Tetracarbonyl(trifluoromethyl)cobalt(I) [Co(CO)4(CF3)] as a Precursor to New Cobalt Trifluoromethyl and Difluorocarbene Complexes

An improved synthesis of the known trifluormethyl cobalt compound Co(CO)(4)(CF3) (1), which gives significantly higher yields than previously reported methods, allows for an investigation of its carbonyl substitution chemistry. Treatment of 1 with P-donor ligands of varying denticity under thermal conditions afforded Co[P(O-o-tolyL)(3)](CO)(3)(CF3) (2), Co(DPPE)(Co)(2)(CF3) (3), and Co(P-3)(CO)(CF3) (4) in high isolated yields [DPPE = Ph2PCH2CH2PPh2; P-3 = PhP ( CH2CH2PPh2)(2)]. The new cobalt N-heterocyclic carbene complex Co(SIPr)(CO)(3)(CF3) (5) [SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene)] was obtained by phosphine substitution from Co(PPh3)(CO)(3)(CF3), a known compound efficiently prepared from 1. Additionally, we report the synthesis of two rare cobalt difluorocarbene complexes ([Co] = CF2) produced by fluoride abstraction from 3 or 4. These results are relevant to our efforts to assess the reactivity of first-row metal perfluoroalkyl and fluorocarbene complexes.