Catalytic dehydrogenative coupling of stannanes by alkoxysilyl heterobimetallic complexes: Influence of the assembling ligand

The heterobimetallic complexes [(OC)(3)(R'Si-3)Fe(mu-P-Z)Pd(eta(3)-allyl)] (1, P-Z = Ph2PNHPPh2 (dppa); 2, P-Z = Ph2P(o-C5H4N) (Ph(2)Ppy); 3, P-Z = Ph 2PCH2PPh2 (dppm); R'(3) = (OMe)(3), Me(OSiMe3)(2)) are very efficient catal ysts for the dehydrogenative coupling of tin hydrides R3SnH (R = Ph, Bu-n). Besides establishing that siloxy complexes are more active catalysts than their alkoxysilyl counterparts, the present study shows that modifications in the nature of the assembling functional phosphine ligand P-Z result in v ariations of catalyst efficiency, expressed by the TON (overall turnover nu mber) and TOF (maximum turnover frequency) values and lifetime. The Ph(2)Pp y-bridged complexes are the most efficient catalysts, and in the case of (B u3SnH)-Bu-n, TON and TOF values higher than 1.2 x 10(6) and 2 x 10(8), resp ectively, have been observed. A marked difference in reactivity is also obs erved between the diphosphine ligands dppa and dppm, with the dppa-bridged complexes being more active than their dppm analogues. The new complex [(OC )(3){(Me3SiO)(2)MeSi}Fe(mu-Ph(2)Ppy)Pd(eta(3)- allyl)] (2b) prepared in the course of this work has been structurally characterized by X-ray diffracti on.