4910 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Organometallics 1996, zyxwv 14, 4910-4919 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Novel CO-Induced Silyl Migration in Heterobimetallic Iron-Palladium Methyl Complexes Leading to p-Siloxycarbene Complexes. Crystal Structures of the Metallasiloxanes [(OC)3Fe{p-Si(OSiMe3)~(OSiMe3))(p-dppm)PdCl] and zy [ (OC)3{ (Me3SiO)3Si}Fe(p-dppm)Pt(l73.CsHs)l zyxwvutsrqponmlkjihgfedcbaZYX Michael Knorr*>+ and Pierre Braunstein" Laboratoire de Chimie de Coordination, Associt? au CNRS (URA 0416), Universiti Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France Antonio Tiripicchio and Franco Ugozzoli Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universita di Parma, Centro di Studio per la Strutturistica Diffrattometrica del CNR, Viale delle Scienze 78, I-43100 Parma, Italy Received March 29, zyxwv 1995@ The heterobimetallic alkyl, siloxyl complex [(OC)3Fe(pC1-Si(OSiMe3)2(OSiMe3)}@-dppm)Pd- (Me)] (2a), which displays a p-y2-Si-0 bridge, was prepared by alkylation of [(OC)3Fe{pu- Si(OSiMe3)2(OSiMe3)}~-dppm)PdClI (1) with MeLi. The analogous complex [(OC)3Fe{p- - SiMe(OSiMe3)(0SiMe3)}(p-dppm)Pd(Me)l (2b) was obtained by reaction of WFe{ SiMe(OSiMe3)z}(C0)3(+dppm)l with a cold THF solution of [Pd(Cl)(Me)(1,5-COD)]. The dynamic behavior of the Si(OSiMe3)s ligand in 2a was investigated by variable- temperature13C-NMRspectroscopy and is consistent with rapid rotation of the siloxyl ligand about the Fe-Si bond at ambient temperature. Upon treatment of a hexane solution of 2a with CO, the siloxycarbene-bridged complex [(OC)3Fe(p-C{OSi(OSiMe3)3}Me)(u-dppm)- Pd(C0)I (3a) was formed quantitatively. Complex 2b reacted in an analogous manner. This transformation results from CO insertion followed by a silyl migration and its mechanism is discussed. The allyl complex KOC)3{(Me3Si0)3Si}Fe~-dppm~Pt(~3-C3H~)l zyx (5) was prepared and addition of RNC (R = t-Bu, 2,6-dimethylphenyl) yielded the labile a-allyl complexes [(OC)3{(Me3SiO)3Si}FeOl-dppm)Pt(y1-C3H5)(CNR)I (6) which are in equilibrium with 5 due to facile RNC dissociation. In the presence of an excess t-BuNC, complex [(OC)3{(Me3- Si0)3Si)FeOl-dppm)Pt(y1-C3H5)(CNR)zl (7) was formed which contains a pentacoordinated platinum center. The solid-state structures of complexes 1 and 5 have been determined by single-crystal X-ray diffraction. - Introduction The insertion of carbon monoxide into the metal- carbon bond of mononuclear complexes plays a funda- mental role in organometallic chemistry and homoge- neous catalysis owing to the importance of C-C coupling rea~tions.l-~ As part of our studies on the reactivity of heterometallic, alkoxysilyl complexes, we prepared a series of alkyl complexes of the type [(OC)3Fe@-Si- (OMe)z(OMe)}@-dppm)MRl (M = Pd, Pt; R = Me, Et, norbornyl) and investigated their ability to insert CO and isocyanides into the metal-alkyl b ~nd.~-~ The acyl - + Present address: Universitat des Saarlandes, Anorganische Che- @ Abstract published in Advance ACS Abstracts, September 1, 1995. (1) Garrou, P. E.; Heck, R. F. J. Am. Chem. zyxwvutsrq Soc. 1976, 98, 4115. (2) Anderson, G. K.; Cross, R. J. Acc. Chem. Res. 19W, 17, 67. (3)Yamamoto, A. Organotrunsition Metal Chemistry; Wiley & (4) Braunstein, P.; Knorr, M.; Stahrfeldt, T. J. Chem. SOC., Chem. (5) Braunstein, P.; Faure, T.; Knorr, M.; Stahrfeldt, T.; DeCian, A.; mie, D-66041 Saarbritcken, Germany. Sons: New York, 1986. Commun. 1994, 1913. Fischer, J. Gazz. Chim. Ital. 1996, 125, 35. complex [(OC)3Fe@-Si(OMe)2(OMe)}@-dppm)Pd{ C(0)- Me}] was shown to insert olefins into the Pd-C a-bond, thus allowing sequential COIolefin incorporation.* PhZP- PPhz I I + t (Me0)pSi -0, (OC)3Fe-Pd-CSo \ f he Me We were intrigued by the possibility that a siloxyl ligand in place of Si(OMe)a could induce a different reactivity toward small molecules. Both silicon ligands are characterizedby a dynamic behavior associated with (6) (a) Knorr, M.; Braunstein, P.; DeCian, A.; Fischer, J. Orguno- metallic8 1996,14,1302. (b)Braunstein, P.; &OR, M. In Metal-Ligand Interactions, Structure and Reactivity; NATO AS1 Series; Russo, N., Salahub, D. R., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1995, in press. (c) Braunstein, P.; Knorr, M. J. Orga- zy "et. Chem. 1996, 500, in press. (d) Braunstein, P.; Knorr, M. Unpublished results. 0276-733319512314-4910$09.00/0 0 1995 American Chemical Society