Estimating Effective Steric and Electronic Impacts of a Ferrocenyl Group in Organophosphines

A series of monodentate
ferrocenylphosphines, Fc3P (1a), Fc2PhP (1b), and Fc2ArP (1c; Fc
= ferrocenyl, Ar = 3,4-methylenedioxyphenyl),
were prepared, and their electronic and steric properties were quantitatively
determined. By the IR measurements of their respective Ni­(CO)3(phosphine) complexes, the electronic properties of the ferrocenyl
group in organophosphines were estimated to be similar to those of
primary alkyl groups. The ferrocenyl group is a better electron donor
than a methyl group and a poorer donor than an ethyl group. The gold­(I)
chloride complexes of 1a–c were prepared and their
X-ray crystal structures were determined. The %Vbur parameters for 1a–c were calculated
using the X-ray structural data, and their ″Tolman cone angles″
were estimated. The steric influence of the ferrocenyl group in organophosphines
was clarified to be larger than those of cyclohexyl, tert-butyl, and o-tolyl groups and is comparable to
that of a mesityl group.