Improved Access to {[ω‐(Phosphanyl)alkyl]cyclopentadienyl}cobalt(I) Complexes: Decomplexation of the Phosphane Arm; Alkyne Complexes; Synthesis of Mononuclear Vinylidenecobalt(I) Complexes

Abstract

Abstract An improved synthesis of [(2‐phosphanylethyl)cyclopenta‐dienyl]cobalt(I) chelate complexes is presented, in which the paramagnetic chloride 3 is a precursor of the ethene complex 4 . The latter readily undergoes ligand exchange reactions which in the case of bidendate reagents (1,5‐cyclooctadiene, 1,2‐bis(diisopropylphosphanyl)ethane, 2,2′‐bipyridine, nor‐bornadiene) cause a decomplexation of the phosphane arm at room temperature with formation of 7, 5, 6, 8 . The ethene ligand in 4 can be replaced by alkynes under equally mild reaction conditions (formation of 9, 11 – 16 ). The reaction with ethyne results in the formation of vinylidene complex 10 . The yields of the reactions with nonaromatic alkynes could be improved by treating 3 with the alkyne in the presence of sodium amalgam. The unsubstituted vinylidene complex 10 and its tert ‐butyl derivative 17 were obtained by this route in 38 and 40% yield, respectively.