(Fluoroalkyl)phosphine complexes of nickel(0) and cobalt(I)

The synthesis of a series of (fluoroalkyl)phosphine complexes of nickel is reported. Treatment of (cod)2Ni with dfepe (dfepe=(C2F5)2PCH2CH2P(C2F5)2) yields (dfepe)Ni(cod) (1), which has been structurally characterized. Treatment of 1 with CO or bipy results in the formation of (dfepe)Ni(CO)2 (2) and (dfepe)Ni(bipy) (3), respectively. Addition of excess dfepe to 1 results in incomplete cod displacement to form (dfepe)2Ni (4). The homoleptic complex 4 may be independently prepared in high yield by reduction of (acac)2Ni with (iBu)3Al in the presence of butadiene and excess dfepe. Solvation of (dfepe)Ni(cod) in acetonitrile gives a new complex tentatively identified as (dfepe)Ni(MeCN)2 (6), whereas dissolution of (dfepe)2Ni in acetonitrile leads to a mixture of 6 and the partial displacement product (dfepe)(η1-dfepe)Ni(MeCN) (5). In contrast to (R3P)4Ni(0) phosphine and phosphite complexes, which undergo protonation by strong anhydrous acids such as HCl, H2SO4 and CF3CO2H to give (R3P)4Ni(H)+ products, Treatment of (dfepe)2Ni with neat CF3CO2H or excess HOTf in dichloromethane gave no spectroscopic evidence for (dfepe)2Ni(H)+. Exposure for extended periods leads to dfepe loss and decomposition to Ni(II) products. The synthesis of the first cobalt complex of dfepe, (dfepe)Co(CO)2H, is also reported.