JOZiRSAL OF OR~GSOUETALLIC CIiEMISTR~~ 577

fluoromethyl)cy3opentadienone~tricarbonyl iron= being 95” and 96.6” respectively. It seems reasonable to believe that a similar model to that which we have elaborated here will rationalise these results.

The bonding electron distribution in all\-1 complexes of transition metal ions is discussed and related to the obserx-ed stereoc’nemistries of z-allylpalladium-chloride and -acetate. Some general comments are made on the application of the theory to the bonding in other organometallic molecules.

REFERESCES

I J_ SL ROWE, Proc. CixrJJI. Sot.. (1961) 66. -2 A. E. SurrH. _~C~CZ Cr>rst.. IS (1965) ~SL_ 3 \V_ E. OBERHASSLI _XSD L. F. DAHL, J_ OY~U~IOJ?!P~U~. CheJJz.. 3 (1965) 43. 1 >I. Ii. CIZURCriILL .ASD R. X~SOX. Snttrre. 201 (1964 ;i~_ ; J. Crra-rr z=,sD L. _\. Dusc~ssor; J_ Chon. So>_: irg$j -z-g3g_ 6 F. A. COTTOS. Chcn:lca! _-l~~licati~~: of Grmrb Theory. Interscience. 1961. p- 1.56. ~__ - ; _A_ G. H_ARRISOS ASD F. ~_~Lossrsc,~. A~~,r:ChcnZ_-~oc.. S.2 (1960) IO=& S C. E. 1100~~. _dt~JJliC EJIzYgy Lmrls. U.S. rational Bureau of Standards. CirCU& 467. o 31. R. CHVRCHILL ASD I<. Xxsos. Pyoc.Cheer. SOL. (19611 226.

10 31. R. CncRcarrr ASD R. Xxsos: Pyoc. Roy. SW. (i&do;;). Ser. A. “79 (1964) 19’. II >\I_ GERLOCH ASD R. Slasos. Pyoc. Roy. Sot. (LoJrdox). 2%~. -3, “79 (x964) 170. IZ S. A_ B.AILEY. 11. GERLOCH _SSD 13. XXSOS, Xafctre, 201 (1964) TZ-

SHORT COMMUNICATIONS

PMR spectra of some neopentyl derivatives of mercury. Long-range lwHg-‘H

coupkg

Recentl- xc reported’~” spin-spin coupling between protons and phosphorus

through four o bonds_ In continuation of our work on the long-range interaction of protons with hetero nuclei, we have now found that mercury (isotope IssHg, spin I/Z,

1GSG 9; natural abundance) couples strongI?- with protons over four single bonds. _a x-en_ recent communication by Kiefer and \\ aters” on the coupling of mercury with 7 protons prompts us to report our findings on this subject.

Scope+-1 derivati\*es, prepared b_v the usual methods*, were used as model compounds because of the simplicity of their PMR spectra. The l%Hg-H7 coupling could be measured easiIy as the two peaks of the split y protons were located sym- metrica$- about the resonance of the corresponding unsplit protons (Fig. I). The pertinent dara are summarized in Table I.

l The preparation of neopent~lmagnesium chloride and its further reactions x5t.h appropriate mercxxic halidesxverecamiedoutm % tetrahydrofuranz.

J_ O~,PUJ:OJJZ&!. ChoJt.. 5 (1966) 577-5;g

57s SHORT CO3I3IUSIC_~-l-IOSS

Fig- f. E+oxm magzrtic nxonancr sprctra of trineopent~lmercuric chloride and dineopratyl- mercury in cfeutcriochloroform soiutions

E&f of s&d ifuznf Thr coupling constant of mercury with cz protom in dineopentylmercu~- lis

~31 within range of the corresponding vaiues for other diaIkyImercuc- compound$. More than two-foid increase in it3 value in the cae of neopentyImercuric halides

cirarl-r- indicates that the replacement of eiectron-donating neopentyI group by more electronegative chIorinc and bromine atoms re4ts in disrrting considerable amount of s-character into the mercue-carbon bond. Hatton rf nC.” obsen-ed the same subsiituent effect on /(imHg-HJ in metlq-1 (and &hi-l) derivatives of mercuq- and atibed it to the change Hg {6s6~) -I- Fig- (6s). In other words. the fractional s-

character of the i-alence orbital of mercur\- in\-oI\-ed in bonding with carbon incress from 1.‘~ in the cake of diaikyimercuq- to I in ionic aIkyImercuric compounds SKIN as

aIl;_vImercuric perchlorate~. =\Iso the h-perfine structure comtan:. which is ap

(CD&CO (CD,),SO CDCI, (CD,)&0 (CD&SO

SHORT COMJIGSIC_~TIOSS 579

proximately related to the spin-spin coupling through Fermi contacP, is greater for Hb”; than Hgi_ The polarity of mercuq--haIogen bond (I$$+--X6-) in neopentyl- mercuric chloride and bromide well explains the substituent effect on Hg-H coupling observed in the present case.

Of interest in the present study is that J(199Hg-H,) experiences the same substituent effect as J(199Hg-H,) ~(199Hg-H3N(199Hg-H,)] = _ x5.5 + I.=J_ It is tempting to conclude that both CC and y protons couple with mercury via the same mechanism. It has been shown previouA>* that the dominant contribution toJ(lmHg- H,) arks from the contact term. However. the couplin, 0‘ mechanism of mercury with gamma protons is comples3, and the possibility of zny contribution throughspace cannot be excluded.

The substituents alter significantly the shielding of 3~ protons; but have only little effect on the electronic enl-ironment of the y protons-

It is interesting to note the effect of solvent on the chemical shifts of CL and y

protons and their coupling constants with mercuq_ -4s expected. in neopentylmercuric

halides, the coupling constants increase with the polarity of the solvent. The greater shielding of protons in more polar sol\-ents is readily explainable

by the well-known fact of facile salvation of mercy- compounds in polar solventssi5. The mercuv- atom in RHg)+ can easil- accept one or more pairs of electrons into its

cmpt>- 6)6-orbitals from the sokents such as dimethyl sulfoside-d, and thus cailcel, at Iewt partl?-, the partial charge on it. CoEequentl>-, depending upon the nature

of the solvating media, the ?: and 7 protons shouid be more shielded.

In the cake of dineopentylmercury. there is only little solvent effect on 5(H) and ]fIzHg-H). It is in line with the above explanation.

The proton chemical shifts and their coup& CT constants with mercury remained

I-irtual!y unchanged when the molarity of the solution was reduced from 2 to I.

The author is thankful to Professor DiEr>r_aR SEYFERTH of M.I.T. for advice and encouragement and to Dr. LEOS PETRAKE for helpful discussions. The help of Dr. R,\~uosn C. FERGUSOE in obtaining the spectrum at 200 MC is gratefully ack-

nowledged.

GURDIAL SISGH

1 F. Ii_xw_.ts. C. SISGIZ .XSD H. ZIYYER.]. Phy. Chem., 67 (1963) zjog. 1 D.~EYFCRTH .xsDG.SISGH,,._ 1 ii?:. Cftem. SOC., ST (1965) 4156. 3 E. F. KIEFER ASD \\-. L. \\-ATERS,]. lnz.Chenr. Sot.. 87 (1965) 4401~ 4 R. E. DES~Y.T_ J_ Frav-r. H. H.JAFFS: .&SD G. F. REYSOLD. J.Cilet~z_PPl~~s.. 30 (1959) 14 5 J_ \-_ H.~_rros,\V. G. SCHSEIDER ASD \V_ SIEBRXSD, J_ Chem.Phys.. 39 (1963) 1330~ 6 3. F. R_~XSEY 3s‘~ E. -\I_ F~CRCELL, E%~s. Rec.. Sg (1952) 1-)3_ ; H. Kuiis. AlumicSpedra, Xcademic Press. X-en- York. 1962. pp. 32%341. S H. SAKATZKY _ISD G. F. \vRIGHi. CUPI. J.Chm.. 36 (195s) 1555. 9 F. C. \VHITUORE,E. L. \\-ITTLEASD B. R. HARRIXAS. J._-lnr.Chen;.Soc.. 61 (1939) 15Sj. IO E_ D. HUGXES ASD H. C.\-OLG~R, ].Chenz.S~~.. (1961) 2359. II F_ C_ \VHITJIORE ASD E. ROHRUASS. J._4mChem. SW.. 61 (19x9) 15gI.

Receil-ed October znd, 1965

21.