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

Abstract

The phosphonites PPh(OPh)₂I and PPh(OC₆H₃F₂-2,6)₂II, and the phosphinites PPh₂(OPh) III and PPh₂(OC₆H₃F₂-2,6) IV reacted with [{RhCl(µ-Cl)(η⁵-C₅Me₅) }₂] to yield the complexes [RhCl₂L(η⁵-C₅Me₅)] [L = PPh(OPh)₂1, PPh(OC₆H₃F₂-2,6)₂2, PPh₂(OPh) 3 or PPh₂(OC₆H₃F₂-2,6) 4]. The perprotio-phosphonite and -phosphinite, I and III, reacted with [{PtCl(µ-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(µ-Cl)(PEt₃)}₂] to give the trans isomers of [PtCl₂(PEt₃){PPh(OC₆H₃ F₂-2,6)₂}] 6a and [PtCl₂(PEt₃){PPh₂(OC₆ H₃F₂-2,6)}] 8a, which isomerize slowly in acetone solution to yield the cis isomers 6b and 8b. Values of ¹J(RhP) and ¹J(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.

References

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