Synthesis and characterisation of bis(amino)silylene–nickel(0), –palladium(II), –platinum(0), –platinum(II) and copper(I) complexes

The bis(amino)silylene Si[(NCH2tBu)2C6H4-1,2] ( SiNN) behaved as a ligand in displacing COD or PPh3 from [Ni(COD)2], [Pt(PPh3)4] or [CuI(PPh3)3], yielding the crystalline d10 complexes [Ni(SiNN)4] (crystallised from Et2O as the 1:1-adduct 2), [Pt(PPh3)(SiNN)3] (5) or [CuI(PPh3)2(SiNN)] (6). Under the same conditions (in C6H6 at ambient temperature), SiNN and [MCl2(PPh3)2] yielded the crystalline (i) d8 complex trans-[M{SiNN(Cl)}2(SiNN)2] [M=Pt (3), Pd (4)] or (ii) the d10 complexes [Ni(PPh3)4−n(SiNN)n] (n=4 (2) or 3 (1), depending on stoichiometry; with Cl2SiNN as co-product). The X-ray structures of 2, 4, 5 and 6 are presented; those of 1 and 3 appeared in a preliminary communication. Compound 3 was shown to undergo three fluxional processes in CDCl3 solution, as shown by detailed variable temperature NMR spectroscopic experiments. These involved in order of increasing energy (a) two conformers of 3, (b) one of these and the cis-isomer, and (c) Si→Si 1,3-shifts of Cl−. These results are placed into the context of related published silylenemetal chemistry.