PNNL

Abstract

The closo-[1-M(CO)3(h4-E9)]4- (E = Sn, Pb; M = Mo, W) anions have been obtained by extracting the binary alloys, KSn2.05 and KPb2.26, in ethylenediamine (en) in the presence of 2,2,2-crypt or in liquid NH3 followed by reaction with M(CO)3?mes (M = Mo, W) or Cr(CO)3.tol and in en or liquid NH3 solution. Crystallization of the molybdenum and tungsten salts was induced by vapor diffusion of tetrahydrofuran into the en solutions. The salts, [2,2,2-crypt-K]4[1-M(CO)3(h4-Sn9)]?en (M = Mo, W) crystallize in the triclinic system, space group P , Z = 4, a = 16.187(3) ?, b = 25.832(4) ?, c = 29.855(5) ?, a = 111.46(1)o, b = 102.84(2)o, g = 92.87(2)o at -95 oC (M = Mo) and a = 17.018(3) ?, b = 27.057(5) ?, c = 28.298(6) ?, a = 66.42(3)o, b = 76.72(3)o, g = 87.27(3)o at 20 oC (M = W). The salts, (CO)3M(en)2[2,2,2-crypt-K]4[1-M(CO)3(h4-Pb9)]? 2.5en (M = Mo, W) crystallize in the triclinic system, space group P , Z = 2, a = 16.319(3) ?, b = 17.078(3) ?, c = 24.827(5) ?, a = 71.82(3)o, b = 83.01(3)o, g = 81.73(3)o at -133 oC (M = Mo) and a = 16.283(4) ?, b = 17.094(3) ?, c = 24.872(6) ?, a = 71.62(2)o, b = 82.91(2)o, g = 81.35(2)o at -153 oC (M = W). The [1-M(CO)3(h4-Sn9)]4- anions were also characterized in liquid NH3 solution by 119Sn, 117Sn and 95Mo NMR spectroscopy. Unlike their fluxional precursor, nido-Sn94-, NMR studies show that the [1-M(CO)3(h4-Sn9)]4- anions are rigid on the NMR time scale. All possible inter- and intraenvironmental couplings, J(119,117Sn-119,117Sn), and J(119,117Sn-183W) and one J(119,117Sn-95Mo) coupling, have been observed and assigned. Complete spin-spin coupling constant assignments were achieved by detailed analyses and simulations of all spin multiplets that comprise the 119Sn and 117Sn NMR spectra and that arise from natural abundance tin isotopomer distributions and from natural abundance 183W, in the case of [1-W(CO)3(h4-Sn9)]4-.