SYNTHESES AND SPECTRAL PROPERTIES OF NEW NITROSYL-[POLY(1-PYRAZOLY)BORATO]RUTHENIUM COMPLEXES

Trichloro(nitrosyl)ruthenium(III) was treated with alkali-metal or thallium poly(1-pyrazolyl)borates M(BRPz3) (Pz = 1-pyrazolyl) to give new nitrosyl[poly(1-pyrazolyl)borato]ruthenium(III) complexes [RuCl2-(BRPz3)(NO)] (1, R = Pz; 2, R = H). A similar reaction with thallium tris(3,5-dimethyl-1-pyrazolyl)hydroborate TlBH(3,5-Me2Pz)3 (3,5-Me2Pz = 3,5-dimethyl-1-pyrazolyl) afforded the complex [RuCl2{BH(3,5-Me2Pz)3}(NO)] (3) as the minor product and the 3,5-dimethylpyrazole complex [RuCl3(NO)(3,5-Me2PzH)2] as the major one. The observation of nu(NO) bands over the range 1870 to 1900 cm-1 determined the NO+ linear coordination mode in these complexes, rather than NO- bent one. The nu(NO) values of 1-3 were larger than those of the corresponding known pi-cyclopentadienyl analogues by ca. 90 cm-1, indicating a smaller degree of pi-back donation of metal-NO bonds in the former complexes. H-1, C-13, and B-11 NMR data of the new complexes are described. In H-1 NOE measurements of 1, irradiation at a chemical shift of 5-H protons in the coordinated pyrazolyl groups induced a positive NOE on the 5-H proton in the uncoordinated group, and individual assignments of the pyrazolyl protons were carried out with the help of H-1-H-1 and C-13-H-1 COSY.