Dithiocarbamate complexes of trivalent aluminium and gallium via metal hydrides

Article abstract of DOI:10.1016/S0020-1693(99)00480-6

Reaction of the thiurams [R₂NC(=S)S]₂ (R = Me, Et, Bz) with the trimethylamine complexes of alane (AlH₃) and gallane (GaH₃) results in the high yield production of the tris-dithiocarbamate complexes [M(S₂CNR₂)₃] (M = Al, Ga) formed via the reductive cleavage of the S-S bond. Transmetallation reactions of [(Et₂O)(k)·AlH₃](n) with.[M'(S₂CNEt₂)(n)] (M' = As, Sb, n = 3, M'= Se, n = 2) also result in the synthesis of [Al(S₂CNEt₂)₃] in high yield. A number of these complexes have been structurally characterised: [Al(S₂CNEt₂)₃] (1), isomorphous with its chromium(III) analogue, belonging to the monoclinic P2₁/n, Z = 4, form of the [M(S₂CNEt₂)₃] family; Al-S are 2.377(6)-2.390(6) A?, similar to values previously established for [Al(S₂CNMe₂)₃]·CH₂Cl₂, which is isostructural with its Ga analogue, 3, (triclinic P1?, Z = 2), for which Ga-S are 2.418(2)-2.449(2) A? solvent···tris-dithiocarbamate interactions in these species appear to be of negligible significance. Al-S are anomalously long cf. Ga-S in counterpart complexes ca. 2.37, 2.44 A, Al, Ga-OH₂ in their alums being 1.877(3), 1.944(3) A?. These observations are reinforced by studies of [M(S₂CNBz₂)₃], M = Al, Ga, 2, 5, monoclinic P2₁, Z = 4, isomorphous with previously reported M = Fe, Co, Ir complexes, and of orthorhombic Fdd2 [Ga(S₂CNEt₂)₃]·2CHCl₃, 4, in which the molecule lies on a crystallographic 2-axis, the hydrogen atoms of the chloroform molecules being wedged between the sulfur atoms of the pairs of ligands. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00480-6

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Inorganica Chimica Acta 300–302 (2000) 56–64
Dithiocarbamate complexes of trivalent aluminium and gallium
via metal hydrides
Philip C. Andrews a, Stacey M. Lawrence c, Colin L. Raston a,*, Brian W. Skelton b,
Vicki-Anne Tolhurst a, Allan H. White b
a Department of Chemistry, Monash Uni6ersity, Clayton, Melbourne, Victoria 3168, Australia
b Department of Chemistry, Uni6ersity of Western Australia, Nedlands, WA 6907, Australia
c School of Science and Technology, Griffith Uni6ersity, Nathan, Brisbane Queensland 4101, Australia
Received 17 June 1999; accepted 19 October 1999
Abstract
Reaction of the thiurams [R2NC(ꢀS)S]2 (R=Me, Et, Bz) with the trimethylamine complexes of alane (AlH3) and gallane
(GaH3) results in the high yield production of the tris-dithiocarbamate complexes [M(S2CNR2)3] (M=Al, Ga) formed via the
reductive cleavage of the SꢁS bond. Transmetallation reactions of [(Et2O)k·AlH3]n with [M%(S2CNEt2)n] (M%=As, Sb, n=3,
M%=Se, n=2) also result in the synthesis of [Al(S2CNEt2)3] in high yield. A number of these complexes have been structurally
characterised: [Al(S2CNEt2)3] (1), isomorphous with its chromium(III) analogue, belonging to the monoclinic P21/n, Z=4, form
,
of the [M(S2CNEt2)3] family; AlꢁS are 2.377(6)–2.390(6) A, similar to values previously established for [Al(S2CNMe2)3]·CH2Cl2,
(
,
which is isostructural with its Ga analogue, 3, (triclinic P1, Z=2), for which GaꢁS are 2.418(2)–2.449(2) A; solvent···tris-dithio-
carbamate interactions in these species appear to be of negligible significance. AlꢁS are anomalously long cf. GaꢁS in counterpart
,
,
complexes ca. 2.37, 2.44 A, Al, GaꢁOH2 in their alums being 1.877(3), 1.944(3) A. These observations are reinforced by studies
of [M(S2CNBz2)3], M=Al, Ga, 2, 5, monoclinic P21, Z=4, isomorphous with previously reported M=Fe, Co, Ir complexes, and
of orthorhombic Fdd2 [Ga(S2CNEt2)3]·2CHCl3, 4, in which the molecule lies on a crystallographic 2-axis, the hydrogen atoms of
the chloroform molecules being wedged between the sulfur atoms of the pairs of ligands. © 2000 Elsevier Science S.A. All rights
reserved.
Keywords: Crystal structures; Aluminium complexes; Gallium complexes; Dithiocarbamate complexes
namic parameters for dynamic processes throughout
the molecule. Symmetrical species of the above form
are also found for some closed-shell main group metal
ions. The most extensively studied are the heavier triva-
lent species of Group 13, only a few of which have been
structurally characterised in the solid state, and almost
all synthesised via the facile metathetical exchange reac-
tion of the metal halide with the hydrated parent
sodium dithiocarbamate. This method depended on the
stability and ease of handling of the metal chloride and
the subsequent dithiocarbamate derivative. The lattice
water molecules in Group 1 dithiocarbamate salts are
difficult to remove so that the resulting metal dithiocar-
bamate species must be stable to both hydrolysis and be
able to be formed via sodium hydroxide elimination, if
the metal halide first reacts with the entrained water
molecules to form the metal hydroxide.
1. Introduction
The N,N-disubstituted dithiocarbamate species
[−S2CNR2] in its symmetrical chelating mode is one of
the classical anionic bidentate ligands for which arrays
of model complexes of bis(bidentate)metal(II) and tris(-
bidentate)metal(III) form are found, with D2h and D3
core symmetry respectively having been extensively
defined by numerous structural, magnetic, and spectro-
scopic studies [1]. Its unique bonding characteristics,
and the potential for systematic symmetrical or unsym-
metrical variation in the organic substituents R, R%,
further offer scope for accessing kinetic and thermody-
* Corresponding author. Tel.: +61-3-9905 4593; fax: +61-3-9905
4597.
E-mail address: c.l.raston@sci.monash.edu.au (C.L. Raston)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00480-6

P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
57
It is not surprising therefore that those Group 13
complexes authenticated by single crystal X-ray diffrac-
tion are weighted towards the heavier metals, In and Tl,
any further light that its structure determination might
shed on the nature of possible solvent interactions
associated with the anomalous, temperature-dependent
proton NMR spectrum found for the analogous
[Co(S2CNEt2)3] system in deuterochloroform but not
other solvents [11]. While the structure determination of
2[Ru(S2CN(CH2)4O)3]·5CHCl3 remains a useful pointer
as to a possible cause of this anomaly [11,12], the
chloroform solvate of [Ga(S2CNEt2)3] may provide a
more direct analogy, with its structure now more read-
ily accessible with modern techniques.
i
viz. [M(S2CNR2)3], M=In, R=Et [2], Pr [3]; NR2=
pyrrolyl (=C5H5N) [3], pentamethylene (‘pyrrolidyl’)
(ꢀC5H10N) [4], M=Tl, R=Me [5], Et [6], while for
M=Al, Ga only one example is known for each metal,
M=Al, R=Me [7]; M=Ga, R=Et [2]. The gallium
derivative is formed from the metathetical exchange
reaction of the trichloride and the sodium salt of the
ligand in aqueous solution; however, this is not possible
for Al due to the relative strength of the AlꢁO bond,
meaning that the hydroxide is unreactive and that once
formed [Al(S2CNR2)3] is susceptible to hydrolytic at-
tack of the AlꢁS bonds. As such, [Al(S2CNMe2)3] has
only been prepared via the insertion of carbon disulfide
into the AlꢁN bonds of the aluminium amide,
[Al(NMe2)3].
Herein we wish to report new, high yielding, syn-
thetic routes to the homoleptic (trivalent) aluminium
and gallium dithiocarbamates, involving Lewis base
complexes of alane [L·AlH3]n and gallane, [L·GaH3].
The first method involves the reductive cleavage of the
SꢁS bonds in the parent thiuramdisulfides [R2NC-
(ꢀS)S]2, leading to the synthesis of [Al(S2CNEt2)3] (1),
[Al(S2CNBz2)3] (2), [Ga(S2CNMe2)3]·CH2Cl2 (3),
[Ga(S2CNEt2)3]·2CHCl3 (4), and [Ga(S2CNBz2)3] (5)
(Bz=PhCH2) which have been structurally character-
ised. Secondly, [Al(S2CNEt2)3] (1) has also been ob-
tained from transmetallation reactions of [L·AlH3]n
with [M%(S2CNEt2)n] (n=3, M%=Sb, As: n=2, M%=
Se).
2. Experimental
All reactions and compound manipulations were per-
formed under inert atmosphere conditions (Ar gas)
using standard Schlenk techniques. All solvents were
dried by reflux over Na/K alloy prior to use.
Na(S2CNR2)·(H2O)n (n=2 or 3), LiAlH4, SbCl3, AsCl3,
SeO2 (for use in synthesis of Na2SeS4O6) were pur-
chased from Aldrich. SbCl3 was purified by sublimation
prior to use with all other chemicals used as received.
The dimethyl, diethyl and dibenzyl thiuramdisulfides
were synthesised according to a general literature
procedure [14] and water free [As(S2CNEt2)3],
[Sb(S2CNEt2)3] and [Se(SC2NEt2)2] synthesised by vari-
ations on literature procedures [15]. All NMR spectra
were recorded on a Bruker AM300 MHz spectrometer
or Varian Mercury 200 MHz and are referenced to the
deuterated solvent used.
The present study provides the opportunity to secure
a number of historical loose ends in the field:
2.1. Syntheses of tris(N,N-diethyldithiocarbamato)-
aluminium(III), Al(S2CNEt2)3 (1)
(i) A single crystal X-ray study of [Al(S2CNMe2)3]·
,
CH2Cl2 has been reported [7], giving ŽAlꢁS 2.396 A;
2.1.1. Method (i)
given that in [M(OH2)6]3+ in various caesium a-alums,
A cooled yellow toluene solution of [Sb(S2CNEt2)3]
(3.5 mmol, 1.98 g) was added to an Et2O (20 ml)
solution of [(Et2O)k·AlH3]n (3.5 mmol) at −78°C. The
reaction mixture was stirred and allowed to warm
slowly over 4 h to room temperature. Over this time the
solution colour changed from yellow to colourless.
Above 30°C a grey solid formed with visible gas evolu-
tion and elemental antimony coating the flask. Filtra-
tion gave a clear, colourless solution. Et2O was
removed in vacuo and small colourless crystals of 1
obtained at 4°C. (Yield 0.94 g, 71%).
,
MꢁO are 1.877(3) (Al), 1.873(3) (Co), 1.944(3) A (Ga)
[8], it is remarkable that that AlꢁS distance more
,
closely resembles ŽGaꢁS in [Ga(S2CNEt2)3] (2.436 A)
rather than ŽCoꢁS in [Co(S2NR2)3], R=Me [9], Et
,
[10] (2.26(4), 2.26(7) A), a phenomenon deserving of
confirmation in an independent system.
(ii) If a similar distance for AlꢁS were to be ob-
served in [Al(S2CNEt2)3], its position in the wide-rang-
ing [M(S2CNEt2)3] C2/c//P21/a//A2/a structural
hierarchy would be of interest, such a value placing it
close to the C2/c//P21/a transition point.
(iii) In the course of the earlier study of unsolvated
[Ga(S2CNEt2)3] [2], it was observed that that compound
readily formed large crystals as a chloroform solvate; at
that time the material, desolvating rapidly under ambi-
ent conditions, was difficult of determination and the
then more desirable unsolvated form was successfully
crystallised from a different solvent. Nevertheless, the
chloroform solvate remained of interest in respect of
2.1.2. Method (ii)
A cooled yellow toluene solution of [As(S2CNEt2)3],
(1.90 mmol, 0.94 g) was added to an Et2O (20 ml)
solution of [(Et2O)k·AlH3]n (1.9 mmol) at −78°C. The
reaction mixture was stirred and allowed to warm
slowly over 4 h to room temperature. Over this time the
solution colour changed from yellow to colourless.
Above 0°C a brown suspension formed with visible gas

58
P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
evolution and elemental arsenic coating the flask. In
vacuo removal of Et2O followed by filtration gave a clear
colourless solution from which a moderate yield of small
colourless crystals of 1 were obtained at −25°C. (Yield
0.41 g, 58%).
ml) solution of [Me2NC(ꢀS)S]2 (2.1 mmol, 0.50 g). The
reaction mixture was stirred overnight with the yellow
colour disappearing to leave a white precipitate. Et2O was
removed in vacuo and CH2Cl2 (15 ml) added causing
immediate gas evolution and giving a pale yellow colour
to the subsequent solution. On filtration and cooling to
−25°C a crop of colourless crystals of 3 were obtained
2.1.3. Method (iii)
1
(Yield 0.4 g, 68%). M.p. 251–253°C (orange melt); H
[Me3N·AlH3]2 (4.2 mmol, 0.37 g) was dissolved in Et2O
(30 ml) and cooled to −78°C. [Se(SC2NEt2)2] (6.3 mmol,
2.3 g) was added slowly as a solid resulting in an orange
coloured suspension. Gas evolution was visible at this
point. The reaction mixture was stirred and allowed to
warm to room temperature. In doing so the colour of the
solution became less orange, then slightly violet and
finally light brown. Et2O was removed in vacuo and thf
(15 ml) added and filtered to give a clear colourless
solution. Over 4 weeks at −25°C a crop of small
colourless crystals of 1 were grown alongside an amor-
phous white solid. (Yield 0.48 g, 31%). M.p. 256–258°C
NMR (300 MHz, CD2Cl2, 25°C): l 4.25 (2H, s, CH2Cl2)
2.48 (18H, s, CH3). Found: C, 24.7; H, 4.1; N, 9.6.
C9H18GaN3S6 (desolvated) requires: C, 24.1; H, 4.0; N,
2.8%.
2.4. Synthesis of tris(N,N-diethyldithiocarbamato)-
gallium(III)·bis(chloroform) sol6ate, [Ga(S2CNEt2)3·
2CHCl3] (4)
A chilled Et2O (30 ml) solution of Me3N·GaH3 (3.24
mmol, 0.43 g) was added to a cold (0°C) yellow Et2O (20
ml) solution of [Me2NC(ꢀS)S]2 (4.86 mmol, 1.45 g). On
addition a white precipitate immediately formed which
subsequently dissolved on warming to room temperature.
After stirring for 2 h Et2O was removed in vacuo and
CHCl3 (15 ml) added causing immediate gas evolution
and giving pale yellow colour to the subsequent solution.
On filtration and cooling to −25°C a crop of colourless
crystals of 4 were obtained. (Yield 1.51 g, 62%) M.p.
1
(orange melt and gas evolution); H NMR (300 MHz,
C7D8, 25°C): l 3.29 (3H, q, CH3), 0.78 (2H, t, CH2); 13
C
NMR (75.5 MHz, C7D8, 25°C): l 48.5 (CH3), 12.1 (CH2).
1H NMR (300 MHz, CD2Cl2, 25°C): l 4.01 (3H, q, CH3,
J=0.03 Hz), 1.37 (2H, t, CH2, J=0.02 Hz); 13C NMR
(75.5 MHz, CD2Cl2, 25°C): l 201.1 (qC), 48.9 (CH3), 12.3
1
(CH2). H NMR (300 MHz, CDCl3, 25°C): l 3.78 (3H,
q, CH3, J=0.03 Hz), 1.26 (2H, t, CH2, J=0.02 Hz); 13
C
1
239–240°C; H NMR (300 MHz, CDCl3, 25°C): l 3.74
NMR (75.5 MHz, CDCl3, 25°C): l 200.5 (qC), 48.4
(CH3), 12.3 (CH2). Found: C, 37.9; H, 6.5; N, 8.9.
C12H30AlN3S6 requires: C, 38.2; H, 6.4; N, 8.9%.
(2H, q, CH2, J=0.025 Hz) 1.26 (3H, t, CH3, J=0.025
Hz); 13C NMR (75.5 MHz, CDCl3, 25°C): l 200.8 (qC),
49.5 (CH2), 12.2 (CH3). Found: C, 36.1; H, 5.6; N, 8.1.
C15H30GaN3S6 (desolvated) requires: C, 35.0; H, 5.8; N,
7.8%.
2.2. Synthesis of tris(N,N-dibenzyldithiocarbamato)-
aluminium(III), [Al(S2CNBz2)3] (2)
2.5. Synthesis of tris(N,N-dibenzyldithiocarbamato)-
gallium(III), [Ga(S2CNBz2)3] (5)
A colourless solution of [Me3N·AlH3]2 (0.09 g, 1.01
mmol) in toluene (ca. 15 ml) was gradually added to a
yellow solution of [Bz2NC(ꢀS)S]2 (1.04 g, 1.91 mmol) in
toluene (ca. 35 ml) at room temperature. Gas evolution
was observed. The resulting yellow solution was allowed
to stir at room temperature for 15 h whereupon it was
filtered and the solvent volume reduced in vacuo (ca. 15
ml). Recrystallisation from toluene at room temperature
afforded cream prismatic crystals (Yield 0.47 g, 55%).
A colourless solution of [Me3N·GaH3] (0.11 g, 0.83
mmol) in toluene (ca. 10 ml) was gradually added to a
yellow solution of [Bz2NC(ꢀS)S]2 (0.61 g, 1.12 mmol) in
toluene (ca. 20 ml) at room temperature. Gas evolution
was observed. The resulting yellow solution was allowed
to stir at room temperature for 16 h whereupon it was
filtered and the solvent volume reduced in vacuo (ca. 15
ml). Recrystallisation at room temperature afforded
cream prismatic crystals of 5 (Yield 0.45 g, 69%). M.p.
1
M.p. 171–173°C (orange melt). H NMR (200 MHz,
C7D8, 25°C): l 7.16–7.03 (5H, m, C6H5), 4.81 (2H, s,
CH2); 13C NMR (50.3 MHz, C7D8, 25°C): l 140.4, 138.3,
132.2–130.4 (m, C6H5), 58.1 (CH2). Found: C, 62.5; H,
5.4; N, 5.1. C45H42AlN3S6 requires: C, 64.0; H, 5.0; N,
5.0%.
1
216–217°C (decomp. to orange melt); H NMR (200
MHz, C6D6, 25°C): l 7.17–7.13, 7.05–7.01 (5H, m,
C6H5), 4.80 (2H, s, CH2); 13C NMR (50.3 MHz, C6D6,
25°C): l 206.6, 135.2, 129.0, 128.3, 128.0 (C6H5), 56.5
(CH2); Found: C, 61.0; H, 4.7; N, 4.9. C45H42GaN3S6
requires: C, 60.9; H, 4.8; N, 4.7%.
2.3. Synthesis of tris(N,N-dimethyldithiocarbamato)-
gallium(III) dichloromethane monosol6ate,
[Ga(S2CNMe2)3·CH2Cl2] (3)
2.6. Structure determinations
A chilled Et2O (10 ml) solution of Me3N·GaH3 (1.37
mmol, 0.18 g) was added to a cold (0°C) yellow Et2O (20
Unique room-temperature diffractometer data sets
,
(monochromatic Mo Ka radiation, u=0.71073 A,

P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
59
,
2qmax=50°, 2q/q scan mode; Tꢀ295 K) were mea-
sured on capillary-mounted specimens yielding N inde-
pendent reflections, No with I\3|(I) being considered
‘observed’ and used in the full-matrix least-squares
refinements after Gaussian absorption correction. An-
isotropic thermal parameter forms were refined for the
non-hydrogen atoms, (x, y, z,Uiso)H being included at
estimated values; difference map residues were mod-
elled as appropriate in terms of CH2Cl2 or CHCl3
solvent. Conventional residuals R, Rw (statistical
weights, derivative of |2(I)=|2(Idiff)+0.0004 |4(Idiff))
are quoted at convergence. Neutral atom complex scat-
tering factors were employed, computation using the
XTAL 3.2 program system [29]. Pertinent results are
given in the Figures and Tables; individual variations in
procedure (etc.) are noted below (‘variata’). Cell and
coordinate settings follow those of previously deter-
mined isomorphs where these exist; present numbering
schemes are such that the ligands are numbered, a,b,c,
followed by 1 or 2 designating association with the
‘upper’ or ‘lower’ triangle of sulfur atoms about the
central metal.
9.174(7), b=9.604(4), c=12.751(8) A, h=75.17(4),
3
,
i=87.64(6), k=82.70(4)°, V=1077 A . Dc (Z=2)=
1.589 g cm−3; F(000)=524. vMo=21.0 cm−1; speci-
men: 0.42×0.32×0.38 mm (capillary); A*min,max=1.64,
1.94. N=3769, No=2993; R=0.042, Rw=0.049.
2.6.2.1. Variata. The complex is isostructural with its
aluminium analogue and was refined in that setting.
The site occupancy of the solvent molecule was set at
unity after trial refinement.
2.6.3. Crystal/refinement data — (4)
[Ga(S2CNEt2)3]. 2CHCl3ꢂC17H32Cl6GaN3S6, Mr=
753.3. Orthorhombic, space group Fdd2 (C , no. 43),
19
26
3
,
,
a=35.46(6), b=18.30(2), c=10.35(1) A, V=6717 A .
Dc (Z=8)=1.490 g cm−3; F(000)=3072. vMo=16.8
cm−1; specimen: 0.50×0.62×0.40 mm (capillary);
A*min,max=1.68, 1.93. N=1554, No=1206; R=0.051,
Rw=0.056 (preferred hand).
2.6.3.1. Variata. As modelled in the present space
group, the solvent is disordered with two sets of chlo-
rine atoms disposed over two sets of sites rotationally
related about H-C, site occupancies set at 0.5 after trial
refinement.
2.6.4. Crystal/refinement data — (2), (5)
[M(S2CN(CH2Ph)2)3]ꢂC45H42MN3S6, M=Al, Ga.
Monoclinic, space group P21 (C22, no. 4), Z=4. (2).
M=Al. −Mr=844.2. a=11.900(2), b=29.953(4),
2.6.1. Crystal/refinement data — (1)
3
,
,
c=12.480(2) A, i=97.69(1)° V=4408 A . Dc=1.272
g cm−3; F(000)=1768. vMo=3.7 cm−1; specimen:
0.50×0.45×0.40 mm; A*min,max=1.13, 1.16. N=7893,
No=4657; R=0.056, Rw=0.057 (both hands).
[Al(S2CNEt2)3]ꢂC15H30AlN3S6, Mr=375.6. Mono-
clinic, space group P21/n (C52h, no. 14, variant), a=
,
14.37(1), b=10.348(9), c=17.14(1) A, i=111.31(4)°,
3
V=2375 A . Dc (Z=4)=1.051 g cm−3; F(000)=808.
,
vMo=6.3 cm−1; specimen: 0.24×0.24×0.32 mm;
A*min,max=1.07, 1.09. N=4422, No=1802; R, Rw=
0.071 (×2).
(5). M=Ga−Mr=887.0. a=11.885(6), b=
3
,
,
29.87(1), c=12.511(3) A, i=97.58(3)° V=4402 A .
Dc=2.427 g cm−3; F(000)=1840. vMo=9.4 cm−1
;
specimen: cuboid, ca. 0.2 mm; A*min,max=1.18, 1.28.
N=7877, No=5394; R=0.046, Rw=0.048 (preferred
chirality).
2.6.1.1. Variata. Ethyl group c was modelled (with
isotropic thermal parameter refinement) as disordered
over two sets of sites, occupancies set at 0.5 after trial
refinement. This complex is isostructural with its
chromium(III) counterpart [16] and was refined in the
same cell and coordinate setting. As in the Cr(III)
structure, ethyl group C(2,3c) was disordered over a
pair of sites, modelled with equal occupancies after trial
refinement. Residuals are high because of the weak
primitive lattice superimposed upon the basically C2/c
array, characteristic of a smaller central metal atom
(e.g. Co) [10]. Caveat: the P21/a cell has similar
dimensions.
2.6.4.1. Variata. These two complexes are isomorphous
and isomorphous with the previously studied M=Co
[10], Fe [17] analogues, and are presented in the same
cell and coordinate setting.
3. Results and discussion
Complexes 1–5 were prepared by the general reac-
tion procedures outlined in Schemes 1 and 2. The
parent thiuramdisulfides were synthesised by known
literature procedures. As noted above the only previ-
ously reported synthesis of an aluminium dithiocarba-
mate compound was of dichloromethane solvated
2.6.2. Crystal/refinement data — (3)
[Ga(S2CNMe)3]·CH2Cl2ꢂC10H20Cl2GaN3S6,
Mr=
1
(
515.3. Triclinic, space group P1 (Ci , no. 2), a=

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P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
In consequence of the limited solubility of the diben-
zyl dithiuram in Et2O, the reaction of [Bz2NC(ꢀS)S]2
with [Me3N·MH3]n (M=Al, Ga) was carried out in
toluene as the solvent. The reaction mixtures were
allowed to stir for approximately 10–16 h at ambient
temperature whereupon they were filtered and the
toluene reduced in vacuo. Crystals of [Al(S2CNBz2)3]
(2) and [Ga(S2CNBz2)3] (5) were obtained at 4°C.
Our current interest in targeting the synthesis of
mixed Group 13/15 and Group 13/16 complexes [18] as
potential binary compounds for thin film deposition
[21] led to an examination of the reactions of
(Et2O)n·AlH3 with [As(S2CNEt2)3], [Sb(S2CNEt2)3] or
[Se(S2CNEt2)2]. However, in all cases, solvent free
[Al(S2CNEt2)3], was the only stable crystalline product
obtained, inclusive of reactions at low temperature.
Moisture free yellow crystals of arsenic and antimony
diethyldithiocarbamates were grown in pre-dried
toluene after preparation in thf via the 1:2 addition of
Na(S2CNR2)·3H2O to M%Cl3 in the presence of Et3N
[15]. [Se(S2CNEt2)2] was synthesised via the reaction of
Na(S2CNEt2)·(H2O)3 with Na2SeS4O6 [15]. Crystals
were obtained from pre-dried toluene and dried in
vacuo.
A toluene solution of [M%(S2CNEt2)3] (M%=Sb, As)
was reacted with a cold (−78°C) solution of preformed
(Et2O)n·AlH3 in Et2O. Transmetallation occurs below
−30°C possibly producing volatile SbH3 or AsH3 as
indicated by the coating of the Schlenk flask by a film
of elemental arsenic or antimony as the hydrides slowly
decompose. [Al(S2CNEt2)3] was crystallised from Et2O/
toluene solution at 4C after filtration. The reaction of
[Me3N·AlH3]2 with [Se(S2CNEt2)2] in Et2O went
through a variety of colour changes — orange, pale
orange, violet, light brown — as the reaction mixture
warmed from −78°C to room temperature. This was
accompanied by visible gas evolution, presumably
SeH2. On removal of Et2O the resulting precipitate was
dissolved in thf. At 4°C this solution produced a mod-
erate yield of crystalline [Al(S2CNEt2)3] and an amount
of white amorphous powder which is yet to be fully
characterised.
[Al(S2CNMe2)3] prepared via the insertion of CS2 into
[(Me2N)3Al] in petroleum ether (40–50°C) followed by
recrystallisation from CH2Cl2. Our synthetic method
exploited the reduction of thiuramdisulfides by Lewis
base complexes of alane and gallane, in a similar man-
ner to the formation of [L·M(ER)3], M=Al, Ga, E=
Se, Te from the same metal hydride and R2E2, and
related compounds [18].
The dimethyl- and diethyl-thiuramdisulfides have
considerable solubility in Et2O and their reaction with
[Me3N·MH3]n (M=Al, n=2, M=Ga, n=1) could be
carried out at low temperature (−78°C) in either Et2O
or toluene, or alternatively in situ with the alane ether-
ate complex, [(Et2O)k·AlH3]n which is formed from the
low temperature stoichiometric addition of H2SO4
(98%) to an ether solution of LiAlH4 [19]. After allow-
ing the reaction mixtures to warm to ambient tempera-
ture and stirring for a further 4–6 h the solutions could
be filtered, volatiles removed and the remaining white
powders recrystallised from either dichloromethane or
chloroform. Thus [Ga(S2CNMe2)3]·CH2Cl2 (3), and
[Ga(S2CNMe2)3]·2CHCl3 (4) were isolated as their re-
spective CH2Cl2 or CHCl3 solvates. It should be noted
though that with [NMe3·AlH3]2 elimination of H2 oc-
curs at room temperature in Et2O; with [Me3N·GaH3]
no gas evolution is evident under the same conditions.
Instead, on removal of the Et2O the white precipitate
which is formed rapidly eliminates H2 on addition of
the CH2Cl2 or CHCl3 at room temperature. The white
precipitate is most likely a Lewis base complex of the
thiuram of gallane formed at the expense of complexa-
tion of Me3N, noting that gallane preferentially binds
to third row elements in contrast to alane, and forms
almost exclusively four-coordinate species [20]. Com-
plexation of alane by the thiuram may be the primary
process in the formation of 1 and 2 with subsequent
facile reduction more favoured due to the greater polar-
isation of the AlꢁH bonds relative to GaꢁH [20].
The aluminium dithiocarbamate complexes are both
air and moisture sensitive with the colourless crystals
slowly becoming opaque on exposure to air. The gal-
lium compounds are, as expected, more stable with no
perceptible decomposition on exposure to air. All of the
compounds melt at high temperature to pale yellow/or-
ange melts with some evidence of gas evolution.
Scheme 1.
1
The H and 13C NMR spectra of compounds 1–5 at
298 K are largely unexceptional with spectra obtained
in C6D6, d8-toluene, CDCl3 and CD2Cl2 all giving the
expected chemical shifts and splitting patterns associ-
ated with respective methyl, ethyl and benzyl groups.
1
Scheme 2.
Low temperature H NMR studies in the range 208–

P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
61
Table 1
Metal atom environments
a
i.d./M/R(/S)
–/Al/Me/CH2Cl2 1/Al/Et
2/Al/Bz
3/Ga/Me/CH2Cl2
4/Ga/Et/CHCl3
5/Ga/Bz
,
Distances (A)
MꢁS(1a)
MꢁS(2a)
MꢁS(1b)
MꢁS(2b)
MꢁS(1c)
MꢁS(2c)
2.404(2)
2.388(2)
2.405(2)
2.398(2)
2.393(2)
2.386(2)
2.908(3)
2.905(2)
2.902(3)
2.383(5)
2.397(6)
2.377(6)
2.387(5)
2.384(6)
2.390(6)
2.894(6)
2.889(6)
2.903(6)
2.370(4), 2.366(4)
2.449(2)
2.418(2)
2.441(2)
2.437(2)
2.428(2)
2.425(2)
2.922(2)
2.916(3)
2.912(2)
2.437(4)
2.389(2), 2.415(2)
2.420(4), 2.409(4)
2.389(3), 2.384(4)
2.373(4), 2.390(4)
2.424(4), 2.410(4)
2.383(3), 2.374(4)
2.913(4), 2.917(4)
2.903(4), 2.895(4)
2.912(3), 2.909(3)
2.484(3), 2.419(2)
2.407(2), 2.440(2)
2.412(2), 2.411(2)
2.461(3), 2.480(2)
2.475(2), 2.391(2)
2.927(3), 2.919(3)
2.913(3), 2.919(3)
2.921(3), 2.921(3)
2.421(4)
2.434(4)
S(1a)···S(2a)(1a%)
S(1b)···S(2b)
S(1c)···S(2c)
2.915(6)
2.910(5)
Angles (°)
S(1a)ꢁMꢁS(2a)(1a%)
S(1b)ꢁMꢁS(2b)
S(1c)ꢁMꢁS(2c)
74.9(1)
74.6(1)
74.9(1)
100.0(1)
96.7(1)
95.6(1)
93.7(1)
96.3(1)
95.3(1)
96.5(1)
93.0(1)
94.3(1)
164.8(1)
164.2(1)
164.2(1)
74.5(2)
74.7(2)
74.9(2)
100.1(2)
98.7(2)
98.9(2)
93.8(2)
94.7(2)
94.6(2)
94.4(2)
93.7(2)
94.1(2)
162.8(2)
163.2(2)
163.2(2)
74.9(1), 75.3(1)
75.1(1), 74.7(1)
74.6(1), 74.9(1)
94.7(1), 93.9(1)
100.2(1), 99.8(1)
95.3(1), 95.5(1)
95.9(1), 96.6(1)
97.12(9), 96.3(1)
89.8(1), 91.9(1)
99.5(1), 99.4(1)
98.2(1), 95.7(1)
90.6(1), 91.0(1)
168.6(2), 169.1(2)
166.5(2), 166.5(2)
157.8(1), 160.4(1)
73.77(6)
73.44(6)
73.76(6)
100.61(7)
96.84(6)
95.78(6)
93.99(7)
97.25(6)
95.74(6)
97.36(6)
93.37(7)
94.67(6)
163.92(6)
163.47(5)
162.98(6)
73.5(1)
73.6(1)
73.78(8), 74.31(8)
74.39(8), 73.74(7)
73.25(8), 73.66(3)
94.30(8), 93.62(8)
101.50(9), 100.66(9)
95.13(8), 95.00(8)
97.29(8), 96.37(8)
98.38(8), 95.63(8)
89.95(8), 91.19(8)
100.02(8), 101.90(8)
98.74(8), 97.10(8)
90.70(8), 92.11(9)
168.69(9), 168.77(9)
165.73(9), 165.52(9)
155.65(8), 159.20(8)
S(1a)ꢁMꢁS(2c)(1b%)
S(1b)ꢁMꢁS(2a)
S(2b)ꢁMꢁS(1c)(2b%)
S(1a)ꢁMꢁS(1b)
S(1b)ꢁMꢁS(1c)
S(1a)ꢁMꢁS(1c)(2b%)
S(2a)ꢁMꢁS(2b)
S(2b)ꢁMꢁS(2c)(1b%)
S(2c)ꢁMꢁS(2a)
100.6(1)
99.6(2)
93.8(1)
95.0(1)
94.6(2)
S(1a)ꢁMꢁS(2b)
S(1b)ꢁMꢁS(2c)(1b%)
S(1c)ꢁMꢁS(2a)
161.4(1)
162.1(1)
a Here the molecule lies on a crystallographic 2-axis; for the angles, the second atom, given in parentheses (number only, primed), is generated
by rotation about that axis. Entries for the A1/Me/CH2Cl2 complex are taken from the data of Ref. [1]. For the R=Bz complexes, the two values
in each entry are for the two independent molecules of the asymmetric unit.
Figure 1. Unit cell contents of [Ga(S2CNMe2)3]·CH2Cl2 (3), projected down a; 20% thermal ellipsoids are shown for the non-hydrogen atoms, in
,
this and subsequent figures, hydrogen atoms where shown having arbitrary radii of 0.1 A.

62
P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
323 K were carried out on [Al(S2CNEt2)3] in d8-toluene
and on [M(S2CNEt2)3] (M=Ga, Al) in CDCl3 in the
range 213–298 K. Taking first the spectra in d8-toluene,
we note that at 273 K the quartet related to the CH3 is
slightly broadened but becomes significantly sharper as
the temperature is raised to 323 K. At the lowest
observed temperature, 208 K, it separates into two
equally intense broad quartets centered on 3.49 and
3.90 ppm with coalescence occurring at 253 K. While
this type of phenomenon has been ascribed to be a
Figure 2. (a) Molecular projection of [Ga(S2CNEt2)3] (4) in association with the pair of (disordered) chloroform solvent molecules, down the
quasi-3 axis; the crystallographic 2-axis lies vertically in the page. (b) Unit cell contents, 4, projected down c.

P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
63
Figure 3. Unit cell contents of [Al(S2CNBz2)3] (2), projected down a.
result of hindered rotation around the CꢁN bond [22] it
is also characteristic of labile tris(dithiocarbamato)
metal(III) species involving rapid unidentate/bidentate
interconversion [5,23] and/or rapid l/u equilibration via
a trigonal prismatic transition state. Only at 208 K are
there indications of the triplet (CH2) beginning to
broaden. In CDCl3 the CH3 quartet splits for the Al
compound at the lowest recording temperature of 213
K, though not into two completely resolved signals.
There is no evidence of splitting for the Ga compound
at this temperature although the signal does broaden,
perhaps indicating a lower coalescence temperature.
when crystals have been obtained. The only trivalent
metal complexes thus studied to date are the complexes
of aluminium(III) (as its dichloromethane monosol-
vate), iron(III) (unsolvated; a spin-crossover system
studied at 25, 150, 295 and 400 K) [5,24] cobalt(III) [4],
and thallium(III) (monohydrate) [5]. All contain
neutral molecular species of quasi-32 symmetry, but,
despite this, no examples of isomorphism are reported,
not surprisingly at least, among the diverse solvation
types; the present gallium(III)/dichloromethane mono-
solvate, 3, isostructural with its aluminium(III)
counterpart, now provides the first such example, one
[Ga(S2CNMe2)3]·CHCl2 aggregate, devoid of crystallo-
graphic symmetry, comprising the asymmetric unit of
the structure. No close interactions are found between
putative solvent hydrogen atom sites and any part of
the [Ga(S2CN)3] molecular core, a feature also true of
the aluminium analogue; unit cell contents are depicted
in Fig. 1 as an example of this structural type.
4. X-ray crystallography
Pertinent bond lengths and angles for compounds
1–5 are presented in Table 1. Despite the appealing
simplicity of the system, relatively few tris(N,N-
dimethyldithiocarbamato)metal(III) complexes, [M-
(S2CNMe2)3], have been characterised by single crystal
X-ray studies. Possible reasons include their relatively
low solubility in common crystallisation solvents, and
the occurrence of twinning among many complexes
Symmetrical unsolvated complexes, [M(S2CNEt2)3],
are more widely characterised, the majority falling
within a monoclinic, Z=4, unit cell, aꢀ14, bꢀ10,
,
cꢀ18 A, iꢀ110 or 118°, C2/c (or variant) for the
,
smaller metal atoms (CoꢁS 2.267, FeꢁS 2.306 A (70 K),

64
P.C. Andrews et al. / Inorganica Chimica Acta 300–302 (2000) 56–64
IrꢁS 2.367 [25]) degraded to P21/a for larger species
(FeꢁS 2.357 (297 K) [17], RuꢁS 2.376 [23c,26] CrꢁS
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,
[Al(S2CNEt2)3] (1) has ŽAlꢁS 2.386 A, in keeping with
its status as a member of the P21/n class, and in
agreement with the previous record of the dimethyl
analogue (see above). Presumably the ‘long’ AlꢁS dis-
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gallium(III) homologues is to be attributed to the status
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concomitant enhanced reactivity. Molecular and cell
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in Ref. [16].
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chloroform disolvate, one half of the complex molecule
(the latter lying with a crystallographic 2-axis passing
through the metal and the NꢁC bond of one ligand)
(Fig. 2(a)) and one solvent molecule making up the
asymmetric unit for the structure; this is a new struc-
.
tural type for [M(S2CNEt2)3], the cell contents being
,
shown in projection in Fig. 2(b). ŽGaꢁS, 2.431 A, is
comparable with the value observed in the unsolvated
parent [3] and the dimethyl substituted/dichloro-
methane solvate analogue reported above. The chloro-
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way; as in 2[Ru(S2CN(CH2)4O)3]·5CHCl3 [13], we find
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,
ligands (H…S (1a, 1b) 2.88, 3.07 A (est.)), reinforcing
the earlier suggestion [11–13] of interactions of that
type as a possible cause of the NMR anomalies found
with some members of the series of complexes.
The complexes [M(S2CN(CH2C6H5)2)3], [M=Al (2),
Ga (5)] are isostructural and crystallise as cream-
coloured prismatic crystals from toluene in the mono-
clinic space group P21. Both complexes have four
monomeric molecules in their unit cells with the asym-
metric units comprised of two discrete such monomers
and, as such, are isomorphous with their M=Co, Fe
counterparts. Core geometries are similar to those of
the other complexes studied in the present work.
Molecular projections for the cobalt analogue are given
in Ref. [10]; unit cell contents
for the type are shown in Fig. 3.
Acknowledgements
We thank the Australian Research Council for finan-
cial support.