Molybdenum and tungsten nitrosyl complexes containing bulky alkoxy, aryloxy, and arylamido ligands: their electrochemical behaviour and the structure of [Mo{HB(Me2pz)3}(NO)I(OCH2CH2CH2Br)]

Abstract

The complexes [Mo{HB(Me₂pz)₃}(NO)X(NHR′)](X = I, R′=o-C₆H₄Me, 2,5-Me₂C₆H₃, CHPh₂, p-C₆H₄CN, p-C₆H₄N₂Ph, p-C₆H₄N₂C₆H₄NO₂-p; XCl, R′=p-C₆H₄I), [W{HB(Me₂pz)₃}(NO)Cl(NHR′)](R′= CHPh₂ or p-C₆H₄I), [Mo{HB(Me₂pz)₃}(NO)I(OR)](R = CH₂CH₂CH₂Br, p-CH₂C₆H₄Br, or p-C₆H₄CN), and [W{HB(Me₂pz)₃}(NO)Cl(OR)](R = Ph, CH₂CH₂CH₂Br, or p-CH₂C₆H₄-Br)(Me₂pz = 3,5- dimethylpyrazolyl) have been prepared and characterised spectroscopically. Electrochemical studies (cyclic voltammetry, coulometry) of these complexes in acetonitrile established that all underwent at least one one-electron reduction process, some of which were reversible. The E_1/2 values for the reduction were dependent on the nature of the metal, the halide, and the NHR′ or OR group. The structure of [Mo{HB(Me₂pz)₃}(NO)I(OCH₂CH₂CH₂Br)] was determined crystallographically. The six-co-ordinate nature of the complex was confirmed and the Mo–O bond distance was 1.89 Å, comparable to that in other related compounds.