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Inorganic Chemistry Communications 1 (1998) 317-319

Atom addition and insertion reactions of ( MeCp) 2Ta( H) CO with sulfur, tellurium, carbonyl sulfide and carbon disulfide

Uwe Winkler, Masood A. Khan, Kenneth M. Nicholas * Department of Chemistry and Biochemistry, Universiry of Oklahoma, Norman, OK 73019, USA

Received 24 June 1998; received in revised form 25 July 1998; accepted 11 August 1998

Abstract

The reaction of (MeCp),Ta( H)CO (lb) with Ss produces (MeCp),Ta( SH)CO (2) and one or more transient q*-COS complexes. Tellurium reacts with lb to afford unstable (MeCp),Ta( TeH)CO (4) and putative (MeCp),Ta( TeH) ( q*-COTe) (5). Photoreaction of lb with COS produces (MeCp),Ta( k-S) (h-S)Ta( MeCp), (6) which has been characterized by X-ray diffraction. The reaction of lb with CS, gives (MeCp),Ta( CO) ( 77’-S2CH) (8). 0 1998 Published by Elsevier Science S.A. All rights reserved.

Keywords: Addition reactions; Insertion reactions; Metal complexes; Carbonyl ligand complexes

1. Introduction

In connection with our studies of carbon dioxide activation by metal complexes, we recently discovered that ( MeCp) *- Nb(R) CO derivatives undergo novel atom addition reactions with molecular oxygen and sulfur to produce carbon dioxide and carbonyl sulfide complexes respectively [ 1,2]. Corre- sponding reactions of Group 16 elements with metal carbonyl hydrides offer the prospects of either atom addition and/or insertion pathways. Oxygenation of (MeCp),M(H)CO (M = Nb, la; Ta, lb) results in the formation of metal for- mat0 complexes [ 31, apparently the result of initial oxygen- ation of the coordinated carbon monoxide and subsequent insertion of the resulting hydrido carbon dioxide complex. We now report our initial findings on the interaction of lb with S and Te as well as with COS and CS2 which probe further the balance between atom addition and insertion pathways.

2. Reaction of lb with sulfur

The interaction of lb with excess S, in toluene at - 50°C over 2-3 h resulted in a gradual color change from purple to green to yellow and, upon warming to 20°C finally to orange. Low temperature IR, ‘H and 13C NMR monitoring revealed the presence of a number of transient intermediates. The major species 2 present at the green stage exhibited an IR

* Corresponding author. Tel.: + l-405-325 3696; Fax: + I-405-325 6111; E-mail: knicholas@ou.edu

absorption at 1905 cm-’ (1847 cm-’ starting from (MeCp),Ta(H)‘3CO=1*), a ‘H NMR resonance at -2.1 ppm (J( 13C-H) = 3.7 Hz), and a 13C NMR absorption at 254.6 ppm. Unstable 2 could be isolated in impure form by low temperature crystallization and incorporated approxi- mately one atom of S ‘. These features lead us to formulate 2 as ( MeCp ) ,Ta( SH) CO, the result of novel S insertion into the Ta-H bond. ‘H NMR M-S-H resonances in the 0 to - 2 ppm region have been observed in a number of other metal- locene-SH derivatives 2 [ 4,5]. This S insertion reaction may be contrasted with the initial oxygen additions to 1 a,b cited above.

At the yellow phase the carbonyl IR absorption of 2 was largely replaced by two new bands at 1687 and 1683 cm- ’ (1652, 1646 cm-’ from l*). Low temperature ‘H and “C NMR monitoring revealed the presence of at least two spe- cies, one of which had a proton NMR absorption (inter alia) at 0.1 (s) ppm and a 13C NMR signal at 254.3 ‘. These data

’ 2: green solid, dec. > - 30°C. ‘H NMR (ds-toluene, 6) : - 2.1 (s, IH), 1.9 (s, 6H), 4.2 (s, 2H), 4.3 (s, 2H), 4.4 (s, 2H), 4.5 (s, 2H). “C NMR (ds-toluene, 6): 254.6,94.2,92.5,92.0,85.2,22.8.IR (toluene) 1905cm- ‘.

’ An alternative formulation for 2 is (MeCp) *Ta( S) (H)CO, the product of S atom addition to the metal. However, the 20 electron count of the latter, the reported 7.10 ppm Ta-H NMR shift of (t-Bu-Cp) >Ta( =S)H [ 61, and the absence of IR absorptions in the 400-600 cm ’ region (for Ta=S [ 61) render this option less likely.

’ 3: unstable yellow solid, dec. > -25°C. ‘H NMR (ds-toluene, 6): 0.10 (s, IH), 1.81 (s, 6H), 4.9 (bs, 2H), 5.3 (bs, 2H), 5.9 (bs, 2H), 6.1 (bs, 2H). “CNMR (d,-toluene, S): 254.3. IR (toluene): 1683 cm- ’ (noabsorp- tions in the 400600 cm- ’ region for possible Ta=Te).

1387.7003/98/$ - see front matter 0 1998 Published by Elsevier Science S.A. All rights reserved. PIIS1387.7003(98)00085-9

318 U. Winkler et al. /Inorganic Chemistry Communications I (1998) 317-319

together suggest the formation of one (or two) C&bound q*-COS complexes [ 71 4, (MeCp) ,Ta( SH) ( v*-COS) (3)) the result of S atom addition to 2. This constitutes only the second example of the sulfurization of a metal-carbonyl ligand to produce an n2-COS complex [ 21. Solutions con- taining 3 decompose at room temperature to an orange prod- uct mixture which is devoid of significant IR absorptions between 1500 and 2000 cm- ‘.

3. Reaction of lb with Te

Complex lb reacts with elemental tellurium in toluene at room temperature over several days, forming a dark red solu- tion from which a thermally unstable species 4 can be isolated (73% yield). The IR and NMR spectra of 4 are similar to those of 2, i.e. v(C0) at 1903 cm- ‘, a high field ‘H NMR signal at - 1.58 ppm, and a low field 13C NMR absorption at 254.8 ppm 5. These features of 4 are thus in accord with the formulation of 4 as a rare hydrotellurido complex, ( MeCp) *- Ta( TeH) CO, apparently the first to be reported via insertion of the element into an M-H bond [lo]. A Te analog of 3, (MeCp),Ta( TeH) ( q2-COTe) (5)) appears to be produced in long term reactions of lb with Te as well, judging from the presence of an intense IR absorption at 17 16 cm- ‘. How- ever, this unstable species could not be isolated in pure form.

4. Reaction of lb with COS

It was of interest to determine if a Ta-COS complex, e.g. 3, or COS insertion products would result from the interaction of lb with COS. Although no reaction was observed when lb and COS were combined in THF at room temperature, irradiation ( > 300 nm) in THF at - 40°C (40 min) caused rapid disappearance of lb, but no new IR absorptions indic- ative of an q2-COS complex were observed between 1600 and 2000 cm- ‘. NMR analysis of the residue after solvent removal indicated the presence of two major components. Selective crystallization from toluenelpentane produced brown crystalline 6 (64%) whose IR and NMR spectra gave no evidence of carbonyl, hydride or thiol groups and whose mass spectrum suggested a bimetallic composition 6. X-ray diffraction established that 6 is the bridging disulfido species

4 The closely spaced v(C0) absorptions may indicate the presence of ‘inside’ and ‘outside’ $-COS isomers as observed for some Cp,M (COR) R complexes [ 8.91. ’ 4: ‘H NMR (CsD6, S): - 1.58 (s, 1H; Te-H satellite (7%) JTbH 76 Hz),

2.05 (s, 6H), 4.24 (m, 2H), 4.38 (m, 2H), 4.83 (m, 2H), 5.30 (m, 2H). “C NMR (C.&): 254.8, 106.1, 98.0, 94.8, 94.6,93.3, 15.5. IR (toluene) 1903 cm-‘. 66:‘HNMR(CaDs):2.38(s,6H),4.04(s,4H),4.89(s,4H).‘3CNMR

(C,D,). 105.2, 102.7, 99.4,30.2; MS (FAB) 742.l(M+).

Fig. 1. ORTEP diagramOof 6 using 50% thermal probability ellipsoids. Selected bond lengths (A): Ta(l)-Ta(2) 3.211(l), Ta(l)-S(l) 2.422 (1),Ta(1)S(2)2.401(1),Ta(2)S(1)2.404(1),Ta(2)S(2)2.413(1),

Ta(l)-Cp(l),.., 2.152(6), Ta(l)-Cp(&,,, 2.128(6), Ta(2)qp(3),,,, 2.143(6), Ta(2)-Cp(4),,,, 2.133(6). Selected bond angles (*): Ta( l)- Ta(2)S(l)48.51(3),Ta(l)-Ta(2)S(2)48.00(3),Ta(2)-Ta(l)S(l) 48.04(3), Ta(2)-Ta(l)-S(2) 48.31(3), S(2)-Ta(l)-S(l) 96.35(5), S(l)-Ta(2)S(2)96.51(5),Ta(2)S(l)-Ta(l)83.45(5),Ta(l)S(2)-

Ta(2) 83.69(4),Cp(lL-Ta(l)-Cp(&,, 125.W).

(MeCp),Ta(k-S)(h-S)Ta(MeCp), (Fig. 1) 7). Com- pound 6 is the net result of sulfide extraction from COS, a rare process in its reactions with metal complexes, and may derive from photodissociation of CO from lb [ 111, COS coordination and decarbonylation, and hydrogen loss. The highly symmetrical 6 is essentially isostructural with the reported Nb analog [ 121. Its diamagnetic, Ta( IV) state and relatively short Ta-Ta distance suggest the presence of a Ta- Ta bonding (or antiferromagnetic coupling) interaction.

The second major (and unstable) product from the lb + COS reaction could not be isolated in pure form but is tentatively formulated as the sulfido hydride (MeCp),- Ta(=S)H (7) based on a distinctive ‘H NMR peak at 7.4 ppm [6] and an MS molecular ion peak at m/e 372 ‘. Com- plex 7 may thus be an intermediate in the formation of dimer 5 from lb.

5. Reaction of lb with CS2

In contrast to the thermal unreactivity of lb towards car- bony1 sulfide, dissolution of lb in CS2 results in a rapid color

’ X-ray crystal data for 6. C,H,,S,Ta,; M, 742.48; T= 173(2) K, ortho- rhombic, space group P&a; a = 14.087(2), b= 16&l(2), c= 18.244(3) A; V=4225.4( 10) A3; Z=8; D, 2.334 Mg/m3; F(OO0) 2800; f?=2-25 “; 4257 reflections were collected. The structure was solved by the heavy-atom method and relined by full-matrix least-squares on p using all reflections. Hydrogen atoms were located in the difference map and refined isotropically. The final R=0.027 is baaed on 3377 observed reflections (1>20(1)), wR2=0.0641, GOF= 1.138. The final difference map was featureless and did not show any peaks which could be attributed to hydrogen atoms near the Ta or S atoms.

’ 7: ‘H NMR (CsDs): 2.36 (s), 4.7 (d, 2.5 Hz, 2H), 4.8 (d, 2.4 Hz, 2H), 5.6 (d, 1.9 Hz, 2H), 5.7 (d, 1.8 Hz, 2H), 7.4 (s, 1H). MS (70 eV EI): 372(M+).

U. Winkler et al. /Inorganic Chemistry Communications I (1998) 317-319 319

2 (X=S) 3 (X=S) 4 (X=Te) 5 (X=Te)

t X (X=S,Te)

6 lb 6

Scheme 1

change from which the dithioformate insertion product ( MeCp) ,Ta( CO) ( #-S&H) (8) was isolated as an orange oil in 90% yield. The spectroscopic data 9 for 8 are compa- rable with previously reported Cp,M( CO) ( #-S$H) (M =Nb,Ta) complexes [ 13,141 (Scheme 1). Attempts to eliminate CS from 8 by boiling in toluene [ 141 to generate (MeCp),Ta( SH)CO (2) were unsuccessful.

In summary the carbonyl hydride complex lb undergoes both insertion reactions into the Ta-H bond and the addition of Group 16 elements to the carbonyl ligand providing an

9 8: ‘H (C,D,): NMR 12.11 (br, 4.82 (b, lH), 2H), 4.42 2H), 4.38 (b, (b, 4H), 1.79 (s, 6H). 13C NMR (C,D,): 251.4, 241.8, 108.7, 95.0, 94.8, 92.1,88.8,30.1,14.2.IR(toluene): 1911,1005cm-1.MS (12eVEI):416 (M+ -CO).

entry to both M-XH and M-COS complexes. A novel sulfide extraction results from the photoreaction of lb and COS.

Acknowledgements

We are grateful for financial support provided by the U.S. Department of Energy, Office of Basic Energy Sciences.

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