Manganese and rhenium dihydrobis(pyrazolylato)borate-complexes

Abstract

Reaction of BrM(CO)₅ or M₂(CO)₁₀(M = Mn or Re) with potassium dihydrobis(pyrazolylato)borate affords the crystallline complexes [{H₂B(N₂C₃H₃)₂}M(CO)₃(pyrazole)]. Reaction with phosphines or phosphites (L) leads to the rapid formation of the disubstitued compounds [{H₂B(N₂C₃H₃)₂}M(CO)₂L₂]; in the case of the phosphines the ligands (L) have a relative cis-configuration, whereas, with phosphites the corresponding trans-complexes are obtained. The lability of the co-ordinated pyrazole is attributed to the effect of the ‘hard’ co-ordinated pyrazole nitrogen atoms. Tetra-alkylammonium halides react with [{H₂B(N₂C₃H₃)₂}M(CO)₃(prazole)] to form the stable anions [{H₂B(N₂C₃H₃)₂}M(CO)₃X]^–(X = Br or l).