Regiospecific influences of phenyl ring substituents in monoimido complexes of tantalum and tungsten and bis imido complexes of molybdenum

Article abstract of DOI:10.1039/b006420n

Imido exchange of [TaCl₃(NCMe₃)(py)2] with 2-/erf-butylaniline in refluxing benzene and crystallisation of the product from CH2C12 gave the anionic complex [Hpy][TaO4(C6H4CMe3-2)(py)] 1. X-Ray structural analysis shows that with the Ta-N-C bond angle at 165.1(5)° two of the tcrt-buly substituent methyl groups sit above two meridional chloro ligands but NMR spectroscopy indicates that the fe/7-butyl group can still rotate in solution. Reaction of isocyanates ArNCO [Ar = C10H7 (naphthyl), C6H4CMer2 or C6H4Ph-2] with VOC14 in refluxing benzene gave [{WC14(NC10H7)} J 2, [{WCl4(NC₆H₄CMe3-2)}J 3, and [{WCl4(NC6H4Ph-2)} J 4 which NMR spectra show convert from two species into one in CDC13. In refluxing toluene, 2-/e/7-butylphenyl isocyanate also forms the metallacyclic amido complex [WCl4{NHC₆H₄(CMe₂CH₂)-2(C,AO}] 5. The d1 complexes [WCl3(NC10H7)(PMe3)2] 6, [VCl3(NC6H4CMe3-2)(PMe3)2] 7, [VCl3(NC₆H₄Ph_-2)(PMe3)2] 8, [WCl3(NC10H7)(PMe2Ph)2] 9 and [WC13(NC10H7)(PMePh2)2] 10 were prepared, and show hindered imido ligand aryl C-N bond rotation. A crystal structure determination of 6 shows the naphthyl ring C-8 proton positioned between a chloro and phosphine ligand. Also prepared to demonstrate hindered aryl C-N bond rotation were the d2 complexes [WCl2(NC10H7)(PMe3)3] 11, [WCl2(NC₆H₄CMe₃-2)(PMe3)3] 12, [WCl2(NC6H4Ph-2)(PMe3)3] 13 and [VCl2(NC10H7)(PMe2Ph)3] 14. Crystal stucture determinations show the /erf-butyl group in 12 located above a chloro ligand and the phenyl group in 13 located between a chloro and phosphine ligand. They also show the methyl and isopropyl substituents in [MoClj(NC6H3Me-2-Pr'-6)2(dme)] 15 form an anti configuration and in [MoCl2(NC6H4CMe3-2)2(dme)] 16 a syn configuration is identified where the Mo-N-C bond angles are determined by steric effects and crystal packing forces. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b006420n

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Regiospecific influences of phenyl ring substituents in monoimido
complexes of tantalum and tungsten and bis imido complexes of
molybdenum
Alastair J. Nielson,*a Mark W. Glenny,b Clifton E. F. Rickardb and Joyce M. Watersa
a Chemistry, Institute of Fundamental Sciences, Massey University at Albany,
Private Bag 102904, North Shore Mail Centre, Auckland, New Zealand
b Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland,
New Zealand
Received 7th August 2000, Accepted 11th October 2000
First published as an Advance Article on the web 28th November 2000
Imido exchange of [TaCl3(NCMe3)(py)2] with 2-tert-butylaniline in refluxing benzene and crystallisation of the
product from CH2Cl2 gave the anionic complex [Hpy][TaCl4(C6H4CMe3-2)(py)] 1. X-Ray structural analysis
shows that with the Ta–N–C bond angle at 165.1(5)Њ two of the tert-butyl substituent methyl groups sit above two
meridional chloro ligands but NMR spectroscopy indicates that the tert-butyl group can still rotate in solution.
Reaction of isocyanates ArNCO [Ar = C10H7 (naphthyl), C6H4CMe3-2 or C6H4Ph-2] with WOCl4 in refluxing
benzene gave [{WCl4(NC10H7)}x] 2, [{WCl4(NC6H4CMe3-2)}x] 3, and [{WCl4(NC6H4Ph-2)}x] 4 which NMR spectra
show convert from two species into one in CDCl3. In refluxing toluene, 2-tert-butylphenyl isocyanate also forms the
metallacyclic amido complex [WCl4{NHC6H4(CMe2CH2)-2(C,N)}] 5. The d1 complexes [WCl3(NC10H7)(PMe3)2] 6,
[WCl3(NC6H4CMe3-2)(PMe3)2] 7, [WCl3(NC6H4Ph-2)(PMe3)2] 8, [WCl3(NC10H7)(PMe2Ph)2] 9 and [WCl3(NC10H7)-
(PMePh2)2] 10 were prepared, and show hindered imido ligand aryl C–N bond rotation. A crystal structure
determination of 6 shows the naphthyl ring C-8 proton positioned between a chloro and phosphine ligand. Also
prepared to demonstrate hindered aryl C–N bond rotation were the d2 complexes [WCl2(NC10H7)(PMe3)3] 11,
[WCl2(NC6H4CMe3-2)(PMe3)3] 12, [WCl2(NC6H4Ph-2)(PMe3)3] 13 and [WCl2(NC10H7)(PMe2Ph)3] 14. Crystal
stucture determinations show the tert-butyl group in 12 located above a chloro ligand and the phenyl group in
13 located between a chloro and phosphine ligand. They also show the methyl and isopropyl substituents in
[MoCl2(NC6H3Me-2-Pri-6)2(dme)] 15 form an anti configuration and in [MoCl2(NC6H4CMe3-2)2(dme)] 16 a syn
configuration is identified where the Mo–N–C bond angles are determined by steric effects and crystal packing forces.
TaCl5 and silylated arylamines8 but we were interested to estab-
Introduction
lish whether imido exchange9 (eqn. 1) could be used to intro-
In co-ordination chemistry it is often difficult to achieve specific
environments if a constrained ligand system is not used. Regio-
specifically to influence sections of a complex it may then be
[TaCl3(NCMe3)(L)2] ϩ ArNH2 →
[TaCl3(NAr)(L)2] ϩ Me3CNH2 (1)
necessary to restrict certain bond rotations so that steric inter-
actions can be localised. In the field of organoimido chemistry,
use of the symmetrically substituted 2,6-di-isopropylphenylimide
ligand has given rise to a variety of bis and tris complexes which
involve low co-ordination numbers.1 Monoimido complexes of
tungsten containing this ligand do not show steric properties
different from those of the unsubstituted phenylimide,2 whereas
attempts to form complexes with 2,6-di-tert-butyl substituents
have been unsuccessful3 and only one complex is known which
contains 2,6-diphenyl substituents.4 Recent work on d2 complexes
of molybdenum containing the mesitylimide ligand (NC6H3Me2
-2,6) shows that free rotation about the imido C–N bond can be
restricted at low temperatures5 but most imido complexes reported
to date lack regiospecific influence. Use of a single sterically
bulky substituent in the 2 position of a phenylimide ring
appears one way of achieving this. There is also the possibility
of unusual complex formation and the observance of M–N–C
bond angles which are directly related to steric interactions of
the substituent with other parts of the molecule.6,7 We report
here the results of studies directed towards assessing how lig-
ands of this type regiospecifically influence molecular structure.
duce a 2-substituted phenylimide, given the ease of preparation
of tert-butylimido complexes of tantalum.10,11 In a series of
preliminary investigations it was found by 13C-{1H} NMR
spectroscopy that [TaCl3(NCMe3)(py)2]11/2-tert-butylaniline
mixtures required refluxing in benzene or toluene to exchange
the imido ligand. This contrasts with the reaction of the d0
titanium complex [TiCl2(NCMe3)(py)3] with 2,6-diisopropyl-
amine where refluxing is not needed.12 When the tantalum
product was recrystallised from CH2Cl2 the analytical data
(Table 1) and NMR spectra (Table 2) were inconsistent with
the expected complex [TaCl3(NC6H4CMe3-2)(py)2]. However
X-ray structural analysis showed that the complex was [Hpy]-
[TaCl4(NC6H4CMe3-2)(py)]ؒCH2Cl2 1 (Fig. 1). Further work is
in progress to establish the role of CH2Cl2 during the crystal-
lisation process. The structure of the anion in 1 is a distorted
octahedron with the py ligand lying trans to the imido function
and the four chloro ligands lying in the equatorial plane.
Selected bond lengths and angles are shown in Table 3. The
imido phenyl ring is rotated so that two tert-butyl substituent
methyls [C(8) and C(10)] lie over Cl(1) and Cl(2) respectively
with the C(8) ؒ ؒ ؒ Cl(1) and C(10) ؒ ؒ ؒ Cl(2) contacts being 3.73
and and 3.77 Å respectively. This positioning appears to have
no effect on the Ta–N bond length [1.779(5) Å] which is
similar to those found in a variety of other imido complexes of
Results and discussion
Monoimidotantalum(V)
Tantalum d0 phenylimido complexes can be prepared from
DOI: 10.1039/b006420n
J. Chem. Soc., Dalton Trans., 2000, 4569–4578
This journal is © The Royal Society of Chemistry 2000
4569

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Table 1 Physical and analytical data
Analysesa(%)
C
Complex
Yield(%)
Colour
H
N
1 [Hpy][TaCl4(C6H4CMe3-2)(py)]b
66
85
70
90
76
79
80
69
61
57
66
80
77
89
63
68
Orange
Brown
Brown
Brown
Dark brown
Brown
Brown
Brown
Brown
Brown
Purple
Purple
Purple
Yellow
Deep red
Purple red
37.2 (36.7)
26.1 (25.7)
24.6 (25.4)
29.4 (29.2)
25.2 (25.4)
30.3 (30.5)
31.6 (31.4)
35.7 (35.5)
43.2 (43.5)
51.6 (52.0)
36.2 (36.6)
33.8 (33.6)
39.1 (38.8)
50.1 (50.4)
52.2 (52.3)
51.6 (52.3)
4.1 (3.8)
1.4 (1.5)
2.8 (2.8)
1.5 (1.8)
2.7 (2.8)
4.2 (4.1)
5.3 (5.1)
5.1 (4.5)
4.2 (4.1)
3.9 (4.0)
5.2 (5.5)
6.2 (5.9)
5.3 (5.6)
5.0 (5.0)
6.6 (6.6)
6.6 (6.6)
6.1 (6.3)
3.1 (3.0)
2.6 (3.0)
2.6 (2.8)
3.1 (3.0)
2.1 (2.1)
2.1 (2.3)
1.7 (2.3)
1.8 (1.9)
1.7 (1.7)
2.4 (2.2)
2.0 (2.0)
2.1 (2.2)
1.7 (1.7)
5.3 (5.1)
5.2 (5.1)
2 [{WCl4(NC10H7)}x]
3 [{WCl4(NC6H4CMe3-2)}x]
4 [{WCl4(NC6H4Ph-2)}x]
5 [WCl4{HNC6H4(CMe2CH2)-2(C,N)}]
6 [WCl3(NC10H7)(PMe3)2]c
7 [WCl3(NC6H4CMe3-2)(PMe3)2]b
8 [WCl3(NC6H4Ph-2)(PMe3)2]
9 [WCl3(NC10H7)(PMe2Ph)2]d
10 [WCl3(NC10H7)(PMePh2)2]
11 [WCl2(NC10H7)(PMe3)3]
12 [WCl2(NC6H4CMe3-2)(PMe3)3]c
13 [WCl2(NC6H4Ph-2)(PMe3)3]
14 [WCl2(NC10H7)(PMe2Ph)3]
15 [MoCl2(NC6H3Me-2-Pri-6)2(dme)]
16 [MoCl2(NC6H4CMe3-2)2(dme)]
a Calculated values given in parentheses. b Calculated values for 0.5 CH2Cl2 solvate. c Calculated values for CH2Cl2 solvate. d Calculated values for
0.17 CH2Cl2 solvate.
tert-butyl group resonances appear as narrow singlets indicat-
ing that the group is free to rotate in solution. Since the struc-
ture of complex 1 shows the tert-butyl substituent is easily
accommodated in the molecule, rotation about the N(1)–C(1)
bond should be uninhibited.
Each pyridinium cation ring interleaves between a co-
ordinated pyridine and an imido ligand phenyl ring, a sequence
which is extended by back-to-back approaches of co-ordinated
pyridine rings for two adjacent complexes related by a centre of
symmetry. However the stacking arrangement is marred by the
interplanar angles between the co-ordinated pyridines and also
between the pyridinium ion and the imido ligand rings of 11.3
and 21.2Њ respectively. Thus a perfectly parallel set of aromatic
rings is not achieved. The distances between adjacent aromatic
rings in the series vary from 3.5 to a little over 4.0 Å. The
pyridinium cation nitrogen atom [N(3)] makes contact with
Cl(4) and Cl(2) at 3.38 and 3.46 Å respectively, distances which
are slightly longer than those recognised as involving strong
hydrogen bonding in an N–H ؒ ؒ ؒ Cl system.17 N(3) makes even
longer contacts with Cl(4) and Cl(2) [3.62 and 3.70 Å respect-
ively] on an adjacent anion.
Fig. 1 Molecular structure of the anion of complex 1, without H
atoms and with key atoms labelled.
Monoimido tungsten-(VI), -(V) and -(IV)
tantalum such as [Ta(NCMe3)(NMe2)3] [1.77(2) Å],13
The reaction of an isocyanate with WOCl4 in benzene
solution18–20 was used to prepare the complexes [{WCl4-
(NC10H7)}x] 2, [{WCl4(NC6H4CMe3-2)}x] 3, and [{WCl4-
(NC6H4Ph-2)}x] 4. Non-crystalline solids were formed which
are expected to be chloro-bridged dimers based on the crystal
structures of like molecules.21 However, 1H NMR spectra of the
naphthylimide complex 2 in CDCl3 showed two C-8 proton
resonances (δ 9.22 and 9.10) in a ratio 1:4 slowly converting
in the CDCl3 solution to the less predominant form over time
(24 h). This process was also evident in the 13C-{1H} NMR
spectrum in which one set of resonances converted into another
over time. Addition of thf (tetrahydrofuran) to the NMR tube
containing complex 2 led to only one set of resonances in both
spectra (expected to be the monomeric thf adduct [WCl4-
(NC10H7)(thf)]) where the single C-8 proton resonance position
(δ 9.08) is similar to that found for the transforming [{WCl4-
(NC10H7)}x] species.
[TaCl3(NC6H5)(PEt3)(thf)]
[1.765(5)
Å]14
and
[TaCl2(NC6H3Pri2-2,6)(C5Me5)] [1.780(5) Å].15 The Ta–Cl bond
lengths lie in the range 2.391(2)–2.445(2) Å.
The N(1)–Ta–Cl(1) and N(1)–Ta–Cl(2) bond angles [98.8(2)
and 98.6(2)Њ respectively] widen out a little under the influence
of the tert-butyl substituent methyl groups [cf. N(1)–Ta–Cl(3),
94.3(2)Њ and N(1)–Ta–Cl(4), 96.4(2)Њ] and the angle C(8)–C(7)–
C(10) at 109.9(6)Њ is a little larger than the 107.7(6) and
107.1(7)Њ observed for C(8)–C(7)–C(9) and C(9)–C(7)–C(10)
respectively as a result of the proximity of Cl(1) and Cl(2). The
tert-butyl substituent is thus easily accommodated without
forcing the Ta–N(1)–C(1) bond angle to bend more than the
observed 165.1(5)Њ. This latter angle is not very different
from those found in other tantalum complexes which contain
more symmetrical imido ligands (e.g. Ta–N–C bond angles
of 171.4(5)Њ in [TaCl2(NC6H3Pri2-2,6)(C5Me5)]15 and 165.8Њ in
[TaCl(NCMe3){N(SiMe3)2}2]16) hence the tert-butyl substituent
does not distort this angle unduly. For organoimido ligands in
general, it has been recognised that M–N–C bond angles as
low as ca. 150Њ can be achieved from crystal packing and intra-
molecular effects without involving electronic changes to the
imido linkage.6,7 In both the 1H and 13C-{1H} NMR spectra the
The 2-tert-butylphenylimido and 2-phenylphenylimido tung-
sten complexes show similar NMR spectral features to those of
2. Initially there are two tert-butyl resonances in the spectra of
complex 3 and two doublets for the ortho-protons of the phenyl
substituent for 4. The NMR spectra of complex 3 indicate that
the tert-butyl group rotates since there are no diastereotopic
4570
J. Chem. Soc., Dalton Trans., 2000, 4569–4578

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Table 2 Selected NMR spectroscopic data (δ, J/Hz)a
Complex
1Hb
13C-{1H}
1
1.61 (s, 9 H, CMe3); 5.5 (s, 1 H, CH2Cl24); 6.81 [td, 3J(HH) 7.7,
30.9 (CMe3); 35.1 (C); 124.8 (CH); 124.9 (CH); 125.5 (CH);
125.6 (CH); 128.3 (CH); 133.1 (CH); 139.0 (CH); 140.2 (CH);
146.3 (o-C); 151.9 (CH); 152.2 (CH); 152.4 (ipso-C)
3
4J(HH) 1.2, 1 H]; 7.20 [td, JHH) 7.7, J(HH) 1.2, 2 H]; 7.30
3
4
[dd, J(HH) 7.7, J(HH) 1.2, 1 H]; 7.41 [prt, 2 H, β-H py or
Hpy]; 7.48 [prt, 2 H, β-H Hpy or py]; 7.90 (m, 2 H, χ-H py and
Hpy); 8.80 [d, 3J(HH) 5.2, 3 H, α-H py or Hpy and NH]; 9.25
(bd, 2 H, α-H py or Hpy)
3
2
7.22–7.40 (m); 7.50–7.86 (m); 7.88–8.23 (m); 9.10 [d, J(HH)
122.5 (CH minor); 122.7 (CH major); 123.3 (CH major); 123.7
(CH major); 124.9 (CH minor); 126.3 (CH minor); 127.5 (CH
major); 128.0 (C minor); 128.5 (CH minor); 129.2 (CH
minor); 129.6 (CH minor); 130.1 (CH major); 130.6 (CH
major); 131.6 (C minor); 132.2 (CH minor); 135.0 (C major);
135.4 (CH major); 136.0 (C major); 136.9 (ipso-C minor);
137.8 (ipso-C major)
8.3, 1 H, H8 (major)]; 9.22 [d, 3J(HH) 8.2, 1 H, H8 (minor)]
3
1.59 [s, 18 H, CMe3 (major)]; 1.67 [s, 18 H, CMe3 (minor)]; 6.85
[t, 3J(HH) 7.4, 1 H, p-H (major)]; 7.30–7.75 (m, aromatics)
30.7 [CMe3 (major)]; 31.1 [CMe3 (minor)]; 34.7 [C (minor)];
35.1 [C (major)]; 124.9 [CH (major)]; 126.1 [CH (major)];
128.4 [CH (major)]; 128.5 [CH (minor)]; 129.9 [CH (minor)];
131.5 [CH (minor)]; 135.6 [CH (major)]; 144.7 [CH minor)];
150.1 [C (major)]; 150.9 [ipso-C (major)]; 153.2 [C (major)];
154.1 [ipso-C (minor)]
117.9 (CH); 123.1 (CH); 123.4 (CH); 124.1 (CH); 124.5 (CH);
125.1 (CH); 125.6 (CH); 127.6 (CH); 127.8 (CH); 128.7 (CH);
128.9 (CH); 129.1 (CH); 129.4 (CH); 130.0 (CH); 130.1 (C);
130.2 (C); 130.6 (C); 134.5 (C); 153.8 (ipso-C); 163.2 (ipso-C)
30.1 (CH2); 32.0 (CMe2); 32.8 (C); 124.2 (CH); 125.6 (CH);
128.5 (CH); 130.2 (CH); 134.4 (ortho-C); 141.8 (ipso-C)
4c
7.32–7.74 (m, aromatics); 7.93 [t, J(HH) 7.7, 2 H, p-H]; 8.46
3
3
3
[d, J(HH) 8.1, 2 H, o-H (major)]; 8.55 [d, J(HH) 7.9, 2 H,
o-H (minor)]
5
1.46 (s, 6 H, CMe2); 1.62 (s, 2 H, CH2); 7.26 [prt, 1 H, p-H];
7.36 [d, 3J(HH) 7.1, 1 H, m-H]; 7.48 [d, 3J(HH) 7.1, 1 H, m-H];
7.66 [m, 1 H, o-H]; 9.27 (bs, 1 H, NH)
11
1.61 [t, 2J(HP) 3.7, 18 H, PMe3]; 1.90 [d, 2J(HP) 8.3, 9 H,
17.8 [t, 1J(HP) 13.5, PMe3]; 26.8 [d, 1J(HP) 28.8, PMe3]; 121.5
(CH); 123.9 (CH); 125.3 (CH); 126.1 (CH); 126.3 (CH); 126.9
(CH); 127.2 (CH); 129.7 (C); 134.1 (C); 153.7 (ipso-C)
3
3
PMe3]; 7.20 [d, J(HH) 7.9, 2 H, H4 and H5]; 7.44 [d, J(HH)
7.4, 1 H, H2]; 7.57 [t, 3J(HH) 7.4, 1 H, H3]; 7.75 [t, 3J(HH) 7.4,
2 H, H6 and H7]; 8.90 [d, 3J(HH) 7.4, 1 H, H8]
2
1
1
12
13
1.33 (s, 9 H, CMe3); 1.52 [t, J(HP) 3.7, 18 H, PMe3]; 1.72 [d,
17.2 [t, J(HP) 13.4, PMe3]; 26.0 [d, J(HP) 28.5, PMe3]; 30.4
(CMe3); 35.7 (C); 124.1 (p-CH); 126.1 (m-CH); 126.4 (m-CH);
138.29 (o-CH); 143.3 (o-C); 155.5 (ipso-C)
2J(HP) 8.0, 9 H, PMe3]; 7.02 [td, 3J(HH) 7.4, 4J(HH) 1.4, 1 H,
3
4
p-H]; 7.09 [td, J(HH) 7.4, J(HH) 1.4, 1 H, m-H]; 7.14 [dd,
3J(HH) J(HH) 7.4, J(HH) 1.4, 1 H, m-H]; 7.18 [dd, J(HH)
3
4
3
7.4, 4J(HH) 1.4, 1 H, o-H]
1.34 [t, 2J(HP) 3.7, 18 H, PMe3]; 1.60 [d, 2J(HP) 8.1, 9 H,
PMe3]; 7.04 [bt, 2 H, m- and p-H (imido)]; 7.10–7.18 [m, 2 H,
17.8 [t, 1J(HP) 13.5, PMe3]; 26.3 [d, 1J(HP) 28.3, PMe3]; 124.3
[p-CH (imido)]; 127.2 and 127.3 [m-CH (imido) and p-CH
(phenyl)]; 128.2 [m-CH (phenyl)]; 129.0 [o-CH (phenyl)]; 131.4
[m-CH (phenyl)]; 133.3 [o-CH (imido)]; 136.3 [ipso-C
(phenyl)]; 139.1 [o-C (imido)]; 153.5 [ipso-C (imido)]
18.7 (o-Me); 24.3 (Me); 27.5 (CH); 62.0 (OMe); 71.2 (CH2);
122.8 (m-CH); 126.9 (p-CH); 127.4 (m-CH); 134.7 [o-C(Me)];
144.2 (o-C(CHMe2)]; 154.6 (ipso-C)
30.4 [Me (anti)]; 31.5 [Me (syn)]; 34.3 [C (syn)]; 35.1 [C (anti)];
62.3 [b, OMe (syn and anti)]; 71.4 [CH2 (syn and anti)]; 125.0
[CH (anti)]; 125.5 [CH (syn)]; 126.2 [CH (anti)]; 126.7 [CH
(syn)]; 126.9 [CH (syn)]; 128.1 [b, 2CH (anti)]; 129.7 [CH
(syn)]; 140.4 [o-C (anti)]; 141.6 [o-C (syn)]; 154.9 [ipso-C (syn)];
155.2 [ipso-C (anti)
3
m- and o-H (imido)]; 7.21 [t, J(HH) 7.5, 1 H, p-H (phenyl)];
7.35 [t, J(HH) 7.5, 2 H, m-H (phenyl)]; 7.46 [d, J(HH) 7.5,
2 H, o-H (phenyl)]
3
3
3
15
16
1.06 [d, J(HH) 6.9, 12 H, CHMe2]; 2.43 (s, 6 H, o-Me); 3.75
(bs, 4 H, CH2CH2); 3.83 (obsc. sept, 2 H, CHMe2); 3.87 (bs,
6 H, OMe); 6.91 (m, 4 H, m-H); 7.05 (m, 2 H, p-H)
1.39 [s, 18 H, CMe3 (anti)]; 1.44 [s, 18 H, CMe3 (syn)]; 3.73 [bs,
6 H, OMe (anti and syn)]; 3.90 [bs, 4 H, CH2CH2 (anti and
syn)]; 6.85 [t, 3J(HH) 7.4, 4 H, m and p-H (syn)]; 7.00 [t,
3J(HH) 7.5, 2 H, p-H (anti)]; 7.02 [obsc, 2 H, m-H (syn)]; 7.08
[t, 3J(HH) 7.5, 2 H, m-H (anti)]; 7.21 [d, 3J(HH) 7.5, 2 H, m-H
(anti)]; 7.27, [obsc. d, 2 H, o-H (syn)]; 7.67 [d, 3J(HH) 7.5, 2 H,
o-H (anti)]
a Spectra obtained in CDCl3 solution. b b = broad, bd = broad doublet, bs = broad singlet, bt = broad triplet, d = doublet, dd = doublet of doublets,
m = multiplet, obsc = obscured, obsc d = obscured doublet, obsc sept = obscured septet, prt = poorly resolved triplet, s = singlet, t = triplet, td = tri-
plet of doublets. c Major and minor components not distinguishable in 13C-{1H} NMR spectrum.
Table 3 Selected bond lengths (Å) and bond angles (Њ) for [Hpy]-
[TaCl4(C6H4CMe3-2)(py)]ؒCH2Cl2 1
methyl groups observed. Low temperature studies of this
feature have been hampered by low solubility in non-co-
ordinating solvents. When thf was added to the 2-tert-butyl-
phenylimido complex 3 and the solvent removed the NMR
spectra showed only one set of resonances characteristic of the
adduct [WCl4(NC6H4CMe3-2)(thf)]. Addition of Et4NCl to 3
gave [NEt4][WCl4(NC6H4CMe3-2)] which NMR spectra also
showed as a single compound. Previously we have not observed
the formation of two species in the NMR spectra of other
[{WCl4(NR)}x] complexes which suggests that in the present
complexes there are either some rotational differences regarding
the position of the imido ligands if a dimer persists in solution
or dimer–monomer solution dynamics is involved.
Ta–N(1)
Ta–N(2)
Ta–Cl(1)
1.779(5)
2.437(5)
2.391(2)
Ta–Cl(2)
Ta–Cl(3)
Ta–Cl(4)
2.420(2)
2.421(2)
2.445(2)
N(1)–Ta–Cl(1)
N(1)–Ta–Cl(2)
N(1)–Ta–Cl(3)
N(1)–Ta–Cl(4)
Cl(1)–Ta–Cl(2)
Cl(1)–Ta–Cl(4)
Cl(2)–Ta–Cl(4)
Ta–N(1)–C(1)
C(5)–C(6)–C(7)
C(6)–C(7)–C(9)
C(8)–C(7)–C(9)
C(9)–C(7)–C(10)
N(1)–C(1)–C(2)
98.8(2)
98.6(2)
94.3(2)
N(2)–Ta–Cl(1)
N(2)–Ta–Cl(2)
N(2)–Ta–Cl(3)
N(2)–Ta–Cl(4)
Cl(1)–Ta–Cl(3)
Cl(2)–Ta–Cl(3)
Cl(3)–Ta–Cl(4)
C(1)–C(6)–C(7)
C(6)–C(7)–C(8)
C(6)–C(7)–C(10)
C(8)–C(7)–C(10)
N(1)–Ta–N(2)
N(1)–C(1)–C(6)
82.1(1)
84.0(1)
83.1(1)
96.4(2)
82.7(1)
91.15(6)
164.77(5)
86.20(6)
165.1(5)
121.5(6)
112.2(6)
107.7(6)
107.1(7)
115.5(6)
91.06(6)
166.44(6)
88.18(6)
123.0(5)
108.7(6)
111.1(6)
109.9(6)
177.3(2)
124.5(6)
In the preparations of complexes 2–4 the product usually
precipitates from the benzene reaction medium in high yield.
When the reaction of 2-tert-butylphenyl isocyanate and WOCl4
was carried out in the higher boiling solvent toluene a signifi-
cant portion of the product remained in solution. A dark
J. Chem. Soc., Dalton Trans., 2000, 4569–4578
4571

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Table 4 Selected bond lengths (Å) and bond angles (Њ) for [WCl3-
(NC10H7)(PMe3)2] 6
brown solid was isolated which analysed as [{WCl4(NC6H4-
CMe3-2)}] but which had completely different NMR spectra
from those of complex 3. In the 1H NMR spectrum there were
resonances at δ 1.46 and 1.62 in a ratio of 3:1 consistent with
2 methyl and one methylene group and there was a broad
1-proton resonance at δ 9.27 assigned as an NH proton. The
ortho-proton of the aromatic ring apparently couples to this
NH proton since there is a multiplet present and not the
expected doublet. The 13C-{1H} NMR spectrum contained a
resonance for the methyl groups and also a resonance at δ 30.1
shown to be a methylene group by DEPT-135. The NMR
spectra thus show the metallacycle amide complex [WCl4-
{NHC6H4(CMe2CH2)-2(C,N)}] 5 (structure I) forming at the
elevated temperature of the toluene solvent. Simple molecular
models indicate that the NH proton for this complex lies in the
same plane as the ortho-proton of the aromatic ring which may
W–N
W–Cl(1)
W–Cl(2)
1.707(13)
2.451(4)
2.407(4)
W–Cl(3)
W–P(1)
W–P(2)
2.379(4)
2.531(3)
2.536(4)
N–W–Cl(1)
N–W–Cl(2)
N–W–Cl(3)
N–W–P(1)
173.7(5)
91.2(5)
99.3(5)
95.2(4)
91.2(4)
173.4(1)
82.7(2)
86.8(2)
123.3(15)
Cl(1)–W–P(1)
Cl(1)–W–P(2)
Cl(2)–W–P(1)
Cl(2)–W–P(2)
Cl(3)–W–P(1)
Cl(3)–W–P(2)
Cl(2)–W–Cl(3)
W–N–C(1)
86.5(2)
87.0(2)
88.7(1)
91.6(1)
90.1(1)
88.5(2)
169.4(2)
167.4(1)
119.3(13)
N–W–P(2)
P(1)–W–P(2)
Cl(1)–W–Cl(2)
Cl(1)–W–Cl(3)
N–C(1)–C(2)
N–C(1)–C(9)
1
explain the coupling observed in the H NMR spectrum. The
reaction represents the first example of a cyclometallation
observed during the interaction of an isocyanate and a metal
oxo complex. As yet, we have been unable to obtain the
cyclometallate by refluxing complex 3 in toluene for extended
periods.
Reduction of complexes 2–4 with one equivalent of Na/Hg
amalgam in the presence of 2 equivalents of PMe3 19,20 gave the
d1 complexes [WCl3(NC10H7)(PMe3)2] 6, [WCl3(NC6H4CMe3-
2)(PMe3)2] 7, and [WCl3(NC6H4Ph-2)(PMe3)2] 8 for which
simple molecular models indicate rotation about the aryl C–N
bond will be hindered by steric interaction of the imido ligand
with the PMe3 ligand methyls. The naphthylimido ligand is
expected to produce the least steric constraint and hence the
more bulky phosphine derivatives [WCl3(NC10H7)(PMe2Ph)2]
Fig. 2 Molecular structure of complex 6, without H atoms and with
key atoms labelled.
[173.7(5)Њ] in comparison with the 2,6-diisopropylphenylimido
complex [N–W–Cl(1) bond angle 178.0(5)Њ]. The W–Cl(3) bond
length [2.379(4) Å] is marginally shorter in terms of 3σ than
the W–Cl(2) bond length [2.407(4) Å] whereas in the phe-
nylimido and 2,6-diisopropylphenylimido complexes these
bond lengths are similar [2.387(2), 2.390(2) and 2.387(3),
2.382(3) Å respectively].
Simple molecular models indicate that the N–W–P(1) bond
angle would need to open significantly for the C(8) proton to
rotate over the phosphine ligand and such a rotation would
need the C(8) and C(2) protons to enter the space between the
phosphine carbons at the same time (geared rotation5). This
suggests that the naphthylimido ligand is regiospecific to Cl(3).
It is also noted that whereas an isopropyl group itself can rotate
to remove contacts, the naphthyl ligand offers a much more
rigid system and can thus be expected to exert different steric
properties.
Reduction of complexes 2–4 with two equivalents of Na/Hg
amalgam in the presence of 3 equivalents of PMe3 19,20 gave the
d2 complexes [WCl2(NC10H7)(PMe3)3] 11, [WCl2(NC6H4CMe3-
2)(PMe3)3] 12, and [WCl2(NC6H4Ph-2)(PMe3)3] 13. The com-
plex [WCl2(NC10H7)(PMe2Ph)3] 14 could be prepared but the
reaction failed with PMePh2. Complexes 11–13 all show a
doublet and a triplet for the PMe3 ligands in the 1H NMR and
13C-{1H} NMR spectra and 14 shows two triplets for the
phosphine methyls. These features are consistent with a mer-
phosphine arrangement.18,19 Naphthylimido complex 11 shows
a doublet for the C(8) proton at δ 8.90 in the 1H NMR spectrum
and is expected to show a similar interaction and ligand
rotational properties to those of the d1 complex 6. There is only
one resonance in the 1H NMR and 13C-{1H} NMR spectra for
the CMe3 group in complex 12 indicating that the tert-butyl
9
and [WCl3(NC10H7)(PMePh2)2] 10 were prepared. A
crystal structure determination of the trimethylphosphine
complex 6 was carried out to assess the steric contribution a
naphthyl ligand makes in the presence of the smaller PMe3
ligand.
Complex 6 shows a distorted octahedral geometry with trans
phosphines, trans chloro ligands and a third chloro ligand lying
trans to the naphthylimido ligand (Fig. 2). Selected bond
lengths and angles are contained in Table 4. The W–N bond
length [1.707(13) Å] is not significantly different from those
found in [WCl3(NC6H5)(PMe3)2] [1.731(6) Å]19 and [WCl3-
(NC6H3Pri2-2,6)(PMe3)2] [1.750(6) Å]2 nor is the P(1)–W–P(2)
bond angle [173.4(1)Њ in 6] compared with that in the phenyl-
imido complex [172.3(1)Њ] but this angle is slightly smaller
[169.5(1)Њ] in the 2,6-diisopropylphenylimido complex. The
imido ligand in 6 tilts away from Cl(3) [W–N–C(1) bond angle
167.4(1)Њ] more than in the phenylimido or 2,6-diisopropyl-
phenylimido complexes [W–N–C bond angles 175.8(6) and
178.0(5)Њ respectively]. As well, the naphthyl group twists
slightly to the P(1) side of Cl(3) in 6 to reduce contact between
the C(8) proton and Cl(3) as similarly found in the 2,6-
diisopropylphenylimido complex, but the N–W–Cl(3) bond
angle in 6 is much larger [99.3(5) and 90.8(5)Њ respectively]
showing that Cl(3) still needs to move away from the C(8)
proton. The calculated Cl(3) ؒ ؒ ؒ H(8) distance is 3.04 Å which is
slightly less than the sum of the van der Waals radius of these
atoms (3.18 Å). Thus the widening out of the N–W–Cl(3) bond
angle is accompanied by a bend in the N–W–Cl(1) bond angle
4572
J. Chem. Soc., Dalton Trans., 2000, 4569–4578

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Table 5 Selected bond lengths (Å) and bond angles (Њ) for [WCl2-
(NC6H4CMe3-2)( PMe3)3] 12
Table 6 Selected bond lengths (Å) and bond angles (Њ) for [WCl2-
(NC6H4Ph-2)(PMe3)3] 13
W–N
W–Cl(1)
W–Cl(2)
1.770(3)
2.4974(9)
2.5096(9)
W–P(1)
W–P(2)
W–P(3)
2.5039(10)
2.5074(10)
2.4845(10)
W–N
W–Cl(1)
W–Cl(2)
1.764(3)
2.4989(8)
2.4918(7)
W–P(1)
W–P(2)
W–P(3)
2.5010(10)
2.5148(9)
2.4581(10)
N–W–Cl(1)
N–W–Cl(2)
N–W–P(1)
N–W–P(2)
177.5(5)
98.9(1)
98.0(1)
98.2(1)
91.1(1)
162.99(3)
92.57(3)
92.33(3)
115.9(3)
123.5(3)
109.5(3)
107.3(3)
106.5(3)
Cl(1)–W–Cl(2)
Cl(1)–W–P(1)
Cl(1)–W–P(2)
Cl(1)–W–P(3)
Cl(2)–W–P(1)
Cl(2)–W–P(2)
Cl(2)–W–P(3)
W–N–C(1)
N–C(1)–C(6)
C(5)–C(6)–C(7)
C(6)–C(7)–C(9)
C(8)–C(7)–C(9)
C(9)–C(7)–C(10)
83.62(3)
82.75(3)
81.31(3)
86.45(3)
86.20(3)
86.17(3)
170.07(3)
172.9(3)
124.8(3)
120.3(3)
109.3(3)
111.7(3)
107.3(3)
N–W–Cl(1)
N–W–Cl(2)
N–W–P(1)
N–W–P(2)
N–W–P(3)
P(1)–W–P(2)
P(1)–W–P(3)
P(2)–W–P(3)
N–C(1)–C(2)
C(1)–C(6)–C(7)
171.84(9)
102.79(9)
95.29(9)
89.97(9)
93.57(9)
166.79(3)
92.55(3)
99.22(3)
118.6(3)
123.0(3)
Cl(1)–W–Cl(2)
Cl(1)–W–P(1)
Cl(1)–W–P(2)
Cl(1)–W–P(3)
Cl(2)–W–P(1)
Cl(2)–W–P(2)
Cl(2)–W–P(3)
W–N–C(1)
84.28(3)
89.28(3)
87.02(3)
79.45(3)
85.41(3)
81.61(3)
163.63(3)
171.84(9)
122.2(3)
118.4(3)
N–W–P(3)
P(1)–W–P(2)
P(1)–W–P(3)
P(2)–W–P(3)
N–C(1)–C(2)
C(1)–C(6)–C(7)
C(6)–C(7)–C(8)
C(6)–C(7)–C(10)
C(8)–C(7)–C(10)
N–C(1)–C(6)
C(5)–C(6)–C(7)
Fig. 4 Molecular structure of complex 13, without H atoms and with
key atoms labelled.
Fig. 3 Molecular structure of complex 12, without H atoms and with
key atoms labelled.
between P(2) and P(3). The best fit of these hydrogens with the
phosphine methyls is in a staggered arrangement with the W–N
bond for the trans phosphines [P(1) and P(2)] and eclipsed with
P(3).
group is able to rotate. The ortho-protons of the phenyl
1
substituent in 13 show a doublet in the H NMR spectrum
which suggests rapid rotation of this group.
In complex 12 the effect of the tert-butyl group is to push
P(1) and P(2) towards P(3) more than is observed in [WCl2-
(NC6H5)(PMe3)3] [P(1)–W–P(2) angles 162.99(3) and 169.1(1)Њ
respectively] and also towards Cl(1). Interestingly, the
N(1)–W–Cl(2) and N(1)–W–P(3) angles in complex 12 [98.9(1)
and 91.1(1)Њ respectively] are smaller than in the phenylimido
complex [103.3(1) and 95.2(1)Њ respectively]. The 1H NMR
spectrum indicates that in solution the tert-butyl group itself is
able to rotate so there is apparently room for the methyls to
move over the top of Cl(2). However molecular models show
that it is unlikely that C(1)–N bond rotation occurs easily to
allow the tert-butyl group to pass over the phosphine ligands.
Low temperature studies in CD2Cl2 down to Ϫ75 ЊC show no
broadening of the tert-butyl group resonance that would
indicate geared rotation5 and no changes were observed in the
aromatic region of the spectrum.
A crystal structure determination of the 2-tert-butylphenyl-
imido complex 12 showed a distorted octahedral geometry
(Fig. 3) similar to that found for [WCl2(NC6H5)(PMe3)3].19
Selected bond lengths and angles are contained in Table 5. The
W–N bond lengths are similar in both complexes [1.770(3) and
1.755(3) Å respectively] as are the W–Cl(1) bond lengths for
the chloro ligand lying trans to the imido ligand [2.497(1) and
2.501(1) Å respectively]. The W–Cl(2) bond in which the chloro
ligand lies cis to the imido group is marginally longer where
the tert-butyl substituent is present [2.510(1) and 2.494(1) Å
respectively] as are the W–P bonds for the trans phosphines
[W–P(1) bond lengths 2.504(1) and 2.483(1) Å respectively;
W–P(2) 2.507(1) and 2.497(1) Å]. The W–P(3) bond is signifi-
cantly longer with a tert-butyl substituent present [2.485(1) and
2.453(1) Å respectively].
The 2-tert-butyl substituent in complex 12 has a pronounced
effect on the orientation of the imido ligand phenyl ring and the
bond angles. Two of the tert-butyl group methyls straddle Cl(2)
[C(8) ؒ ؒ ؒ Cl(2) and C(9) ؒ ؒ ؒ Cl(2) contacts 3.55 and 3.58 Å
respectively] which brings the phenyl ring close to the plane of
the atoms P(3), W, Cl(2) and N. The best fit for these two
methyls with the phosphine methyls on P(1) and P(2) is where
one P–C bond eclipses the W–N bond, whereas the best fit of
the phenyl group C(2) proton with P(3) forces two of its methyls
to adopt a staggered conformation with respect to the W–N
bond. In [WCl2(NC6H5)(PMe3)3] the phenyl group swings
around so that the hydrogen in the 2 position falls over and
between P(1) and Cl(2) and that in the 6 position over and
A crystal structure determination shows that the 2-phenyl-
phenylimido complex 13 (Fig. 4) is more like [WCl2(NC6H5)-
(PMe3)3] than 2-tert-butylphenylimido complex 12. Selected
bond lengths and angles for 13 are contained in Table 6. The
W–N bond lengths are similar [1.764(3) and 1.755(3) Å respect-
ively], as are the W–Cl(1) bond lengths [2.499(1) and 2.501(1)
Å] and W–Cl(2) bond lengths [2.492(1) and 2.494(1) Å]. How-
ever, the W–P bonds for the trans phosphines in 13 are more
similar in length to those in 2-tert-butylphenylimido complex
12 [W–P(1) and W–P(2) 2.504(1) and 2.507(1) Å for 12 and
2.501(1), 2.515(1) Å for 13 respectively] whereas the W–P(3)
bonds in 13 are more like those in the phenylimido complex
[2.458(1) and 2.453(1) Å respectively].
J. Chem. Soc., Dalton Trans., 2000, 4569–4578
4573

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Table 7 Selected bond lengths (Å) and bond angles (Њ) for [MoCl2-
(NC6H3Me-2-Pri-6)2(dme)] 15
Mo(1)–N(1)
Mo(1)–N(2)
Mo(1)–Cl(1)
1.769(7)
1.718(7)
2.415(2)
Mo(1)–Cl(2)
Mo(1)–O(1)
Mo(1)–O(2)
2.415(2)
2.317(6)
2.372(5)
N(1)–Mo(1)–N(2)
N(1)–Mo(1)–Cl(1)
N(1)–Mo(1)–Cl(2)
N(1)–Mo(1)–O(1)
N(1)–Mo(1)–O(2)
N(2)–Mo(1)–Cl(1)
N(2)–Mo(1)–Cl(2)
N(2)–Mo(1)–O(1)
N(1)–C(5)–C(6)
N(1)–C(5)–C(10)
C(5)–C(6)–C(11)
C(7)–C(6)–C(11)
C(5)–C(10)–C(12)
C(9)–C(10)–C(12)
C(10)–C(12)–C(13)
C(10)–C(12)–C(14)
C(13)–C(12)–C(14)
105.4(1)
96.2(2)
96.8(3)
92.2(3)
162.2(3)
97.2(3)
N(2)–Mo(1)–O(2)
Cl(1)–Mo(1)–O(1)
Cl(1)–Mo(1)–O(2)
Cl(1)–Mo(1)–Cl(2)
Cl(2)–Mo(1)–O(1)
Cl(2)–Mo(1)–O(2)
Mo(1)–N(1)–C(5)
Mo(1)–N(2)–C(15)
N(2)–C(15)–C(16)
N(2)–C(15)–C(20)
C(15)–C(16)–C(21)
C(17)–C(16)–C(21)
C(15)–C(20)–C(22)
C(19)–C(20)–C(22)
C(20)–C(22)–C(23)
C(20)–C(22)–C(24)
C(23)–C(22)–C(24)
92.4(3)
82.6(2)
79.2(2)
158.57(2)
80.0(2)
82.7(2)
165.8(6)
171.3(6)
117.4(7)
122.3(8)
118.1(7)
124.8(7)
120.5(8)
119.8(8)
109.5(8)
115.4(9)
110.8(9)
95.7(3)
162.3(3)
121.8(7)
115.2(8)
123.9(6)
116.9(7)
121.8(8)
123.8(8)
108.8(8)
110.6(8)
110.3(9)
Fig. 5 Molecular structure of complex 15, without H atoms and with
key atoms labelled.
The 2-phenyl substituent in complex 13 lies over and between
P(1) and Cl(2) to avoid placing the aromatic ring over Cl(2)
and this places the C(2) proton over and between P(2) and
P(3). The phenylimide ring orientation is thus similar to that
found in the phenylimido complex. So also are the configur-
ations of the PMe3 ligands where two of the P(1) and P(2)
methyls are staggered with respect to the W–N bond and a P(3)
methyl is eclipsed. Whereas the N–W–P(2) bond angles are
similar in complex 13 and the phenylimido complex [89.9(1)
and 90.0(1)Њ respectively], the 2-phenyl substituent forces the
N–W–P(1) angle to widen [95.3(1) and 89.7(1)Њ for the respect-
ive complexes] but the N–W–P(3) angles are similar [93.6(1)
and 95.2(1)Њ] as are the N–W–Cl(2) angles [102.8(1) and
103.2(1)Њ]. The 2-phenyl substituent thus does not appear to
influence the molecule drastically since there is room for the
imido ligand to bend back between P(2) and P(3) in the absence
imido ligands lie with isopropyl and methyl groups of the two
rings opposite to each other thus forming the anti type isomer.
Whereas the methyl groups lie almost over and above the two
chloro ligands, the isopropyl groups lie over, but between, a
chloro ligand and a methyl group of the dme ligand. These
methyl groups push away towards the chloro ligand side of
the molecule to relieve interaction with the isopropyl methine
proton. Based on the crystal structure and an analysis of simple
molecular models it appears unlikely that the imido ligands are
able to rotate since it would be difficult for the isopropyl and
methyl groups to pass over the dme ligand methyls without the
Mo–N–C bond angles [165.8(6) and 171.3(6)Њ] bending con-
siderably which in turn would force the other ortho substituent
into the π-electron density of an adjacent phenyl ring. In
5-co-ordinate bis-imido complexes where the dme ligand is not
present the N–M–N bond angles can open out more than in 15
[bond angle 105.4(1)Њ] and allow an ortho substituent to pass
over an adjacent phenyl ring without overdue M–N–C bond
angle bending.25
[MoCl2(NC6H4CMe3-2)2(dme)] 16 has been prepared
before.26 The NMR spectra of this complex prepared in the
present work indicated that two isomers were present in CDCl3
solution (ratio 8.3:1.7). When a concentrated dme solution was
allowed to stand a small quantity of crystalline material was
produced and no more was formed after filtering and concen-
trating the solution further. NMR spectra of the solid obtained
from this solution showed the minor component of the original
mixture to be almost absent. A crystal structure determination
of the minor component 16a showed two crystallographically
distinct but chemically similar molecules, A and B, in the
asymmetric unit. Each molecule exhibits a distorted octahedral
structure (Fig. 6 for molecule A) in which both tert-butyl sub-
stituents of the phenyl rings lie on the same side of the molecule
characteristic of the syn-type isomer. A similar structure has
been found for [MoCl2(NC6H4CN-2)2(dme)]26 but the 1H NMR
spectrum reported does not indicate the presence of syn and
anti isomers.
1
of a substituent at C(2). The H NMR spectrum shows that
rotation of the 2-phenyl group is possible but molecular models
suggest it is unlikely that it will pass easily over the phosphines.
It should be noted that the absence of C–N bond rotations in
the d2 molecules is predicted on the basis of structural data and
an analysis of simple molecular models. The NMR spectra
observed could arise from either locked or free C–N bond
rotation and it would be difficult to differentiate between the
two unless locking gave rise to asymmetry in the molecules.
Bis(imido)molybdenum(VI)
In bis-imido complexes with different phenyl ring ortho-
substituents there is the possibility of forming syn and anti type
isomers (structures II and III) if rotation of the imido C–N
bonds is impeded. Preparation of [MoCl2(NC6H3Me-2-Pri-6)2-
(dme)] 15 was carried out by treating the arylamine with
Na2MoO4 in dimethoxymethane in the presence of Me3SiCl
and Et3N.22 The 1H and13C-{1H} NMR spectra of 15 show the
presence of what appears to be only one isomer in solution with
one set of resonances for the isopropyl and methyl group
substituents on the imido ligand phenyl ring.
A crystal structure determination of complex 15 shows a dis-
torted octahedral molecule (Fig. 5) which has bond distances
and bond angles (Table 7) little different from a variety of bis-
imido complexes of the same type.6,22–24 The phenyl rings of the
There is very little difference in the bond lengths between
complexes 16a (Table 8) and 15 except that the two Mo–N
bonds are more similar [1.773(2),1.773(2) and 1.746(2), 1.739(2)
Å in 16a; 1.769(7) and 1.718(7) Å in 15]. The N–Mo–N bond
angles are not very different in both complexes [104.6(1),
102.9(1)Њ in 16a and 105.4(1)Њ in 15] but the tert-butyl groups
in 16a push away from the adjacent chloro ligand [Cl(1) in A
and Cl(3) in B],opening out the N–Mo–Cl bond angles
[N(1)–Mo(1)–Cl(1), 98.4(1); N(3)–Mo(2)–Cl(3) 99.3(1); cf.
N(2)–Mo(1)–Cl(2), 93.4(1); N(4)–Mo(2)–Cl(4) 91.5(1)Њ]. These
4574
J. Chem. Soc., Dalton Trans., 2000, 4569–4578

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Table 8 Selected bond lengths (Å) and bond angles (Њ) for [MoCl2-
(NC6H4CMe3-2)2(dme)] 16
methyls if the ortho-proton of either imido ligand were to pass
over the face of the adjacent imido phenyl ring. Thus imido
ligand N–C bond rotation is unlikely to occur indicating
that interconversion of the syn and anti forms of [MoCl2-
(NC6H4CMe3-2)2(dme)] is not easy. This is also apparent from
the absence of syn [MoCl2(NC6H4CMe3-2)2(dme)] from NMR
studies after crystallisation.
Molecule A
Molecule B
Mo(1)–N(1)
Mo(1)–N(2)
Mo(1)–Cl(1)
Mo(1)–Cl(2)
Mo(1)–O(1)
Mo(1)–O(2)
1.773(2)
1.746(2)
2.3957(7)
2.4277(8)
2.324(2)
2.395(2)
Mo(2)–N(3)
Mo(2)–N(4)
Mo(2)–Cl(3)
Mo(2)–Cl(4)
Mo(2)–O(3)
Mo(2)–O(4)
1.773(2)
1.739(2)
2.3984(8)
2.4102(8)
2.324(2)
2.435(2)
In general, M–N bond lengths and M–N–C bond angles are
of interest in applications of imido complexes as nitrene trans-
fer reagents.1,27 In complex 16a the two imido bond lengths are
clearly different (ca. 0.02 Å). The longer Mo–N bond [bond
length 1.773(2) Å for molecules A and B] is no different from
that of the electronically controlled 1σ–2π W–N bond in
the bis-imide [WCl2(NC6H3Pri2-2,6)(NCOC6H4Me-4)(OPMe3)-
(PMe3)]28 [bond length 1.769(5) Å] (Mo and W have similar
atomic radii29) whereas the Mo–N–C bond angle [146.6(2) and
141.0(2)Њ for A and B] is much reduced in comparison with this
tungsten complex [174.5(5)Њ]. The Mo–N bond length and
Mo–N–C bond angle in molecule B are very similar to those
found for the “bent” imido ligand in the classic “linear” and
“bent” imido ligands in [MoCl2(NC6H5)2(S2CNEt2)2]7,30 for
which studies of related compounds point to the bending
arising from crystal packing effects.7
Analysis of the structure of complex 16a points to steric and
crystal packing effects for this bending. From the diagram it can
be seen that in molecule A the puckering of the dme ligand
brings C(4) forward and C(1) back. As a result, C(22) and C(23)
of the N(2) tert-butyl group straddle Cl(1) with contacts of 3.74
and 4.24 Å respectively. These approaches contribute to the
bending of the Mo(1)–N(2)–C(15) angle [167.4(2)Њ] but there
is an intermolecular contact of 3.64 Å [C(23) ؒ ؒ ؒ C(48)] which
also must have an effect. For the other phenylimido ligand
[N(1)] the Mo(1)–N(1)–C(5) angle is even lower [146.6(2)Њ] and
this appears to result from steric pressures between the tert-
butyl group and Cl(1) as well as a crystal packing effect
[C(12) ؒ ؒ ؒ C(16)Ј, 3.51 Å ]. With the bending of this phenyl
imido ligand, C(6) of the aromatic ring approaches to within
3.69 Å of Cl(2) so that there is little leeway for this angle to
reduce still further, although in molecule B a value of 141.0(2)Њ
is observed. The lower angle is apparently accommodated by
small changes elsewhere in the molecule. The crystal structure
of [MoCl2(NC6H4CN-2)2(dme)]24 also shows a syn arrange-
ment of the ortho substituents but with the less bulky cyano
groups present there is more room on the substituent side of
the complex and the Mo–N–C bond angles are 166.5(3) and
158.4(3)Њ. A steric effect responsible for “linear” bis-imide lig-
ands has been identified in [Mo(NC6H3Pri2-2,6)2(S2CNEt2)2].31
N(1)–Mo(1)–N(2)
N(1)–Mo(1)–Cl(1)
N(1)–Mo(1)–Cl(2)
N(1)–Mo(1)–O(1)
N(1)–Mo(1)–O(2)
N(2)–Mo(1)–Cl(1)
N(2)–Mo(1)–Cl(2)
N(2)–Mo(1)–O(1)
N(2)–Mo(1)–O(2)
104.62(11)
98.36(8)
92.89(8)
96.71(9)
166.92(9)
99.88(8)
93.40(8)
157.73(9)
88.19(9)
N(3)–Mo(2)–N(4)
N(3)–Mo(2)–Cl(3)
N(3)–Mo(2)–Cl(4)
N(3)–Mo(2)–O(3)
N(3)–Mo(2)–O(4)
N(4)–Mo(2)–Cl(3)
N(4)–Mo(2)–Cl(4)
N(4)–Mo(2)–O(3)
N(4)–Mo(2)–O(4)
102.89(12)
99.30(8)
93.61(8)
97.07(10)
167.06(10)
100.23(8)
91.47(8)
158.64(10)
89.74(10)
Cl(1)–Mo(1)–Cl(2) 159.78(3)
Cl(3)–Mo(2)–Cl(4) 160.12(3)
Cl(1)–Mo(1)–O(1)
Cl(1)–Mo(1)–O(2)
Cl(2)–Mo(1)–O(1)
Cl(2)–Mo(1)–O(2)
O(1)–Mo(1)–O(2)
Mo(1)–N(1)–C(5)
83.00(5)
81.68(5)
79.02(6)
83.59(5)
70.28(7)
146.6(2)
Cl(3)–Mo(2)–O(3)
Cl(3)–Mo(2)–O(4)
Cl(4)–Mo(2)–O(3)
Cl(4)–Mo(2)–O(4)
O(3)–Mo(2)–O(4)
Mo(2)–N(3)–C(35) 141.0(2)
Mo(2)–N(4)–C(45) 165.1(2)
83.78(6)
80.93(6)
79.66(6)
83.13(6)
70.05(7)
Mo(1)–N(2)–C(15) 167.4(2)
N(1)–C(5)–C(6)
N(1)–C(5)–C(10)
C(5)–C(10)–C(11)
C(9)–C(10)–C(11)
C(10)–C(11)–C(12) 109.9(2)
C(10)–C(11)–C(13) 111.9(3)
C(10)–C(11)–C(14) 110.0(2)
C(12)–C(11)–C(13) 107.7(3)
C(12)–C(11)–C(14) 110.1(3)
C(13)–C(11)–C(14) 107.2(3)
116.1(3)
123.5(3)
122.5(3)
121.1(3)
N(3)–C(35)–C(36)
N(3)–C(35)–C(40)
116.5(3)
123.0(3)
C(35)–C(40)–C(41) 122.5(3)
C(39)–C(40)–C(41) 121.6(3)
C(40)–C(41)–C(42) 110.7(3)
C(40)–C(41)–C(43) 109.4(3)
C(40)–C(41)–C(44) 112.3(3)
C(42)–C(41)–C(43) 110.2(3)
C(42)–C(41)–C(44) 107.1(3)
C(43)–C(41)–C(44) 107.0(3)
N(2)–C(15)–C(16)
N(2)–C(15)–C(20)
114.7(3)
124.1(3)
N(4)–C(45)–C(46)
N(4)–C(45)–C(50)
114.6(3)
124.1(3)
C(15)–C(20)–C(21) 122.8(2)
C(19)–C(20)–C(21) 121.5(3)
C(20)–C(21)–C(22) 108.3(2)
C(20)–C(21)–C(23) 111.4(2)
C(20)–C(21)–C(24) 111.7(3)
C(22)–C(21)–C(23) 110.1(3)
C(22)–C(21)–C(24) 107.9(3)
C(23)–C(21)–C(24) 107.3(3)
C(45)–C(50)–C(51) 122.8(3)
C(49)–C(50)–C(51) 121.5(3)
C(50)–C(51)–C(52) 108.6(2)
C(50)–C(51)–C(53) 112.5(2)
C(50)–C(51)–C(54) 111.3(3)
C(52)–C(51)–C(53) 109.2(3)
C(52)–C(51)–C(54) 108.8(3)
C(53)–C(51)–C(54) 106.4(2)
Conclusion
The results of this work show that, to restrict phenylimido
ligand C–N bond rotation with a large ortho substituent,
ligands larger than the 4 chloro groups in [Hpy][TaCl4-
(NC6H4CMe3-2)(py)] 1 are needed. This type of substituent
leads to solution dynamics in the [{WCl4(NAr)}x] complexes
and cyclometallation is possible during complex formation with
the isocyanate reaction. The substituted phenylimido ligands
are easily accommodated in the relative d1 [WCl3(NAr)(P)2] and
d2 [WCl2(NAr)(P)3] complexes by small distortions within the
molecules and a suitable positioning of the imido phenyl ring
substituent over, but between, phosphine and chloro ligands
(naphthylimido and 2-phenylphenylimido complexes 6 and 13)
or over a chloro ligand (2-tert-butylphenylimido complex 12).
The naphthylimido ligand is similar in effect to an isopropyl
group as seen in a 2,6-diisopropylphenylimide but is much more
rigid and operates sterically in one direction only. Structural
analysis and simple molecular models indicate that movement
of substituents over the phosphines is unlikely. Recent theo-
retical calculations on [WCl3(NPh)(PH3)2] show that even an
unsubstituted phenylimido ligand experiences unfavourable
Fig. 6 Molecular structure of complex 16a, without H atoms and with
key atoms labelled.
widened angles are slightly greater than that observed for N(1)–
Mo(1)–Cl(1) in complex 15 [96.2(2)Њ]. However, the Cl–Mo–Cl
bond angles are very similar [158.57(2) in 15 and 159.78(3),
160.12(3)Њ in 16a]. It is apparent from the structure of complex
16a and from a consideration of simple molecular models
that the tert-butyl groups cannot easily pass over dme ligand
J. Chem. Soc., Dalton Trans., 2000, 4569–4578
4575

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steric effects as it rotates over a PH3 ligand.32 Low temperature
NMR studies indicate that geared rotation does not occur for
the 2-tert-butylphenylimido complex 12. With the bis-imido
molybdenum complexes 15 and 16 where unsymmetrically sub-
stituted imido ligands could give rise to rapid syn- and anti-type
isomer interconversion, if imido ligand N–C bond rotation
occurred, the studies indicate that both these isomer types can
exist independently where the imido ligand phenyl ring contains
a 2-tert-butyl substituent.
gene (approximately 2 L) as for the synthesis above. Distillation
(118–119 ЊC, 0.8 mmHg) gave 6.35 g (82%) of the isocyanate.
[{WCl4(NC10H7)}x] 2. 1-Naphthyl isocyanate (5.3 cm3, 36.9
mmol) was added to a suspension of WOCl4 (12.6 g, 36.9
mmol) in benzene (100 cm3) and the mixture refluxed for
14 h. The solution was filtered and the solid washed twice with
benzene (20 cm3) followed by light petroleum (30 cm3) and
dried under vacuum to give 14.7 g of product.
[{WCl4(NC6H4CMe3-2)}x] 3. 2-tert-Butylphenyl isocyanate
(5.3 g, 30.4 mmol) and WOCl4 (10.4 g, 30.4 mmol) were refluxed
in benzene (60 cm3) for 14 h. The solution was filtered and the
solid washed twice with benzene (15 cm3) followed by light
petroleum (20 cm3) and dried under vacuum to give 10 g of
product.
Experimental
All preparations and manipulations were carried out under dry
oxygen-free nitrogen using standard bench-top techniques for
air-sensitive substances. 2-tert-Butylaniline, 2-aminobiphenyl,
2-isopropyl-6-methylaniline and 1-naphthyl isocyanate were
obtained from Aldrich. Chlorotrimethylsilane was distilled
before use and trimethylamine dried over and distilled from
freshly ground CaH2. Trimethylphosphine was prepared by
reaction of MgMeI with P(OPh)3 in di-n-butyl ether33 and
PMe2Ph by the reaction of MgMeI with PCl2Ph. Na2MoO4 was
obtained by drying Na2MoO4ؒ2H2O under vacuum with a heat
gun. [{WCl4(O)x}] was prepared by refluxing H2WO3 in thionyl
chloride.34 [TaCl3(NCMe3)(py)2] was prepared by a literature
procedure.11 Phosgene COCl2 was obtained from Matheson
Gases and used as supplied. Light petroleum (bp 40–60 ЊC),
benzene, toluene and dimethoxyethane were distilled from
sodium wire and dichloromethane from freshly ground CaH2.
1H and 13C-{1H} NMR spectra were recorded at 400 and
100 MHz respectively on a Bruker AM400 spectrometer. C, H
and N analyses were determined by Dr A. Cunninghame and
associates, University of Otago, New Zealand.
[{WCl4(NC6H4Ph-2)}x] 4. 2-Phenylphenyl isocyanate (2.0 g,
10.2 mmol) and WOCl4 (3.5 g, 10.2 mmol) were refluxed in
toluene (90 cm3) for 15 h. The solution was filtered and the solid
washed twice with light petroleum (15 cm3) and dried under
vacuum to give 4.5 g of product.
[WCl4{HNC6H4(CMe2CH2)-2(C,N)}] 5. 2-tert-Butylphenyl
isocyanate (3.55 g, 20.3 mmol) and WOCl4 (6.7 g, 19.6 mmol)
were refluxed in toluene (60 cm3) for 14 h. The solution was
filtered and the solid washed with toluene (7 cm3) followed by
light petroleum (20 cm3) and dried under vacuum to give 3 g
(32%) of complex 2. The solvent was removed from the reaction
filtrate leaving an oil which on washing with toluene (10 cm3)
and light petroleum (20 cm3) gave the metallacyclic amide (4 g).
[WCl3(NC10H7)(PMe3)2] 6.
A
suspension of [{WCl4-
(NC10H7)}2] (1.2 g,1.3 mmol) in benzene (80 cm3) was added to
sodium–mercury amalgam (Na, 0.060 g, 2.6 mmol; Hg, 26 g)
under benzene (20 cm3) containing PMe3 (0.54 cm3, 5.3 mmol)
using a cannula and the mixture stirred for 1.5 h. The solution
was filtered, the solvent removed, and the solid recrystallised
from toluene at Ϫ20 ЊC to give 1.2 g of the product. Crystals
for X-ray analysis and the analytical sample were grown from
a dichloromethane solution layered with light petroleum.
Preparations
[Hpy][TaCl4(C6H4CMe3-2)(py)] 1. A solution of 2-tert-
butylaniline (0.28 g, 1.88 mmol) in benzene (20 cm3) was added
to a solution of [TaCl3(NCMe3)(py)2] (1.07 g, 2.07 mmol) in
benzene (40 cm3) and the mixture refluxed for 14 h. The cooled
solution was filtered and the solvent removed giving an orange
microcrystalline solid after drying in vacuo. The solid was
extracted into CH2Cl2 and the solution cooled to Ϫ20 ЊC giving
0.43 g of the complex as orange needles. X-Ray structural
analysis showed this material to be [Hpy][TaCl4(C6H4CMe3-2)-
(py)]ؒCH2Cl2. Under vacuum some CH2Cl2 is lost and the
solid analyses as [Hpy][TaCl4(C6H4CMe3-2)(py)]ؒ0.5CH2Cl2
(see Table 1).
[WCl3(NC6H4CMe3-2)(PMe3)2] 7. A suspension of [{WCl4-
(NC6H4CMe3-2)}2] (1.5 g,1.6 mmol) in benzene (80 cm3) was
added to sodium–mercury amalgam (Na, 0.080 g, 3.3 mmol;
Hg, 29 g) under benzene (10 cm3) containing PMe3 (0.71 cm3,
6.4 mmol) using a cannula and the mixture stirred for 7 h. The
solution was filtered, the solvent removed and the solid
recrystallised from CH2Cl2 and light petroleum to give 1.5 g of
product.
Isocyanates. Method A: 2-tert-butylphenyl isocyanate. 2-tert-
Butylaniline (7.96 g, 53.3 mmol) was dissolved in toluene (150
cm3) in a 500 cm3 two necked round bottom flask containing a
magnetic stirring bar and equipped with a gas tap and a reflux
condenser to which a balloon was attached at the top as well
as a ventilating gas tap. CAUTION: phosgene is an extremely
toxic gas and should be used in a well ventillated hood. Traces
of the gas produce a smell similar to that formed by rotting hay.
Phosgene was passed into the system via the gas tap to blow the
balloon to approximately 500 cm3 (judged by comparison with
the size of the reaction vessel) and the gas tap turned off. The
solution was stirred until the balloon had collapsed and the
process repeated 4 times more. (This method ensures that more
than the required 2 equivalents of phosgene dissolve in the
toluene solution.) The mixture was heated to reflux and the HCl
gas vented from the balloon via the gas tap attached to the
reflux condenser until gas production ceased. The balloon was
filled with 500 cm3 of phosgene and the solution refluxed for 1h.
Distillation (42–44 ЊC, 0.2 mmHg) gave 15.7 g (85%) of the
isocyanate.
[WCl3(NC6H4Ph-2)(PMe3)2] 8. A suspension of [{WCl4-
(NC6H4Ph-2)}2] (0.7 g, 0.71 mmol) in benzene (40 cm3) was
added to sodium–mercury amalgam (Na, 0.038 g, 1.7 mmol;
Hg, 23 g) under benzene (10 cm3) containing PMe3 (0.71 cm3,
6.4 mmol) using a cannula and the mixture stirred for 14 h.
The solution was filtered, the solvent removed and the solid
recrystallised from CH2Cl2 and light petroleum to give 0.5 g of
product.
[WCl3(NC10H7)(PMe2Ph)2] 9.
A suspension of [{WCl4-
(NC10H7)}2] (1.3 g, 1.4 mmol) in benzene (50 cm3) was added to
sodium–mercury amalgam (Na, 0.066 g, 2.9 mmol; Hg, 25 g)
under benzene (10 cm3) containing PMe2Ph (0.78 cm3, 5.6
mmol) using a cannula and the mixture stirred for 5 h. The
solution was filtered, the solvent removed and the solid
recrystallised from CH2Cl2 and light petroleum to give 1.2 g of
the product.
Method B: 2-phenylphenyl isocyanate. 2-Aminobiphenyl
[WCl3(NC10H7)(PMePh2)2] 10. A suspension of [{WCl4-
(NC10H7)}2] (1.0 g, 1.1 mmol) in benzene (50 cm3) was added to
(6.76 g, 39.9 mmol) in toluene (100 cm3) was treated with phos-
4576
J. Chem. Soc., Dalton Trans., 2000, 4569–4578

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Table 9 Crystallographic data for compounds
1
6
12
13
15
16
Formula
[C15H18Cl4N2Ta]-
[C5H6N]ؒCH2Cl2
714.10
C16H25Cl3P2W
C19H40Cl2NP3Wؒ
0.5 C7H8
675.74
C21H36Cl2NP3W
C24H36Cl2MoN2O2
C24H36Cl2MoN2O2
M
583.51
650.17
551.39
551.39
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
β/Њ
Triclinic
P1
Monoclinic
P21/n
Triclinic
P1
Orthorhombic
P21 21 21
9.1057(1)
15.0474(1)
19.8071(1)
90.0
90.0
90.0
2713.91(4)
4
1.591
Monoclinic
Cc
17.5980(1)
10.0198(2)
14.9081(3)
90.0
99.119(1)
90.0
2595.50(8)
4
Triclinic
P1
¯
¯
¯
8.3472(1)
10.0506(2)
16.8679(2)
100.66(1)
93.253(1)
93.475(1)
1384.82(4)
2
8.618(1)
27.756(4)
9.486(2)
90.00(1)
103.90(2)
90.00(1)
2202.7(7)
4
8.6878(8)
9.4309(1)
19.9949(8)
90.391(8)
94.694(1)
116.93(1)
1453.94(3)
2
8.7929(1)
16.8765(1)
18.3315(2)
76.505(1)
88.259(1)
86.306(1)
2639.34(4)
4
γ/Њ
U/Å3
Z
Dc/g cm3
1.713
4.562
203(2)
1.760
5.752
293(2)
1.544
4.332
203(2)
1.411
0.733
203(2)
1.388
0.721
203(2)
µ(Mo-Kα)/mmϪ1
T/K
4.638
203(2)
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
Data, parameters
Observed data
[I > 2σ(I)]
0.0427, 0.1107
0.0507, 0.1157
6022, 283
5279
0.0603, 0.1560
0.0933, 0.1756
4268, 255
3106
0.0261, 0.0675
0.0275, 0.0683
6288, 263
6046
0.0206, 0.0465
0.0216, 0.0468
6009, 262
5817
0.0198, 0.0526
0.0230, 0.0543
3639, 281
3347
0.0344, 0.0749
0.0499, 0.0914
11281, 559
9295
sodium–mercury amalgam (Na, 0.041 g, 2.1 mmol; Hg, 27 g)
under benzene (10 cm3) containing PMePh2 (0.8 cm3, 4.2 mmol)
using a cannula and the mixture stirred for 2 h. The solution
was filtered, the solvent removed and the solid recrystallised
from CH2Cl2 and light petroleum to give 1.0 g of the product.
cm3) followed by triethylamine (4.6 cm3, 33.0 mmol). Chloro-
trimethylsilane (8.4 cm3, 66.0 mmol) was added dropwise and
the mixture stirred for 16 h and refuxed for 8 h. The solution
was filtered while hot and the residue washed with hot dme
(2 × 50 cm3). The combined dme solutions were kept hot while
the solvent was removed to about 40 cm3 and on cooling and
standing the complex formed as a crystalline solid (2.86 g). A
crystal from the sample was used for X-ray crystallography.
[WCl2(NC10H7)(PMe3)3] 11.
A suspension of [{WCl4-
(NC10H7)}2] (1.35 g, 1.5 mmol) in benzene (80 cm3) was added
to sodium–mercury amalgam (Na, 0.141 g, 6.1 mmol; Hg, 105
g) under benzene (20 cm3) containing PMe3 (1.0 cm3, 9.7 mmol)
using a cannula and the mixture stirred for 4 h. The solution
was filtered, the solvent removed and the solid recrystallised
from CH2Cl2 and light petroleum to give 1.2 g of the product.
[MoCl2(NC6H4CMe3-2)2(dme)] 16. 2-tert-Butylaniline (2.46
g, 16.5 mmol) in dme (50 cm3) was added to a stirred suspension
of Na2MoO4 (1.7 g, 8.25 mmol) in dme (50 cm3) followed by
triethylamine (4.6 cm3, 33.0 mmol). Chlorotrimethylsilane (8.4
cm3, 66.0 mmol) was added dropwise and the mixture stirred
for 16 h and refluxed for 8 h. The cooled solution was filtered
and the solvent removed giving 4.43 g of crystalline solid. The
analytical sample was obtained by dissolving a small portion of
this solid in CH2Cl2 and layering the solution with light petrol-
eum. The syn isomer was obtained by dissolving the remainder
of the crude solid in dme (50 cm3) and reducing the volume
(ca. 20 cm3). On standing at room temperature a small quantity
of red-purple crystals was obtained one of which was used for
X-ray crystallography.
[WCl2(NC6H4CMe3-2)(PMe3)3] 12. A suspension of [{WCl4-
(NC6H4CMe3-2)}2] (2.5 g, 2.64 mmol) in toluene (120 cm3) was
added to sodium–mercury amalgam (Na, 0.080 g, 3.3 mmol;
Hg, 29 g) under toluene (10 cm3) containing PMe3 (1.3 cm3, 7.9
mmol) using a cannula and the mixture stirred for 14 h. The
solution was filtered and the solvent removed giving 2.9 g of
the product. Recrystallisation from CH2Cl2 layered with light
petroleum gave the analytical sample and the crystals used for
X-ray crystallography were obtained from toluene.
[WCl2(NC6H4Ph-2)(PMe3)3] 13. A suspension of [{WCl4-
(NC6H4CMe3-2)}2] (1.5 g, 1.5 mmol) in benzene (60 cm3) was
added to sodium–mercury amalgam (Na, 0.15 g, 6.5 mmol; Hg,
46 g) under benzene (20 cm3) containing PMe3 (1.0 cm3, 9.1
mmol) using a cannula and the mixture stirred for 14 h. The
solution was filtered and the solvent removed giving 1.5 g of the
product. Recrystallisation from toluene at room temperature
gave crystals that were used for the analytical sample and one
was used for X-ray crystallography.
X-Ray crystallography
Data for all structures except 6 were collected on a Siemens
SMART diffractometer using Mo-Kα radiation (λ = 0.71073
Å). These data collections covered a nominal sphere of recipro-
cal space by a combination of 4 sets of exposures. Each set had
a different φ angle for the crystal and each exposure covered
0.3Њ in α. Coverage of the unique data sets was at least 98%
complete to 56Њ in 2θ. Crystal decay was monitored by repeat-
ing the initial frames at the end of the data collection and
analysing the duplicate reflections. Unit cell parameters were
obtained by a least-squares fit of all the data with I > 10σ(I).
Lorentz and polarisation corrections were applied and absorp-
tion corrections made by the method of Blessing.35 Data for
6 were collected on a CAD4 diffractometer with graphite
monochromated Mo-Kα radiation and ω–2θ scans at variable
speed. Lorentz and polarisation corrections were applied using
locally written programs and absorption corrections applied
from empirical ψ scans. All structures were solved by Patterson
and Fourier techniques and refined (on F2) by full-matrix
least-squares methods. All non-hydrogen atoms were allowed
to assume anisotropic thermal motion. Hydrogen atoms were
placed geometrically and refined with a riding model. In 6
[WCl2(NC10H7)(PMe2Ph)3] 14.
A
solution of [WCl3-
(NC10H7)(PMePh2)2] 10 (0.8 g, 1.1 mmol) in benzene (40 cm3)
was added to sodium–mercury amalgam (Na, 0.027 g, 1.2
mmol; Hg, 26 g) under benzene (10 cm3) containing PMe2Ph
(0.15 cm3, 1.1 mmol) using a cannula and the mixture stirred
for 14 h. The solution was filtered twice and the solvent
removed giving 0.8 g of the product. The analytical sample was
obtained by recrystallising from a mixture of CH2Cl2 and light
petroleum.
[MoCl2(NC6H3Me-2-Pri-6)2(dme)] 15. 2-Isopropyl-6-methyl-
aniline (2.46 g, 16.5 mmol) in dme (50 cm3) was added to a
stirred suspension of Na2MoO4 (1.7 g, 8.25 mmol) in dme (50
J. Chem. Soc., Dalton Trans., 2000, 4569–4578
4577

View Article Online
18 D. C. Bradley, M. B. Hursthouse, K. M. A. Malik and A. J. Nielson,
disorder was observed with the PMe3 groups. Crystallographic
data for the complexes are contained in Table 9. Programs used
were SHELXS36 for structure solution, SHELXL 9337
for refinement and ORTEP 338 for diagrams.
CCDC reference number 186/2226.
See http://www.rsc.org/suppdata/dt/b0/b006420n/ for crystal-
lographic files in .cif format.
J. Chem. Soc., Chem. Commun., 1981, 103.
19 D. C. Bradley, M. B. Hursthouse, K. M. A. Malik, A. J. Nielson and
R. L. Short, J. Chem. Soc., Dalton Trans., 1983, 2651.
20 A. J. Nielson, R. E. McCarley, S. L. Laughlin and C. D. Carlson,
Inorg. Synth., 1986, 24, 193.
21 B. R. Ashcroft, G. R. Clark, A. J. Nielson and C. E. F. Rickard,
Polyhedron, 1986, 5, 2081; W. Clegg and R. J. Errington, Acta
Crystallogr., Sect. C, 1987, 43, 2223; D. C. Bradley, R. J. Errington,
M. B. Hursthouse and R. L. Short, J. Chem. Soc., Dalton Trans.,
1990, 1043.
22 P. W. Dyer, V. C. Gibson, J. A. K. Howard, B. Whittle and
C. Wilson, J. Chem. Soc., Chem. Commun., 1992, 1666; R. C. B.
Copley, P. W. Dyer, V. C. Gibson, J. A. K. Howard, E. L. Marshall,
W. Wang and B. Whittle, Polyhedron, 1996, 15, 3001.
23 V. C. Gibson, C. Redshaw, W. Clegg, M. A. J. Elsegood,
U. Siemeling and T. Turk, J. Chem. Soc., Dalton Trans., 1996, 4513;
E. A. Kretzschmar, J. Kipke and J. Sundermeyer, Chem. Commun.,
1999, 2381; D. delRio, F. Montilla, A. Pastor, A. Galindo,
A. Monge and E. Gutierrez-Puebla, J. Chem. Soc., Dalton Trans.,
2000, 2433.
Acknowledgements
We thank the Lottery Grants Board for a grant (to C. E. F. R.)
towards the purchase of equipment.
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