1,3-Cyclopentadiene vanadium complex

C,Hk, 1,3-Cyclopentadiene, 1-methyl-, preparation and purification of, 27 52 titanium complex, 27 52 vanadium complex, 27 54, 55 QH,Oj, Ascorbic acid, platinum complex, 27 283... 

The low-valency cyclopentadienyl vanadium complexes are usually stabilized by carbon monoxide, and VCp(CO)4 is the most useful precursor to various low-valency organovanadium complexes. There are a number of synthetic routes to VCp(CO)4. One convenient method is to carry out the reaction between NaCp and VCl3 in THF in situ and then to carbonylate under 60 atm CO pressure at 120 °C [19]. Reduction of preformed vanadocene by potassium, and subsequent carbonylation also gives rise to VCp(CO)4 [20]. These methods, however, cannot be applied to alkyl-substituted cyclopentadienyl derivatives. It is necessary to treat alkyl-substituted cyclopentadiene... 

Congeneric Nb species are known [4]. A (trimpsi)V(NO)(CO)2 complex (trimpsi = BuSi(CH2PMe2)3) has been reported [5] which undergoes a reversible oxidation to the cationic V(0) complex at —0.74 V versus Cp2Fe/CH2Cl2 and a second, irreversible oxidation at 0.61 V. More highly reduced complexes of vanadium have been prepared, but their electrochemistry has evidently not been explored. The electrochemical synthesis of CpV(CO)4 from a vanadium anode, cyclopentadiene, and 115 bar of CO at 100 °C in DMF has been reported [6]. 

CpV(CO)4, which is a typical half-sandwich complex, is prepared by reduction of vanadocene with sodium or potassium under carbon monoxide. Another route to CpV(CO)4 involves the direct reaction of hexacarbonylvanadium(O) with cyclopentadiene. The Cp ring is disordered between staggered and eclipsed conformations. The distance between the centroid and vanadium is 1.9-2.0 A. 

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