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(OC 6 H 3 F 2 -2,6) 2 II, and the phosphinites PPh 2 (OPh) III and PPh 2 (OC 6 H 3 F 2 -2,6) IV reacted with [{RhCl(µ-Cl)(η 5 -C 5 Me 5 ) } 2 ] to yield the complexes [RhCl 2 L(η 5 -C 5 Me 5 )] [L = PPh(OPh) 2 1, PPh(OC 6 H 3 F 2 -2,6) 2 2, PPh 2 (OPh) 3 or PPh 2 (OC 6 H 3 F 2 -2,6) 4]. The perprotio-phosphonite and -phosphinite, I and III, reacted with [{PtCl(µ-Cl)(PEt 3 )} 2 ] to yield exclusively the cis isomers of [PtCl 2 (PEt 3 ){PPh(OPh) 2 }] 5 and [PtCl 2 (PEt 3 ){PPh 2 (OPh)}] 7. The fluorine-containing phosphonite and phosphinite, II and IV, reacted with [{PtCl(µ-Cl)(PEt 3 )} 2 ] to give the trans isomers of [PtCl 2 (PEt 3 ){PPh(OC 6 H 3 F 2 -2,6) 2 }] 6a and [PtCl 2 (PEt 3 ){PPh 2 (OC 6 H 3 F 2 -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.