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

The cage monophosphinites CgPOR {where CgP = 6-phospha-2,4,8-trioxa-adamantane and R = C6H5 (L-a); 2-C6H4CH3 (L-b); 2,4,6-C6H2(CH3)(3) (L-c); 2,4-(C6H3Bu2)-Bu-t (L-d); CH3 (L-e); CH2CF3 (L-f)} and diphosphinites CgPZPCg {where ZH(2) = 2,2'-biphenol (L-g) or 1,2-benzenedimethanol (L-h)} 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 (Bu2AlOAlBu2)-Bu-i-Bu-i), and tentative structure-activity relationships are suggested. The hydrocyanation activities obtained with catalysts derived from monophosphinite L-f (with (Bu2AlOAlBu2)-Bu-i-Bu-i) and diphosphinite L-h (with ZnCl2) are comparable with the commercial catalyst based on P(OTol)(3). The complexes trans-[PtCl2(L)(2)] where L = L-a (1a), L-e (1e), and L-f (1f) and the chelate cis-[PtCl2(L-h)] (1h) are reported. From the nu(CO) values for the complexes trans-[RhCl(CO)(La-f)(2)] (2a-f), it is concluded that ligand L-f is the most phosphite-like of the monophosphinites. Treatment of [Ni(cod)(2)] (cod = 1,5-cyclo-octadiene) with L-h leads to a mixture of products, one of which was characterized as the binuclear [Ni-2(L-h)(2)(mu-cod)] (3h). The crystal structures of L-h, 1a, 1e, 1f, 1h center dot 2CH(2)Cl(2), and 3h center dot 3C(6)H(5)CH(3) are reported.