Preparation of ortho-substituted aryldifluorophosphines, 2-XC6H4PF2 (X = MeO or Me2N), and some of their derivatives. X-ray crystal structure determination of (2-MeOC6H4P)4 and of the platinum complex,Cl2Pt(2-MeOC6H4PF2)2

The preparation of the ortho-substituted aryldifluorophosphines 2-MeOC₆H₄PF₂ and 2-Me₂NC₆H₄PF₂ by chlorine-fluorine exchange from the corresponding dichlorophosphines using sodium fluoride in acetonitrile in the presence of a crown ether is described. The ortho-substituted aryldichlorophosphines 2-MeOC₆H₄PCl₂ and 2-Me₂NC₆H₄PCl₂ were prepared from the respective bis(N,N-dimethylamino) phosphines by cleavage of the PN bonds with hydrogen chloride. The reaction of 4-fluoroanisole and 2-methoxy-phenyllithium with phosphorus trichloride did not yield the expected chlorophosphines, i.e. 2-MeO-5-F-C₆H₃PCl₂ and 2-MeOC₆H₄PCl₂, but led to formation of 4-fluorophenyldichlorophosphite in the former, and to tris(2-methoxyphenyl)phosphine in the latter case. The difluorophosphine 2-MeOC₆H₄PF₂ was found to undergo a spontaneous oxidation-reduction reaction with formation of the tetrafluorophosphorane 2-MeOC₆H₄PF₄, and the cyclotetraphosphine (2-MeOC₆H₄P)₄. A single-crystal X-ray structure determination of the latter indicated the presence of a strongly puckered four-membered ring with PP bond lengths ranging between 222 and 223 pm, and endocyclic bond angles of 84°. Vicinal MeOC₆H₄ groups were found arranged trans to each other. Dichloroplatinum(II) complexes were prepared, involving the two new fluorophosphines, 2-XC₆H₄PF₂ (X = MeO or Me₂N), as ligands. In neither case was any evidence found for coordination between platinum and oxygen or nitrogen, and the fluorophosphines were found to function solely as phosphorus donors. The absence of interaction between platinum and the oxygen atom in the ortho position of the ligand 2-MeOC₆H₄PF₂ was confirmed in a single-crystal X-ray determination of the complex Cl₂(2-MeOC₆H₄PF₂)₂Pt. The compound was found to exist as a planar, cis-coordinated species with PtCl bond lengths between 232 and 234 pm, and a PtP bond length of 218 pm. All compounds were characterized by NMR spectroscopy (¹H, ³¹P and ¹⁹F, where applicable).