REACTIONS OF TRIDENTATE-TYPE TRIS(1-PYRAZOLYL)BORATES AND TETRASIS(1-PYRAZOLYL)BORATES ANIONS WITH CIS-[RUCL2(DMSO)4

Suspensions of thallium tris- and tetrakis(1-pyrazolyl)borates Tl(BRPz3) (Pz = 1-pyrazolyl; R = Pz, H) and cis-[RuCl2(dmso)4](dmso=dimethyl sulfoxide ligand) in CH2Cl2 were refluxed for 6h, and afforded a boron-free pyrazole complex, [RuCl2(PzH)(dmso)3] [1] as a pale yellow powder. Isolated yields were 13 and 17% from BPz4 and BHPz3 salts, respectively. Bond cleavage between boron and 1-nitrogen atoms occurred for the BRPz3 ligands in the course of the reactions. All of the three dmso ligands in 1 were associated with their S-bonded coordination mode on the basis of H-1-NMR and IR spectroscopy. The singlet H-1-resonance (CDCl3) at delta-3.53 was attributed to two spectroscopically equivalent methyl groups of one dmso ligand. On the other hand, the remaining two dmso ligands showed methyl-proton signals at delta-3.17 and 3.46, of which the mutual long-range coupling (4J(HH)) was observed in the H-1-H-1 COSY, indicating spectroscopic nonequivalence of the two geminal methyl groups in the respective ligands. As a whole, the complex 1 was concluded to have the facial configuration of three S-bonded dmso ligands around ruthenium. In addition to 1, [RUCl2(PzH)2(dmso)2] was formed as a minor product, by use of a large excess of PzH in the reaction with [RuCl2(dmso)4].