Vanadium cyclopentadienyl tetracarbonyl VCp(CO)4 is orange solid, having meting point 138-139°C (under N2). Microanalyis: Calc. for C5H5V(CO)4,: C, 47.4; H, 2.2; V, 22.3. Found: C, 47.4; H, 2.1; V, 22.1.
Characterization: Qualitative IR analysis (CS2 solution of VCp(CO)4): CO groups present (two strong maxima at 1890 and 1982 cm-1, similar to the spectra of corresponding Ta and Nb compounds).
Synthesis: NaCp (1.5 parts, dimethoxyethane (DME) solution) was mixed with HgCl (5.0 parts, DME solution), then 7.0 parts of NaV(CO)6 (DME solution) were slowly added (2 hours) to the reaction mixture (N2, 25°C). Reaction mixture was filtered under N2, solvent evaporated and solids extracted with H2O, then mixture filtered under N2, the precipitate washed with H2O, extracted with Et2O, solution filtered under N2, ether removed by distillation). The solid crude VCp(CO)4 was sublimed, washed with Et2O and dried (yield 78%).
VCp(CO)4 can be also synthesized in good yield by using analogous strontium etherate salt of vanadium hexacarbonyl (Sr[V(CO)4]2), or using calcium cyclopentadienide
CaCp2 instead of NaCp. [i]
[i] R.P.M. Werner, Switlana Manastyrskyj, US Patent, US3144472A, « Preparation of cyclopentadienyl vanadium tetracarbonyl compounds », https://patents.google.com/patent/US3144472A/en
Cyclopentadienyl vanadium tetracarbonyl VCp(CO)4 was applied as precursor for the vapor phase plating of a Steel with vanadium metal layer by thermal MOCVD method, at pressure <0.2 Torr; the reservoir with VCp(CO)4 was sufficiently heated to volatilize the precursor and provide a steady continuous precursor flow. The growth temperature was ~200-300°C.