Structural and electronic impact of fluorine in the ortho positions of the phenoxy groups of phenyl-phosphonite and -phosphinite ligands in compounds of platinum-group metals

The phosphonites PPh(OPh)(2) I and PPh(OC6H3F2-2,6)(2) II, and the phosphinites PPh2(OPh) III and PPh2(OC6H3F2-2,6) IV reacted with [{RhCl(mu-Cl)(eta(5)-C5Me5)}(2)] to yield the complexes [RhCl2L(eta(5)-C5Me5)] [L = PPh(OPh)(2) 1, PPh(OC6H3F2-2,6)(2) 2, PPh2(OPh) 3 or PPh2(OC6H3F2-2,6) 4]. The perprotio-phosphonite and -phosphinite, I and III, reacted with [{PtCl(mu-Cl)(PEt3)}(2)] to yield exclusively the cis isomers of [PtCl2(PEt3){PPh(OPh)(2)}] 5 and [PtCl2(PEt3){PPh2(OPh)}] 7. The fluorine-containing phosphonite and phosphinite, II and IV, reacted with [{PtCl(mu-Cl)(PEt3)}(2)] to give the trans isomers of [PtCl2(PEt3){PPh(OC6H3F2-2,6)(2)}] 6a and [PtCl2(PEt3){PPh2(OC6H3F2-2,6)}] 8a, which isomerize slowly in acetone solution to yield the cis isomers 6b and 8b. Values of (1)J(RhP) and (1)J(PtP) strongly suggest that the presence of fluorine atoms in the ortho positions of the phenoxy groups has a negligible effect on the electronic properties of the phosphorus atoms of these ligands. X-Ray single-crystal structural studies on 1, 4, 6a, 6b, 7, 8a and 8b revealed that the fluorine atoms do, however, exert a profound steric influence.