Coupling of Alkynes on a Pd−Pd Bond to Generate an Electrophilicμ-Butenediylidene Moiety

Abstract
The first dipalladium μ -PPh3 complex (1) was obtained by the facile loss of two CH3CN ligands from [Pd2(PPh3)2(CH3CN)4](PF6)2 in CH2Cl2. Coupling of p-tolylacetylene (p-TolC≡CH) with 1 or its precusor afforded the μ-butenediylidene complex 2, treatment of which with CH3CN resulted in PPh3 migration to give 3.