PH-Functional Phosphines with 1,1′-Biphenyl-2,2′-bis(methylene) and 1,1′-Binaphthyl-2,2′-bis(methylene) Backbones

The first PH-functional phosphines (1, 3, and 5) containing the 1,1′-binaphthyl-2,2′-bis(methylene) or 1,1′-biphenyl-2,2′-bis(methylene) backbone have been obtained by two-phase phosphination of 2,2′-bis(halomethyl)-1,1′-binaphthyls with PH₃ or in a protected-group synthesis using P(SiMe₃)₃ as the starting material. The 4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′-e]phosphepine (1) is configurationally stable, as indicated by the inequivalence of the two CH₂ and naphthyl substituents in the ¹³C{¹H} NMR spectra. The X-ray crystal structure of 1·0.5C₆H₅CH₃ shows an intracyclic C - P - C angle of 99.5(2)°, the interplanar angle of the phosphepine ring system being 67.6(5)°. The borane adduct 7 of the secondary phosphine 1 has been employed for the syntheses of atropisomeric mono-and bidentate ligands (8-14) with the bulky 1,1′-binaphthyl moieties. Results of force field calculations on the conformations of 1, 3, and 14 are presented. The ability of these phosphines to form mononuclear and polynuclear complexes with transition-metal centers is discussed. Compound 14 exhibits a large variety of low-energy conformations, and some of them seem to be capable of forming mononuclear transition-metal complexes.