1,3-diphenylamidine and methylaminopyridine compounds of gallium

Abstract

Reaction of Ga( t Bu) 3 with the 1,3-diphenylamidine [PhN(H)C(H)NPh, H-dpam] yields monomeric ( t Bu) 2 Ga( dpam) ( 1). The partial hydrolysis of 1 results in the isolation of ( t Bu) 2 Ga(μ- dpam)(μ- OH) Ga( t Bu) 2 ( 2), whose structure consists of a gallium dimer in which the amidine and hydroxide ligands bridge two Ga( t Bu) 2 moieties. Reaction of [Me 2Ga(μ-Cl)] 2 with H-dpam results in the complex [H 2-dpam] [Me 2GaCl 2] ( 3). The solid state structure of 3 indicates the presence of a hydrogen bonded cation-anion complex, in which the core has a twisted eight-membered ring configuration. The versatility of amidines as both chelating and bridging ligands to gallium is discussed with respect to the predominance of bridging and chelating modes of coordination of carboxylates and triazenides, respectively. Reaction of 2-(methylamino)pyridine (H-map) with Ga( t Bu) 3 allows for the isolation of ( t Bu) 2 Ga( map) ( 4). In contrast, reaction with [( t Bu) 2 Ga(μ- Cl)] 2 and [Me 2Ga(μ-Cl)] 2 yields the Lewis acid base adducts, ( t Bu) 2 GaCl( H-map) ( 5) and Me 2GaCl(H-map) ( 6), respectively. Reaction of compound 6 with n PrNH 2 does not result in the deprotonation of the H-map ligand, but ligand metathesis and the formation of ( t Bu) 2 GaCl( NH 2 n Pr) ( 7). The structures of 2, 3, 6, and 7 have been determined by X-ray crystallography.