Novel cyclic pentacoordinate and pseudo-pentacoordinate lead compounds

The new bicyclic lead(II) phosphinate [(t-Bu)(2)PO2]Pb-2 (1) was synthesized by the reaction of p-tolyllead triacetate with di-t-butylphosphinic acid and water. An X-ray study showed that it had a pseudo-trigonal bipyramidal geometry (p-TBP) with a stereochemically active lone pair of electrons occupying an equatorial site. Infrared data ruled out the possible presence of a Pb-H bond. A series of new monocyclic Pb(IV) compounds, [Et(4)N][(MeC(6)H(3)S(2))PbPh(2)X] where X = Br (2), Cl (3), and F (4), was synthesized from the addition reaction of tetraethylammonium halide to 2,2-diphenyl-1,3,2-toluene dithiolato plumbole(IV), (MeC(6)H(3)S(2))PbPh(2) (5). An X-ray study of 3 revealed a monocyclic anionic TBP geometry which was compared with related dithiolato cyclic structures formed earlier by Lighter elements of Group IVA. The lead(II) compound 1 crystallizes in the monoclinic space group C2/c with a = 15.594(4) Angstrom, b = 16.889(3) Angstrom, c = 12.642(2) Angstrom, beta = 136.85(1)degrees, and Z = 4. The lead(IV) compound 3 crystallizes in the monoclinic space group P2(1)/c with a = 12.245(5) Angstrom, b = 12.049(3) Angstrom, c = 19.048(4) Angstrom, beta = 96.22(2)degrees, and Z = 4. The conventional unweighted residuals are 0.023(1) and 0.0387 (3).