Israel Journal of Chemistry Vol. 41 2001 pp. 139–144 *Author to whom correspondence should be addressed. E-mail: icac@mahendra.iacs.res.in A Family of Thioxanthato Ruthenium and Osmium Aryls SWARUP CHATTOPADHYAY, a BIKASH KUMAR PANDA, a KAUSHIK GHOSH, a AND ANIMESH CHAKRAVORTY a,b, * a Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India b Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India (Received 30 August 2001) Abstract. The title complexes of type M(RL 2 )(PPh 3 ) 2 (CO)(S 2 CSEt) (2a: M = Ru; 2b: M = Os) have been synthesized in excellent yields by reacting M(RL 1 )(PPh 3 ) 2 (CO)X (1a: M = Ru, X = Cl; 1b: M = Os, X = Br) with potassium ethyl thioxanthate and have been characterized with the help of spectral and electro- chemical data. The RL 2 ligand in 2 is the imine-phenol tautomer of N-C 6 H 4 R(p)-4- methylsalicylaldimine (R = Me, MeO, Cl) coordinated at the carbanionic-C2 atom only while RL 1 in 1 is the iminium-phenolato tautomer chelated via carbanionic-C2 and phenolato-O atoms. The synthetic reaction is thus attended with tautomerization of the Schiff base ligand. It is also associated with a rotation of the ligand by ~180º around the M–C bond in order to exclude steric repulsion. These features have been revealed by structure determination of 2a (R = Me). The metallated aldimine ring is found to be highly noncoplanar (dihedral angle ~40 o ) with the thioxanthate chelate ring due to steric repulsion originating from the relatively large size of the sulfur atom. This phenomenon, which is absent in both the precursor 1 (R = Me) and in the carboxylate analogue Ru(MeL 2 )(PPh 3 ) 2 (CO)(O 2 CMe), 7, has distinctive effects on bond parameters of 2a (R = Me). Thus the two Ru–P bonds in 2a (R = Me) differ in length by as much as 0.06 Å. The thioxanthate 2 is thermodynamically more stable than the precursor 1 as well as the carboxylate 7. Accordingly, both of these are irreversibly transformed to 2a (R = Me) upon treatment with thioxanthate. INTRODUCTION Ruthenium and osmium organometallics of type M(RL 1 )(PPh 3 ) 2 (CO)X, 1, were discovered in this labo- ratory as the product of decarbonylative metallation of 4-methyl-2,6-diformylphenol by M(PPh 3 ) 2 X 2 in the pres- ence of primary amines (RNH 2 ). 1, 2 The reactivity of these compounds is under our scrutiny. Thus, the Ru–C(aryl) bond in 1a has been found to be prone to alkyne inser- tion. 3,4 A second reaction concerned the displacement of the coordinated halide ligand by O/N donor anions such as carboxylate, 5 nitrate, and nitrite. 6 Herein we explore the feasibility of introducing sul- fur donors into the coordination sphere via anion dis- placement. The reaction of 1 with potassium ethyl thioxanthate is accompanied by changes in the coordi- nation mode, tautomeric state, and rotameric conforma- tion of the Schiff base ligand, affording a new family of sulfur-chelated organometallics. Their structure and properties are described and rationalized in this work. Very few thioxanthates of ruthenium 7 and osmium 8 have been documented in literature. 1