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

The new bis(phosphino)amido ligand, [MePNPPh], that incorporates (i) an ortho-tolylene linker between nitrogen and phosphorus and (ii) phenyl substituents on phosphorus, has been synthesized as its protonated derivative, [MePNPPh]H, via sequential treatment of (2-Br,4-Me-C6H3)2NH with (i) BunLi, (ii) Ph2PCl and (iii) HCl. Deprotonation of [MePNPPh]H with BunLi in THF affords the lithium derivative which has been isolated as both mono and bis THF adducts, [MePNPPh]Li(THF) and [MePNPPh]Li(THF)2. Treatment of [MePNPPh]Li(THF)2 with GaCl3 and InX3 (X = Cl, Br, I) gives a series of [MePNPPh]MX2 complexes in which the [PNP] donor binds in a “T”-shaped manner and the metal has a distorted trigonal bipyramidal geometry. The reaction of [MePNPPh]Li(THF)2 with “GaI” yields the Ga–Ga bonded complex [κ2-MePNPPh](GaI)(GaI)[κ2-MePNPPh] in which the [MePNPPh] ligand binds in a κ2-P,N manner. The bis(phosphino)amine [MePNPPh]H may also serve as a ligand and treatment of [MePNPPh]H with GaBr3 affords [κ2-{[MePNPPh]H}GaBr2][GaBr4], in which the [MePNPPh]H ligand coordinates in a κ2-P,P manner such that the gallium adopts a tetrahedral geometry.

The new bis(phosphino)amido ligand, [MePNPPh], has been used to synthesize a series of gallium and indium halide complexes of the types [MePNPPh]MX2, [κ2-MePNPPh](GaI)(GaI)[κ2-MePNPPh], and [κ2-{[MePNPPh]H}GaX2]+, in which the [PNP] donor binds with a variety of coordination modes.Figure optionsDownload as PowerPoint slide