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B.K. Nicholson, S.K. Whitley / Journal of Organometallic Chemistry 689 (2004) 515–521
Although
the
tris-mercury
oxonium
species
3.58%. NMR (CDCl3): 1H d 2.08 (s, CCH3), 2.95 (s,
NCH3), 7.12, 6.69 (two d, J 8.8 Hz, Haryl); 13C d 23.5
[(PhHg)3O]þ has been shown to exist in aqueous solu-
tion by electrospray mass spectrometry (ES-MS) [11], no
solid compounds incorporating this cation have yet been
characterised.
3
(CCH3), 40.3 (NCH3), 113.0 (C3, JC–Hg 212 Hz), 128.5
2
(C1), 136.8 (C2, JC–Hg 142 Hz), 151.0 (C4), 177.5
(C@O); 199Hg d 930. ES-MS (MeOH, HPF6) m=z 382
[M + H]þ. IR (KBr, cmꢀ1) 945m, 926m, 803vs, 794sh,
752w, 690s, 650w, 614w, 570w, 509m, 476w.
The reason for the tendency for RHgþ groups to
aggregate about the oxygen centre to form bis- and tris-
oxonium species is not clear; there are no apparent
Hgꢁ ꢁ ꢁHg intramolecular metallophilic attractions in
these Hg(II) species corresponding to the well-estab-
lished aurophilic interactions that account for the for-
mation of analogous Au(I) oxonium cations such as
[(Ph3PAu)3O]þ [14].
The study of the phenyl-mercury hydroxides and
oxides has been limited by the tendency for the com-
pounds to form powders or very thin crystals unsuitable
for X-ray diffraction studies, and by the absence of clear
spectroscopic characteristics. We have therefore now
examined the corresponding chemistry of the aryl-
mercury compounds formed by the 4-Me2NC6H4Hg-
moiety. This was chosen because the Me2N-group is
readily protonated allowing neutral, as well as cationic,
species to be detected by electrospray mass spectrome-
try; this concept of using ‘‘electrospray friendly’’ ligands
has been successfully utilised in other areas [15].
2.1.2. Preparation of 4-Me2NC6H4HgCl (2)
4-Me2NC6H4HgOAc was dissolved in hot acetone
and treated with excess of a saturated aqueous solution
of LiCl. After the solution was stirred for a few minutes,
the resulting solid was collected by filtration and air-
dried to give a quantitative yield of 4-Me2NC6H4HgCl.
M.p. 219–222 ꢁC, dec (lit. [20,21] 223–5 ꢁC, dec); Anal.
Calc. C8H10NClHg: C, 26.97; H, 2.82; N, 3.93. Found:
C, 25.59; H, 2.64; N, 3.67%. NMR (dmso-d6): 1H d 2.87
(s, NCH3), 7.23, 6.67 (two d, J 7.8 Hz, Haryl); 13C d 40.5
(NCH3), 113.0 (C3), 137.4 (C2), 150.7 (C4) (C1 not
observed); 199Hg insufficient solubility. ES-MS (MeOH)
m=z 358 [M + H]þ. IR (KBr, cmꢀ1) 943m, 805vs, 752w,
702w, 572w, 515m.
2.1.3. Preparation of 4-Me2NC6H4HgOH (3)
An aqueous solution of NaOH (8%, 7.5 mL) was
added to a slurry of 4-Me2NC6H4HgOAc (1.90 g, 5
mmol) in MeOH (2 mL) and the mixture was heated
under reflux for 30–60 min. After cooling, the crude
product was collected by filtration. This solid was re-
crystallised from boiling water to give colourless needles
of 4-Me2NC6H4HgOH, 50-60% yield. M.p. 177–182 ꢁC
(with rapid heating, cf. lit. [19] 152–156 or 180 ꢁC). Anal.
Calc. C8H11NOHg: C, 28.44; H, 3.28; N, 4.14. Found:
2. Experimental section
2.1. General
Electrospray mass spectra were recorded on a VG
Platform II spectrometer, operated as detailed elsewhere
[16]. Assignments were confirmed by simulation of the
characteristic isotope patterns using the ISOTOPE
program [17]. The peaks reported are the most intense in
the isotopic envelope. NMR were obtained on a Bruker
AC300 instrument operating under standard conditions,
with 199Hg shifts referenced to PhHgOAc in dmso at 816
ppm [18]. IR spectra were recorded on a Digilab FTS-40
instrument; only the peaks 1000–400 cmꢀ1 are listed in
Section 2 since this is the diagnostic region. DSC was
performed on a Perkin–Elmer DSC 6 instrument.
1
C, 28.53; H, 3.35; N, 4.00%. NMR (CDCl3): H d 1.6–
2.1 (broad, OH), 2.98 (s, NCH3), 7.18, 6.67 (two d, J 8.0
3
Hz, Haryl); 13C d 40.3 (NCH3), 112.8 (C3, JC–Hg 142
2
Hz), 137.8 (C2, JC–Hg 125 Hz), 151.1 (C4), (C1 not
observed); 199Hg d 1140 (CDCl3), 1044 (dmso-d6).
ES-MS (MeOH/H+) m=z 340 [M + H]þ; 659
[(RHg)2O + H]þ; 978 [(RHg)3O]þ; ES-MS (MeOH/
NaOH) m=z 362 [M + Na]þ; 394 [M + Na + MeOH]þ. IR
(KBr, cmꢀ1) 3552 (mO–H), 944m, 886m (dM–O–H), 804vs,
753w, 707w, 528s (mHg–O), 515s, 473w.
2.1.1. Preparation of 4-Me2NC6H4HgOAc (1)
2.1.4. Preparation of (4-Me2NC6H4Hg)2O (4)
N,N-Dimethylaniline (12.7 mL, 12.1 g, 0.100 mol)
was added to a stirred slurry of mercury(II) acetate (31.9
g, 0.100 mol) in EtOH (150 mL). The mixture was
stirred overnight and the insoluble crude product was
collected by filtration. This solid was recrystallised from
hot acetone to give colourless needles. The supernatant
was concentrated and stored at )20 ꢁC to give a second
crop of crystals, combined yield of 4-Me2NC6H4HgOAc
was 28.5 g, 75%. M.p., from acetone, 155 ꢁC (lit. [19,20],
from ethanol, 165 ꢁC); Anal. Calc. C10H13NO2Hg:
C, 31.62; H, 3.45; N, 3.67. Found: C, 31.76; H, 3.38; N
A small sample of 4-Me2NC6H4HgOH was pow-
dered and then heated to 120 ꢁC at 1 mm Hg for 4–5 h.
The residue was dissolved in dichloromethane and di-
ethyl ether was allowed to slowly diffuse, to give very
fine crystals which were collected by filtration and air-
dried to give (4-Me2NC6H4Hg)2O. M.p. >230 ꢁC. Anal.
Calc. C16H20N2OHg2: C, 29.23; H, 3.07; N, 4.25.
Found: C, 29.37; H, 3.23; N, 4.10%. NMR (dmso-d6):
1H d 2.85 (s, NCH3), 7.17, 6.67 (two d, J 7.8 Hz, Haryl);
13C d 40.4 (NCH3), 113.1 (C3), 137.7 (C2), 150.7 (C4)
(C1 not observed); 199Hg d 1000. IR (KBr, cmꢀ1) 945m,