A series of new half-sandwich vanadium complexes have been prepared. The structures of two new anionic vanadium half-sandwich complexes, [CpVCl(3)](-) and [CpV(N)Cl(2)](-) are presented. (15)N isotopic labelling studies have been conducted to unambiguously assign the V[triple bond, length as m-dash]N infra red stretching frequencies of both a neutral and an anionic (cyclopentadienyl)vanadium nitrido complex. The influence of strongly pi-basic coligands on the hapticity of the cyclopentadienyl ligands in half-sandwich complexes of vanadium is discussed.