Gallium and indium compounds supported by a [ PNP] pincer ligand

Abstract

The new bis(phosphino)amido ligand, [MePNP Ph], that incorporates (i) an ortho-tolylene linker between nitrogen and phosphorus and (ii) phenyl substituents on phosphorus, has been synthesized as its protonated derivative, [MePNP Ph]H, via sequential treatment of (2-Br,4-Me-C 6H 3) 2NH with (i) Bu nLi, (ii) Ph 2PCl and (iii) HCl. Deprotonation of [MePNP Ph]H with Bu nLi in THF affords the lithium derivative which has been isolated as both mono and bis THF adducts, [MePNP Ph]Li(THF) and [MePNP Ph]Li(THF) 2. Treatment of [MePNP Ph]Li(THF) 2 with GaCl 3 and InX 3 (X = Cl, Br, I) gives a series of [MePNP Ph]MX 2 complexes in which the [ PNP] donor binds in a “T”-shaped manner and the metal has a distorted trigonal bipyramidal geometry. The reaction of [MePNP Ph]Li(THF) 2 with “GaI” yields the Ga–Ga bonded complex [κ 2-MePNP Ph](GaI)(GaI)[κ 2-MePNP Ph] in which the [MePNP Ph] ligand binds in a κ 2- P, N manner. The bis(phosphino)amine [MePNP Ph]H may also serve as a ligand and treatment of [MePNP Ph]H with GaBr 3 affords [κ 2-{[MePNP Ph]H}GaBr 2][GaBr 4], in which the [MePNP Ph]H ligand coordinates in a κ 2- P, P manner such that the gallium adopts a tetrahedral geometry.