Syntheses and characterizations of group 6 metal cyanotrihydroborate complexes

The anions, [M(CO)6–n(NCBH3)n]n− (n=2, M=Cr(1); n=3, M=Cr(2), Mo(3), W(4)), were prepared either from the reactions of sodium cyanotrihydroborate with group 6 transition metal hexacarbonyls, M(CO)6 (M=Cr, Mo, W), or through the reactions of M(CO)3(CH3CN)3 (M=Cr, W) with sodium cyanotrihydroborate. The cyanotrihydroborate ligand bonds to the metal through a nitrogen atom, which was confirmed by the Infrared, proton and boron NMR spectroscopies. Crystal structures of the above complexes were determined by single crystal X-ray diffraction analyses. A cis configuration is found in 1. Molecular structures of 2, 3, and 4 are similar and a facial configuration is observed.