1,3-DIPHENYLAMIDINE AND METHYLAMINOPYRIDINE COMPOUNDS OF GALLIUM

Reaction of Ga(Bu-t)(3) with the 1,3-diphenylamidine [PhN(H)C(H)=NPh, H-dpam] yields monomeric (Bu-t)(2)Ga(dpam) (1). The partial hydrolysis of 1 results in the isolation of (Bu-t)(2)Ga(mu-dpam)(mu-OH)Ga(Bu-t)( 2) (2), whose structure consists of a gallium dimer in which the amidi ne and hydroxide ligands bridge two Ga(Bu-t)(2) moieties, Reaction of [Me2Ga(mu-Cl)](2) with H-dpam results in the complex [H-2-dpam] [Me2Ga Cl2] (3). The solid state structure of 3 indicates the presence of a h ydrogen bonded cation-anion complex, in which the core has a twisted e ight-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 c arboxylates and triazenides, respectively. Reaction of 2-(methylamino) pyridine (H-map) with Ga(Bu-t)(3) allows for the isolation of (Bu-t)(2 )Ga(map) (4). In contrast, reaction with [(Bu-t)(2)Ga(mu-Cl)](2) and [ Me2Ga(mu-Cl)](2) yields the Lewis acid base adducts, (Bu-t)(2)GaCl(H-m ap) (5) and Me2GaCl(H-map) (6), respectively. Reaction of compound 6 w ith (PrNH2)-Pr-n does not result in the deprotonation of the H-map lig and, but ligand metathesis and the formation of (Bu-t)(2)GaCl((NH2Pr)- Pr-n) (7). The structures of 2, 3, 6, and 7 have been determined by X- ray crystallography. (C) 1998 Elsevier Science Ltd. All rights reserve d.