1822 Organometallics zyxwvu 1987, 6, 1822-1824 Scheme I A / C i I @co)nMo-co-o-cnncH=cn2 @tcoi#-co-o-cn2cn= - lb 1s into tetrahydrof~ans.~ In this process an intramolecular attack by the C 4 group of the acetate upon the epoxide ring is the key step, and the mechanism we suggest for the complex formation is outlined in Scheme Ia. zyxwvut This involves the initial formation of a u-bonded epoxymethyl complex A, followed by migratory CO insertion to produce the 16e coordinatively unsaturated complex B. This may be trapped by the phosphine to form C which contains a very nucleophilic acyl group by virtue of the contributing res- onance structure C,. We suggest this group participates in an intramolecular attack to yield the ultimately isolated furan complex. A previous example of an intramolecular attack by a metal acyl group due to ita nucleophilicity is provided by the isolation of a cyclic cationic carbene complex upon treatment of (v~-C,H,)F~(CO)~(CH~),B~ with PPh,., Support for the proposed mechanism was obtained from the reaction of the molybdenum carbonylate and epi- bromohydrin in the absence of triphenylphosphine (eq 2). In this reaction no furan ring was formed and a different intramolecular rearrangement involving CO incorporation took place. This result shows the importance of trapping the 16e complex B by PPh3 (Scheme Ia). In the absence of this ligand, the 0 atom of the epoxide interacts with the electron-deficient Mo atom, probably to form a transient allyloxy complex which upon rapid migratory CO insertion (4) Coxon, J. M.; Hartachorn, M. P.; Swallow, W. W. zyxwvutsr J. Og. Chem. (5) Curtis, P. J.; Davies, S. G. J. Chem. SOC., Chem. zyxwvutsrqp Commun. 1984, 1974,39, 1142. 747. 0276-7333/87/2306-1822$01.50/0 I CtS-(7'-CsHs )Mo(C0)2 -CO- O - =CHz (2) will form the isolated zyxw u-r complex (Scheme Ib).6 If tri- phenylphosphine is added to a reaction mixture of [(q5- C5H5)Mo(CO),]-Na+ and epibromohydrin, only the u-7r complex is isolated. Furthermore, thermal (refluxing THF solution) or photochemical treatment of the u-r complex with PPh, leads to the isolation of [ (V~-C~H~)~MO~(CO),- (PPh,)] .' These reactions preclude the intermediacy of the u-7r complex in the formation of the furan complex. Extension of this new chemistry to oxiranes, episulfides, and related ring systems along with formation of variously substituted furans is currently in progress. Acknowledgment. Support of this research by the Robert A. Welch Foundation, Houston, TX, and by a Texas Advanced Technology Research Award is gratefully acknowledged. Financial support and leave of absence to R.C.-0. from the Instituto de Quimica, UNAM, are also acknowledged. Supplementary Material Available: Tables of crystal data, atom coordinates, bond lengths and angles, anisotropic temper- ature factors, and hydrogen coordinates (6 pages); a listing of observed and calculated structure factors (16 pages). Ordering information is given on any current masthead page. (6) The reaction was performed on the same scale, in the same man. ner, as that in the presence of triphenylphoephine to yield 0.85g (2.8 mmol, 74%) of the u-7r complex. Elution of the column with a 4060 hexane/CHzClz solvent mixture removed any [(q6-C6H5)Mo(CO)& formed, and the product was eluted with CH2ClZ: orange solid; mp 95 "C darkens, 112-113 OC dec. Anal. Found (Calcd): C, 44.1 (43.7);H, 3.45 (3.31). IR d C 0 ) (CH,Cld. 2012 (s. 1949 (8. bd). 1646 (m) cm-'. NMR ipp& CP~): '13~; 235,5(c8), 228.4 ico), 215.3 ih;lo-co:oj, 93.1 (c,Hj, 79.3 (CHZzCH), 65.7 (CHZ=CH), 31.8 (CHJ; 'H, 2.14 (d, J = 3.8 Hz, CH=CH,,Hh), 4.41 (d. J Mo-CO-O-CH,H,), 2.36 (d, J = 6.5 Hz, Mo-CO-O-CH,,Hb), 3.89 (m, 5.9 Hz, CH=CH.Hd, 4.84 (CsHd. (7) Ha%&, R. J.; Nyholm, R. SI; Stiddard; M. .H. B. J.%keem. SOC. A 1968, 43. Reaction of the (Tr1methylsilyl)dlaromethane Anion with Metal Complexes: Synthesis and X-ray Study of Iodomethyltris(trhnethylphosphlne)rhodlum( I I I ) (Trimethylsllyl)dlaromethane, RhICH,( PMe,),(C( N,)SlMe,] Marie Joelle Menu, Peter Desroslers, Michile Dartlguenave, and Yves Dartlguenave' Laboratoire de Chimie de Co6rdlnation du CNRS associ6 Ii I'Universit6 P. Sabatier, Touiouse 3 1077, France Guy Bertrand' Laboratoire des Organom6taiiiques, UA CNRS 4 77 Universit6 P. Sabatier, Toulouse 3 1062, France Received March 3, 1987 Summary: LiC(N2)SiMe3 reacts with Rh(PMe3),CI at low temperature to give Rh(C(N2)SiMe3}(PMe3), (1) in high yield. This complex adds Me1 oxidatively in benzene to tallizes in the space group Pnma , with a = 9.352 (1) A, b = 10.916 (2) A, c = 29.358 (5) A, Z = 4, and V = 2997 A3. Controlled thermolysis generates several rho- dium species, of which RhI(Me),(PMe,), has been isolated as the final product. give Wan* Rh~C(N,)SiMe3)MeI(PMe3),.C,H, (2). 2 CVS- 0 1987 American Chemical Society