follows: str = strong, m = medium

and w = weak. Melting point determinations were carried out using an Electrothermal digital apparatus.

Crystals suitable for diffraction work were grown by slow evaporation of a chloroform solution and X-

ray structures were obtained using either SuperNova or Oxford Xcalibur Sapphire2 diffractometers

using Mo Kα radiation (λ = 071073 Å). All the raw data frames were reduced and corrections were

applied for Lorentz, polarisation and absorption using the multi-scan methods with CrysAlisPro[40].

The X-ray structural data were solved by direct methods, with full-matrix least-squares refinement of F2

using: Olex2[41], Shelx[42] and Shelxtl[43] programs. Ortep3[44] was used to generate the graphical

representations and Mercury [45]and Pluton [46] were used to investigate and report the structures.

Crystallographic data (excluding structure factors) for the structures in this paper have been deposited

with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC 1560701-

1560705. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road,

Cambridge CB2 1EZ, UK, (fax: +44 1223 336033 or e-mail: deposit@ccdc.cam.ac.uk).

4-2. Procedure for the synthesis and reactions of (LiCF=CFCF3)

In all the synthetic reactions, LiCF=CFCF3 was prepared using a similar method: In a three-necked

round-bottom flask under a positive pressure of nitrogen cooled to -75 to -80 °C were placed dry diethyl

ether (150 mL) and (Z)-HFC-1225ye. One equivalent of n-BuLi (2.5 M solution in hexanes) was added

slowly so as to maintain the temperature at least below -78 °C. The solution was stirred at low

20

temperature for 1 h to ensure complete deprotonation and formation of pentafluoropropenyllithium.

Subsequently, to this solution was added a solution of the appropriate metal-halide. The mixture was left

to warm slowly to room temperature overnight, after which time work-up was affected by addition of

hexane (25 mL), filtration through celite, solvent removal on a rotary evaporator and then column

chromatography (see below for specific details).

4-3. Synthesis of [(Ph3P)Au(CF=CFCF3)]

Using the procedure described above with (Z)-HFC-1225ye (0.43 mL, 4.24 mmol), n-BuLi (2.5 M, 1.70

mL, 4.24 mmol), and Ph3PAuCl (0.70 g, 1.41 mmol) which was prepared by a published method.[47] A

white, crystalline product was obtained after purification by column chromatography on silica with a

(1:1) diethyl ether: chloroform eluent. Yield (0.10 g, 77%). M.P (119-121°C). Anal. Calcd for

C21H15AuF5P: C, 42.71; H, 2.56; P, 5.25; Au, 33.38 %; found: C, 43.30; H, 2.61; P, 5.07; Au, 34.76 %.

19F{1H} and 31P{1H} NMR data are listed in Table 2. 1H NMR (400 MHz, CDCl3) δ ppm: 7.41-7.50 (m,

15H, Ph). 13C{H} NMR (100.59 MHz, CDCl3) δ ppm: 121.00 (q.d.d, 1J(C3 3F) = 269 Hz, 2J(C3 Ftrans) =

39 Hz, 3J(C3 Fgem) = 14 Hz, C3), 129 (d, 2J(C P) = 11 Hz, Ph), 129.35 (d,1J(C P) = 55 Hz, Ph), 131.8 (d,

4J(C P) = 3 Hz, Ph), 134.2 (d, 3J(C P) = 14 Hz, Ph), 145.8 (d.q.d, 1J(C2 Ftrans) = 266 Hz, 2J(C2 3F) = 34

Hz, 2J(C2 Fgem) = 17 Hz, C2), 192.0 (d.m, 1J(C1 Fgem) = 312 Hz, C1). νmax/cm-1 1350, 1435,1480 (C-F, s),

1650 (C=C, w).

4-4. Synthesis of [(COD)Pt(CF=CFCF3)2]

(Z)-HFC-1225ye (0.55 mL, 5.40 mmol), n-BuLi (2.5 M, 2.16 mL, 5.40 mmol), and (COD) PtCl2 (0.50g,

1.33 mmol), which was prepared by a published method.[48] After purification on a silica column,

eluting with CHCl3, the product was obtained as a black solid. Yield (0.33g, 44%). M.P (185- 189 oC),

Anal.Calcd for C14H12F10Pt: C, 29.85; H, 1.79; Pt, 34.63 %; found: C, 30.81; H, 2.39; Pt, 35.07%.

19F{1H} NMR data are listed in Table 2. 1H NMR (400 MHz, CDCl3) δ ppm: 2.50 (m, 8H, CH2), 5.49 (s, 21

4H, 195Pt satellites 2J(H Pt)= 42.24 Hz, CH). 13C{H} NMR (100.59 MHz, CDCl3) δ pmm : 29.7 (s, CH2),

108.8 (s,195Pt satellites 1J(C Pt) = 65 Hz, CH), 120.5 (q.d.d, 1J(C3 3F)= 270 Hz, 2J(C3 Fgem)= 37 Hz, 2J(C3

Ftrans)= 11 Hz, C3), 139.0 (d.q, overlap 1J(C2 Fgem) = 256 Hz, C2), 156.0 (q, 1J(C1 Fgem) = 318 Hz, C1).

νmax/cm-1 1350, 1430, 1475 (C-F, s), 1655 (C=C, w), 2935(C-H, m).

4-5. Synthesis of [Cp2Ti(CF=CFCF3)Cl] As described above, using (Z)-HFC-1225ye (2.00 mL, 20.00 mmol), n-BuLi (2.5 M, 8.0 mL, 20.00

mmol), and Cp2TiCl2 (1.24 g, 5.00 mmol) dissolved in dry THF (10 mL). A red solid resulted after

purification by column chromatography on silica with chloroform eluent. Yield (0.88 g, 45%). M.P

(190-195 oC). Anal.Calcd for C13H10ClF5Ti: C, 45.30; H, 2.93; Cl, 10.29; Ti, 13.90 %; found: C, 44.25;

H, 2.81; Cl, 9.43; Ti, 12.98 %. 19F{1H} NMR data are listed in Table 2. 1H NMR (400 MHz, CDCl3) δ

ppm: 6.38 (s, 10H, Cp). 13C{H} NMR (100.59 MHz, CDCl3): δ ppm 120.5 (q.d.d, 1J(C3 3F)= 269 Hz,

2J(C3 Ftrans)= 38 Hz, 3J(C3 Fgem)=12 Hz, C3), 143.0 (d.q.d, 1J(C2 Ftrans)= 262 Hz, 2J(C2 3F)= 39 Hz, 2J(C2

Fgem) = 20 Hz, C2), 177.3 (s, Cp) 187.2 (d.q, 1J(C1 Fgem) = 331 Hz, 3J(C1 3F)= 7 Hz, C1). νmax/cm-1 1240,

1340, 1440(C-F, str),1600 (C=C, w), 3100 (C-H, m).

4-6. Synthesis of trans-[(Ph3P)2Pd(CF=CFCF3)Cl]

As described above, using (Z)-HFC-1225ye (0.43 mL, 4.26 mmol), n-BuLi (2.5 M, 1.70 mL, 4.26

mmol), and trans-[PdCl2(PPh3)3] (1.00g, 1.42 mmol), which was prepared by a published method.[49]

After purification on a silica column, eluting with chloroform, the product was isolated as a dark orange

solid. Yield (0.14g, 20 %). M.P (329-331oC). Anal.Calcd for C39H30ClF5P2Pd: C, 58.72; H, 3.79; P, 7.77;

Cl, 4.45; Pd, 13.87%; found: C, 58.73; H, 3.91; P, 7.22; Cl, 4.57; Pd, 13.27%. 19F{1H} and 31P{1H}

NMR data are listed in Table 2. 1H NMR (400 MHz, CDCl3) δ ppm: 7.29 and 7.56 (m, 30H, Ph). 13C{H}

NMR (100.59 MHz, CDCl3) δ ppm: 120.8 (q, 1J(C 3F) = 251 Hz, C3), 128.43(t, virJ (CP)= 5 Hz, Ph), 22

129.91(t, virJ(CP)= 25 Hz, Ph), 130.86 (s, Ph), 134.66 (t, virJ (CP)= 6 Hz, Ph), 168.5 (d, 1J(C Fgem)= 334

Hz, C1), the signal for C2 was masked by the Ph signals. νmax/cm-1 1350, 1435, 1480 (C-F, s),1650

(C=C,w).

4-7. Synthesis of trans-[(Ph3P)2Pt(CF=CFCF3)Cl](Z)-HFC-1225ye (0.50 mL, 5.04 mmol), n-BuLi (2.5 M, 2.01 mL, 5.04 mmol), and trans-[PtCl2(PPh3)2]

(1.00 g, 1.26 mmol) that was prepared by a published method[50]. After purification on a silica column,

eluting with CHCl3, produced a black solid. Yield (0.10g, 8 %). M.P (160-165 oC), Anal.Calcd for

C39H30F5ClP2Pt: C, 52.84; H, 3.41; Cl, 4.00; P, 6.99; Pt, 22.03%; found: C, 53.40; H, 3.88; Cl, 3.91; P,

5.11; Pt, 21.80 %. 19F{1H} and 31P{1H} NMR data are listed in Table 2. 1H NMR (400 MHz, CDCl3) δ

ppm: 7.34, 7.64 (m, 30H, Ph ). 13C{H} NMR (100.59 MHz, CDCl3) δ ppm: 127.95 (t, virJ(C P)= 5 Hz,

Ph), 128.24(t, virJ(C P)= 5 Hz, Ph), 130.79 (s, Ph),134.67 (t, virJ(C P)= 6 Hz, Ph); sample was

insufficiently soluble to allow unambiguous identification of C1, C2 and C3. νmax/cm-1 1360, 1435, 1460

(C-F, s), 1655 (C=C, w), 3100 (C-H, m).

23

ACKNOWLEDGEMENTS

LA would like to acknowledge the financial support of the Saudi Arabian Government (King Abdullah

Scholarship Program). The EPSRC is acknowledged for NMR spectrometer and X-ray diffraction

equipment provision (Grant: EP/K039547/1)

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