The 16-electron dithiolene complexes (p-cymene)M[S2C2(B10H10)] (M = Ru, Os) containing both eta(6)(p-cymene) and eta(2)-(ortho-carborane-dithiolate):adduct formation with Lewis bases, and X-ray crystal structures of (p-cymene)-Ru[S2C2(B10H10)](L) (L = PPh3) and {(p-cymene)-Ru[S2C2(B10H10)]}(2)(mu-LL) (LL = Ph2PCH2CH2PPh2 and N2H4)

The reaction of the eta(6)-arene complexes [(p-cymene)MCl2](2) (M = Ru, Os; p-cymene = 4-isopropyl-toluene) with dilithium 1,2-dicarba-closo-dodecabor ane-1,2-dithiolate (a) leads to the new 16e dithiolene complexes (p-cymene) M[S2C2(B10H10)] (M = Ru (1), Os (1A)). Addition of monodentate Lewis bases (L) to 1 gives 18e dithiolate complexes of the type (p-cymene)Ru[S2C2(B10H1 0)](L) (L = PPh3 (2), P(OMe)(3) (3), NH3 (4), NC5H5 (5), CO (6), (CNBu)-Bu- t (7), SEt2 (8), SC4H8 (9), CN- (10) and SCN- (11)), whereas bidentate brid ging Lewis bases (LL) give centrosymmetric binuclear analogues, {(p-cymene) Ru[S2C2(B10H10)]}(2)(LL) (LL = Ph2PCH2CH2PPh2 (12), N2H4 (13) and 4,4'-dipy ridine (14)). The stability of the Lewis base adducts depends on the nature of the ligating atom and decreases in the order C > P > N > S > O. The add ucts were characterized by their H-1-, C-13- and B-11-NMR spectra, and X-ra y crystal structures were determined for 2, 12 and 13. The phosphane ligand s in 2 and 12 cause stronger folding of the planar dithiolene ring RuS2C2 i n 1 along the S ... S vector (by 25.6 degrees in 2 and 21.0 degrees in 12) than the hydrazine ligand in 13 (7.5 degrees). (C) 2000 Elsevier Science S. A. All rights reserved.