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there are two complex molecules in the crystallographic
asymmetric unit, a phenomenon which appears to be a con-
sequence of the conformational variability possible partic-
ularly in the aryl substituents on the phosphine ligand. This
factor may be controlled to some extent by energetics, e.g.
method of synthesis together with the conditions and sol-
vents employed both in the synthesis and in recrystalliza-
tion, e.g. [AuP(otol)3Cl] gives a monoclinic modification
(the a-polymorph) from ethanol [5] while the orthorhombic
b-polymorph [6] is obtained from dimethylformamide, and
a similar dimorphism is observed with the isomeric [AuP(p-
tol)3Cl] set [6,7].
It has also been noted that the methoxy oxygen atoms in
tris(2,4,6-trimethoxylphenyl)phosphine [P(tmp)3] affect
both the basicity of the ligand and the gold environment
in the [AuP(tmp)3X] complexes [3,12]. Previously, it was
also observed that the presence of ortho-methyl substitu-
ents in the [P(otol)3] complexes gave Auꢀ ꢀ ꢀH(methyl) inter-
actions, resulting in regularity in the disposition of the
phosphine phenyl rings [6]. We therefore were interested
in determining the effect of a single methoxy substituent
on both the intramolecular interactions (2-methoxy-
Oꢀ ꢀ ꢀAu) as well as upon intermolecular associations and
crystal packing. With the unsymmetrically substituted
0.255 g; Br, 0.300 g; I, 0.346 g) and the appropriate phos-
phine (0.50 mmol, 0.152 g) dissolved in 5 mL of dimethyl-
formamide at ca. 50 ꢀC. The resultant solutions were
cooled to room temperature and allowed to stand for sev-
eral days to yield well-formed colourless crystals of the
expected complexes. Yields were 96%, 93%, 96%, 95%
and 88% for 1–5, respectively. Melting points and m(Au–
X) stretching frequencies obtained from FT raman data
for 1–5 are listed in Table 1. No chemical analyses were
completed.
Just as for the analogous Au(I) complex series with the
isomeric ortho- and para-tolylphosphines [6,24], the chlo-
ride and bromide complexes 1, 2 and 4 but not the iodide
complexes 3 and 5 may be synthesized using either poten-
tiostatic methods or galvanostatic methods.
2.2. Spectroscopy
Solution 31P{1H} NMR spectra were recorded in CDCl3
solution on
a Varian Gemini-2000 spectrometer at
80.86 MHz with 256 transients collected. Spectra were ref-
erenced internally to 85% H3PO4.
2.3. X-ray structure determinations
complexes
chloro(2-hydroxyphenyl)diphenylphosphine-
gold(I) [13], and iodo(2-aminophenyl)diphenylphosphine-
gold(I) [14], both the hydroxy oxygen and the amino
X-ray crystal data indicated that the Series A bromide
and iodide complexes with [P(oanis)3] (2 and 3) appeared
to comprise a trigonal isomorphous set. Similarly, in the
Series B set the bromo complex with [P(panis)3] (4) had cell
parameters and space group which indicated that it was
isomorphous with the previously reported chloro analogue
[11]. Both of these isomorphous series were confirmed in
the structure analyses. With the iodo complex of [P(panis)3]
(5), although having four molecules in a centrosymmetric
triclinic cell could not be transformed into a higher symme-
try cell, and this was subsequently justified in the analysis
with the presence of two conformationally dissimilar mol-
ecules in the asymmetric unit.
˚
proton give significant short Auꢀ ꢀ ꢀO [3.160(7) A] and
˚
Auꢀ ꢀ ꢀN [3.61(3) A] interactions. This effect is not present
in the analogous but sterically demanding ortho-substi-
tuted phosphine complex, chloro[(2-trimethylsiloxyphe-
nyl)diphenylphosphine]gold(I) [13] where no substituent
group interaction is found. Similar steric effects are seen
with the 2-iodo-substituted analogues iodo(2-iodophe-
nyl)diphenylphosphinegold(I) [15] and iodo(2-iodo-3-
methylphenyl)diphenylphosphinegold(I) [16].
We therefore set out to look at the structural effects of
both ortho- and para-methoxy phosphine substitution on
a series of gold(I) complexes. Reported here is the synthe-
sis, the X-ray structures and solution 31P{1H} NMR spec-
tra of the series of five halo-gold(I) complexes with the
ortho- and para-anisyl-substituted phosphines, tris(2-meth-
oxyphenyl)phosphine [P(oanis)3], [AuP(oanis)3X] [Series A:
compounds 1–3] and tris(4-methoxyphenyl)phosphine
[P(panis)3], [AuP(panis)3X] [Series B: compounds 4, 5]
(X = Br, I). The structure of the Series B chloro analogue
[AuP(panis)3Cl] has been previously reported [11].
Unique data sets for all compounds were measured at
297(2) K within the specified 2hmax limit using a Rigaku
AFC 7R four-circle diffractometer [h–2h scan mode, mono-
˚
chromatized MoKa radiation (k = 0.71073 A), from a
12 kW rotating anode source] yielding N independent
reflections, N0 with I > 3.0r(I) (compounds 1, 4 and 5) or
I > 2.0r(I) (compounds
2 and 3) being considered
‘observed’ and used in the expression of the conventional
refinement residual R. Crystal decay was negligible in most
cases [1.5% maximum in 5] and in the worst cases was
allowed for by using a linear correction. The structures
were solved by direct methods and refined by full-matrix
least-squares refinement {on F for 1, 4 and 5 or on F2 for
2 and 3 (the latter using SHELX-97) [25]} after semi-empiri-
cal absorption corrections based on w-scans. Anisotropic
thermal parameters were refined for all non-hydrogen
2. Experimental
2.1. Preparation of compounds
The complexes [AuP(oanis)3X] [Series A: for X = Cl
(1); X = Br (2); X = I (3)] and [AuP(panis)3X] [Series B:
for X = Br (4); X = I (5)] were synthesized using a previ-
ously described procedure [6] by the interaction of equi-
molar quantities of [Bu4N][AuX2] (0.50 mmol; Cl,
atoms while (x,y,z,Uiso H were included and constrained
)
at estimated values. Neutral atom complex scattering fac-
tors were employed while computation used the TeXsan
Bott, Raymond C.
