Triamidostannates(II) as Sterically Demanding Ligands for Rhodium and Iridium

Reaction of the triamidostannates(II) MeSi[SiMe2N(3,5-xyl)]3SnLi(OEt2) (2a) and MeSi[SiMe2N(p-tol)]3SnLi(OEt2) (2b) with 0.5 molar equiv of [RhCl(COD)]2 gave the zwitterionic complexes [MeSi[SiMe2NAryl]2Sn[SiMe2N(η6-Aryl)]Rh(diolefin)] (Aryl = 3,5-xyl: 3a, p-tol: 3b). In these one of the aryl groups acts as a η6-ligand, thus resulting in the 18-electron rhodium species. Addition of 1 equiv of PPh3 to a solution of 3a or 3b yielded the square-planar complexes [MeSi[SiMe2NAryl]3SnRh(PPh3)(COD)] (Aryl = 3,5-xyl: 4a, p-tol: 4b), in which the stannates are directly bonded to rhodium through Rh−Sn bonds. Treatment of the complexes 4a,b and 5a,b with hydrogen gas in the presence of benzene leads to the hydrogenation of the diolefin and its replacement by benzene as a formal six-electron donor ligand. These 18-electron complexes [MeSi[SiMe2N(p-tol)]3SnRh(PPh3)(η6-arene)] 6a,b and 7a,b are also accessible by reacting the stannates with 0.5 equiv of [RhCl(C2H4)2]2, PPh3, and the appropriate arene. Upon reacting the xylyl stannate 2a with [IrCl(COD)]2 and Ph3P, it was possible to isolate the square-planar Ir complex [MeSi[SiMe2N(3,5-xyl)]3SnIr(PPh3)(COD)] (8a). In contrast, for the tolyl stannate CH-activation occurred to give the IrIII compound [MeSi[SiMe2N(p-tol)]2[SiMe2N(2-C6H3-4-CH3)]SnIr(H)(PPh3)(COD)] (8b).