SYNTHESIS AND STRUCTURE OF BIMETALLIC ALLYL, ALKOXYSILYL COMPLEXES [FE(SI(OME)3)(CO)3(MU-DPPM)M(ETA-3-2-RC3H4)] (M = PD, PT, R = H, ME) AND OF [FE(MU-SI(OME)2(OME))(CO)3(MU-DPPM)PD(SNPH3)], A SN-PD-FE-SI CHAIN COMPLEX WITH A MU-2-ETA-2-SIO BRIDGE

The bimetallic allyl, alkoxysilyl complexes [ activated Fe{Si(OMe)3}(CO)3(mu-dppm)M(eta-3-2-RC3H4)] (M = Pd, R = Me, 2a; M = Pd, R = H, 2b; M = Pt, R = H, 3) have been prepared from the iron metalate [Fe{Si(OMe)3}(CO)3(eta-1-dppm)]-, in which the dppm ligand helps in assembling and stabilizing the dinuclear unit. The crystal structure of 2a was determined by X-ray diffraction (Fe-Pd = 269.94 (7) pm). Reaction of 2a with HSnPh3 afforded [ activated Fe{mu-Si(OMe)2(OMe)}(CO)3(mu-dppm)Pd(SnPh3)] (4a), the first Sn-Pd-Fe-Si chain complex, in which the presence of an unusual mu-2-eta-2-SiO bridge between the Fe and Pd atoms was established by X-ray diffraction (Fe-Pd = 266.55 (5), Sn-Pd = 259.50 (4), Pd-O(4) = 216.5 (2) pm). The lability of the O --> Pd bond accounts for the dynamic behavior of the alkoxysilyl ligand, evidenced by variable-temperature H-1 NMR spectroscopy, which renders the methoxy protons equivalent above 313 K (DELTA-G-dagger almost-equal-to 65 +/- 2 kJ/mol).