Vanadium (beta-(dimethylamino)ethyl)cyclopentadienyl complexes with diphenylacetylene ligands

Reduction of the V(III) (beta-(dimethylamino)ethyl)cyclopentadienyl dichloride complex [eta(5):eta(1-) C5H4(CH2)(2)NMe2]VCl2(PMe3) (1) with 1 equiv of Na/Hg yielded the V(II) dimer {[eta(5):eta(1)-C5H4(CH2)(2)NMe2]V(mu-Cl)}(2) (2). This compound reacted with diphenylacetylene in THF to give the V(II) alkyne adduct [eta(5):eta(1)-C5H4(CH2)(2)NMe2]VCl(eta 2-PhC CPh) (3). Further reduction of 2 with Mg in the presence of diphenylacetylene resulted in oxidative coupling of two diphenylacetylene groups to yield the diamagnetic, formally V(V), bent metallacyclopentatriene complex [eta(5):eta(1)-C5H4(CH2)(2)NMe2]V(C4Ph4) (4).