Hydrocarbyl derivatives of dppm- or dppa-bridged alkoxysilyl heterobimetallic Fe-Pd complexes and CO insertion reactions. Crystal structures of [(OC)(3){(MeO)(3)Si}Fe(mu-dppm)Pd(8-mq)] (dppm = Ph2PCH2PPh2), [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu-dppa)PdCl] and [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu-dppa)PdPh] (dppa = Ph2PNHPPh2)

The complexes [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu-dppm)PdR] (R=alkyl, aryl) h ave been obtained either by treatment of [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu- dppm)PdCl] 1a with organolithium or Grignard reagents or, in the case where R=Me, by reaction of [PdCl(Me)(COD)] (COD=1,5-cyclooctadiene) with the met allate K[Fe{Si(OMe)(3)}(CO)(3)(dppm-P)] 2a. When dppa was used as an assemb ling ligand, reaction of the hydrido complex mer-[HFe- {Si(OMe)(3)}(CO)(3)( dppa-P)] 7b with [PdCl(Me)(COD)] or [Pd(eta(3)-allyl)(mu-Cl)](2) proceeded via elimination of methane or propene, respectively, to afford [(OC)(3)Fe{m u-Si(OMe)(2)(OMe)}(mu-dppa)PdCl] 1b and not via HCl elimination which would have resulted in hydrocarbyl complexes. However, reaction of 7b with [PdX( R)(TMEDA)] (X=Cl, R=Me; X=I, R=Ph; TMEDA=Me2NCH2CH2NMe2) afforded the hydro carbyl complexes [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu-dppa)PdMe] 3b or [(OC)(3 )Fe{mu-Si(OMe)(2)(OMe)}(mu-dppa)PdPh] 5b. The latter and [(OC)(3){(MeO)(3)S i}Fe(mu-dppa)Pd(eta(3)-allyl)] 8b were obtained by reaction of the carbonyl metallate 2b with [PdCl(Me)(COD)], [PdI(Ph)(TMEDA)] or [Pd(eta(3)-allyl)(mu -Cl)](2), respectively. The stabilizing but labile four-membered mu-eta(2)- SiO --> Pd bridging interaction facilitates CO insertion into the Pd-Me bon d of 3a or 3b to afford the corresponding acetyl complexes. For comparison, [(OC)(3){(MeO)(3)Si}Fe(mu-dppm)Pd(8-mq)] 6a which contains a stable five-m embered (C,N) chelate at Pd did not insert CO under similar conditions. The reaction of CO with the benzyl derivative [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(m u-dppm)Pd(CH2Ph)] 4a was more complex since the resulting acyl [(OC)(3)Fe{m u-Si(OMe)(2)(OMe)}(mu-dppm)Pd{C(O)CH2Ph}] 11a rearranged into the mu-siloxy carbene complex [(OC)(3)Fe{mu-C(CH2Ph)OSi(OMe)(3)}(mu-dppm)Pd(CO)] 12a. Com parisons are made between complexes containing dppm or dppa and different R groups. The structures of complexes 1b, 5b . THF and 6a . hexane have been determined by X-ray diffraction.