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E.C. Spencer et al. / Journal of Organometallic Chemistry 692 (2007) 1081–1086
solutions were via Direct Methods. Refinement was on F2
+
+
(Ph)3P
(Ph)3P
(Ph)3P
using full-matrix least-squares techniques. All data were
corrected for absorption using SADABS [7]. All hydrogen
atoms are placed at calculated positions, and have been
refined with a riding model. The exception being the hydro-
gen atoms residing on the ylide carbon, these were located
in the difference Fourier map and their positional parame-
ters were refined (Uiso fixed at 120% of the parent atom).
These were then fixed for the final round of least-squares
refinement.
-
-
O
OEt
O
OEt
O
OEt
i
ii
Scheme 1. The canonical forms of EPPY.
iii
to an aqueous solution of the prepared phosphonium salt.
A thick pasty solid separated out from this solution, which
was subsequently refrigerated to give a white solid. This
solid was then re-crystallised from benzene via the vapour
diffusion method using petroleum ether as the diffusing sol-
vent. m.p. 126–127 ꢁC, yield: 89.5%.
3. Results and discussion
3.1. X-ray crystallography
Table 1 provides crystallographic results and refinement
information for all complexes. The molecular structures of
1, 2, and 3 are shown in Figs. 1–3, respectively. The dimeric
complexes crystallise in the centrosymmetric space group
2.1.2. Complexes 1, 2 and 3
A solution of the appropriate mercury (II) halide
(0.05 mmol) in methanol was added to a methanolic solu-
tion of EPPY (0.20 g, 0.05 mmol) at room temperature
and stirred overnight. The solvent was then removed in
vacuo. White crystals were obtained by crystallisation of
the crude product from chloroform using the vapour diffu-
sion method using petroleum ether as the diffusing solvent.
1: m.p. 431–433 K, yield: 87.2%. Anal. Found: C,
35.48%; H, 2.84%. C22H21O2PHgBr2 Anal. Calc.: C,
37.29%; H, 2.99%.
2: m.p. 423–425 K, yield: 92.6%. Anal. Found: C,
41.42%; H, 3.34%. C22H21O2PHgCl2 Anal. Calc.: C,
42.63%; H, 3.42%.
3: m.p. 425–427 K, yield: 80.1%. Anal. Found: C,
33.10%; H, 2.63%. C22H21O2PHgI2 Anal. Calc.: C,
32.92%; H, 2.64%.
ꢀ
P1, and straddle the crystallographic inversion centre.
Monomeric material was found to be present as a minor
component, approximately 5%, of the crystalline state of 2
(Fig. 2). The monomer is of the form [(EPPY)(HgCl)] in
which EPPY is C-coordinated to the Hg(II) centre. The
chlorine atom of this second component could not be
resolved from the disordered CHCl3 solvent molecule.
The crystallographic model for 3 also includes a disordered
component. In this case, approximately 5% of un-reacted
(HgI2)2 had crystallised with the complex. The positional
and atomic displacement parameters for the disordered
components in 2 and 3 were refined freely. The occupancy
values were fixed at 0.05 for the final round of least-squares
refinement. Further discussion of complexes 2 and 3 will be
confined to consideration of the principal components
only.
In all three complexes the mercury atom is sp3 hybri-
dised and resides in a distorted tetrahedral environment.
The inter-nuclear distances between mercury atoms of the
dimer units are greater than twice the ionic radii for 4-coor-
2.2. Instrumentation
Solution-state 1H, 31P and 13C NMR spectra at ambient
probe temperature were obtained on solutions in CD2Cl2
using a Varian Mercury-400 spectrometer operating at
˚
dinate Hg (II) (2.20 A) [8], indicating the absence of signif-
399.97 MHz for H, 161.91 MHz for 31P and 100.57 MHz
1
icant bonding interactions between the mercury atoms in
these complexes.
for 13C. Solution-state H and 31P spectra at 193 K were
1
obtained in CD2Cl2 using a Varian Inova-500 spectrometer
The dimeric structure adopted by complexes 1, 2 and 3 is
in contrast to the C-coordinated trinuclear mercury (II)
complex of the phosphorus ylide Ph3PCHCOPh [9], but
are similar to the structure of trans-Di-l-iodo- diiod-
obis(triphenylphosphoniumcyclopentadienylide)dimercury
(II) reported by Baenziger et al. [10] and the C-coordinated
dinuclear mercury (II) halide complexes of Ph3PCHCOPh
(BPPY) [11].
operating at 499.77 MHz for H, and 202.31 MHz for 31P.
1
All spectra were referenced to the relevant IUPAC stan-
dards via the frequency of the lock signal.
Solid-state 31P NMR spectra at ambient probe tempera-
ture were obtained using a Varian Inova-300 spectrometer
operating at 121.37MHz for 31P by cross-polarisation with
a contact time of 3 ms and a recycle delay of 120 s.
Tables 2–4 list key bond lengths and angles for com-
plexes 1, 2 and 3, respectively. The Hg–C, Hg–Cl bond
lengths are notably shorter in 2 in comparison with the cor-
2.3. X-ray crystallography
˚
All data were collected at 120 K using graphite mono-
chromated X-radiation (k = 0.71073 A) on a Bruker
SMART 6 K diffractometer. Data processing was per-
formed using standard Bruker software [6]. Structure
responding BPPY complex (Hg–C: 2.208(8) A, Hg–Cl(l):
˚
˚
˚
2.710(2) A, and Hg–Cl: 2.417(3) A.). A similar scenario is
found for complex 3 and the equivalent BPPY-Hg(II)
dimer, with the exception being the terminal Hg–I bond