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.
Analytical Investigation on the Effect of Test Setup on Bond Strength