The Deprotonated Iminophosphorane o-C6H4PPh2P=NSiMe3 as a Novel Chelating Ligand in Organocopper(I) and zinc(II) Chemistry

Lithiation of triphenyl(trimethylsilylimino)phosphorane Ph3P=NSiMe3 with MeLi gives the ortho-metallated species [Li(oC6H4PPh2NSiMe3)]2·Et2O (1), which exhibits all the requirements of an organometallic ligand capable of side-arm donation. The deprotonated ortho-phenyl carbon atom gives access to metal-carbon (sigma) bonds in transmetallation reactions, while the Ph2P=NSiMe3 moiety can donate to the same metal center through the imine nitrogen atom. In transmetallation reactions with CuBr, the dimeric organocopper complex [Cu(o-C6H4PPh2NSiMe3)]2 (2) is obtained, while application of ZnCl2 yields the monomeric zinc complex [Zn(o-C6H4PPh2NSiMe3)2] (3). Reaction with CuCl2 gives access to the new diiminophosphorane (o-C6H4PPh2NSiMe3)2 (4) through oxidative coupling at the ortho positions. In all the metal complexes, the Ph2P=NSiMe3 residue acts as a side-arm donating group through the nitrogen atom. The intermolecular N-Cu donor bond in 2 is as short as copper-amide bonds, while the N-Zn bond lengths in 3 are in the region normally found for donor bonds. Compound 4 is a molecule, possessing two Ph2P=NSiMe3 moieties bridged by a biphenylene group.