Vanadium (β-(Dimethylamino)ethyl)cyclopentadienyl Complexes with Diphenylacetylene Ligands

Reduction of the V(III) (β-(dimethylamino)ethyl)cyclopentadienyl dichloride complex [η⁵:η¹-C₅H₄(CH₂)₂NMe₂]VCl₂(PMe₃) (1) with 1 equiv of Na/Hg yielded the V(II) dimer {[η⁵:η¹-C₅H₄(CH₂)₂NMe₂]V(μ-Cl)}₂ (2). This compound reacted with diphenylacetylene in THF to give the V(II) alkyne adduct [η⁵:η¹-C₅H₄(CH₂)₂NMe₂]VCl(η²-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 [η⁵:η¹-C₅H₄(CH₂)₂NMe₂]V(C₄Ph₄) (4).