Starke metallorganische Lewissäuren: Tricarbonyl-π-cyclopentadienylkationen von Molybdän und Wolfram [(π-C5H5 )(OC)3M]+⊕(M = Mo, W)/Strong Organometallic Lewis Acids: Tricarbonyl-π-cyclopentadienyl Cations of Molybdenum and Tungsten [(π-C5H5)(OC)3M]+ (M = Mo, W)

Abstract

Hydride abstraction from the hydrides (π-C₅H₅)(OC)₃MH (M = Mo, W) using Ph₃C⁺X^_ (X = BF₄, PF₆) affords the compounds (π-C₅H₅)(OC)₃MX in high yields. IR data indicate that in these complexes tetrafluoroborate and hexafluorophosphate are coordinated to the metal. The complexes behave as strong Lewis acids; they react with σ- and π-donors L to give [(π-C₅H₅)(OC)₃ML]+X- [L = CO, PPh₃, PCl₃, C₂H₄, CH₃CN, H₂O, (CH₃)₂CO, C₄H₈O(THF)]. The hexafluorophosphate compounds add methylene chloride to give [(π-C₅H₅)(OC)₃M(CH₂Cl₂)]⁺PF₆ ^-. Reaction with diphenylacetylene yields [(π-C₅H₅)(OC)M(PhC ≡CPh)₂]⁺BF₄- (M = Mo, W). The hydride-bridged complexes {[(π-C₅H₅)M(CO)₃]₂H}+X- have been obtained by reaction of (π-C₅H₅)(OC)₃MX with (π-C₅H₅)(OC)₃MH.