Chemistry of the Ag-2(dmb)(2)(2+) template (dmb=1,8-diisocyano-p-menthane). Preparation, characterization, and x-ray structures of the Ag-2(dmb)(2)Y-2 dimers (Y = NO3-, ClO4-, CH3CO2-) and the paramagnetic [Ag-4(dmb)(4)(TCNQ)(3)]TCNQ complex (TCNQ=7,

摘要

Direct reactions of the AgY salts with dmb (1,8-diisocyano-p-menthane) in a 1:1 stoichiometric amount generate the binuclear Ag-2(dmb)(2)Y-2 complexes. The X-ray crystallography establishes that the structure consists of two Ag+ atoms bridged by two dmb ligands forming a 20-membered ring and by two counteranions via one of the O-atoms, forming a four-membered ring (local symmetry D-2h) The Ag-I... Ag-I separations are 3.909(1) and 3.6831(8) Angstrom for Y = NO3- and CH3CO2-, respectively. Reactions of Ag-2(dmb)(2)Y-2 (Y = NO3-, ClO4-) with LiTCNQ lead to the paramagnetic tetranuclear species [Ag-4(dmb)(4)(TCNQ)(3)]TCNQ. The structure at 180 K consists of two Ag-2(dmb)(2)(2+) species (d(Ag ... Ag) = 4.113(1) Angstrom held together by three parallel TCNQ(-')s, with Ag+... N=C distances ranging from 2.359(5) to 2.787(5) Angstrom. Two of the Ag+ atoms are tricoordinated, and the other two are tetracoordinated placed within in a centrosymmetric geometry. The three bridging TCNQ-'s exhibit interplanar distances of 3.333(1) Angstrom, and the Ag-4 species are packed side-by-side with two adjacent TCNQ-'s face-to-face (separation 3.372(1) Angstrom) forming an infinite pi-stacked chain TCNQ(-')s. The TCNQ(-) counteranion also exhibits weak pi-contacts via the -CN groups with other counteranions. The magnetic susceptibilities, EPR spectra, and unit cell parameters have been measured as a function of temperature. The magnetic data are best explained by extended chains of anti Ferromagnetically coupled S = 3/2 and S = 1/2 centers for the [Ag-4(dmb)(4)-(TCNQ)(3)](+) and TCNQ(-) moieties, respectively. No hyperfine structure has been observed between 106 and 290 K, indicating the presence of rapid exchange in the paramagnetic system. Crystal data: Ag-2(dmb)(2)(NO3)(2), crystal system, orthorhombic, space group = C-cmb, a = 8.6464(15) Angstrom, b = 16.375(3) Angstrom, c = 20.663(5) Angstrom, Z = 4; Ag-2(dmb)(2)(O2CCH3)(2). 2H(2)O, crystal system triclinic, space group P (1) over bar, a = 9.1175(9) Angstrom, b = 9.1451(10) Angstrom, c = 11.7247(8) Angstrom, alpha = 80.294(7)degrees, beta = 71.124(7)degrees, gamma = 64.258(8)degrees, Z = 1; [Ag-4(dmb)(4)(TCNQ)(3)]TCNQ, crystal system triclinic, space group = P (1) over bar, a = 9.9837(12) Angstrom, b = 13.5194(14) Angstrom, c = 17.1788(9) Angstrom, alpha = 99.423(6)degrees, beta = 101.512(8)degrees, gamma = 96.917(11)degrees, Z = 1. [References: 43]