Chemistry of Coordinatively Unsaturated Bis(thiolato)ruthenium(II) Complexes (η6-arene)Ru(SAr)2[SAr = 2,6-Dimethylbenzenethiolate, 2,4,6-Triisopropylbenzenethiolate; (SAr)2= 1,2-Benzenedithiolate; Arene = Benzene,p-Cymene, Hexamethylbenzene

Abstract

Mononuclear 16-electron arene−ruthenium(II)−thiolate complexes of the general formula (η6-arene)Ru(SAr)2 (2, Ar = 2,6-C6H3Me2 = Xyl; 3, Ar = 2,4,6-C6H2(CHMe2)3; arene = C6H6 (a), arene = p-MeC6H4(CHMe2) = p-cymene (b), arene = C6Me6 (c)) have been prepared by treatment of [(η6-arene)RuCl2]2 (1) with the corresponding sodium arenethiolate in methanol. Reaction of 2b with disodium of 1,2-benzenedithiolate (=S2C6H4) led to a mixture of monomer and dimer complexes (η6-p-cymene)Ru(S2C6H4) (4b) and [(η6-p-cymene)Ru(S2C6H4)]2 (5b) in solution. A complex (η6-C6Me6)Ru(S2C6H4) (4c) was predominantly monomeric, revealed by a crystal structure analysis of 4c. All these monomeric complexes show intense blue color of the LMCT band due to the donation from the filled S(pπ) orbital to the empty Ru(dπ*) orbital, which stabilizes coordinatively unsaturated ruthenium(II). The structures of these complexes are characterized by NMR and mass spectra and elemental analysis in addition to the X-ray crystal structure determinations of 2a,b, 3c, and 4c, indicating the two-legged piano stool geometry. The newly prepared 16-electron complexes react with π-accepting molecules such as isocyanide, carbon monoxide, and trialkylphosphine. Treatment of 2b with an excess of tert-butyl isocyanide resulted in the release of the p-cymene ligand to give trans-Ru(SXyl)2(CNtBu)4 (8). Similarly, reaction of 5b with an excess of tert-butyl isocyanide afforded cis-Ru(S2C6H4)(CNtBu)4 (10), while reaction of 5b with 6 equiv of tert-butyl isocyanide gave a binuclear complex [Ru(S2C6H4)(CNtBu)3]2 (11). In the case of more strongly coordinating C6Me6 derivatives 2c and 4c, one molecule of tert-butyl isocyanide can coordinate to the ruthenium atom, resulting in the formation of (η6-C6Me6)Ru(SXyl)2(CNtBu) (9c) and (η6-C6Me6)Ru(S2C6H4)(CNtBu) (12c), respectively. Reactions of 5b and 4c with an excess of triethylphosphine afforded (η6-p-cymene)Ru(S2C6H4)(PEt3) (13b) and (η6-C6Me6)Ru(S2C6H4)(PEt3) (13c), respectively. In the carbonylation, 2b gave a binuclear carbonyl complex (CO)3Ru(μ-SXyl)3Ru(CO)2(SXyl) (14), while the carbonylation of the C6Me6 complex 2c afforded (η6-C6Me6)Ru(SXyl)2(CO) (15). Versatile reactivity of 16-electron ruthenium(II) thiolate complexes is thus demonstrated.