NEW ACCESS TO 1,3-DIPHOSPHOLYL ANIONS - APPLICATION TO THE SYNTHESIS OF THE 1ST PHOSPHORUS ANALOG OF A FERROCENOPHANE

The reaction of acyl chlorides RC(O)Cl with a 2-sila-1,3-diphosphacyclopent-4-ene gives the corresponding 2-R-2-siloxy-1,3-diphosphacyclopent-4-enes via the formal replacement of the silicon by the acyl carbon in the five-membered ring. The substituents at P1, P3, and C2 in the resulting heterocycles are all cleaved by an excess of lithium in THF to afford the 1,3-diphospholyl anions. The dianion obtained from glutaryl dichloride, Cl(O)C(CH2)3C(O)Cl, reacts with a bis(eta(6)-p-xylene)iron(II) salt, ([(p-xylene)2Fe][PF6]2, to give the corresponding 2,2'-trimethylene-1,1',3,3'-tetraphosphaferrocene, {[(PhC)2P2CCH2]2CH2}Fe (9), whose structure has been established by X-ray crystallography. 9 crystallizes in the monoclinic space group P2(1)/c with unit cell parameters a = 18.913 (1) angstrom, b = 11.362 (1) angstrom, c = 29.621 (3) angstrom, beta = 106.49 (1)-degrees, and d(calcd) = 1.396 g cm-3 for Z = 8. Least-squares refinement based on 2441 observed reflections with intensities F(o) greater-than-or-equal-to 3-sigma(F) in the range of 2-degrees less-than-or-equal-to 2-theta less-than-or-equal-to 50-degrees converged at R = 4.5% (R(w) = 5.6%).