The Lewis basicity of transition metals. Reactions of the group vib triphenylphosphonium (tricarbonylmetal)cyclopentadienylides with trifluoroacetic acid and boron trifluoride

Coordination complexes of aryl- and alkylphosphonium cyclopentadienylides (cyclopentadienylidene ylides), C5R4PR′R′′R′′′ (R=H, alkyl, aryl; R′, R′′, R′′′=alkyl, aryl)

“…Further evidence for the presence of a direct W-H bond was provided by the observation of 183 W-1 H spin-spin coupling. IR spectroscopy also showed the expected increase in CO stretching frequencies from those of the neutral precursors, but the (M-H) were not observed [10].…”

“…Successful attempts to prepare the group 6 compounds were carried out and the molybdenum compound was obtained analytically pure [9]. The compounds were characterized by 1 H NMR and IR spectroscopy and 5 -structures were suggested although the structures and Table 2 Representative bond length data (Å) chemistry of these compounds were in fact only explored many years later [10][11][12].…”

“…Kotz and Pedrotty first reported the first detailed synthetic procedures for the group 6 tricarbonyl compounds [10], excesses of the metal hexacarbonyls, Cr(CO) 6 and Mo(CO) 6 , being refluxed in diglyme with C 5 H 4 PPh 3 to provide the tricarbonyl compounds ( 5 -C 5 Ph 4 PPh 3 )M(CO) 3 (M = Cr, Mo) in good yields [10]. For tungsten, the tris-acetonitrile tricarbonyl precursor, W(CO) 3 (CH 3 CN) 3 , was heated to 110 • C in diglyme with C 5 H 4 PPh 3 to generate the tungsten compound since little or no product was isolated when W(CO) 6 was used.…”

“…16) [10] for which 1 H NMR spectroscopy revealed high field resonances (δ −5 to −8) characteristic of metal hydrides. Further evidence for the presence of a direct W-H bond was provided by the observation of 183 W-1 H spin-spin coupling.…”

“…17). It was determined that the coordination of BF 3 was reversible (tensimetric titrations) as no change in vapour pressure occurred when more than one equivalent of BF 3 had been added [10]. In addition, removal of the volatile materials from the reaction mixture always resulted in recovery of the starting materials (IR).…”