Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXIV Syntheses, Spectroscopy and Structures of Some 1 : 4 Adducts of Copper(I) and Silver(I) Perchlorates with Triphenylarsine and Triphenylstibine

Abstract

Syntheses and room-temperature single crystal X-ray structure determinations are recorded for adducts [M(EPh₃)₄] (ClO₄), M = Cu, E = As (1), Sb (2); M = Ag, E = As (3), Sb (4), enabling comparison with analogous, previously studied MP₄ and MN₄ environments. The four complexes so characterized all crystallize in the familiar rhombohedral R^-3 array (a ≈ 14·4, c ≈ 52 Å, hexagonal setting) with the metal and chlorine atoms located on crystallographic threefold axes. In these arrays Cu–E (axial, off axis) are 2·493(2), 2·533(1) for (1), and 2·572(1), 2·577(1) Å for (2), the disparity in the two independent M-E distances being diminished relative to those of previously studied phosphorus analogues, perhaps in consequence of increasing E size. In (3) and (4), some cation disorder is evident in respect of the ligand pnictide atom (E); for the major components Ag-E are 2·652(3), 2·680(2) in (3); 2·732(2), 2·7295(8) Å in (4). Problems associated in defining the metal atom environment geometries in the latter are, nevertheless, more satisfactorily overcome in two further determinations of nitrate salts: [Ag(SbPh₃)₄] (NO₃) (5) is of the rhombohedral family with no cation core disorder, Ag–E (axial, off axis) being 2·720(4), 2·725(2) Å, while the structural characterization of a 1 : 4 triphenylarsine adduct of silver nitrate is recorded as its tetraethanol solvate, namely [Ag(AsPh₃)₄] (NO₃).~ 4C₂H₅OH(6), monoclinic, C2/c, a 18·373(4), b 20·786(5), c 21·070(8) Å, β 108·18(3)°, Z = 4 f.u. The silver atom of the [Ag(AsPh₃)₄]⁺cation unusually lies on a crystallographic 2 (rather than a 3 ) axis of the incipiently23 (T) array, with Ag-As 2·649(2), 2·650(2) Å and As-Ag-As ranging from 108·22(4) to 111·41(6)°. The structure determination of a chloroform solvate of (2), denoted (2a), of low precision, is noted, together with the structure of an interesting artefact, isomorphous with the rhombohedral oxoanion array, modelled as [Ag(PPh₃)₄]₂ (SiF₆).py (7). Bands in the far-infrared spectra of [M(AsPh₃)₄] (ClO₄) are assigned to v(MAs) vibrations at 119 (M = Cu) and 103 cm¯¹ (M = Ag); this produces a more consistent picture of the variation in the wavenumbers of the v(ME) modes in [M(EPh₃)₄]⁺ compounds than was available previously.