Para-Functionalised Molybdenum Aryl-Imido Complexes [Mo(NAr)(S2CNEt2)2Cl2] and Diimido Complexes [{Mo(S2CNEt2)2Cl2} 2(μ-1,5-NC10H6N)] and [{Mo(S2)(S2CNEt2)2}2 (μ-p-NC6H4N)]

Article abstract of DOI:10.1016/S0277-5387(98)00419-7

A range of para-substituted aryl-imido complexes [Mo(NAr)(S₂CNEt₂)₂Cl₂] has been prepared upon reaction of [MoO(S₂CNEt₂)₂Cl₂] with substituted anilines. With diamines similar mononuclear complexes result containing a pendant amino group which is deactivated towards further addition of molybdenum. This is attributed to the significant reduction in basicity of the remaining amine functionality upon coordination of the first to the electron-deficient molybdenum(VI) centre, and suggests that the two centres communicate strongly via the π-conjugated organic linking group. Diimido-bridged [{Mo(S₂CNEt₂)Cl₂}₂(μ-1,5-NC ₁₀H₆N)] was isolated from the reaction with naphthalene-1,5-diamine, while reaction of [MoO₂(S₂CNEt₂)₂] with para-phenylene diisocyanate afforded [{Mo(S₂)(S₂CNEt₂)₂} ₂(μ-p-NC₆H₄N)].

Full text of DOI:10.1016/S0277-5387(98)00419-7

Polyhedron 18 (1999) 1221–1227
Para-Functionalised Molybdenum Aryl–Imido Complexes
[Mo(NAr)(S2CNEt2)2Cl2] and Diimido Complexes
[hMo(S2CNEt2)2Cl2j2(m-1,5-NC10H6N)] and
[hMo(S2)(S2CNEt2)2j2 (m-p-NC6H4N)]
*
Graeme Hogarth , Tim Norman, Simon P. Redmond
Chemistry Department, University College London, 20 Gordon Street, London, WC1H 0AJ, U.K.
Received 24 August 1998; accepted 17 November 1998
Abstract
range of para-substituted aryl–imido complexes [Mo(NAr)(S2CNEt2)2Cl2] has been prepared upon reaction of
A
[MoO(S2CNEt2)2Cl2] with substituted anilines. With diamines similar mononuclear complexes result containing a pendant amino group
which is deactivated towards further addition of molybdenum. This is attributed to the significant reduction in basicity of the remaining
amine functionality upon coordination of the first to the electron-deficient molybdenum(VI) centre, and suggests that the two centres
communicate strongly via the p-conjugated organic linking group. Diimido-bridged [hMo(S2CNEt2)Cl2j2(m-1,5-NC10H6N)] was isolated
from the reaction with naphthalene-1,5-diamine, while reaction of [MoO2(S2CNEt2)2] with para-phenylene diisocyanate afforded
[hMo(S2)(S2CNEt2)2j2(m-p-NC6H4N)].
1999 Elsevier Science Ltd. All rights reserved.
1. Introduction
mediate formation of monoimido complexes with pendant
isocyanate functionalities, suggesting that coordination of
the first imido group leads to activation of the second
towards further oxidative-addition.
Interest in the chemistry of the imido ligand continues
unabated [1]. While a wide-range of synthetic approaches
to this class of complex have been established, use of
amines as the imido source is most appealing as their
variety and easy accessibility offer an almost unlimited
potential for imido functionalisation. One of our recent
research goals has been the preparation of diimido-bridged
complexes in which metal centres are linked via a strongly
p-conjugated diimido ligand, such that there is potential
for strong electronic communication between the two [2].
Such complexes are relatively rare, although a number of
para-phenylene diimido complexes have been reported
[2–10]. Our strategy has been to vary the p-conjugated
organic moiety linking the imido metal centres together
and investigate the effects that this has on the communica-
tion between metal centres. In this respect, we have
prepared a wide-range of tungsten(IV) diimido-bridged
complexes of the type [hW(CO)Cl2(Ph2PMe)2j2(N–link–
N)], via oxidative-addition of two equivalents of
[WCl2(Ph2PMe)4] to diisocyanates [2,11]. It is noteworthy
that in this system no evidence is found for the inter-
While the oxidative-addition of diisocyanates to
[WCl2(Ph2PMe)4] afforded a simple clean route to tung-
sten(IV) diimido-bridged complexes, it was restricted with
respect to the range of commercially available or easily
prepared diisocyanates. Thus, in extending our studies to
the molybdenum(VI) centre, we looked for simple prepara-
tions of such complexes which utilised amines. One such
synthesis is that developed by Minelli and coworkers for
the
preparation
of
aryl–imido
via
complexes
of
[Mo(NAr)(S2CNEt2)2Cl2]
reaction
[MoO(S2CNEt2)2Cl2] with anilines in methanol [12]. This
synthetic route to substituted imido complexes is especially
appealing as the precursor oxo-complex is easily prepared,
in high yield, from inexpensive starting materials. Herein
we describe our attempts to prepare diimido-bridged
complexes via this route utilising aromatic diamines. Two
new diimido-bridged complexes of molybdenum(VI) have
been prepared and characterised, including the first naph-
thalene-bridged complex of this type. We have also,
however, noted for other aromatic diamines a significant
and general deactivation of the pendant amino function-
*
Corresponding author. E-mail: G.HOGARTH@UCL.AC.UK
0277-5387/99/$ – see front matter
PII: S0277-5387(98)00419-7
1999 Elsevier Science Ltd. All rights reserved.

1222
G. Hogarth et al. / Polyhedron 18 (1999) 1221–1227
ality upon coordination of the first to the electron-deficient
molybdenum(VI) centre, an effect which suggests that the
nitrogen lone-pair is significantly delocalised in these
systems.
previously prepared the ortho isomer of 2a, namely [Mo(o-
NC6H4NH2)(S2CNEt2)2Cl2] via the same preparative
route and spectroscopic data are similar [12]. The un-
coordinated amine was clearly seen as a broad resonance at
d 4.27 in the 1H NMR spectrum, while in the mass
spectrum peaks associated with loss of one and two
chlorides were evident. Other para-phenylene diamines
reacted with [MoO(S2CNEt2)2Cl2] in an analogous fash-
ion leading to the formation of complexes 2b–g in
moderate yields. Most were oily red solids and in many
cases we failed to isolate analytically pure solids.
2. Results and discussion
2.1. Para-substituted complexes 1a–c
Our initial experiments were aimed at extending Minel-
li’s synthesis of molybdenum(VI) aryl–imido complexes
to simple para-substituted derivatives. These proved suc-
cessful, for example, addition of para-iodoaniline to a
suspension of yellow [MoO(S2CNEt2)2Cl2] in methanol
resulted in the slow formation of an orange solution, from
which a yellow precipitate was deposited. Dissolution of
the latter in dichloromethane and addition of light-petro-
leum resulted in the isolation of [Mo( p-NC6H4I)(S-
2CNEt2)2Cl2] 1a as yellow crystals in 68% yield. The
beige para-nitro 1b (54%) and orange para-di-
methylamino 1c (46%) complexes were prepared in an
analogous fashion, but being more soluble, did not precipi-
tate from solution. Characterisation was straight-forward,
each displaying two doublets in the aromatic region of the
1H NMR spectrum, that shifted to higher-field being
associated with the aromatic protons adjacent to the imido
With asymmetric diamines mixtures of isomers are
potentially possible. For 2b, 2f–g, however, only a single
isomer was observed by 1H NMR spectroscopy, being
assigned on the basis of the chemical shift of the uncou-
pled proton(s) adjacent to the substituent on the aryl ring.
For example, in 2b this appears as a singlet at d 6.47, the
high-field shift being indicative of its close–proximity to
the free amine group. Thus, here the more sterically
hindered amine has reacted preferentially. In contrast, 2f is
assigned as the isomer in which the least hindered amine
has reacted since the proton adjacent to the nitro group
appears at d 8.19. This may be an electronic effect as the
nitro group will deactivate the amine ortho to it. Assign-
ment of 2g is less ambiguous with the aryl protons
appearing as a singlet at d 7.39. This can be compared to
their chemical shift of d 6.60 in the free amine, suggesting
that they are now located away from the molybdenum(VI)
centre.
functionality.
A number of related seven-coordinate
molybdenum(VI) complexes have previously been char-
acterised crystallographically [12–14] and the imido ligand
always occupies an axial site.
2.2. Para-Substituted phenylene amine complexes 2a–g
2.3. Biaryl and alkynyl diamine derived complexes 3a–b
Extending this preparative method to prepare para-
phenylene bridged diimido complexes we reacted two
equivalents of [MoO(S2CNEt2)2Cl2] with a range of
commercially available para-phenylene diamines. For all
however, whatever the reaction conditions used, only a
single amine functionality reacted to produce an imido
ligand, the second remaining unreacted. Thus, addition of
The deactivation of the second amine group on para-
phenylene diamines described above is ascribed to the
delocalisation of the nitrogen lone-pair via the p-conju-
gated aryl group to the electron-deficient molybdenum(VI)
centre. This, then, suggests that there is a strong degree of
communication between the metal centre and the pendant
amine as a result of extensive p-conjugation. In order to
further probe the extent of this communication we carried
out reactions of [MoO(S2CNEt2)2Cl2] with more extended
diamines. Addition of biaryldiamines 3,39,5,59-tetra-
para-phenylenediamine
to
a
suspension
of
[MoO(S2CNEt2)2Cl2] in methanol at room temperature,
resulted over 4h in the formation of a deep red solution
with dissolution of all molybdenum–oxo starting material.
After work-up, an oily red solid was isolated which proved
difficult to purify, requiring three recrystallisations from
dichloromethane and light-petroleum, yielding red [Mo( p-
NC6H4NH2)(S2CNEt2)2Cl2] 2a in 63% yield. Minelli has
methylbiphenylene
ybiphenylene
diamine
diamine
and
3,39-dimethox-
suspensions of
to
[MoO(S2CNEt2)2Cl2] in methanol resulted in the isolation
of 3a (56%) and 3b (47%) respectively as oily red solids
after work-up. Attempts to prepare diimido-bridged com-

G. Hogarth et al. / Polyhedron 18 (1999) 1221–1227
1223
plexes upon further reaction of either 3a–b with
[MoO(S2CNEt2)2Cl2] were not successful.
[MoO(S2)(S2CNEt2)2] with para-phenylene diisocyanate
in toluene for 1d. Characterisation was made on the basis
of analytical and spectroscopic data, the aryl protons
1
appearing as a singlet at d 7.06 in the H NMR spectrum.
A number of other products were also isolated from these
reactions but eluded full characterisation. Attempts to
extend the scope of this reaction to other diisocyanates
were generally unsuccessful; in all cases reactions did
occur but product separation and characterisation proved
difficult and was inconclusive.
2.4. naphthalene-1,5-diamine complexes 4a–b
Unlike all reactions detailed above, the outcome of the
reaction
of
naphthalene-1,5-diamine
with
[MoO(S2CNEt2)2Cl2] was dependent upon the relative
stoichiometry of reactants. Thus, addition of one equiva-
lent of the oxo complex resulted in the formation of a
purple solution from which the expected mononuclear
product, [Mo(1,5-NC10H6NH2)(S2CNEt2)2Cl2] 4a, in ca.
1
2.6. Attempted coupling of [Mo(N-p-
C6H4I)(S2CNEt2 )2Cl2 ] 1a to prepare diimido-bridged
complexes
70% yield. Pure samples of 4a were not obtained as H
NMR analysis indicated that it was contaminated with a
second minor and symmetrical species, namely the
diimido-bridged complex 4b. Thus, addition of two equi-
valents of [MoO(S2CNEt2)2Cl2] to the diamine resulted in
the isolation of dimeric [hMo(S2CNEt2)2Cl2j2(1,5-
NC10H6N)] 4b as a purple crystalline solid in 78% yield.
Elemental analysis supported this formulation, while in the
mass spectrum peaks due to successive loss of four
chlorines were observed. The aromatic region of the 1H
NMR spectrum was diagnostic, consisting of three signals
at d 7.48 (t, J 8.6), 7.91 (d, J 8.6) and 8.69 (d, J 8.6). The
formation of diimido-bridged 4b demonstrates that the
second amine is much less deactivated (if at all) than those
in the linear systems.
Thus far the synthetic approach adopted towards the
formation of diimido-bridged complexes has been to link
the metal centres via coordination to the preformed organic
bridge. An alternative strategy involves the linking of
mononuclear imido complexes via carbon–carbon bond
formation. Sharp and co-workers [17] have recently re-
ported the successful application of this strategy. Thus,
oxidation of [(m-dppm)2(CO)2Rh2(m-NPh)] by half an
equivalent of ferricinium resulted in formation of the
benzidine
derivative
[h(m-dppm)2(CO)2Rh2j2(m-p-
NC6H4 –C6H4N)] via coupling of the initially formed
cationic radicals. Our approach is somewhat different,
being based on the well-established Ullman coupling of
bromo- and iodo-arenes [18] which has previously been
successfully applied to the coupling of low-valent metal
centres.
Treatment of yellow 1a with activated copper in di-
methylformamide at high temperatures, resulted in the
formation of a bright red solution and the deposition of
copper iodide. Filtration and removal of solvent left an oily
2.5. Synthesis of [hMo(S2 )(S2CNEt2 )2 j2(m-p-NC6H4 )] 5
1
red solid. The H NMR spectrum was poorly resolved but
In earlier work, we showed that thermolysis of
[MoO2(S2CNEt2)2] with phenylisocyanate yielded the
imido–disulfur complex [Mo(NPh)(S2)(S2CNEt2)2] in
moderate yield [15,16]. This results from both oxo substi-
tution by the imido group, and the formal double sulfur–
carbon bond cleavage of a dithiocarbamate ligand. As an
extension to this chemistry, we were interested in utilising
diisocyanates towards the synthesis of diimido-bridged
molybdenum(VI) complexes. Thermolysis of two equiva-
lents of [MoO2(S2CNEt2)2] with para-phenylene
diisocyanate in toluene for 3d resulted, after chromatog-
raphy, in the isolation of a green diimido-bridged
[hMo(S2)(S2CNEt2)2j2(m-p-NC6H4)] 5 in 26% yield; also
appeared to contain a number of products, all attempts at
separation and purification of which were unsuccessful.
Some evidence for carbon–carbon bond formation was
seen in the mass spectrum, as envelopes of peaks at 646
and 611 mass units relate to the molecular ion of
[Mo(NC6H4 –C6H4NH2)(S2CNEt2)2Cl2] and subsequent
loss of chlorine respectively. Other higher mass peaks
were, however, also observed which should not easily be
accounted for. A further coupling reaction was attempted
between two equivalents of 1a and para-diiodo benzene,
which again lead to the formation of an oily red solid.
Here, the mass spectrum contained an envelope of peaks at
1116 mass units, corresponding to diimido-bridged ter-
prepared
(18%
yield)
upon
thermolysis
of
phenyl
complex
[hMo(S2CNEt2)2Cl2j(m-p-NC6H4 –

1224
G. Hogarth et al. / Polyhedron 18 (1999) 1221–1227
1
C6H4 –C6H4N)] after loss of two chlorines. Again, the H
NMR spectrum was uninformative and all attempts to
isolate a pure product were unsuccessful.
while further, the mono-substituted complex was not
observed. Such an activation might be expected as the
delocalisation of electron density away from the isocyanate
will render it more susceptible to nucleophilic attack by the
a second metal-bound oxo moiety.
These results suggest that, at least to some extent,
carbon–carbon bond formation may occur under these
conditions. Reactions are not, however, clean and thus it is
not a suitable synthetic method towards the preparation of
high-valent diimido-bridged complexes. The contrast be-
tween the high yield coupling of free aryl halides and also
those linked to low-valent metal centres is striking. One
explanation of this is that metal reduction may also take
place under the reaction conditions. In support of this, a
preliminary cyclic voltammetry study of 1a revealed an
irreversible reduction at 0.7 V [19], a value similar to that
of the Cu(0)/Cu(I) couple. Thus, it appears that reduction
of the metal centre and the reductive-coupling of the aryl
iodide are in competition.
4. Experimental
All reactions were carried out using standard schlenk
techniques under a nitrogen atmosphere, but sample sepa-
ration and purification were carried out in air. Unless
otherwise stated in the text, substituted anilines, diamines
and para-phenylene diisocyanate were purchased from
standard suppliers and used as supplied. Molybdenum–oxo
complexes
[MoO(S2CNEt2)2Cl2]
[21],
[MoO2(S2CNEt2)2] [21] and [MoO(S2)(S2CNEt2)2] [22]
were prepared by literature methods. Chromatography was
carried out using deactivated alumina as the stationary
phase. Infrared spectra were recorded on a Nicolet 205
FTIR spectrometer, NMR spectra on Varian XL-200 or
VXR-400 spectrometers and mass spectra on VG 7070
high resolution and VG Analytical ZAB2F spectrometers.
Elemental analyses were performed in house.
3. Conclusions
This study reveals the strong deactivation of an amino-
functionality in a para-site on an arylimido ligand when
bound to the molybdenum(VI) centre. It appears that this
is due to the delocalisation of the amine lone-pair via the
p-conjugated aryl group(s) onto the electron-deficient
metal centre. This in turn suggests that in such high-valent
diimido-bridged complexes, the metal centres communi-
cate strongly through the full p-conjugated linking unit.
Such deactivation may be a general phenomenon. As long
ago as 1964, Chatt and co-workers noted a similar effect
during their pioneering studies on the synthesis of
rhenium(V) imido complexes, which utilised the addition
of anilines to [ReOCl3(PEt2Ph)2]. For example, while
addition of aniline itself afforded the phenylimido complex
[Re(NPh)Cl3(PEt2Ph)2], reaction with para-phenylene
diamine afforded only the para-amino-substituted imido
complex [Re( p-NC6H4NH2)Cl3(PEt2Ph)2] [20]. These
observations are in marked contrast to the oxidative-addi-
tion of isocyanates to the tungsten(II) centre, where the
second isocyanate is activated upon coordination of the
first to a tungsten(IV) centre [11]. At the molybdenum(VI)
centre, it is only with 1,5-naphthalene diamine that a
diimido-bridged complex was isolated. Here the rate of
reaction of both amines to the molybdenum-oxo moiety
appear to be similar, suggesting that little deactivation
occurs through this organic spacer group, despite that fact
that it is fully p-conjugated.
4.1. Synthesis of para-substituted complexes 1a–c
Iodoaniline (0.22 g, 1.00 mmol) in methanol (20 cm3)
was
added
to
a
suspension
of
yellow
[MoO(S2CNEt2)2Cl2] (0.50g, 1.04mmol) in methanol (20
cm3) and the reaction was stirred overnight. A yellow
precipitate formed within an orange solution. The volume
of solvent was reduced to ca. 5 cm3 and the precipitate was
isolated by filtration and washed with light-petroleum.
Slow diffusion of light-petroleum into a saturated dichloro-
methane solution afforded [Mo( p-NC6H4I)(S2CNEt2)2-
Cl2] 1a as small yellow crystals (0.46g, 68%).
1a: IR (KBr) 1560 s, 1521 vs, 1459 s, 1441 m, 1381 w,
1355 m, 1278 s, 1208 m, 1148 m, 1052 w, 1002 s, 817 m
1
cm21; H NMR (CDCl3) d 7.67 (d, J 8.7, 2H, Ar), 7.20 (d,
J 8.7, 2H, Ar), 3.85 (m, 4H, CH2), 3.76 (m, 4H, CH2), 1.35
(t, J 7.2, 6H, CH3), 1.34 (t, J 7.2, 6H, CH3); 13C NMR
(CDCl3) 198.0 (CN), 137.8, 129.1, 113.0, 43.9, 43.0, 12.7,
12.6 ppm; mass spectrum (FAB1) m/z 646 (M12Cl),
611 (M122Cl); Anal: Calc. for Mo1C16H24N3S4Cl2I1,
%C 28.24, %H 3.53, %N 6.11; Found, %C 28.38, %H
3.51, %N 6.11.
A molybdenum(VI) para-phenylene diimido complex,
[hMo(S2)(S2CNEt2)2j2(m-p-NC6H4)] 5, was isolated from
the slow, high temperature, reaction of [MoO2(S2CNEt2)2]
with para-phenylene diisocyanate. Here it is difficult to
say anything about the relative rates of the reactions of the
two ends of the isocyanate. Circumstantial evidence points
to the activation of the second isocyanate. Thus, reaction
with phenylisocyanate proceeds at a similarly slow rate;
An orange solution of para-nitroaniline (0.012 g, 0.084
mmol) in methanol (20 cm3) was added to a suspension of
[MoO(S2CNEt2)2Cl2] (0.040 g, 0.084 mmol) and the
mixture was stirred for 6 h. The solvent was removed
under reduced pressure to give an oily orange–red solid
which was washed with light-petroleum (10 cm3). Dissolu-
tion in dichloromethane (7 cm3) and addition of light-
petroleum (10 cm3) afforded [Mo( p-NC6H4NO2)(S2-

G. Hogarth et al. / Polyhedron 18 (1999) 1221–1227
1225
CNEt2)2Cl2] 1b as a beige powder (0.027g, 54%). Orange
1c (46%) was prepared in a similar fashion after stirring
overnight.
NMR (CDCl3) d 7.60 (d, J 7.6, 1H, Ar), 7.17 (s, 1H, Ar),
6.47 (d, J 7.6, 1H, Ar), 3.84 (m, 10H, CH2 1NH2), 1.75 (s,
3H, CH3), 1.30 (t, J 7.0, 12H, CH3); mass spectrum
(FAB1) m/z 545 (M12Cl), 510 (M122Cl).
1b: IR (KBr) 1626 m, 1587 m, 1528 s, 1458 m, 1345 m,
1279 m, 1205 m, 1151 w, 1096 w, 1075 m, 852 m cm21
;
2c: IR (KBr) 1623 m, 1590 vs, 1521 vs, 1400 m, 1343
1
m, 1158 s, 841 w cm21; H NMR (CDCl3) d 7.57 (d, J
1H NMR (CDCl3) d 8.18 (d, J 9.3, 2H, Ar), 7.59 (d, J 9.3,
2H, Ar), 4.02–3.72 (m, 8H, CH2), 1.43 (t, J 7.3, 6H, CH3),
1.42 (d, J 7.3, 6H, CH3); 13C NMR (CDCl3) 198.4 (CN),
131.1, 127.3, 113.8, 43.7, 42.8, 12.5, 12.6 ppm; mass
spectrum (FAB1) m/z 565 (M12Cl), 528 (M122Cl);
Anal: Calc. for Mo1C16H24N4S4Cl2O2, %C 32.05, %H
4.01, %N 9.34; Found, %C 31.05, %H 3.85, %N 8.56.
1c: IR (KBr) 1627 m, 1566 vs, 1443 m, 1400 s, 1312 s,
1245 m, 1156 m, 1054 w, 1016 m, 967 m, 937 m, 907 m,
8.4, 1H, Ar), 6.38 (d, J 8.4, 1H, Ar), 4.14 (br, 2H, NH2),
3.84 (m, 4H, CH2), 3.74 (m, 4H, CH2), 2.54 (s, 3H, CH3),
1.97 (s, 3H, CH3), 1.33 (t, J 6.9, 12H, CH3); mass
spectrum (FAB1) m/z 562 (M12Cl), 526 (M122Cl);
Anal: Calc. for Mo1C18H30N4S4Cl2.0.5CH2Cl2, %C
34.71, %H 4.84, %N 8.76; Found, %C 34.41, %H 4.89,
%N 9.38.
2d: IR (KBr) 1620 m, 1591 vs, 1551 s, 1342 m, 1160 s,
1
1
798 vw, 708 vw, 632 m, 581 m cm21; H NMR (CDCl3) d
841 w cm21; H NMR (CDCl3) d 7.36 (s, 1H, Ar), 6.29 (s,
7.49 (d, J 9.0, 2H, Ar), 6.46 (d, J 9.0, 2H, Ar), 3.84 (m, 4H,
CH2), 3.74 (m, 4H, CH2), 3.11 (s, 6H, NMe2), 1.33 (t, J
7.0, 12H, CH3); mass spectrum (FAB1) m/z 562 (M12
Cl), 526 (M122Cl).
1H, Ar), 4.70 (br, 2H, NH2), 3.91 (m, 4H, CH2), 3.69 (m,
4H, CH2), 2.43 (s, 3H, CH3), 1.99 (s, 3H, CH3), 1.40 (t, J
7.0, 6H, CH3), 1.29 (t, J 7.0, 6H, CH3); mass spectrum
(FAB1) m/z 562 (M12Cl), 526 (M122Cl).
2e: IR (KBr) 1635 m, 1573 s, 1519 vs, 1456 s, 1438 s,
1380 w, 1355 w, 1312 s, 1296 m, 1277 s, 1204 m, 1149 m,
1092 w, 1075 m, 942 w, 910 s, 847 w, 800 m, 731 w, 713
4.2. Synthesis of para-substituted phenylene amine
complexes 2a–g
1
w, 663 w, 571 w, 557 w cm21; H NMR (CDCl3) d 3.90
A solution of para-phenylenediamine (0.045 g, 0.42
mmol) in methanol (15 cm3) was added to a stirred
suspension of [MoO(S2CNEt2)2Cl2] (0.20 g, 0.42 mmol)
in methanol (20 cm3). The solution turned orange within
seconds and darkened to red over 10 mins. After stirring
for 4h there was no remaining yellow solid. The solvent
was removed under reduced pressure at 408C and a small
amount of unreacted diamine sublimed onto the walls of
the schlenk tube. The oily red solid remaining was
dissolved in dichloromethane (5 cm3) and filtered. Remov-
al of the solvent afforded a dry red solid which was
washed with light-petroleum (10 cm3). Three recrystallisa-
tions from cooled dichloromethane:light-petroleum solu-
(m, 10H, CH2 1 NH2), 2.66 (s, 6H, CH3), 1.96 (s, 6H,
CH3), 1.39 (t, J 7.0, 6H, CH3), 1.29 (t, J 7.0, 6H, CH3);
mass spectrum (FAB1) m/z 590 (M12Cl), 554 (M12
2Cl).
2f: IR (KBr) 1530 vs, 1404 m, 1345 m, 1280 m, 1202
1
m, 1148 m, 1096 m, 853 m cm21; H NMR (CDCl3) d
8.19 (s, 1H, Ar), 7.52 (d, J 9.0, 1H, Ar), 6.88 (d, J 9.0, 1H,
Ar), 3.79 (m, 8H, 3CH2 1 NH2), 3.47 (q, J 6.4, 2H, CH2),
1.37 (t, J 7.0, 6H, CH3), 1.34 (t, J 7.0, 6H, CH3); mass
spectrum (FAB1) m/z 579 (M12Cl), 541 (M122Cl).
2g: IR (KBr) 1611 vs, 1565 w, 1524 vs, 1458 m, 1441
m, 1358 s, 1281 s, 1208 m, 1150 m, 1078 m, 1036 m, 871
1
m, 794 w, 475 w cm21; H NMR (CDCl3) d 7.39 (s, 2H,
tions
afforded
red–orange
crystalline
[Mo( p-
Ar), 4.98 (br, 2H, NH2), 3.84 (m, 4H, CH2), 3.76 (m, 4H,
CH2), 1.35 (t, J 7.2, 6H, CH3), 1.34 (t, J 7.2, 12H, CH3);
mass spectrum (FAB1) m/z 603 (M12Cl), 568 (M12
2Cl); Anal: Calc. for Mo1C16H24N4S4Cl4, %C 30.09, %H
3.76, %N 8.78; Found, %C 30.26, %H 3.91, %N 8.41.
NC6H4NH2)(S2CNEt2)2Cl2] 2a (0.15 g, 63%). Other
complexes were prepared in a similar manner giving; red
2b (47%), red 2c (61%), red 2d (61%), red 2e (56%),
orange 2f (50%), red 2g (59%).
2a: IR (KBr) 1623 m, 1589 vs, 1521 vs, 1442 s, 1380
sh, 1345 s, 1278 s, 1207 m, 1158 s, 1076 m, 1006 w, 840
4.3. Synthesis of biaryl and alkynyl diamine complexes
3a–c
1
m, 600 w, 553 w, 476 w cm21; H NMR (CDCl3) d 7.38
(d, J 8.8, 2H, Ar), 6.45 (d, J 8.8, 2H, Ar), 4.27 (br, 2H,
NH2), 3.83 (m, 4H, CH2), 3.74 (m, 4H, CH2), 1.35 (t, J
7.1, 6H, CH3), 1.33 (t, J 7.3, 6H, CH3); 13C NMR
(CDCl3) 198.2 (CN), 151.7, 144.7, 132.1, 130.7, 113.8,
43.7 (CH2), 42.8 (CH2), 12.5 (CH3) ppm; mass spectrum
(FAB1) m/z 534 (M12Cl), 498 (M122Cl); Anal: Calc.
for Mo1C16H26N4S4Cl2, %C 33.74, %H 4.56, %N 9.90,
%Cl 12.48, %S 22.50; Found, %C 33.72, %H 4.28, %N
9.57, %Cl 12.86, %S 22.53.
Methanol (40 cm3) was added to a mixture of 3,39,5,59-
tetramethylbiphenylene diamine (0.02 g, 0.084 mmol) and
[MoO(S2CNEt2)2Cl2] (0.04 g, 0.084 mmol) and the
suspension was stirred at room temperature for 10h.
Filtration afforded an orange solution from which volatiles
were removed under reduced pressure. The oily red solid
was washed with light-petroleum (10 cm3) and diethyl
ether (10 cm3) and pumped dry to give oily red 3a (0.06g,
56%). Attempts at crystallisation from a range of common
organic solvents was unsuccessful. Oily red 3b (47%) was
prepared in an analogous fashion.
2b: IR (KBr) 1624 w, 1592 w, 1536 vs, 1458 m, 1440
m, 1380 m, 1354 m, 1277 s, 1204 m, 1150 m, 1092 m,
1
1073 m, 946 s, 849 w, 777 w, 576 w, 411 w cm21; H

1226
G. Hogarth et al. / Polyhedron 18 (1999) 1221–1227
3a: IR (KBr) 1624 m, 1590 s, 1518 s, 1507 s, 1457 m,
pressure and the resulting oily green solid was absorbed
onto deactivated alumina via dissolution in dichlorome-
thane and subsequent removal of solvent. Column chroma-
tography afforded a number of bands. Eluting with dich-
loromethane:light-petroleum (3:1) gave a yellow band
which afforded [MoO(m-S)(S2CNEt2)]2 (0.83 g, 13%)
[23]. Eluting with dichloromethane:light-petroleum (4:1)
1438 m, 1380 w, 1336 m, 1276 m, 1205 m, 1160 s, 1074
m, 1003 w, 955 m, 914 w, 836 m, 798 m, 598 vw, 574 vw,
1
554 vw cm21; H NMR (CDCl3) d 7.13 (s, 2H, Ar), 7.04
(s, 2H, Ar), 3.78 (m, 10H, CH2 1NH2), 2.77 (s, 6H, CH3),
2.20 (s, 6H, CH3), 1.32 (t, J 7.0, 6H, CH3), 1.30 (t, J 7.1,
6H, CH3); mass spectrum (FAB1) m/z 667 (M12Cl).
3b: IR (KBr) 1580 s, 1521 vs, 1440 s, 1270 s, 1205 m,
gave
a
green
band
which
afforded
1
1150 m, 809 w cm21; H NMR (CDCl3) d 7.65 (d, J 8.2,
[hMo(S2)(S2CNEt2)2j2(m-p-NC6H4N)] 5 (1.62 g, 26%).
Further purple, orange and red bands were eluted from the
column but were not successfully characterised. Dark
green crystals of 5 were grown upon mixing of methanol
into a saturated dichloromethane solution. When this
solution was left to stand for long periods (over 2d)
substantial decomposition was noted. Complex 5 was also
1H, Ar), 7.00–6.89 (m, 4H, Ar), 6.73 (d, J 8.2, 1H, Ar),
3.89 (s, 3H, OMe), 3.86 (s, 3H, OMe), 3.69 (m, 8H, CH2),
3.01 (br, 2H, NH2), 1.33 (t, J 7.0, 12H, CH3); mass
spectrum (FAB1) m/z 670 (M12Cl), 634 (M122Cl).
4.4. Synthesis of naphthalene-1,5-diamine complexes
4a–b
isolated in 18% yield from
a similar reaction of
[MoO(S2)(S2CNEt2)2] with para-phenylenediisocyanate
in refluxing toluene for 1d.
Addition of methanol (30 cm3) to a mixture of 1,5-
naphthalene diamine (0.04 g, 0.25 mmol) and
[MoO(S2CNEt2)2Cl2] (0.12 g, 0.25 mmol) resulted in the
slow formation of a purple solution over 10h. Filtration
and removal of solvent under reduced pressure afforded a
purple solid which was washed with light-petroleum (10
cm3). Cooling an acetonitrile–diethyl ether solution af-
forded a microcrystalline purple solid (0.084g, 54%) which
consisted predominantly of 4a but was contaminated with
4b. All attempts to separate the two were unsuccessful.
When the same reaction was carried out over 20h with a
0.5 equivalents of the diamine, a similar work-up afforded
pure 4b (0.11 g, 78%).
5: IR (KBr) 1508 s, 1467 m, 1458 m, 1450 m, 1436 s,
1418 w, 1378 w, 1356 w, 1310 m, 1271 m, 1206 m, 1151
m, 1095 m, 1074 m, 1002 w, 978 w, 842 m, 551 w cm21
;
1H NMR (CDCl3) d 7.06 (s, 4H, C6H4), 3.97–3.47 (m,
16H, CH2), 1.45–1.1 (m, 24H, CH3); Anal: calc. for
Mo2C26H44N6S12.0.5CH2Cl2; %C 30.03, %H 4.28, %N
7.93, %S 36.30; Found, %C 30.05, %H 4.58, %N 7.73, %S
36.75; Epc (irrev) 20.91 V, Epa (irrev) 10.61 V.
4.6. Attempted imido coupling reactions
Activated copper (0.05 g, 0.74 mmol) was added to a
yellow solution of 1a (0.10 g, 0.15 mmol) in dmf (20
cm3). Upon heating to 1108C, the solution became red and
a fine grey precipitate of copper iodide was deposited. The
solution was cooled and filtered and volatiles were re-
moved under reduced pressure to give an oily red solid. A
number of attempts were made to wash and triturate the
oily solid but with little success. IR (KBr) 1644 s, 1513 m,
1436 m, 1264 s, 1203 w, 1147 w, 1094 s, 1075 sh, 1051
sh, 1025 s, 1001 s, 804 s, 684 m cm21; mass spectrum
(FAB1) m/z 759, 727, 698, 658, 646, 611, 510. When the
reaction was carried out in the presence of half an
equivalent of para-diiodobenzene a similar red solution
was formed. IR (KBr) 1646 s, 1559 m, 1520 vs, 1439 m,
4a: IR (KBr) 1624 m, 1577 w, 1522 vs, 1457 s, 1439 s,
1393 w, 1379 w, 1354 m, 1275 s, 1263 s, 1204 m, 1149 m,
1094 m, 1075 m, 1045 m, 955 m, 916 m, 848 w, 800 s,
1
721 w, 705 w, 609 vw, 572 vw cm21; H NMR (CDCl3) d
8.06 (d, J 8.4, 1H, Ar), 7.84 (d, J 8.0, 1H, Ar), 7.75 (d, J
8.4, 1H, Ar), 7.29–7.15 (m, 3H, Ar), 6.69 (d, J 8.0, 1H,
Ar), 3.77 (m, 10H, CH2 1 NH2), 1.32 (t, J 7.0, 12H,
CH3); mass spectrum (FAB1) m/z 585 (M12Cl), 549
(M122Cl).
4b: IR (KBr) 1533 vs, 1438 m, 1354 m, 1277 s, 1025 m,
1
933 m, 786 s cm21; H NMR (CDCl3) d 8.69 (d, J 8.6,
2H, Ar), 7.91 (d, J 8.6, 2H, Ar), 7.48 (t, J 8.6, 2H, Ar),
3.78 (m, 16H, 7CH2 1NH2), 3.45 (q, J 7.0, 2H, CH2), 1.32
(t, J 7.0, 12H, CH3), 1.30 (t, J 7.0, 12H, CH3); mass
spectrum (FAB1) m/z 1046 (M12Cl), 1010 (M122Cl);
Anal: Calc. for Mo2C30H46N6S8Cl4, %C 33.33, %H 4.26,
%N 7.78; Found, %C 33.83, %H 4.60, %N 7.48.
1381 w, 1355 m, 1277 s, 1204 m, 1001 m, 823 w cm21
;
mass spectrum (FAB1) m/z 1116, 727, 657, 625, 510,
478, 426, 394.
4.5. Synthesis of [hMo(S2 )(S2CNEt2 )2 j2(m-p-NC6H4N)] 5
Acknowledgements
Heating
a
toluene solution (200 cm3) of
We thank the EPSRC for funding this work and for the
provision of a studentship to S.P.R, and University College
London for partial funding to T.N. Dr David Humphrey is
thanked for his interest in this work and for the preliminary
electrochemical study of 1a.
[MoO2(S2CNEt2)2] (5.30 g, 12.5 mmol) and para-
phenylenediisocyanate (1.0 g, 6.25 mmol) for 3d resulted
in the formation of a green solution after filtering off a
brown precipitate. Volatiles were removed under reduced

G. Hogarth et al. / Polyhedron 18 (1999) 1221–1227
1227
Lee, R.L. Mallors, T. Norman, S.P. Redmond, Manuscript in
preparation.
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