A Kinetically Inert Proton on a Metal−Metal Bond in [{(η5-C5H3)2(SiMe2)2}Ru2(CO)4(μ-H)]+ that Promotes Reactions with Amines

A ruthenium racemisation catalyst for the synthesis of primary amines from secondary amines

A Ru-based half sandwich complex used in amine and alcohol racemization reactions was found to be active in the splitting of secondary amines to primary amines using NH3. Conversions up to 80% along with very high selectivities were achieved. However, after about 80% conversion the catalyst lost activity. Similar to Shvo's catalyst, the complex might deactivate under the influence of ammonia. It was revealed that not NH3 but mainly the primary amine is responsible for the deactivation.

Synthesis of 3-substituted quinolines via transition-metal-catalyzed reductive cyclization of o-nitro Baylis-Hillman acetates

Reductive cyclization of o-nitro-substituted Baylis-Hillman acetates by carbon monoxide, catalyzed by [CpFe(CO)(2)](2), gives moderate to good yields of 3-substituted quinolines.

pH-dependent H2-activation cycle coupled to reduction of nitrate ion by CpIr complexes

This paper reports a pH-dependent H2-activation [H2 (pH 1-4) --> H+ + H- (pH -1) --> 2H+ + 2e-] promoted by CpIr complexes [Cp = eta5-C5(CH3)5]. In a pH range of about 1-4, an aqueous HNO3 solution of [CpIr(III)(H2O)3]2+ (1) reacts with 3 equiv of H2 to yield a solution of [(CpIr(III))2(mu-H)3]+ (2) as a result of heterolytic H2-activation [2[1] + 3H2 (pH 1-4) --> [2] + 3H+ + 6H2O]. The hydrido ligands of 2 display protonic behavior and undergo H/D exchange with D+: [M-(H)3-M]+ + 3D+ <==>[M-(D)3-M]+ + 3H+ (where M = CpIr). Complex 2 is insoluble in a pH range of about -0.2 (1.6 M HNO3/H2O) to -0.8 (6.3 M HNO3/H2O). At pH -1 (10 M HNO3/H2O), a powder of 2 drastically reacts with HNO3 to give a solution of [CpIr(III)(NO3)2] (3) with evolution of H2, NO, and NO2 gases. D-labeling experiments show that the evolved H2 is derived from the hydrido ligands of 2. These results suggest that oxidation of the hydrido ligands of 2 [[2] + 4NO3- (pH -1) --> 2[3] + H2 + H+ + 4e-] couples to reduction of NO3- (NO3- --> NO2- --> NO). To complete the reaction cycle, complex 3 is transformed into 1 by increasing the pH of the solution from -1 to 1. Therefore, we are able to repeat the reaction cycle using 1, H2, and a pH gradient between 1 and -1. A conceivable mechanism for the H2-activation cycle with reduction of NO3- is proposed.

Reactions of the protonated dinuclear ruthenium complex [[(eta(5)-C(5)H(3))(2)(SiMe(2))(2)]Ru(2)(CO)(4)(mu-H)]+ with nucleophiles

Complex [[(eta(5)-C(5)H(3))(2)(SiMe(2))(2)]Ru(2)(CO)(4)(mu-H)](+)BF(4)(-) (1H(+)BF(4)(-)), which features a protonated Ru-Ru bond, reacts with F(-) to give (eta(5)-C(5)H(5))(2)Ru(2)(CO)(4) (2), resulting from the cleavage of both SiMe(2) groups, with I(-) to give the Ru-Ru cleaved product [(eta(5)-C(5)H(3))(2)(SiMe(2))(2)]Ru(2)(CO)(4)(H)(I)(3), and with phosphines (PEt(3), PMe(2)Ph) to give [[(eta(5)-C(5)H(3))(2)(SiMe(2))(2)]Ru(2)(CO)(4)(H)(PR(3))](+) (4a-b). Reaction of 1H(+)BF(4)(-) and NaOMe in THF generates [(eta(5)-C(5)H(4))(2)SiMe(2)]Ru(2)(CO)(4) (5), resulting from the cleavage of a single SiMe(2) group, while the reaction of 1H(+)BF(4)(-) and NaOMe in MeOH generates [mu-eta(5):eta(5)-(C(5)H(3)SiMe(2)OMe)(C(5)H(4))SiMe(2)]Ru(2)(CO)(4) (6), resulting from the partial cleavage of a SiMe(2) group. Reaction of 1H(+)BF(4)(-) and NaSR (R = Me, Et) in THF generates [(eta(5)-C(5)H(3))(2)(SiMe(2))(2)]Ru(2)(CO)(4)(H)(SR) (R = Me, Et; 7a-b), which undergoes rearrangement upon contact with neutral and basic alumina or silica to give complexes [mu-eta(5):eta(1):eta(5)-(C(5)H(3)C=O)(C(5)H(4))(SiMe(2))(2)O]Ru(2)(mu-SR)(CO)(3) (R = Me, Et; 8a-b). Molecular structures of 4a, 6, and 8a as determined by X-ray diffraction studies are also presented.