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

Abstract

The synthesis of a series of (fluoroalkyl)phosphine complexes of nickel is reported. Treatment of (cod) 2Ni with dfepe (dfepe=(C 2F 5) 2PCH 2CH 2P(C 2F 5) 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 ( i Bu) 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)(η 1-dfepe)Ni(MeCN) ( 5). In contrast to (R 3P) 4Ni(0) phosphine and phosphite complexes, which undergo protonation by strong anhydrous acids such as HCl, H 2SO 4 and CF 3CO 2H to give (R 3P) 4Ni(H) + products, Treatment of (dfepe) 2Ni with neat CF 3CO 2H 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.