A Discrete N,O,N-Supported Gallium Amido Complex for the Intermolecular Hydroamination of Terminal Alkynes

The diamino-ether ligand {(C 5 H 9 )NH-C 6 H 4 } 2 O ( 1 ) was found to readily react with 0.5 equiv of Ga 2 (NMe 2 ) 6 via an amine elimination route to afford the N,O,N-supported Ga amido species {η 3 - N,O,N -((C 5 H 9 )N-C 6 H 4 ) 2 O}GaNMe 2 ( 2 ) in a reasonable yield (51%). As determined by X-ray crystallography, the four-coordinate Ga center in 2 adopts an unusual trigonal-monopyramidal geometry. Compound 2 effectively catalyzes the hydroamination of terminal alkynes (such as 1-hexyne and phenylacetylene) in the presence of primary amines (aniline and butylamine). Kinetic studies on the latter catalytic reactions suggest that these proceed with a first-order rate dependence on alkyne and on species 2 . In preliminary studies aiming at the isolation of intermediates relevant to the present catalysis, the dimeric Ga complex [{η 2 - N,N -((C 5 H 9 )N-C 6 H 4 ) 2 O}Ga(μ-NHPh)] 2 ( 3 ) was synthesized by an aminolysis reaction between compound 2 and aniline; its identity was confirmed by X-ray crystallographic analysis.