The iminophosphorane Ph₃PNSiMe₃ as a synthon for M-C_aryl σ bonds (M = In, Fe, Ge) implementing imino sidearm donation

Abstract

Lithiation of triphenyl((trimethylsilyl)imino)phosphorane, Ph₃P=NSiMe₃ (1), with MeLi gives the ortho-metalated species [Li(o-C₆H₄PPh₂NSiMe₃)]₂·Et₂O (2). It has all the requirements of an organometallic ligand capable of sidearm donation: the deprotonated ortho phenyl carbon atom leads to metal-carbon s bonds in reactions with metal halides, and the Ph₂P=NSiMe₃ moiety donates an electron pair to that metal via the imine nitrogen atom. In reactions with InCl₃ the In(III) organometallic complex [In(o-C₆H₄PPh₂NSiMe₃)₃] (3) was obtained, while with FeCl₂ a new example of the rare iron(II) 14-VE complexes [Fe(o-C₆H₄PPh₂NSiMe₃)₂] (4) was obtained. Reaction of 2 with Ph₃GeCl gave [Ph₃Ge(o-C₆H₄PPh₂NSiMe₃)] (5). While in 4 both imino sidearms coordinate to the metal, because of steric crowding only two of the three present coordinate in 3. Because of the low Lewis acidity of the tetraorganogermanium moiety the imino sidearm does not donate to the central germanium atom in 5.