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

Abstract

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)d NNH 2 )(H[Xy 2 NSN])] (6). Structures of 1a, 1b, 2, 5, and 6 have been determined by X-ray crystallography.

A Surprising Reaction of Trimethylphosphane with the Unsaturated Diruthenium Complex [(η6‐C6Me6)2Ru2(μ2‐H)3]+: Synthesis and Molecular Structure of the Cations [(η6‐C6Me6)Ru2(PMe3)3(μ2‐H)3]+ and [(η6‐C6Me6)2Ru2(PMe3)2(μ2‐H)(H)2Tschan1, Cherioux2, Therrien3 et al. 2007Eur J Inorg Chem6120View full textAdd to dashboardCite

“…Cation 1 is obtained in 28 % yield and it can be isolated as the tetrafluoroborate salt (Scheme 1). The substitution of an η 6 -arene ligand at a ruthenium atom by three phosphane ligands has been observed so far for benzene, [4] toluene [5] and pcymene [6] ligands, but never for the strongly bound η 6 -C 6 Me 6 ligand. The single-crystal X-ray structure analysis of [1][BF 4 ], crystallised by slow diffusion of diethyl ether in a concentrated acetone solution of [1][BF 4 ], reveals for cation 1 the presence of three bridging hydrido ligands coordinated to the two ruthenium atoms, one ruthenium atom being coordinated to an η 6 -C 6 Me 6 ligand and the other one to three PMe 3 ligands.…”

Alkene Metathesis Catalysis: A Key for Transformations of Unsaturated Plant Oils and Renewable Derivatives

“…Takemoto et al [58] and Li et al [59] reported examples of homogeneous hydrogenation of nitriles into primary amines when alkoxide were added to ruthenium catalyst. Das et al [60] and Enthaler et al [61,62] also showed that addition of t BuOK and phosphine to simple ruthenium complex led to the fast hydrogenation of various nitriles and by replacing the phosphine ligand by a N-heterocyclic carbene, milder conditions could be operating [63].…”

A Practical and Benign Synthesis of Primary Amines through Ruthenium‐Catalyzed Reduction of Nitriles

“…[16] To improve the selectivity towards benzylamine, addition of an appropriate base was investigated. [15,17] Indeed, in the presence of potassium tert-butoxide, benzylamine is formed in good yield and with reasonable selectivity.…”

“…[14] Notably, an improvement in the selectivity for the primary amine was reported by Hidai and co-workers by carrying out the reaction in the presence of catalytic amounts of base. [15] Nevertheless, with all of the above-mentioned catalyst systems, side products were formed in reasonable amounts thus lowering the selectivity towards primary amines and the overall atom efficiency. As shown in Scheme 1, the formation of secondary amines is caused by the reaction of the primary amine 3 with the imine intermediate 2.…”

“…is desirable to suppress formation of the secondary amine, and 2) the equilibrium between 2 and 4 should be shifted towards 2 by the addition of ammonia or an appropriate base. [15,17] Recently, we demonstrated that an in situ catalyst system composed of [RuA C H T U N G T R E N N U N G (cod)(methylallyl 2 )] (cod = 1,5-cyclooctadiene) and 1,1'-bis(diphenylphosphino)ferrocene (dppf) allows for excellent chemoselectivities (> 99 %) towards primary amines and high turnover frequencies up to 5783 h À1 . [18] Herein, we report our ongoing studies of the catalytic reduction of nitriles.…”