Reactions of Tridentate-type Poly(1-pyrazolyl)borate Anions with cis-[RuC12(dmso)4]

Abstract

Suspensions of thallium tris- and tetrakis(1-pyrazolyl)borates T1(BRPz₃) (Pz=1-pyrazolyl R=Pz, H) and cis-[RuC1₂(dmso)₄](dmso=dimethyl sulfoxide ligand) in CH2C12 were refluxed for 6 h, and afforded a boron-free pyrazole complex, [RuC1₂(PzH)(dmso)3] [1] as a pale yellow powder. Isolated yields were 13 and 17% from BPz₄ and BHP_z3 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-NMR and IR spectroscopy. The singlet 'H-resonance (CDCl₃) at δ 3.53 was attributed to two spectroscopically equivalent m ethyl groups of one dmso ligand. On the other hand, the remaining two dmso ligands showed methyl-proton signals at δ 3.17 and 3.46, of which the mutual long-range coupling (⁴JHH)was observed in the H-1-H 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].