Treatment of the bis(alkynyl)phosphane Ar-P(C drop CPh)(2) (3) (Ar = 2,4,6-
t-Bu3C6H2) with Cp2V gives the vanadacyclopropene phosphane 5, which was ch
aracterized by X-ray diffraction. The reactivity of 5 toward HCL in THF or
toluene gives 3 or the alkenyl alkynyl phosphane (E/Z isomers) isolated as
its sulfur analogue (PhCH=CH)(PhC equivalent to C)PAr(=S).