Structural Investigations of Silver(I) and Copper(I) Complexes with Neutral N4Donor Ligands: X-ray Crystal and Molecular Structure of the Dimer [Ag2{μ-(R,S)-l,2-(py-2-CH=N)2Cy}2](03SCF3)2and 1H, 13C, and INEPT 109Ag and 15N NMR Solution Studies
Van Stein, GC; Van Koten, G; Vrieze, K; Brevard, C; Spek, AL
The reactions of the neutral N4donor system (R,S)-l,2-(6-R-py-2-CH=N)2Cy (R = H or Me, Cy = cyclohexane) with [M(O3SCF3)] (M = Ag(I) or Cu(I)) yielded ionic complexes, consisting of a dinuclear [M2(N4)2]2+dication and O3SCF3−monoanions. An X-ray crystallographic study defined the molecular structure of [Ag2{μ-(R,S)-l,2-(py-2-CH=N)2Cy}2](O3SCF3)2as monoclinic, space group P21/c, a = 10.412 (2) Å, b, = 33.310 (8) Å, c = 13.197 (2) Å, ಲ = 105.38 (2)°, and Z = 4, for 3092 independent reflections. The structure was refined to R = 6.7. The two N4ligands coordinate to the silver(I) centers as dibidentates with alternating short Ag-N(imine) [Ag(l)-N(2), 2.251 (11) Å; Ag(2)-N(6), 2.240 (12) Å] and Ag-N(pyridine) [Ag(l)-N(8), 2.242 (11) Å; Ag(2)-N(4), 2.252 (13) Å] and two longer Ag-N(imine) [Ag(l)-N(7), 2.440 (11) Å; Ag(2)-N(3), 2.430 (11) Å] and Ag-N(pyridine) distances [Ag(l)-N(l), 2.455 (12) Å; Ag(2)-N(5), 2.429 (11) Å], The silver(I) centers have distorted tetrahedral geometries and lie in a distance of 3.254 (2) Å of each other. The structures of these metal IB complexes in solution have been studied by multinuclear 1H, 13C, 15N, and 109Ag NMR spectroscopy. The 1H and 13C NMR (room temperature) results revealed by the presence of two nonequivalent pyridine imine moieties that (i) the structural features found for the [Ag2(N4)2]2+dication in the solid are retained in solution and (ii) the silver(I) and copper(I) complexes have similar structures in solution. The imine proton resonances in the 1H NMR spectra of the silver(I) complexes have been split due to 3J(lH-107109Ag) couplings which enabled the application of INEPT 109Ag NMR. The δ 109Ag appeared to be very sensitive with regard to the ligand environment (e.g., Δδ 109Ag for [Ag2(N4)2]2+with R = H and R = Me is 32 ppm). Natural abundance INEPT 15N NMR spectra of the silver(I) complexes unambiguously established through the 15N chemical shift and the 1J(15N-107109Ag) values that the characteristic sequence of Ag-N distances found in the solid is also present in the solution structures of these dications. 1984, American Chemical Society. All rights reserved.