Bis(benzene)vanadium V(h6-C6H6)2 is black solid (mp. 227°C), it is paramagnetic (1.68 BM), has d5 electron configuration (i.e valency of vanadium is V(0)), it is 17-electron VE compound. The bond strength of V-CCp is 145 kJ/mol, has moderate the reactivity towards O2 and low reactivity towards H2O.
Bis(benzene)vanadium V(h6-C6H6)2 is synthesized either by direct synthesis of dibenzene vanadium from metallic V and benzene:
V + 2 C6H6 → V(h6-C6H6)2
or by 2-step reaction:
1) reduction of VCl3 by metallic Al in the presence of benzene and AlCl3, producing V(C6H6)+ tetrachloroaluminate salt:
3 VCl3 + 2 Al + AlCl3 + 6 C6H6 → 3 [(C6H6)V]+AlCl4-
2) Reduction of V(C6H6)+ ion by dithionite ion: (Fischer-Hafner synthesis)
2 [(C6H6)V]+ + S2O4 2- + 2 OH- → 2 V(h6-C6H6)2 + 2 HSO3-
Bis(benzene)vanadium V(h6-C6H6)2 (and for comparison bis(toluene)vanadium) was applied as precursor for the deposition of vanadium carbide coatings on steel substrates in at 673–823 K (400°C-550°C) temperatures by MOCVD. The composition of the films grown using V(C6H6)2 was approximately V0.52C0.48 in the whole temperature range (coating grown using V(C6H5CH3)2 had similar composition). The deposited VCx layers were polycrystalline (having cubic structure V8C7). The C content of the films could be decreased and growth rate increased by addition of C6Cl6 to the gas phase. At 673 K (400°C) various stable phases of the V–C binary system were obtained, including a supersaturated bcc-type V(C) solid solution.
Combining V(C6H6)2 with NH3 as co-precursor and H2 as carrier gas, vanadium nitride δ-VN coatings were deposited at 823 K (550°C).[i]
[i] S. Abisset, F. Maury, Surf. Coat. Tech., 1998, Vol. 108–109, p.200-205, « Low-temperature MOCVD of V–C–N coatings using bis(arene)vanadium as precursors », https://doi.org/10.1016/S0257-8972(98)00619-7, https://www.sciencedirect.com/science/article/abs/pii/S0257897298006197
Bis(toluene)vanadium V(h6-C6H5-Me)2 (and
for comparison bis(benzene)vanadium) was tested as precursor for the growth of vanadium carbide layers at 673–823 K (400°C-550°C) temperatures on steel substrates by
MOCVD. The composition of layers grown using V(C6H5CH3)2 (as well as from V(C6H6)2) was approximately V0.52C0.48 in the whole temperature range; addition of C6Cl6 to the gas phase decreased carbon content and increased growth rate. Supersaturated bcc-type
V(C) solid solution and various V–C binary system stable phases were obtained at 673 K (400°C). The deposited VCx layers were polycrystalline (having cubic structure V8C7).[i]
[i] S. Abisset, F. Maury, Surf. Coat. Tech., 1998, Vol. 108–109, p.200-205, « Low-temperature MOCVD of V–C–N coatings using bis(arene)vanadium as precursors », https://doi.org/10.1016/S0257-8972(98)00619-7, https://www.sciencedirect.com/science/article/abs/pii/S0257897298006197