Dehydrogenative stannane coupling by platinum complexes

The complexes Pt(acac)2, (PhMe2P)2PtMe2, (dppe)PtMe2 (dppe=bis(diphenylphosphino)ethane), and the (P∩N)PtMe2 complexes [(κ2-P,N)Ph2PCH2CH2CH2NMe2]PtMe2 and [(κ2-P,N)Ph2PCH2CH2NMe2]PtMe2 catalyse the formation of distannanes by dehydrogenative coupling of triphenyltin hydride or tri-n-butyltin hydride. While Pt(acac)2 appears to react by a radical mechanism, the bis(stannyl) complexes (PhMe2P)2Pt(SnR3)2 and (dppe)Pt(SnR3)2 were observed in the reaction of (PhMe2P)2PtMe2 and (dppe)PtMe2. At longer reaction periods the complexes (PhMe2P)2Pt(H)SnBu3 and (PhMe2P)2Pt(Ph)SnHPh2, respectively, were formed. There is evidence that the distannanes are formed by a similar mechanism when (P∩N)PtMe2 is employed as the catalyst instead of (R3P)2PtMe2. However, the presence of the P,N-chelating ligand results in the stabilisation of the intermediate (P∩N)Pt(Me)SnR3 and in the formation of redistribution products.