Syntheses of 4-Benzyl-3,5-dimethylpyrazolylborato Complexes of Molybdenum and Tungsten Nitrosyls: Molecular Structure of [ Mo( CO),( NO)(HB(3,5-Me2-4-PhCH,C,N,),)I, a Complex with an 'Inverted' Bowl-like Structure

Summarization: Reaction of [HB(bdmpz),] , obtained by reaction of 4-benzyl-3,5-dimethylpyrazole (Hbdmpz) with KBH,, with [M(CO),] (M = Mo or W) and p-MeC,H,SO,N(NO)Me afforded [M(CO),(NO)- {HB(bdmpz),}] (M = Mo or W). The molybdenum carbonyl was converted into [Mo(NO)- {HB(bdmpz),}X(Y)] (X = Y = CI, I or OC,H,Me-p; X = CI, Y = OMe or OC,H,Me-p) the spectral and electrochemical properties of which are virtually identical to those of [Mo( NO){HB(dmpz),}X(Y)] (Hdmpz = 3.5-dimethylpyrazole), indicating that the addition of a benzyl group has no significant electronic effect in the new species. However, a crystal and molecular structure determination of [Mo(CO),( NO){HB( bdmpz),}] revealed that the molecule has a highly symmetrical structure, the CH, groups of the benzyl groups in the tris(pyrazoly1)borate ligand being disposed in a star-shaped configuration where the phenyl rings adopt an 'inverted' bowl-like structure with the BH group inside and the Mo(CO),(NO) group outside the bowl. The arrangement of the 4-benzyl groups with respect to the pyrazolyl rings and the H-B Mo three-fold axis is strongly reminiscent of an inverted threelegged 'Isle of Man' symbol.Παρουσιάστηκε στο: Journal of the Chemical Society, Dalton Transaction