Cage Phosphinites: Ligands for Efficient Nickel-Catalyzed Hydrocyanation of 3-Pentenenitrile

Abstract

The cage monophosphinites CgPOR {where CgP = 6-phospha-2,4,8-trioxa-adamantane and R = C6H5 (La); 2-C6H4CH3 (Lb); 2,4,6-C6H2(CH3)3 (Lc); 2,4-C6H3tBu2 (Ld); CH3 (Le); CH2CF3 (Lf)} and diphosphinites CgPZPCg {where ZH2 = 2,2′-biphenol (Lg) or 1,2-benzenedimethanol (Lh)} have been made from CgPBr and the corresponding alcohol or phenol. The cage phosphinites are remarkably stable to water. All the ligands La−h have been tested for nickel(0)-catalyzed hydrocyanation of 3-pentenenitrile in the presence of Lewis acids (ZnCl2, Ph2BOBPh2, or iBu2AlOAliBu2), and tentative structure−activity relationships are suggested. The hydrocyanation activities obtained with catalysts derived from monophosphinite Lf (with iBu2AlOAliBu2) and diphosphinite Lh (with ZnCl2) are comparable with the commercial catalyst based on P(OTol)3. The complexes trans-[PtCl2(L)2] where L = La (1a), Le (1e), and Lf (1f) and the chelate cis-[PtCl2(Lh)] (1h) are reported. From the νCO values for the complexes trans-[RhCl(CO)(La−f)2] (2a−f), it is concluded that ligand Lf is the most phosphite-like of the monophosphinites. Treatment of [Ni(cod)2] (cod = 1,5-cyclo-octadiene) with Lh leads to a mixture of products, one of which was characterized as the binuclear [Ni2(Lh)2(μ-cod)] (3h). The crystal structures of Lh, 1a, 1e, 1f, 1h·2CH2Cl2, and 3h·3C6H5CH3 are reported.