LEAD(II)/PLATINUM(II) COMPLEXES WITH AND WITHOUT PB-PT INTERACTIONS

The possibility of obtaining complexes with Pb-Pt bonding that would be analogous to the Tl-Pt bonding in pseudooctahedral Tl2Pt(CN)2 and [Tl(crown-P2)Pt(CN)2]+ (crown-P2 is Ph2PCH2N(C2H4OC2H4OC2H4)2NCH2-PPh2) is examined. Treatment of K2[Pt(CN)4] with Pb(NO3)2 in water produces pale yellow K2Pb[Pt(CN)4]2.6H2O, which crystallizes in the monoclinic space group P2(1) with a = 6.487(1) angstrom, b = 17.928(3) angstrom, c = 9.316(2) angstrom, and beta = 107.76(1)-degrees at 125 K with Z = 2. Refinement of 2371 reflections with I > 2sigma(I) and 134 parameters yielded R = 0.033, R(w) = 0.038. The structure consists of zigzag columns of planar [Pt(CN)4]2- units (Pt-Pt distances 3.267(1), 3.298(1) angstrom) with the lead and potassium ions and water molecules in channels between the columns of tetracyanoplatinates. No direct Pt-Pb interactions are present. Treatment of crown-P2 with trans-Pt(CN)2(PPh3)2 and Pb(O2CCH3)2 yields colorless [(CH3CO2)Pb(crown-P2)Pt(CN)2](O2CCH3).1.5H2O.CH3OH.0.25CHCl3, which crystallizes in the monoclinic space group P2(1)/n with a = 13.483(4) angstrom, b = 24.125(10) angstrom, c = 16.212(4) angstrom, and beta = 90.06(2)-degrees at 130 K with Z = 4. Refinement of 5636 reflections with F > 6.0 sigma(F) and 355 parameters yielded R = 0.074, R(w) = 0,098. The structure consists of a planar P2Pt(CN)2 portion with a lead ion contained within the azacrown portion and positioned directly above the platinum center. One acetate ion is chelated to the lead, while the other is a noncoordinating counterion. The Pt-Pb distance is long (3.313(2) angstrom). Nevertheless, the observation of a small Pt-Pb coupling (J = 274 Hz) in the Pt-195 NMR spectrum indicates that a detectable Pt-Pb interaction is present within this binuclear complex.