SYNTHESIS AND CHARACTERIZATION OF BIS-(PYRAZOL-1-YL)BORATE AND TRIS-(PYRAZOL-1-YL)BORATE ACETYL COMPLEXES OF FE-II AND RU-II AND ISOLATION OF AN INTERMEDIATE OF B-N BOND HYDROLYSIS

Complexes cis,trans-[MI(Me)(CO)(2)(PMe3)(2)] (M = Fe la or Ru Ib), in CH2Cl2, reacted with K[(pz)(2)BH2] and Na[(pz)(3)BH] affording the ace tyl complexes trans-[M(COMe){(pz)(2)BH2}(CO)(PMe3)(2)] 2a and 2b and t rans-[M(CoMe){kappa(2)-(pz)(3)BH} (CO)(PMe3)(2)] 3a and 3b, respective ly, If the reactions are carried out in polar solvents decomposition o f both starting materials occurs. Upon standing in n-hexane solution, the free pyrazol-1-yl arm in complex 3a displaces a co-ordinated PMe3 forming [Fe(COMe){kappa(3)-(pz)(3)BH}(CO)(PMe3)] 4a. The analogous rut henium complex was formed directly from the tricarbonyl complex fac-[R uI(Me)(CO)(3)(PMe3)] 5 with Na[(pz)(3)BH]. One of the intermediates of the decomposition of a pyrazolyl donor, -[Fe(COMe){kappa(2)-(mpz)-OB( C8H14)}(CO)(PMe3)(2)] 6 (mpz = 3-methylpyrazolyl), was isolated from t he reaction of 1a with K[(mpz)(2)-B(C8H14)]. This complex was fully ch aracterised both in solution (IR, multinuclear and multidimensional NM R spectroscopy) and in the solid state (X-ray single-crystal diffracti on).