Ruthenium Complexes Containing Bis(diarylamido)/Thioether Ligands:  Synthesis and Their Catalysis for the Hydrogenation of Benzonitrile

Treatment of the thioethers (RNH- o -C 6 H 4 ) 2 S (H 2 [R 2 NSN]; R = Xy, Xyf; Xy = 3,5-Me 2 C 6 H 3, Xyf = 3,5-(CF 3 ) 2 C 6 H 3 ) with 2 equiv of n -BuLi followed by addition of 0.5 equiv of [(η 6 -C 6 H 6 )RuCl 2 ] 2 in THF gave the bis(diarylamido)/thioether complexes [(η 6 -C 6 H 6 )Ru[R 2 NSN]] (R = Xy ( 1a ), R = Xyf ( 1b )) in moderate yields. In the presence of 1a (1 mol %) and PCy 3 (2 mol %; Cy = cyclohexyl), benzonitrile was catalytically hydrogenated to give benzylamine (72%) and benzylidenebenzylamine (27%) at 80 °C and 30 atm, while the hydrogenation with 1b as a catalyst precursor resulted in the formation of benzylamine (37%) and benzylidenebenzylamine (51%) under the same reaction conditions. The yield of benzylamine was improved up to 92% by using a catalyst mixture of 1a (1 mol %)/PCy 3 (2 mol %)/ t -BuONa (10 mol %). On the other hand, the reaction of 1a with excess PMe 3 afforded the tris(trimethylphosphine) derivative [(PMe 3 ) 3 Ru[Xy 2 NSN]] ( 2 ). Treatment of 2 with excess PhCN, MeCN, or N 2 H 4 ·H 2 O resulted in the replacement of a PMe 3 ligand by these substrates to give [(PMe 3 ) 2 LRu[Xy 2 NSN]] ( 3, L = PhCN; 4, L = MeCN; 5, L = N 2 H 4 ), while the reaction of 2 with benzoylhydrazine gave the κ 2 -benzoylhydrazido complex [(PMe 3 ) 2 Ru( κ 2 -( O, N )-PhC(O) NNH 2 )(H[Xy 2 NSN])] ( 6 ). Structures of 1a, 1b, 2, 5, and 6 have been determined by X-ray crystallography.