LEWIS-BASE ADDUCTS OF GROUP-11 METAL(I) COMPOUNDS .73. SYNTHESIS, SPECTROSCOPY AND STRUCTURAL SYSTEMATICS OF NEW 1 1-CUBANE TETRAMERS OF COPPER(I) AND SILVER(I) HALIDES WITH TRIPHENYLARSINE/

Syntheses and room-temperature single-crystal X-ray structural charact erization of a number of 1:1 'cube tetramer' adducts of copper(I) and silver(I) halides, MX, with triphenylarsine, AsPh3, are recorded, bein g [XM(AsPh3)](4). The CuBr adduct, obtained unsolvated from toluene, o rthorhombic Pbcn, a 17.844(5), b 20.778(8), c 18.430(4) Angstrom, Z = 4 tetramers, conventional R on \F\ 0.058 for N-0 1309 independent 'obs erved' reflections (I > 3 sigma(I)), is isomorphous with previously re corded [ClAg(PPh3)](4), the tetramer having crystallographically impos ed 2 symmetry. The CuI adduct, previously recorded as a monobenzene so lvate, has been isolated unsolvated from toluene, monoclinic, P 2(1)/n , a 19.70(5), b 27.110(7), c 13.59(2) Angstrom, beta 98.84(9)degrees, Z = 4 tetramers, R 0.087 for N-0 4359, isomorphous with previously rec orded [ICu(PPh3)](4), as a 61/2 benzene solvate, triclinic, <P(1)over bar> a 26.688(2), b 15.180(7), c 13.090(1) Angstrom, alpha 85.41(2), b eta 87.580(7), gamma 77.63(2)degrees, Z = 2 tetramers, R 0.049 for N-0 11485, and as a chloroform disolvate, triclinic, <P(1)over bar> a 22. 584(9), b 13.979(2), c 13.892(2) Angstrom, a 68.99(2)) beta 77.31(3), gamma 75.65(3)degrees, Z = 2, R 0.041 for N-0 8701. An unsolvated AgI complex, monoclinic, P 2(1)/c, a 25.26(1), b 12.506(5), c 25.228(9) An gstrom, beta 113.54(4)degrees, Z = 4 tetramers, R 0.054 for N-0 5520, isomorphous with previously recorded [IAg(PPh3)](4) (denoted 'alpha'), was obtained from methanol/saturated potassium iodide solution, while a second 'beta'-form obtained from 2,4,6-trimethylpyridine, rhombohed ral R3c, a 17.048(1) Angstrom, alpha 61.15(5)degrees Z = 2 tetramers, R 0.037 for N-0 1622, is isomorphous with previously recorded [BrAg(PP h3)](4), for which a redetermination is described (R 0.039 for N-0 128 9); the latter has also been obtained in the common orthorhombic Pbcn array: a 18.10(1), b 21.08(1), c 18.39 (1) Angstrom, Z = 4, R 0.041 fo r N-0 2877. A new 'step' form of [1Ag(PPh3)](4), monoclinic, C 2/c, a 26.14(2), b 16.340(9), c 18.64(2) Angstrom, beta 114.04(8)degrees, R 0 .058 for N-0 2107, obtained from acetonitrile and isomorphous with [Br Cu(PPh3)](4) (step), is also recorded. In the far-infrared spectra of [(Ph3As)(4)Cu4X4] bands which have been assigned to vibrations of the Cu4X4 core are: 166, 150, 135, 114 (X = Br); 136, 85 cm(-1) (X = I; 2C HCl(3) solvate). The 166, 150, 135 cm(-1) bands in the bromide are onl y partially resolved. These, and the 136 cm(-1) band in the iodide are assigned to the T-2 v(CuX) mode of the Cu4X4 core; the bands at 114 a nd 85 cm(-1) are assigned to the next highest frequency Ta mode of the cluster. The splitting of the highest frequency Ta band for the bromi de is consistent with the greater degree of distortion of the Cu4X4 co re from ideal T-d symmetry in this complex relative to the iodide.