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 = NO(3)(-), ClO(4)(-), CH(3)CO(2)(-)) and the Paramagnetic [Ag(4)(dmb)(4)(TCNQ)(3)]TCNQ Complex (TCNQ = 7,7,8,8-Tetracyanoquinodimethane).
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(2)(h)()). The Ag(I).Ag(I) separations are 3.909(1) and 3.6831(8) Å for Y = NO(3)(-) and CH(3)CO(2)(-), respectively. Reactions of Ag(2)(dmb)(2)Y(2) (Y = NO(3)(-), ClO(4)(-)) 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) Å held together by three parallel TCNQ(-)'s, with Ag(+).N&tbd1;C distances ranging from 2.359(5) to 2.787(5) Å. 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) Å, and the Ag(4) species are packed side-by-side with two adjacent TCNQ(-)'s face-to-face (separation = 3.372(1) Å) 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 antiferromagnetically 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)(NO(3))(2), crystal system, orthorhombic, space group = C(cmb), a = 8.6464(15) Å, b = 16.375(3) Å, c = 20.663(5) Å, Z = 4; Ag(2)(dmb)(2)(O(2)CCH(3))(2).2H(2)O, crystal system triclinic, space group P&onemacr;, a = 9.1175(9) Å, b = 9.1451(10) Å, c = 11.7247(8) Å, 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&onemacr;, a = 9.9837(12) Å, b = 13.5194(14) Å, c = 17.1788(9) Å, alpha = 99.423(6) degrees, beta = 101.512(8) degrees, gamma = 96.917(11) degrees, Z = 1.
Fortin
Daniel
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Département de Chimie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1, and Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.
Drouin
Marc
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Harvey
Pierre D.
PD
Herring
F. Geoffrey
FG
Summers
David A.
DA
Thompson
Robert C.
RC