Organomercury-based imino-bis(diisopropylphosphine chalcogenide) complexes: Synthesis and characterisation of novel hybrid "single-source precursors" for mercury chalcogenide solid-state materials

Article abstract of DOI:10.1039/b303200k

The synthesis and characterisation of the mercury(II) complexes [RHg{(SePⁱPr₂)₂N}] [R = methyl (2a), ethyl (3a), thienyl (T) (4a), 2-selenyl (SL) (5a) and phenyl (6a)], prepared by the reaction of the sodium salt of NH(SeP

Full text of DOI:10.1039/b303200k

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Organomercury-based imino-bis(diisopropylphosphine
chalcogenide) complexes: synthesis and characterisation of
novel hybrid “single-source precursors” for mercury chalcogenide
solid-state materials
David J. Crouch,a Paul M. Hatton,b Madeleine Helliwell,b Paul O’Brien*a and James Rafterya
a Department of Chemistry, University of Manchester, Oxford Road, Manchester,
UK M13 9PL
b Materials Research Institute, Sheffield Hallam University, Pond Street, Sheffield, UK S1 1WB
Received 20th March 2003, Accepted 20th May 2003
First published as an Advance Article on the web 9th June 2003
The synthesis and characterisation of the mercury() complexes [RHg{(SePiPr2)2N}] [R = methyl (2a), ethyl (3a),
thienyl (T) (4a), 2-selenyl (SL) (5a) and phenyl (6a)], prepared by the reaction of the sodium salt of NH(SePiPr2)2
(1a) with the appropriate alkyl/aryl mercury halide in methanol are reported. Results are compared and contrasted
to the corresponding sulfur analogues [RHg{(SPiPr2)2N}] [R = T (4b), SL (5b) and Ph (6b)], and these new
compounds have been evaluated, by thermogravimetric analysis and mass spectrometry as potential precursors and
powder X-ray diffraction used to identify solid-state products. The solid-state structure of the symmetrical complex
Hg[(SePiPr2)2N]2 7a, and di(2-selenyl)mercury, one of the symmetrisation products of [SLHg{(SePiPr2)2N}] 5a in
solution, have been determined by single crystal X-ray crystallography.
Mercury() chalcogenides are important species as HgE
Introduction
solid-state materials (E = S, Se or Te) have demonstrated,
amongst other phenomena, strong room-temperature infrared
luminescence.15 Such behaviour makes these semiconductor
nanocrystals attractive candidates for integration into light-
emitting devices.16 However, to date, the majority of methods
utilised for fabricating such materials have involved aqueous
solution growth techniques16,17 due to the non-volatile nature
of the chalcogenide-releasing agents used. The general require-
ments for successful precursors are a low degree of association
and adequate volatility, at least sufficient for low-pressure
deposition and solution thermolysis techniques. In terms of
the dichalcogenoimidodiphosphinato compounds, the volatility
associated with these phopshine-based ligands can be drastic-
ally altered by the correct choice of alkyl functionality. For
example introduction of isopropyl moieties [R = CH(CH3)2]
into the core framework drastically increases volatility when
compared to the aryl analogue HN(EPPh2)2.11
In this paper we report on the synthesis and structural
characterisation of organomercury dichalcogenideimido-
diphosphinato complexes. Formed by the reaction of NH(EPi-
Pr2)2 (1) [E = Se (a) and S (b)] with the appropriate alkyl/aryl
mercuric chloride, under basic conditions, examples of methyl
(2), ethyl (3), 2-thienyl (T) (4), 2-selenyl (SL) (5) and phenyl (6)
mercury iminobis(diisopropylphosphinechalcogenide) coordin-
ation complexes [RHg{(EPiPr2)2N}] are described along with
their structural characterisation. Compared and contrasted
with the symmetrical dichalcogenideimidodiphosphinato
analogue, Hg[N(SePiPr2)2]2, 7a, these new compounds have
been characterised by microanalysis, multi-element NMR, IR,
positive-ion APCI mass spectrometry and thermogravimetric
(TGA) analysis. Single-crystal X-ray diffraction crystallography
has been carried on the symmetrical analogue 7a and the
symmetrisation product of 5a, di(2-selenyl)mercury.
The last few decades has seen considerable interest in the
synthesis of molecular “single-source” precursors for solid-state
materials.1–3 Generally the electrical and optical properties of
solid-state materials grown by chemical vapour deposition
(CVD) and solution thermolysis are critically dependant on the
nature and purity of the precursors used. However traditional
materials utilise gaseous and hazardous organometallic com-
pounds for fabrication of the solid-state material.3 Such proper-
ties are obviously disadvantageous when considering industrial
applications. For example II–VI semiconductors, such as group
12 chalcogenides, are one of the more important classes of
solid-state materials as species such as CdHgTe and HgSe have
demonstrated various potential applications, ranging from
integration in display devices,4 and optoelectronic devices5 to
infrared detectors and thermal imaging systems.6 Alternative
“single-source” precursors of materials incorporating group 12
and 16 elements have therefore been sought resulting in various
examples being reported.7–9
As part of our studies into cleaner forms of single-source
precursors, we have demonstrated numerous alternative chalco-
genide-sources for the preparation of solid-state materials. For
example, asymmetrical four coordinate dithio- and diseleno-
carbamates M(E2CNR1R2)2 have proved sufficiently volatile
for the growth of zinc and cadmium chalcogenide films and
nanoparticles.10 More recently we have demonstrated that
imino-bis(dialkylphosphine chalcogenide) [R2P(E)–N–P(E)R2]
complexes11 can be utilised to prepare CdSe quantum dots
using solution thermolysis.12
Dichalcogenoimidodiphosphinato anions [R2P(E)–N–P(E)-
R2]Ϫ (E = O, S or Se) are versatile ligands, with a strong
tendency to form inorganic (carbon free) chelate rings.11 Trans-
ition-metal complexes incorporating such ligands have
demonstrated improved thermal and chemical stability over
traditional organic based ligands such as β-diketonate
complexes.13
Nevertheless, while numerous zinc and cadmium single-
source precursors have been utilised to prepare various
materials, via CVD2,7–9 and solution thermolysis,10,12 there have
been few examples reported on corresponding mercury
complexes.14
Such single-source precursors are of viable interest for the
generation of mercuric chalcogenide materials as we have
recently demonstrated the ability to generate CdSe thin films
from a
related [MeCd(SePiPr2)2N]2 compound via LP-
MOCVD.18 This demonstration make the use of compounds
2–7, a potentially interesting area of endeavour as, to our
knowledge, mercury sulfide and selenides produced via thermo-
lytic reactions have received scant attention.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 7 6 1 – 2 7 6 6
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at low pressure. Due to the extreme biotoxicity and potential for
trans-alkylation, resulting in the formation of extremely toxic
dimethylmercury and diethylmercury,21,22 the simple alkyl
derivatives 2 and 3 were not studied. Thermolytic reactions
were studied on compounds 4–7 at two different temperatures,
300 and 350 ЊC in vacuo. The results are summarised in Table 1.
Thermolysis of the selenide compounds 4a, 5a, 6a and 7a under
the conditions given in the Table 1 results in the clean formation
of mercury() selenide at the higher temperature. Evidently
the P–E bonds rupture under these conditions in preference
to Hg–E. This conjecture is supported by the powder X-Ray
diffraction (PXRD) patterns obtained from the isolated
inorganic residues. Comparison of the observed diffraction
peaks with the standards [JCPDS powder diffraction data sets
no. 15-1554 (HgSe) and 75-1538/1589 (HgS) from the 1-46
database] confirm that most of the deposited material is the
corresponding mercury chalcogenide. For example the diffrac-
tion pattern (Fig. 1) obtained from the thermolysis products for
5a at 350 ЊC clearly illustrate the cubic form of mercury()
selenide (known as tiemannite). The Miller indices in the
diffractograms were taken from the previously mentioned
database. As illustrated in Fig. 1, the resulting HgSe material
shows strong {111} texturing. All of the diselenideimido-
diphosphinato complexes 4a–6a were found to decompose
cleanly at 350 ЊC yielding cubic HgSe. The PXRD patterns
obtained from reactions conducted at 300 ЊC showed in some
cases HgSe formation along with considerable unidentified
inorganic/organic contaminates, as neither elemental selenium/
sulfur or mercury were observed in the PXRD spectra. The
symmetrical analogue 7a showed similar behaviour to 4a–6a,
but required a higher temperature of 400 ЊC to afford clean
decomposition and HgSe formation. This demonstrates the
effect, that with correct choice of functionality within the
precursor, the decomposition temperature and that required for
HgE formation can be significantly lowered.
Results and discussion
Organomercury dichalcogenideimidodiphosphinato complexes
are generally accessible via methods analogous to those for
symmetrical
dichalcogenideimidodiphosphinato
species,
Mn[N(EPR2)2]n [eqn. (1); E = S or Se].11,19 The interaction
of organomercury halides with the corresponding ligand
under basic methanolic conditions (NaOCH3/CH3OH) has the
advantage of yielding compounds free of ionic impurities
under very mild conditions.19 The dichalcogenoimidodiphos-
phinato ligands employed in this study are NH(SePiPr2)2 1a and
NH(SPiPr2)2 1b. The generation of 1a or 1b, in a one-pot
synthesis from chlorodiisopropylphosphine, is relatively
straightforward and has been documented elsewhere.11,19
(1)
We have studied the reactions of 1a and 1b and their salts
with various organomercury halides.20 Improved complex
formation was observed by reaction of 1a or 1b with sodium
methoxide in anhydrous methanol yielding the sodium salt
NaN(EPiPr2)2. As in-situ treatment of NaN(EPiPr2)2, with the
appropriate organomercury halide yields compounds 2–6 in
good-to-excellent yields (Scheme 1). For example, the reaction
of 2-thienylmercuric chloride with NaN(SePiPr2)2 directly
produces THg[(iPr2PSe)2N] 4a as a white powder in 82% yield.
The analogous reaction of 1b with 2-thienylmercury chloride
gave 4b as a pale cream powder in 54% yield. Compound 7a
is obtained in excellent yields under similar conditions using
mercury() chloride. Attempts to obtain methyl- (2b) and ethyl-
(3b) sulfide-precursors using the above method were generally
unsuccessful.
Fig. 1 PXRD of cubic mercury selenide obtained from thermolysis of
compound 5a.
Scheme 1 Synthesis of various mercury complexes.
The corresponding sulfur analogues showed similar
behaviour with clean decomposition being observed only at the
higher temperature of 350 ЊC. Again unidentifiable inorganic/
organic species were observed in the PXRD patterns from the
residues obtained at 300 ЊC. A typical example is illustrated
in Fig. 2, with the PXRD pattern obtained from the decom-
position products of 5b at 350 ЊC. The resulting HgS material
was found to be hexagonal (known as cinabar) in nature with
{101} and {012} texturing.
Mass spectral analysis of the organic by-products, condensed
in the cooler part of the Schlenk tube, using chemical ionisation
revealed that thermolytic decomposition of the complexes is
relatively clean (Table 1). At the lower temperature of 300 ЊC,
the major products isolated were mono- and bis-dechalco-
Complexes 2–7 all show good solubility in common organic
solvents and are air-stable in the solid state for prolonged
periods. The volatility characteristics of the precursors were
determined by thermogravimetric analysis (TGA), showing
clean sublimation without any residues, which is desirable for
use as precursors for MOCVD studies.
Solid-state decomposition
Mercury chalcogenides are widely used in LED technology,
especially the selenides and tellurides.4–6,16 We have investigated
the behaviour of some of the new organo-mercury sulfide and
selenide single-source precursors under thermolysis conditions
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Table 1 Thermal decomposition data of organomercuric dichalcogenideimidodiphosphinato complexes
Compound
Reactor pressure/mm Hg
T /ЊC
Inorganic residuea
Main organic by-productb
4a
4a
4b
4b
5a
5a
5b
5b
6a
6a
6b
6b
7a
7a
0.61
0.58
0.52
0.71
0.48
0.44
0.52
0.54
0.63
0.54
0.53
0.68
0.48
0.52
300
350
300
350
300
350
300
350
300
350
300
350
300
400
HgSe ϩ other
HgSe
iPr2P(E)NPiPr2
(iPr2P)2NH
iPr2P(E)NPiPr2
(iPr2P)2NH
HgS
HgSe ϩ other
HgSe
HgS ϩ other
HgS
HgSe ϩ other
HgSe
HgS ϩ other
HgS
HgSe ϩ other
HgSe
(iPr2P)2NH
iPr2P᎐N
᎐
iPr2P᎐N
᎐
iPr2P᎐N
᎐
iPr2P᎐N
᎐
iPr2P᎐N
᎐
iPr2P᎐N
᎐
iPr2P᎐N
᎐
iPr2P(E)NPiPr2
iPr2P᎐N
᎐
a As determined by powder X-Ray diffraction. b By mass spectrometry (CI).
Fig.
2
PXRD of hexagonal mercury sulfide obtained from
thermolysis of compound 4b.
Fig. 3 31P NMR Spectrum of compound 5a.
shifted from that observed in the free ligand (89.5 ppm).11 This
has been shown24 in other systems to be indicative of selenium
coordination. The corresponding sulfur analogues, 4a, 5a,
showed no such behaviour, with single 31P peaks being observed
in both cases, due to the distinct absence of coupling between
phosphorus and the non-NMR active sulfur nuclei. (Note: 33S
is NMR active with a nuclear spin (I ) of 3/2. However it has a
very low receptivity of 0.0972 with respect to 13C.)
i
genated species, Pr2P(E)NPiPr2 and (iPr2P)2NH. Thus further
demonstrating cleavage of the P–E bonds and HgE formation.
At the higher reaction temperature of 350 ЊC the major product
isolated for almost all of the analogues is the amino-
phosphonium fragment, [(iPr P᎐N)
ϩ
H]ϩ, thus further
᎐
2
illustrating degradation of the imidodiphosphinato framework
and the clean decomposition of the precursor.
As expected, the 199Hg chemical shifts are sensitive to the
electronic effects of the substituents around the metal centre.
The aryl substituted analogues 4–5 show increased nuclear
shielding compared to the simple alkyl analogues 2–3. Ana-
logues prepared from 1a also show increased shielding and thus
larger chemical shifts, resulting from the more effective overlap
of the selenium–mercury orbitals, when compared to the corre-
sponding sulfur species prepared from 1b. For example Fig. 4
shows the 199Hg NMR spectrum of C4H3Se–Hg[(iPr2PSe)2N]
NMR Spectroscopy studies
Among the several elements that have at least one nuclide
suitable for NMR studies, mercury has two magnetically active
isotopes, 201Hg and 199Hg. The latter has nuclear spin I = ½ and
its natural abundance (16.84%) and receptivity (5.42 with
respect to 13C) make its detection easy by NMR. Also, relax-
ation rates are very high, so that a large number of transients
can be acquired in a very short time. Chemical shifts are spread
over a very large range and, as a consequence, are very sensitive
to the electronic environment and geometry at the mercury
centre.23 We have investigated the NMR properties of com-
pounds 2–7 using 199Hg NMR spectroscopy. To complement
these studies 1H and 31P NMR studies were also conducted. 1H,
31P and 199Hg NMR studies were not conducted on the phenyl
analogues 6a and 6b due to their insolubility in almost all
deuterated solvents.
The proton decoupled phosphorus-31 NMR spectra of
compounds, 2a–5a and 7a, at room temperature, all consist of
a triplet with selenium-77 satellites (J(31P–77Se) = 461–566 Hz).
A representative example is illustrated in Fig. 3, with the 31P
spectrum for 5a The phosphorus–selenium coupling constants
(J(P–Se)) are less than that in the free ligand (J(31P–77Se) for 1a
= 757 Hz).11 The phosphorus resonance (57.28 ppm) is also well
Fig. 4 199Hg NMR Spectrum of compound 5a.
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5a. The 199Hg spectrum of 5a in d8-THF is a multiplet with
phosphorus-31 and selenium-77 satelittes (J(Se–Hg) = 737 Hz
and J(P–Hg) = 179 Hz), which compare well with the
J(Se–Hg) and J(P–Hg) values of 642–737 and 127–179 Hz,
observed for the other mercury selenide precursors and
reported examples.23
shortening of the carbon-to-metal bond is attributed to the
electron donating character of the selenyl ring.26 This analogy
is also seen in the C–C bonds in the selenyl ring where the C(1)–
C(2) (1.412 cf. 1.370 Å) bond is longer and the C(2)–C(3) (1.416
cf. 1.423 Å) bond shorter than the corresponding bond in the
selenophene molecule.26
Solid-state structure
Experimental
The monomeric nature of the dichalcogenideimidodiphos-
phinato materials in the solid state has been confirmed by
single-crystal X-ray analyses. X-Ray crystallographic studies
carried out on the symmetrical 7a analogue revealed each metal
centre to be tetrahedrally coordinated by two ligands through
the selenium atoms of the diselenoimidodiphosphinate moiety.
The structure of 7a, illustrated in Fig. 5, is isostructural with
the analogous cadmium() complex,11 revealing a distorted
mercury centre with Se–Hg–Se angles ranging from 106.830
to 113.202Њ. Shortening of the P–N bonds to ∼1.58–1.59 Å and
the subsequently extended P–Se bonds (2.18–2.19 Å) clearly
illustrate delocalisation within the diselenoimidodiphosphinate
architecture.11
Unless, otherwise stated all reactions were performed under
an inert atmosphere of dry nitrogen using standard Schlenk
techniques. All glassware was flame dried under vacuum prior
to use. All solvents and reagents were purchased from Sigma–
i
Aldrich chemical company and used as received. Pr2P(Se)-
i
NHP(Se)iPr2 1a and Pr2P(S)NHP(S)iPr2 1b were synthesised
from 1,1,1,3,3,3-hexamethyldisilazane according to literature
methods.19 2-Thienyl- and 2-selenyl-mercury chloride were
prepared via standard literature methods.22 1H and 31P NMR
studies were carried out using a Bruker AC300 FTNMR
1
instrument operating at room temperature (300 MHz for H,
162 MHz for 31P). 199Hg NMR studies were carried out using
a Bruker AC500 FTNMR instrument operating at room tem-
perature (71.63 MHz for 199Hg). All 199Hg-NMR chemical shifts
are given in ppm and referenced to mercury perchlorate [1 M
Hg(ClO4)2 in 1 M DClO4; δ(199Hg) Ϫ2250 ppm] standard.23
Mass spectra were recorded on a Kratos concept 1S instrument.
Infrared spectra were recorded on a Specac single reflectance
ATR instrument (4000–400 cmϪ1, resolution 4 cmϪ1). X-Ray
powder diffraction patterns were determined on a Phillips 3710
powder diffractometer using nickel-filtered monochromated
Cu-Kα radiation (λ = 1.5418 Å) and were indexed using the
JCPDS programs.27 Elemental analysis was performed by the
University of Manchester micro-analytical laboratory. Melting
points were recorded on a Gallenkamp melting point apparatus
and are uncorrected. Compounds 2–6 were all prepared in an
analogous manner. A generic method is illustrated below for
the synthesis of CH3–Hg[(iPr2PSe)2N] 2a. Compound 7a was
prepared in a similar fashion using mercury() chloride.
Fig. 5 X-Ray crystal structure of Hg[(iPr2PSe)2N]2, 7a.
CH3–Hg[(iPr2PSe)2N] (2a)
The organomercuric dichalcogenideimidodiphosphinate
compounds 2–6, on the other hand, were found to be unstable
in solution and over time undergo rearrangement reactions
yielding dialkyl/aryl mercury compounds. Such behaviour
is common in organomercuric sulfides and selenides22 and is
demonstrated again here in the attempted slow growth of
crystals of 2–6 from dichloromethane–hexane solution. Thus
prolonged periods in solution at room temperature resulted
in the rearrangement of the organomercuric dichalcogenide-
imidodiphosphinato complexes to the corresponding dialkyl/
aryl mercury compound. For example the attempted growth
of crystals of 5a from dichloromethane–hexane results in the
isolation of crystals of the hitherto unknown di(2-selenyl)-
mercury compound, (C4H3Se)2Hg (Fig. 6). This rearranged
product crystallises in the C2/c space group with the Hg atom
on a centre of symmetry, consequently the C–Hg–C bond angle
is exactly 180Њ and the selenium atoms in the anti conformation.
The Hg–C bond lengths (2.051 Å) are typically similar to those
reported by Grdenic et al.25 for the related (C4H3S)2Hg. The
Sodium methoxide (0.42 g, 7.36 mmol) was added to a stirred
solution of 1a (3.00 g, 7.36 mmol) in anhydrous methanol
(100 cm3). The resulting pink solution was stirred at room tem-
perature for 10 min. The solution was then added dropwise over
a period of 45 min to a stirred solution of methylmercury chlor-
ide (1.84 g, 7.36 mmol) in anhydrous tetrahydrofuran (10 cm3).
After complete addition the reaction was stirred at room
temperature for 2 h. The resulting white suspension was filtered
and the recovered solid washed with methanol (100 cm3) before
drying under vacuum. Recrystallisation from tetrahydrofuran–
methanol yielded 3.58 g (79%) of rose pink powder (mp 81–84
ЊC); FT-IR (KBr)/cmϪ1: 2959, 2858 (C–H str.) 1263, 1224, 751
(ν(P–N–P)), 541 (Hg–C str.) 422 (P–Se str.); 1H NMR (CDCl3):
δ 0.85 (s, 3H, CH3–Hg), 1.27 (m, 24H, CH3R), 2.14 (m, 4H,
CHR); 31P{1H} NMR (CDCl3): δ 55.670 [m, 2SeP, 1J(31P–77Se)
461 Hz]; 199Hg{1H} NMR (CDCl3): δ Ϫ246 [m, HgSe, 1J(199Hg–
2
77Se) 686 Hz, J(199Hg–31P) 135 Hz]; MS (APCI): m/z = 1643
(26%, 2M ϩ 2Hg), 624 (21%, M ϩ H), 408 (100%, M Ϫ MeHg)
(Found: C 25.30, H 5.39, N 2.42, P 10.56. C13H31N1P2Se2Hg
requires C 25.11, H 5.02, N 2.25, P 9.96%).
C2H5–Hg[(iPr2PSe)2N] (3a)
Yield = 42% (mp 169–172 ЊC); FT-IR (KBr)/cmϪ1: 2961, 2956
(C–H str.) 1229, 1222, 750 (ν(P–N–P)), 530 (Hg–C str.), 427
1
(ν(P–Se)); H NMR (CDCl3): δ 1.21–1.28 (m, 29H, 8CH3R,
CH3CH2–Hg and CH3CH2–Hg), 2.17 (m, 4H, CHR); 31P{1H}
NMR (CDCl3): δ 55.930 [m, 2SeP, 1J(31P–77Se) 468 Hz]; 199Hg–
{1H} NMR (CDCl3): δ Ϫ317 [m, HgSe, 1J(199Hg–77Se) 642 Hz,
2J(199Hg–31P) 138 Hz]; MS (APCI): m/z = 637 (46%, M ϩ H),
Fig. 6 X-Ray Structure of SL–Hg–SL.
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408 (100%, M Ϫ HgEt) (Found: C 26.30, H 5.37, N 2.69,
P 9.94. C14H33N1P2Se2Hg requires C 26.44, H 5.23, N 2.20, P
9.74%).
Hg[(iPr2PSe)2N]2 (7a)
Yield = 86% (mp 181–184 ЊC); FT-IR (KBr)/cmϪ1: 2967 (C–H
str.) 1259, 1222, 762 (ν(P–N–P)), 427 (P–Se str.); 1H NMR
(CDCl3): δ 1.25 (m, 48H, CH3R), 2.18 (m, 8H, CHR); 31P{1H}
NMR (CDCl3): δ 56.80 [m, 4SeP, 1J(31P–77Se) 518 Hz];
C4H3S–Hg[(iPr2PSe)2N] (4a)
199Hg{1H} NMR (CDCl3): δ Ϫ859 [m, 2HgSe, J(199Hg–77Se)
1
Yield = 82% (mp 146–149 ЊC); FT-IR (KBr)/cmϪ1: 2957 (C–H
855 Hz, 2J(199Hg–31P) 127 Hz]; MS (APCI): m/z = 1015 (85%, M
ϩ H) 608 (100% M Ϫ L) (Found: C 28.47, H 5.52, N 2.72,
P 12.29. C24H56N2P4Se4Hg requires C 28.45, H 5.57, N 2.76, P
12.23%).
1
str.) 1222, 753 (ν(P–N–P)), 538 (Hg–C str.) 429 (P–Se str.); H
NMR (CD2Cl2): δ 1.25 (m, 24H, CH3R), 2.18 (m, 4H, CHR),
7.30 (d, 1H, T-H), 7.55 (m, 1H, T-H), 7.81 (d, 1H, T-H);
31P{1H} NMR (CDCl3): δ 56.816 [m, 2SeP, 1J(31P–77Se) 534 Hz];
199Hg{1H} NMR (CDCl3): δ Ϫ587 [m, HgSe, 1J(199Hg–77Se) 672
2
Hz, J(199Hg–31P) 152 Hz]; MS (APCI): m/z = 692 (41%, M ϩ
Bulk decomposition studies
H), 409 (100%, M Ϫ HgT) (Found: C 28.02, H 4.37, N 2.09, P
9.37, S 3.87. C16H31N1P2Se2SHg requires C 27.85, H 4.53, N
2.03, P 8.98, S 4.65%).
Typically, about 100 mg of the compound were placed in the
bottom of a Schlenk tube connected to a high vacuum line. The
tube was then evacuated to ∼0.5 mm Hg before its tap was
closed. The bottom two-thirds of the Schlenk tube were then
inserted into a tube furnace. The decomposition temperatures
are given in Table 1. The organic by-products condensed in the
cooler part of the Schlenk tube and were analysed by mass
spectrometry using chemical ionisation (NH3 carrier gas) and
the remaining inorganic matter by powder X-ray diffraction
(PXRD). PXRD samples were prepared by slow evaporation
from dichloromethane solution onto clean glass substrates.
C4H3S–Hg[(iPr2PS)2N] (4b)
Yield = 54% (mp 136–139 ЊC); FT-IR (KBr)/cmϪ1: 2959 (C–H
str.) 1259, 1223, 759 (ν(P–N–P)), 673, 634 (N–P–S str.) 538
1
(ν(P–S) and Hg–C str.); H NMR (CD2Cl2): δ 1.25 (m, 24H,
CH3R), 2.15 (m, 4H, CHR), 7.27 (d, 1H, T-H), 7.50 (m, 1H,
T-H), 7.80 (d, 1H, T-H); 31P{1H} NMR (CDCl3): δ 63.085 [s,
2
2SP]; 199Hg{1H} NMR (CDCl3): δ Ϫ464 [t, HgS, J(199Hg–31P)
144 Hz]; MS (APCI) m/z = 599 (15%, M ϩ H) 408 (100%, M Ϫ
HgT) (Found: C 32.45, H 5.50, N 2.42, P 10.55, S 15.86.
C16H31N1P2S3Hg requires C 32.24, H 5.24, N 2.35, P 10.39, S
16.13%).
X-Ray crystallography
Crystals suitable for X-ray diffraction studies were obtained
by slow diffusion of hexane into dichloromethane solutions of
the appropriate compound. Single-crystal structure determin-
ation of 7a and one of the rearrangement products of 5a,
(C4H3Se)2Hg, was carried out from data collected using
graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å)
on an Bruker APEX diffractometer. The structures were solved
by Direct Methods28 and refined by full-matrix least squares
on F 2.29 All non-hydrogen atoms were refined with anisotropic
atomic displacement parameters. Hydrogen atoms were placed
in calculated positions, assigned isotropic thermal parameters
and allowed to ride on their parent carbon atoms.
C4H3Se–Hg[(iPr2PSe)2N] (5a)
Yield = 61% (mp 158–161 ЊC); FT-IR (KBr)/cmϪ1: 2954 (C–H
str.) 1217, 753 (ν(P–N–P)), 538 (Hg–C str.) 554, 429 (P–Se str.);
1H NMR (d8-THF): δ 1.23 (m, 24H, CH3R), 2.18 (m, 4H,
CHR), 7.50 (d, 1H, SL-H), 7.65 (m, 1H, SL-H), 8.41 (d, 1H,
SL-H);31P{1H} NMR (d8-THF): δ 57.276 [m, 2SeP, 1J(31P–77Se)
566 Hz]; 199Hg{1H} NMR (d8-THF): δ Ϫ443 [m, HgSe,
1J(199Hg–77Se) 737 Hz, 2J(199Hg–31P) 179 Hz]; MS (APCI): m/z =
1337 (100%, 2M Ϫ SL), 809 (60%, M ϩ THF), 741 (30%, M ϩ
H) (Found: C 26.14, H 3.97, N 1.80, P 7.93. C16H31NP2Se3Hg
requires C 26.08, H 4.08, N 1.90, P 8.40%).
Crystal data. C24H56N2P4Se4Hg 7a, M = 1013.02, triclinic,
¯
space group P1, a = 9.3488(11), b = 12.9314 (15), c = 16.2877
C4H3Se–Hg[(iPr2PS)2N] (5b)
(19) Å, α = 79.110(2), β = 77.862(2), γ = 70.473(2)Њ, V = 1799.2(4)
Å3, T = 100(2) K, Z = 2 µ(Mo-Kα) = 8.518 mmϪ1, 7239 reflec-
tions measured, 6281 unique (Rint = 0.0222) which were used in
all calculations. The final wR(F 2) was 0.0578 (all data) and final
R(F) was 0.0265 (observed data, I > 2σ(I )).
Yield = 76% (mp 150–153 ЊC); FT-IR (KBr)/cmϪ1: 2967, 2960
(C–H str.) 1222, 1217, 761 (ν(P–N–P)), 540 (Hg–C str.) 638
1
(P–S str.); H NMR [(CD3)2CO]: δ 1.25 (m, 24H, CH3R), 2.18
(m, 4H, CHR), 7.58 (d, 1H, SL-H), 7.65 (t, 1H, SL-H), 8.50 (d,
Di(2-selenyl)mercury: C4H3SeHg, M = 230.31, monoclinic,
space group C2/c, a = 21.847(6), b = 5.3593(14), c = 7.761(2) Å,
β = 104.845(4), V = 878.3(4) Å3, T = 100(2) K, Z = 8 µ(Mo-Kα)
1H, SL-H); 31P{1H} NMR (CDCl3): δ 63.459 [s, 2SP];
199Hg{1H} NMR (d8-THF): δ Ϫ355 [t, HgS, J(199Hg–31P) 165
2
= 25.738 mmϪ1, 3049 reflections measured, 888 unique (Rint
=
Hz]; MS (APCI): m/z = 824 (100%, M ϩ 2THF ϩ MeCN), 643
(25%, M ϩ H) (Found: C 29.96, H 4.78, N 2.11, P 9.44, S 9.90.
C16H31NP2SeS2Hg requires C 29.88, H 4.86, N 2.18, P 9.90, S
9.97%).
0.0477) which were used in all calculations. The final wR(F 2)
was 0.0966 (all data) and final R(F) was 0.0377 (observed data,
I > 2σ(I )).
CCDC reference numbers 206589 and 206590.
See http://www.rsc.org/suppdata/dt/b3/b303200k/ for crystal-
lographic data in CIF or other electronic format.
C6H5–Hg[(iPr2PSe)2N] (6a)
Yield = 47% (mp 130–132 ЊC); FT-IR (KBr)/cmϪ1: 2957 (C–H
str.) 1251, 1222, 752 (ν(P–N–P)), 538 (Hg–C str.) 429 (P–Se
str.); MS (APCI): m/z = 829 (76%, M ϩ THF), 685 (20%, M ϩ
H) (Found: C 31.27, H 4.99, N 2.37, P 9.05. C18H33NP2Se2Hg
requires C 31.61, H 4.86, N 2.05, P 9.06%).
Conclusion
This paper describes the synthesis and characterisation of
organo-mercury imino-bis(diisopropylphosphine chalcogenide)
complexes. The symmetrical complex 7a has been shown to be
monomeric in the solid state by single crystal X-ray diffraction
possessing a distorted tetrahedral configurations with extended
P–Se bonds. The air stable complexes 2–6 demonstrate unstable
behaviour in solution rearranging to dialkyl/diaryl mercury
species. Thermolytic decomposition of the aryl-susbtituted pre-
cursors has been carried in the solid state using simple pyrolysis
studies, affording HgE, thus illustrating that such dichalco-
C6H5–Hg[(iPr2PS)2N] (6b)
Yield = 52% (mp 142–144 ЊC); FT-IR (KBr)/cmϪ1: 2959, 2926,
2867 (C–H str.) 1259, 1224, 761 (ν(P–N–P)), 673, 634 (N–P–S
str.), 540 (ν(P–S) and Hg–C str.); MS (APCI): m/z = 663 (90%,
M ϩ THF), 591(35%, M ϩ H) (Found: C 36.26, H 5.57, N 2.31,
P 10.00, S 10.27. C18H33NP2S2Hg requires C 36.64, H 5.64, N
2.37, P 10.49, S 10.86%).
D a l t o n T r a n s . , 2 0 0 3 , 2 7 6 1 – 2 7 6 6
2765

View Article Online
13 R. C. Mehrotra, R. Bohra and D. P. Gaur, Metal β-Diketonates and
Allied Derivatives, Academic Press, London, 1978.
genoimidodiphosphinato compounds are excellent candidates
as molecular single-source precursors for the preparation of
mercury chalcogenide solid-state materials
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Acknowledgements
We would like to thank Mr J. Friend for experimental assist-
ance. This work was supported by the Engineering and Physical
Sciences Research Council.
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