Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(CCHR)(dppe)(η-C7H7)]+ and [W(CCR)(dppe)(η-C7H7)]n+ (n = 0 or 1)

Article abstract of DOI:10.1039/c0dt01150a

The first examples of vinylidene complexes of the cycloheptatrienyl tungsten system [W(CCHR)(dppe)(η-C₇H₇)]⁺ (dppe = Ph₂PCH₂CH₂PPh₂; R = H, 3; Ph, 4; C₆H₄-4

Full text of DOI:10.1039/c0dt01150a

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PAPER
Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl
+
complexes [W(C CHR)(dppe)(g-C H )] and [W(C CR)(dppe)(g-
7
7
n+
C H )] (n = 0 or 1)†
7
7
a
b
a
c
a
c
Hannah N. Lancashire, Neil J. Brown, Laura Carthy, David Collison,* Emma C. Fitzgerald, Ruth Edge,
a
a
b
a
a
Madeleine Helliwell, Mark Holden, Paul J. Low,* Joseph J. W. McDouall* and Mark W. Whiteley*
Received 1st September 2010, Accepted 29th October 2010
DOI: 10.1039/c0dt01150a
The first examples of vinylidene complexes of the cycloheptatrienyl tungsten system
+
[
W(C CHR)(dppe)(h-C
7
H
7
)] (dppe = Ph
2
PCH
)], 1, with terminal alkynes HC CR; a one-pot
)] facilitates its use as a precursor. The X-ray structure of 4[PF
reveals that the vinylidene ligand substituents lie in the pseudo mirror plane of the W(dppe)(h-C
2
CH
2
PPh
2
; R = H, 3; Ph, 4; C
6
H -4-Me, 5) have been
4
synthesised by reaction of [WBr(dppe)(h-C
synthesis of 1 from [WBr(CO) (h-C
7
H
7
2
7
H
7
6
]
7
7
H )
auxiliary (vertical orientation) with the phenyl group located syn to the cycloheptatrienyl ring. Variable
1
temperature H NMR investigations on [W(C CH
2
)(dppe)(h-C
7
H
7
)][PF
6
], 3, estimate the energy
-
1
-1
barrier to rotation about the W
for the molybdenum analogue. Deprotonation of 4 and 5 with KOBu yields the alkynyls
C
a
bond as 62.5 ± 2 kJ mol ; approximately 10 kJ mol greater than
t
[
W(C CR)(dppe)(h-C
7
H
7
)] (R = Ph, 6; C
6
H
4
-4-Me, 7) which undergo a reversible one-electron
Cl with E 2 values approximately 0.12 V negative of Mo
oxidation at a glassy carbon electrode in CH
2
2
1
+
+
analogues. The 17-electron radicals [6] and [7] have been investigated by spectroelectrochemical IR,
UV-visible and EPR methods. The electronic structures of representative vinylidene (3) and alkynyl (6)
complexes have been investigated at the B3LYP/Def2-SVP level. In both cases, electronic structure is
characterised by a frontier orbital with significant metal dz2 character and this dominates the structural
and spectroscopic properties of the system.
Introduction
the interaction between the metal centre and the carbon chain
ligand and our recent studies, supported by electronic structure
1
,2
Complexes of highly unsaturated carbon-chain ligands are the
focus of significant current activity in organometallic chemistry
with the expectation of future applications as molecular materials
9,10
calculations,
suggest that cycloheptatrienyl complexes of the
Group 6 metals have a significant contribution to make in this
respect. Thus, by comparison with analogous cyclopentadienyl
3
4
5
in electronic, magnetic and optical devices. Two series of
complexes central to the development of this chemistry are the
11,12
based, Group 8 complexes, M(dppe)Cp (M = Fe or Ru),
the
energy ordering of the d-orbital manifold in the Mo(dppe)(h-
metallacumulenylidenes M{ (C)
complexes M{-(C C) -C CR} and in a sequence of investiga-
tions, we have demonstrated the capacity of the cycloheptatrienyl
molybdenum auxiliary Mo(dppe)(h-C ) to support systems
A key requirement for materials applications
n
CR
2
} and alkynyl/poly-ynyl
C
7
H
7
) fragment is altered by strong d interactions between the
n
13,14
e
2
level of the C
7
H
ring and the dxy and dx2 -y2 metal orbitals
7
resulting in a metal-centred HOMO incorporating substantial dz2
7
H
7
9,10
character.
The dz2 symmetry of the HOMO in Mo(dppe)(h-
6–10
of this type.
C
7
H
7
) complexes is manifest both in the structural chemistry
will be an in-depth understanding of the factors which control
9
of cumulenylidene derivatives and in the redox chemistry of
8,10
the alkynyl and poly-ynyl systems where the limited effect of
a one-electron oxidation process in perturbation of the alkynyl
ligand may, in part, be attributed to a poor symmetry match
between the metal dz2 HOMO (directed towards the centre of
the cycloheptatrienyl ring) and the alkynyl p-orbitals.
To explore further the relationship between frontier orbital
symmetry and the structural and redox chemistry of cumulenyli-
dene and alkynyl complexes, we now report the progression
of our studies to cycloheptatrienyl tungsten systems based on
a
School of Chemistry, University of Manchester, Manchester, UK
M13 9PL. E-mail: Mark.Whiteley@manchester.ac.uk, joe.mcdouall@
manchester.ac.uk
b
Department of Chemistry, Durham University, South Road, Durham, UK
DH1 3LE. E-mail: p.j.low@durham.ac.uk
c
EPSRC National Service for EPR Spectroscopy, School of Chemistry,
University of Manchester, Manchester, UK M13 9PL
†
Electronic supplementary information (ESI) available. CCDC refer-
ence numbers 791429 (1·CH Cl ) and 791430 (4[PF ]). For ESI and
crystallographic data in CIF or other electronic format see DOI:
0.1039/c0dt01150a
2
2
6
1
the W(dppe)(h-C
7
H
7
) auxiliary. The principal objectives of this
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n
Scheme 1 Routes to the preparation of [WX(CO)
2
(h-C
7
H
7
)], R = Me, Pr .
investigation were first to establish that a metal-centred dz2 HOMO
is a consistent feature of the cycloheptatrienyl Group 6 metal
series and secondly to evaluate, by a combined experimental and
theoretical approach, the effect of the 5d orbital set of W vs. the
The availability of gram quantities of [WBr(CO)
facilitated an investigation of its direct reaction with dppe.
As reported previously, reaction of [WI(CO) (h-C )] with
dppe affords the ring-slipped adduct [WI(CO) (dppe)(h -C
which is resistant to loss of CO even in refluxing toluene.
(h-C
H )]
2
7
7
2
7
H
7
3
2
7
H )]
7
21
4
d set of Mo upon the electronic structure and chemical reactivity
of carbon chain complexes of these systems.
However, in a modification to the procedure recently developed
for the analogous chemistry of molybdenum, a mixture of
9
[
WBr(CO)
2
(h-C
7
7
H )] and one half equivalent of dppe was added
to a refluxing 1 : 1 toluene/xylene solution followed one hour
later by a second half equivalent of dppe. This procedure
Results and discussion
gave moderate yields of [WBr(dppe)(h-C
7
H
7
)], 1, formed as a
Synthesis of [WBr(dppe)(g-C
7
H
7
)]
15
mixture with [W(CO)(dppe)(h-C
7
H
7
-
)]Br and small quantities
1
The chemistry of the W(dppe)(h-C
7
H
7
) system was initiated
of [W(CO)
4
(dppe)] (IR, n(C O) cm , CH
2
Cl ) 2017, 1915 (sh),
2
15
22
more than a decade ago, but our investigations were impeded
by the poor accessibility of precursor complexes of the type
1901, 1879), which were separated from 1, by column chro-
matography on alumina. The identity of complex 1 was confirmed
1
[
WX(dppe)(h-C
7
H
7
)]; the synthetic challenges involved have been
by microanalysis, mass spectrometry (see Experimental), H and
15,16
31
1
well documented.
Recently however, we have developed a
)] from the dicarbonyl
)] and this led to a re-evaluation of
the analogous tungsten chemistry. Most known complexes of the
cycloheptatrienyl tungsten system are derived from [WX(CO) (h-
)] (X = halide) which is obtained in a four step synthesis from
P{ H} NMR spectroscopy (Table 1) and by a single crystal X-ray
9
direct synthesis of [MoBr(dppe)(h-C
7
H
7
structural study as the CH
2
Cl solvate (Fig. 1).
2
precursor [MoBr(CO)
2
(h-C
7
H
7
2
C
7
H
7
17
W(CO)
6
in relatively low overall yield (Scheme 1).
The final step, involving CO substitution by halide X, is reported
18
to proceed in very low yield for X = Br or Cl and therefore the
majority of syntheses utilise the iodide derivative [WI(CO) (h-
)] as an entry to further chemistry of W(h-C ) complexes.
In the current investigation, the initial objective was to develop an
improved route to the bromide derivative [WBr(CO) (h-C )],
this being preferred to the commonly employed iodide system on
2
C
7
H
7
7
H
7
2
7
H
7
19
the basis of activation to carbonyl substitution and lability of the
W–X bond. Two modifications to the reaction sequence outlined
+
in Scheme 1 have been effected. First, [W(CO)
3
(h-C
6
7
H
7
)] can
-
be conveniently obtained in good yield as the PF
salt by direct
20
reaction of [W(CO)
need to isolate the cycloheptatriene complex [W(CO)
Secondly, modification of the conditions (reduced reaction time
3
(NCR)
3
] with [C
7
H
7
][PF
6
], thus avoiding the
Fig. 1 Molecular structure of complex 1, with thermal ellipsoids plotted
3
(h-C )].
7
H
8
at 50% probability. Hydrogen atoms, and solvent of crystallisation omitted
◦
for clarity. Key bond lengths (A) and angles ( ):W(1)–Br(1), 2.505(3);
W(1)–P(1), 2.469(3); W(1)–P(2), 2.462(3); P(1)–W(1)–P(2), 78.60(9);
P(1)–W(1)–Br(1), 83.31(9); P(2)–W(1)–Br(1), 83.92(9).
˚
+
and reagent excess) in the reaction of [W(CO)
3
(h-C
7
H )] with
7
NaBr, reliably gave product yields in excess of 60%.
1
268 | Dalton Trans., 2011, 40, 1267–1278
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1
13
1
31
1
a
Table 1 H, C{ H} and P{ H} NMR data
1
13
1
31
1
H NMR
C{ H} NMR
P{ H} NMR
R
C
7
H
7
dppe
C
a
C
b
R
C
7
H
7
dppe
1
2
—
5.15
2.30, m, 4H, PCH
.28–8.19, m, PPh
4.79, 2.72, m, 2H; 3.01,
2
2
;
40.3 {228}
30.8 {321}
7
2.53, t, (7.4), 2H,
307.7, t, {14}
—
56.4, C
24.0, C
80.6, C
—
b
g
;
;
84.6
87.0
2
29.9, m, PCH ;
136.8–128.7, PPh
H
b
; 1.29, q, 2H, H
.79, t, (7.2), 2H, H
4.78, br, 1H; 5.69,
g
;
d
t, {3} m, 2H, PCH
2
;
2
2
2
3
7.58–6.97, m, PPh
2.58, br, 2H; 2.86,
2
2
2
d
3
4
5.04
348.6, t, {25} 103.2, t, {9}
28.0, m, PCH
2
;
34.7 {316}
34.4 {316}
br, 1H; C CH
2
br, 2H, PCH
.85–7.01, m, PPh
5.07, 2.68, m, 2H; 2.95,
t, {3} m, 2H, PCH
2
;
137.8–126.0, PPh
7
b
5.74, t, {12.3},
352.2, t, {27} 123.2, t, {10} 136.2–127.1, 87.5
28.3, m, PCH
2
;
C
CHPh;
2
;
Ph
136.2–127.1, PPh
7
.78–6.55, m,
CHC
5.67, t, {12.0},
CHC Me;
7.78–6.55, m, PPh
C
6
H
5
5
4.96, 2.58, m, 2H; 2.85,
t, {3} m, 2H, PCH
352.2, t, {26} 122.8, t, {10} 138.0–125.3, 86.9
28.0, m, PCH
2
;
34.7 {317}
C
6
H
4
2
;
C
6
H
21.1,
4
Me;
138.0–125.3, PPh
2
6
6
.91, d, {7.6}, 2H;
7.68–6.86, m, PPh
2
.37, d, {7.6}, 2H,
C
6
H
4
Me
C
C
6
6
H
H
4
4
Me; 2.20, 3H,
Me
6
7
6.83, m, 2H; 6.65, m, 4.84
2.26, br, 2H; 2.44,
130.2, t, {22} 120.7
140.1–121.7, 81.3
Ph
28.6, m, PCH
2
;
43.6 {329}
41.5 {321}
1
2
H; 5.94, d, {5.6},
br, 2H, PCH
2
;
140.4–121.7 PPh
2
H; C CC
6
H
5
.
7.84–7.25, m, PPh
2.15, m, 2H; 2.32,
2
2
6.54, d, {7.6}, 2H;
.74, d, {7.6}, 2H,
CC Me; 2.07,
4.73
not observed 121.7
141.9–125.9, 82.5
29.7, m, PCH
2
;
5
m, 2H, PCH
2
;
C
6
H
21.0,
4
Me;
141.9–125.9, PPh
2
C
6
H
4
7.72–7.14, m, PPh
3
H, C CC
6
H
4
Me
C
6
H
4
Me
a
1
13
1
31
1
4
00 MHz H, 100 MHz C{ H}, 162 MHz P{ H} NMR spectra unless stated otherwise; d = doublet, t = triplet, q = quintet, m = multiplet, br = broad;
chemical shifts downfield from SiMe
4
, coupling constants in Hz, J(H–H) as (), J(H–P) or J(C–P) as {}; in CD
2 2
Cl solution unless stated otherwise,
labelling as in Scheme 2. All spectra recorded at ambient temperature. Spectra for complexes 1, 6 and 7 recorded with a trace of cobaltocene added to the
solution to prevent accumulation of paramagnetic W(I) species by aerial oxidation. P NMR spectrum in CDCl .
3
b 31
Carbene and vinylidene complexes
orange solid from the reaction of 3-butyn-1-ol/K[PF
der reflux in methanol. Similarly the vinylidene complexes
W(C CHR)(dppe)(h-C )][PF ], (R = H, 3; R = Ph, 4; R =
-4-Me, 5) were obtained by reaction of [WBr(dppe)(h-C )]
with HC CSiMe , HC CPh or HC CC -4-Me respectively
and K[PF ] under methanol reflux. In common with their
molybdenum counterparts, the vinylidene complexes were stable
in refluxing methanol with no evidence for methoxide addition at
a
C . The availability of a series of carbene and vinylidene complexes
6
] un-
+
[W{(C)
n
CR
2
}(dppe)(g-C
7
7
H )]
[
C
7
H
7
6
The synthetic protocol outlined above unlocks the chemistry of
the cycloheptatrienyl tungsten system to a series of advances
based upon the electron-rich, d , W(dppe)(h-C
6
H
4
7
H
7
3
6
H
4
6
7
H ) auxiliary.
7
6
To commence the investigation, the reactions of [WBr(dppe)(h-
)] with terminal alkynes HC CR to give carbene and
C
7
H
7
vinylidene products were explored. An extensive series of iron,
ruthenium and molybdenum, carbene and vinylidene complexes of
+
[
M{(C)
n
CR
2
}(dppe)(h-C
7
H )] (M = Mo or W, n = 0 or 1)
7
+
general formulation [M{ (C)
n
CR
2
}(dppe)(h-L)] {M = Fe, L =
allows a direct comparison of spectroscopic and structural data
23
24
25,26
9
Cp or Cp*; M = Ru, L = Cp;
M = Mo, L = C
7
H
7
} has
13
1
for molybdenum and tungsten analogues. The C{ H} NMR
been developed, based on the reaction of metal halide precursor
complexes [MX(dppe)(h-L)] with terminal alkynes HC CR in
methanol in the presence of a halide acceptor such as NH
chemical shift data for C of the Mo and W carbene and vinylidene
systems are summarised in Table 2 from which it is evident that
the tungsten derivatives exhibit a shift of d C to high field by
approximately 20 ppm. In each case the C resonance is a triplet
a
4
[PF ] or
6
a
K[PF ]. The method depends upon ionisation of the halide ligand
6
a
6
and subsequent addition of the alkyne to the d metal centre which
2
with J(P–C) values similar for the two metals but slightly smaller
promotes alkyne to vinylidene isomerisation. It was therefore our
for the tungsten derivatives.
6
expectation that the d tungsten centre of [WBr(dppe)(h-C
7
H
7
)]
would exhibit analogous reactivity.
The outcome of the reactions of [WBr(dppe)(h-C
7
H
7
)] with
Structural studies
terminal alkynes HC CR is summarised in Scheme 2 and
characterisation details for the complexes described are presented
in Table 1 and the Experimental section.
We have previously reported structural studies on the cyclo-
heptatrienyl molybdenum carbene and vinylidene complexes
Clearly the cycloheptatrienyl tungsten centre is able to support
a range of metallacumulenylidene systems in an equivalent
manner to the molybdenum analogue. The 2-oxacyclopentylidene
27
,
and [Mo(C CHR)-
+
7
27
(
dppe)(h-C
7
H
7
)] (R = Ph or (CH
2
)
3
OH ). A key observation
from this work is the orientation of the carbene or vinylidene
2, was isolated as an
ligand substituents with respect to the pseudo mirror plane which
This journal is © The Royal Society of Chemistry 2011
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13
a
+
Table 2 Comparison of C NMR shifts for C
a
in complexes [M{(C)
n
CR
2
}(dppe)(h-C
7 7
H )]
(
n
C) CR
2
C
CH
2
C
C(H)Ph
M
d C
a
Solvent
d C
a
Solvent
d C
a
Solvent
Mo
W
331.7 {18}
307.7 {14}
acetone-D
6
,
368.0 {30}
348.6 {25}
CD
CD
3
CN
Cl
372.8 {32}
352.2 {27}
acetone-D
6
,
CD
2
Cl
2
2
2
CD Cl
2
2
a 2
J(P–C) values in Hz in parentheses {}.
1
2
1
Scheme 2 Reagents and conditions (i) dppe ( equivalent), toluene/xylene (1 : 1), reflux 1 h, then further dppe ( 2 equivalent) reflux 3 h. (ii)
HC C(CH
or C
2
)
2
OH, in methanol, K[PF
6
], reflux 3 h. (iii) HC CR (R = SiMe
3
, Ph or C
6
H
4
-4-Me) in methanol, K[PF
6
], reflux 2–3 h. (iv) (R = Ph
t
6
H
4
-4-Me), excess KOBu in thf, 40 min.
+
bisects the Mo(dppe)(h-C
7
H
7
) fragment. Thus the oxacarbene
, is disposed ortho-
contrast, structural studies on the [M{(C) CR }(dppe)(h-L)]
n
2
(
n = 0 or 1; L = Cp or Cp*; M = Fe or Ru) series reveal that
25
ring of
carbenes adopt a vertical configuration, whilst vinylidenes are
gonal to the mirror plane in a horizontal alignment whereas
in each of the vinylidene complexes, the substituents lie in the
mirror plane and are assigned to a vertical configuration. By
28
horizontal. In terms of the classical, self-consistent field (SCF)
calculations on these systems, it appears that the preferred
29
plane of the p-interaction of the Mo(dppe)(h-C
7
H ) auxiliary
7
1
270 | Dalton Trans., 2011, 40, 1267–1278
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◦
Table 3 Important bond lengths ( A˚ ) and angles ( ) for complex 4
in 4 is the orientation of the vinylidene ligand which adopts
a vertical configuration with the more bulky Ph substituent
located in the syn position relative to the cycloheptatrienyl ring
in accord with the structures of the molybdenum analogues;
this result suggests that the vertical orientation of the vinylidene
ligand substituents is a consistent feature of the Group 6 metal
Bond lengths/A˚
W(1)–P(1)
W(1)–P(2)
W(1)–C(8)
C(8)–C(9)
C(9)–C(10)
W(1)–C(1)
2.5037(18)
2.5032(18)
1.941(7)
1.323(9)
1.463(9)
2.280(6)
W(1)–C(2)
W(1)–C(3)
W(1)–C(4)
W(1)–C(5)
W(1)–C(6)
W(1)–C(7)
2.328(6)
2.323(6)
2.331(6)
2.290(6)
2.339(6)
2.357(6)
systems, M(dppe)(h-C
7
7
H ) (M = Mo or W). The dihedral angle
between the planes defined by Ct–W–C(8) and C(8)–C(9)–C(10)
◦
(
Ct represents the centroid of the cycloheptatrienyl ring) is 1.5
◦
in 4 (cf . [Mo(C CHPh)(dppe)(h-C
7
H
7
)][BF
4
], 10.6 ) indicating
◦
Bond angles ( )
a small deviation from the precise vertical configuration. An
additional salient structural feature of 4 is the large Ct–W–C(8)
P(1)–W(1)–P(2)
P(1)–W(1)–C(8)
P(2)–W(1)–C(8)
80.19(6)
78.40(19)
81.03(19)
W(1)–C(8)–C(9)
C(8)–C(9)–C(10)
Ct–W(1)–C(8)
172.4(5)
128.8(6)
138
◦
angle (138 ). This is similar to that observed in the molybdenum
◦
7
◦
31
analogue (135 ), and consistent with the optimum value (135 )
for a p-interaction between the cumulenylidene LUMO and a
metal dz2 based HOMO.
Ct = centroid of C
7
H
7
ring
with the vacant p-orbital of the cumulenylidene C
the converse of that in the [M{(C) CR
a
carbon is
Dynamic NMR Investigations
+
n
2
}(dppe)(h-L)] (M =
1
Variable temperature H NMR studies on complexes of the type
Fe or Ru) series and a recent DFT investigation on the vinylidene
+
32
33
+
[M{ (C)
n
CH
2
}(dppe)(h-L)] (n = 0, L = Cp, M = Fe or Ru;
complex [Mo(C CH
2
)(dppe)(h-C
7
H )] has confirmed that the
7
7
+
n = 1, L = C
7
4
H
7
, M = Mo ) and [M( CH
2
)(CO) (PPh )Cp] (M =
2
3
atypical orientation of vinylidene ligands in the cycloheptatrienyl
3
Mo or W) in which the carbene or vinylidene H substituents
are disposed in a vertical orientation may be employed to
confirm low temperature solution conformations and to estimate
molybdenum system can be attributed to a p-interaction between
the cumulenylidene LUMO and the metal dz2 based HOMO of
9
the Mo(dppe)(h-C
7
H
7
) unit. The main purpose of the current
activation energies to rotation about the M
C
a
bond. In the case
study was therefore to establish the ligand orientation preference
+
of [Mo(C CH
2
)(dppe)(h-C
7
H
7
)] the two vinylidene hydrogen
imposed by the W(dppe)(h-C
The crystallographically
W(C CHPh)(dppe)(h-C
numbering scheme is illustrated in Fig. 2. The asymmetric unit of
contains two molecules; in one of these the cycloheptatrienyl
7
H
7
) auxiliary.
1
substituents are inequivalent in the low temperature H NMR
spectrum consistent with a vertical vinylidene orientation with
two discrete vinylidene proton environments located syn or anti to
the cycloheptatrienyl ring. From the coalescence temperature of
determined
structure
of
[
7
H
7
)][PF ], 4 with the crystallographic
6
4
2
68 K (±3 K) in CD
3
CN, the energy barrier to rotation about the
ring is disordered over two sites and therefore the discussion here
is focussed on the non-disordered molecule although structural
parameters are very similar in each case. Important bond lengths
and angles for the non-disordered molecule are given in Table 3
+
Mo bond in [Mo(C CH
C
a
2
)(dppe)(h-C
7
H )] was estimated
7
-
1 7
as 51.9 ±1 kJ mol , significantly larger than the equivalent
+
parameter in complexes of the type [M(C CHR)(dppe)Cp]
23
35
(
[
M = Fe or Ru ). The synthesis of the tungsten analogue
W(C CH )(dppe)(h-C )][PF ], 3, now permits an evaluation
of the effect of the identity of the metal on the M rotation
˚
and it is evident that the key W
C
a
(1.941(7) A) and C
a b
–C
2
7
H
7
6
˚
(
1.323(9) A) distances of the vinylidene ligand lie within normal
30
C
a
)] .
ranges. However the principal structural feature of interest
+
barrier in the complexes [M(C CH
2
)(dppe)(h-C
7
H
7
1
Remarkably, the H NMR spectrum of 3 in CD
3
CN reveals that
the vinylidene protons are inequivalent at ambient temperature
293 K) consistent with a vertical ligand orientation and a high
activation energy to rotation about the W bond. On warming
above 293 K, the vinylidene proton resonances broaden and
a coalescence temperature of 330 K (±5 K) in CD CN was
determined giving an estimated barrier to rotation about the
(
C
a
3
-
1
W
a
C bond in 3 as 62.5 ±2 kJ mol . This is considerably larger
than the equivalent parameter for the molybdenum analogue
determined in the same solvent and may indicate an enhanced p-
interactionbetween the vinylideneligand andthe metal5d orbitals.
A related metal-dependency of rotation barriers has been reported
+
for the Group 6 carbene complexes [M( CH
2
)(CO)
2
(PPh )Cp]
3
-
1
-1 34
[
M = W, 35 kJ mol ; M = Mo, < 28 kJ mol ].
Alkynyl complexes [W(C CR)(dppe)(g-C )]
7
H
7
Fig. 2 Molecular structure of complex 4, with thermal ellipsoids plotted
at 50% probability. Hydrogen atoms [except H(9)] and PF counter anion
6
omitted for clarity. The figure illustrates one of two crystallographically
independent molecules in the asymmetric unit.
-
The vinylidene complexes 4 and 5 undergo deprotonation on
t
treatment with KOBu in thf to afford alkynyl complexes
[W(C CR)(dppe)(h-C
7
H
7
)] (R = Ph, 6; R = C
6
H
4
-4-Me, 7;
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n+
a
Table 4 Electrochemical, IR and UV-visible data for the alkynyl complexes [M(C CR)(dppe)(h-C
7
H
7
)] (n = 0 or 1)
b
c
d
Complex
R
Electrochemical data IR data
UV/visible data
M
n = 0
n = +1
Dn (C C)
-13
n = 0
n = +1
Ph
Ph
Mo -0.72
-0.84
2045
2032
32700 (21000), 27000
33300 (15600), 28300 (8400),
18900 (2100), sh, 16900 (4800)
34700 (6100), 29200 (3140),
26300 (2030), 20000 (970), sh,
(
12200), 18900 (1000)
34300 (8120), 25300
3640), 19100 (650)
W
2042, 1991 (w) 2029
-13
(
1
8000 (1600)
C
C
6
6
H
H
4
4
-4-Me Mo -0.72
-4-Me -0.86
2050
2017
-33
32680 (18300), 27100
12800), 19200 (800)
25700 (7200), 20700
1950)
28250 (7800), 16600 (5300)
(
W
2048, 2036 (sh) 2012, 2002 (sh) -35
29800 (7500), 25500 (4970),
20500 (1600), 17600 (1270)
(
a
b
Data for M = Mo from reference 10.
E
1
2
(V), by cyclic voltammetry at a glassy carbon working electrode, Ag/AgCl reference electrode. All potentials
+
+
-1
n
are reported vs. FeCp
2
/FeCp
2
(FeCp
2
/FeCp
2
= 0.00 V) at a scan rate of 0.100 V s from 0.2 M [NBu
4
][PF
6
]/CH
2
Cl
2
solutions at ambient temperature.
c
-1
n
d
-1
-1
-1
4 6 2 2
n(C C)/cm , spectroelectrochemical measurement in 0.1 M [NBu ][PF ]/CH Cl . nmax/cm , (e/M cm ) determined by spectroelectrochemical
n
4 6 2 2
methods in 0.1 M [NBu ][PF ]/CH Cl .
Scheme 2) which were isolated as red–brown solids following
purification by chromatography on Celite. The deprotonation
reactions proceeded to completion only with a large excess of
base, probably reflecting the high stability and low acidity of the
vinylidenes 4 and 5 conferred by the strongly electron donating
of the redox active frontier orbital within a series of similar
complexes. Thus the large negative shifts of n(C C) upon
n+
-1
oxidation observed for [Ru(C CR)(dppe)Cp*] , (> 100 cm )
are consistent with depopulation of an orbital with a substantial
degree of C C bonding character, and significant radical-ligand
+
12
W(dppe)(h-C
7
H
7
) auxiliary. Complexes 6 and 7 were characterised
character in the cations [Ru(C CR)(dppe)Cp*] . Although less
extensively documented, available data from Os(dppe)Cp* based
ynyl systems also supports the notion of substantially ligand-
as summarised in Tables 1 and 4 and the Experimental section.
Key spectroscopic features are the IR active n(C C) stretching
bands which (with the exception of band splitting in 7) are almost
37
based frontier orbitals in the 5d analogues. Similar analyses
of the shift in alkynyl stretching frequency upon oxidation,
6,10
identical to the molybdenum analogues (see Table 4), and in the
1
3
0/+
C NMR spectrum, the characteristic triplet resonance for the
alkynyl C carbon which is shifted to high field by ca. 10 ppm as
Dn(C C), for the iron complexes [Fe(C CR)(dppe)Cp*] are
38
a
complicated by splitting of the n(C C) band by Fermi coupling.
a result of substitution of Mo with W.
However, it is generally agreed that the 3d cation-radical systems
The redox behaviour of complexes 1, 6 and 7 was investigated
feature more substantial metal-localised radical character than
11
by cyclic voltammetry at a glassy carbon electrode in CH
2
Cl
2
their 4d (Ru) or 5d (Os) counterparts. By contrast with the
ruthenium complexes, the Mo(h-C ) complexes which also
(
details as in Table 4). Under these conditions, each of the
7
H
7
1
2
6
complexes undergoes a diffusion controlled (i
p
/v
is constant for
contain a 4d formal electron configuration, feature a more metal-
-
1
scan rates v = 50–500 mV s ), chemically reversible one-electron
oxidation with the separation between cathodic and anodic peak
potentials comparable to that determined for ferrocene under
centred oxidation process, with less alkynyl ligand character and
10
consequently much smaller shifts in n(C C). Given the essen-
tially identical structure of the complexes [M(C CR)(dppe)(h-
identical conditions. The formal reduction potentials E
1
2
for 6
C
7
7
H )] (M = Mo or W) with those of the group 8 complexes
and 7 are approximately 120 mV to negative potential of the
M(C CR)(dppe)Cp*, a comparison of the shift in n(C C)
following one-electron oxidation should provide a good indicator
of the effect of 4d vs. 5d orbital overlap upon the metal–alkynyl
interaction.
Mo analogues. In principle, the results of the cyclic voltammetry
+
indicate that the 17-electron radicals [W(C CR)(dppe)(h-C
7
7
H )]
+
+
(
R = Ph, [6] ; R = C
6
H -4-Me, [7] ) are isolable synthetic targets.
4
However, whilst the radicals were undoubtedly generated by
The shift in n(C C) resulting from one-electron oxidation of 6
and 7 to the corresponding radicals [6] and [7] was investigated
+
+
reaction of 6 and 7 with [FeCp ][PF ] in CH Cl , isolation as pure
2
6
2
2
materials was impeded by slow decomposition to the carbonyl
by synthetic and spectroelectrochemical methods. Addition of
36
+
-1 15
complex [W(CO)(dppe)(h-C
7
H
7
)] , [n(CO), CH
2
Cl
2
, 1940 cm ]
[FeCp
2
][PF
6
] to red–brown, CH
2
Cl solutions of 6 and 7 resulted in
2
+
+
+
and therefore in the investigations described below, [6] and
the rapid formation of deep red ([6] ) or deep pink ([7] ) solutions
of the 17-electron radicals for which IR data were immediately
recorded; results were confirmed by an IR spectroelectrochemical
analysis (Fig. 3) which also demonstrated the reversibility of the
changes in the IR spectra. In both cases the negative shifts in
+
[
7] were generated in situ or studied by spectroelectrochemical
techniques.
Spectroelectrochemical IR, UV-visible and EPR investigations on
+
n(C C) resulting from one-electron oxidation are small (6/[6] ,
+
the alkynyl radicals [W(C CR)(dppe)(g-C
7
7
H )]
-
1
+
-1
-
13 cm ; 7/[7] , -35 cm ) and almost identical to the Mo
+
A key feature of the redox chemistry of metal alkynyl systems
is the negative shift in the IR active n(C C) stretch resulting
from one-electron oxidation to the 17-electron radical cations.
The magnitude of the negative shift in n(C C) acts as a good
first order indicator of the metal vs. alkynyl ligand character
series (see Table 4); (the interpretation of the data for 7/[7] is
complicated by band splitting in both 7 and [7] , however both
+
bands assigned to n(C C) in complex 7 are Raman inactive and
38
consequently the splitting is attributed to Fermi coupling effects).
The very similar response in n(C C) resulting from one-electron
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1
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+
Table 5 EPR data for the 17-electron radicals [WX(dppe)(h-C
7
H
7
)] (X =
a
Br, C CR)
183
31
1
Complex
A
iso
(
W)/G
a
iso( P)/G
a
iso( H)/G
g
iso
+
b
[1]
[6]
[7]
61
50
50
26
24
24
1.952
1.978
1.977
+
+
4.3
4.2
a
+
+
+
X-band solution spectra in CH
2
Cl
2
at 273 K ([1] ) or 193 K ([6] , [7] );
b
1
hyperfine couplings in Gauss. hyperfine coupling to H not resolved.
-
1
(
590 nm); M = W, 18000 cm (555 nm)] consistent with the higher
lying 5d orbitals of the tungsten centre; the change in position of
this absorption may also account for the marked contrast in the
+
colours of the 17-electron radicals [M(C CPh)(dppe)(h-C
7
7
H )]
(
M = Mo, deep blue; M = W, deep red). Consistent with the
description of oxidation of these W-alkynyl complexes in terms of
metal-centred redox processes, weak W d–d bands were observed
-
1
near 12,000 cm (Fig. 4).
X-band EPR spectra of the radicals [1] , [6] and [7] were
recorded on CH Cl solutions of the complexes generated in situ
at 193 K by addition of [FeCp ][PF ] to the 18-electron precursors;
Fig. 3 The spectroelectrochemically generated IR [n(C C) region]
spectra of [7] (n = 0, 1) recorded in CH Cl /0.1 M [NBu ][PF ].
2 2 4 6
n+
n
+
+
+
2
2
oxidation of directly analogous complexes [M(C CR)(dppe)(h-
)] (M = Mo or W; R = Ph or C -4-Me) suggests that the
2
6
C
7
H
7
6
H
4
+
Fig. 5 illustrates a representative spectrum obtained for [6] and
details of the EPR parameters extracted from the spectra are
presented in Table 5. The spectra of the tungsten complexes
are slightly less well resolved than for their Mo analogues
but hyperfine couplings to W and P were determined in all
cases and for the alkynyl derivatives it was possible to estimate
metal alkynyl interaction is almost independent of the 4d vs. 5d
character of the metal centre; this result is in marked contrast to the
+
vinylidenes [M(C CH
2
)(dppe)(h-C
7
H
7
)] (M = Mo or W) where
10,15,39
the barrier to rotation about M
the 5d metal.
C
a
is significantly increased for
183
31
To probe further, the effects of substitution of Mo by W in
the hyperfine to the hydrogens of the C
7
7
H ring. By comparison
+
+
these systems, comparisons between 6/[6] , 7/[7] and their Mo
analogues were extended to UV-visible and EPR studies. The UV-
visible electronic absorption spectra were recorded by spectro-
31
with Mo analogues, aiso( P) is slightly larger for the W complexes;
183
values for Aiso
(
W) are similar to those determined previously for
40
metal centred cation radical complexes. The shift in giso, typically
from 1.996 for the Mo alkynyl complexes to 1.978 for the W series,
is consistent with the larger spin orbit coupling constant for the
electrochemical methods in CH
2
Cl under identical conditions to
2
10
those previously reported for the Mo analogues; experimental
+
spectra for 6/[6] are shown in Fig. 4. The principal result
5d metal.
features the position of the band at the red end of the visible
region in the radical cations, which for the Mo analogues has
been assigned to a LMCT (alkynyl to metal) transition on the
10
basis of a TD-DFT treatment. In the tungsten complexes this
band is of reduced intensity and shifted to higher energy by ca.
-
1
+
-1
1
000 cm [cf. [M(C CPh)(dppe)(h-C
7
H
7
)] , M = Mo, 16900 cm
+
+
7 7
Fig. 5 X-band solution spectrum of [W(C CPh)(dppe)(h-C H )] , [6] ,
2 2
recorded as a first derivative spectrum in CH Cl at 193 K.
Electronic structure calculations
Density functional calculations were performed on the vinyli-
+
dene complex [W(C CH
2
)(dppe)(h-C
7
H )] , denoted 3-H to
7
distinguish experimental and calculated parameters, the C CH
2
π
rotational transition state of 3-H, (3-H ), and the alkynyl com-
n+
+
Fig.
4
Spectroelectrochemical UV-visible spectra for
6
(dotted
plexes [W(C CPh)(dppe)(h-C
7
41
H )] , 6-H and [6-H] , using the
7
+
line)/[6] (solid line) recorded in 0.1 M NBu
4
PF
6
/CH
2
Cl
2
.
Gaussian03 suite of programs. All calculations employed the
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◦
Table 6 Important bond lengths ( A˚ ) and angles ( ) for complex 3-H
Table 7 B3LYP/Def2-SVP orbital components (%) of HOMO-1 of
π
+
and the rotational transition state 3-H from structures optimized using
the BP86 and B3LYP functionals and the Def2-SVP basis. For atom
numbering, see Fig. 2
[M(C CH
2
)(dppe)(h-C
7
H
7
)] (M = Mo or W) (sum of orbital populations
on non-hydrogen atoms only)
M
Metal
C
C(H
2
)
C
7
(H
7
)
P
2
3
-H
3-Hπ
Mo
W (3-H)
56
53
8
12
27
18
2
2
Bond lengths
BP86
B3LYP
BP86
B3LYP
W(1)–P(1)
W(1)–P(2)
W(1)–C(8)
C(8)–C(9)
W(1)–C(1)
W(1)–C(2)
W(1)–C(3)
W(1)–C(4)
W(1)–C(5)
W(1)–C(6)
W(1)–C(7)
2.553
2.572
1.942
1.332
2.326
2.357
2.346
2.353
2.319
2.401
2.430
2.582
2.601
1.944
1.321
2.325
2.354
2.345
2.352
2.320
2.401
2.429
2.507
2.511
1.982
1.329
2.340
2.381
2.337
2.383
2.337
2.448
2.450
2.534
2.539
1.985
1.318
2.345
2.386
2.339
2.387
2.340
2.458
2.460
carried out a population analysis on 3-H and its Mo analogue
at the B3LYP/Def2-SVP level (for the Mo-analogue we used the
structure obtained previously in reference 9). There is remarkable
qualitative and quantitative similarity between the frontier orbital
energies and compositions of the W and Mo systems but a key
difference is between the HOMO-1 of 3-H and its Mo-analogue.
This orbital consists of p-type bonding interactions between
+
C
a
and the metal centre in the [M(dppe)(h-C
7
H
7
)] (M = W,
Mo) fragment (we have previously established the importance
of this interaction in dictating the orientational preference of
9
Angles
these systems ). On rotation of the C CH unit, this p-bonding
2
interaction is removed and so it must be significant in determining
the rotational energy barrier. The HOMO-1 orbital is shown in
Fig. 6 and its composition in Table 7.
P(1)–W(1)–P(2)
P(1)–W(1)–C(8)
P(2)–W(1)–C(8)
W(1)–C(8)–C(9)
Ct–W(1)–C(8)
80.99
80.87
83.35
178.83
135.52
3.49
80.53
81.33
83.99
178.90
135.07
1.51
79.99
82.81
85.53
178.36
129.65
98.72
79.92
83.64
86.31
178.02
128.71
101.44
W(1)–C(8)–C(9)–H(9)
7 7
Ct = centroid of C H ring.
42,43
Def2-SVP basis set of Ahlrichs et al.
For W, this basis
constitutes a relativistic effective potential with 60 electrons treated
44
in the core. All structures were fully optimized using both the
45
46
BP86 and B3LYP functionals for purposes of comparison,
starting from crystal geometries where X-ray data were available.
All structures were confirmed as minima or transition states
through vibrational analysis.
Optimisation of the geometry of 3-H showed that the minimum
energy structure has the plane of the C CH
2
moiety aligned
perpendicular to the plane of the C ring, in accord with the
7
H
7
observed structure of 4 shown in Fig. 2. The transition state for
π
rotation of the vinylidene ligand around the W–C
has the C CH
to the C plane. Some key geometric parameters for these
a
–C
b
axis (3-H )
2
plane aligned ‘horizontal’, essentially parallel
7
H
7
structures are given in Table 6 and may be compared directly with
Fig. 6 HOMO-1 orbital of 3-H at the B3LYP/Def2-SVP level. For clarity
only the hydrogens of the C CH group are shown and the dppe unit is
2
shown in wireframe. Isosurface value is 0.04 au.
those of 4 shown in Table 3. It can be seen that the main differences
π
in the geometries of 3-H and 3-H , apart from the rotation of the
◦
C
CH
2
group, are the reduction by some 6 of the Ct–W(1)–C(8)
angle and the general lengthening of the W–C distances of the
ring (except for W–C(3) which eclipses the C C bond and
is shortened slightly in the transition state).
Inspection of Table 7 reveals that the bonding HOMO-1 orbital
C
7
H
7
of 3-H contains slightly more C CH
character than in the Mo-analogue. Moreover, the contribution of
the C ring is substantially less in 3-H than in the Mo analogue,
indicating a change in the balance of the bonding between the
metal and the C ring or the C CH ligand. The M CH
2
character and less metal
π
The rotational barrier for the 3-H → 3-H conversion is
7
H
7
-
1
calculated to be 70.7 (BP86)/67.2 (B3LYP) kJ mol . The in-
clusion of zero-point energies reduces these to 67.8 (BP86)/64.0
7
H
7
2
C
2
(
B3LYP) kJ mol- in good agreement with the experimentally
1
p-interaction is therefore more efficient in the tungsten derivative
3-H and consequently this complex features a larger rotational
barrier, as observed experimentally in the dynamic NMR studies
described above.
-
1
9
determined value of 62.5 ± 2 kJ mol . In our previous work
we calculated the rotational barrier for the Mo-analogue of 3 to
-
1
be about 45 kJ mol , which compares with the experimental value
of around 52 kJ mol- observed in dynamic NMR experiments.
The current calculations concur with the experimental findings
that the W systems have larger rotational barriers than the
Mo analogues. To investigate the origin of this difference we
1
For the alkynyl complex 6-H, we wished to establish the nature
of the HOMO orbital and compare it with the analogous Mo
10
system. For reasons that we have described elsewhere the HOMO
of [Mo(C CPh)(dppe)(h-C
)] is dominated by the dz2 orbital
7
H
7
1
274 | Dalton Trans., 2011, 40, 1267–1278
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7 7
Table 8 B3LYP/Def2-SVP orbital energies and compositions of [W(C CPh)(dppe)(h-C H )], 6-H (values in parentheses for Mo analogue)
Orbital composition (%)
Orbital
Energy/eV
metal
C
7
(H
7
)
C
C
C
6
(H
5
)
P
2
LUMO
HOMO
HOMO–1
HOMO–2
–1.10
-3.94
-4.82
-5.08
7 (14)
17 (34)
4 (4)
40 (37)
39 (37)
1 (2)
0 (2)
9 (9)
6 (6)
2 (2)
12 (12)
4 (3)
4 (4)
61 (62)
23 (24)
44 (47)
16 (16)
23 (25)
6 (6)
3 (3)
Fig. 7 HOMO orbital of 6-H at B3LYP/Def2-SVP level. For clarity hydrogens are omitted and the dppe unit is shown in wireframe. Isosurface value is
.04 au.
0
of the metal. Fig. 7 shows the HOMO of 6-H and it can be seen
that it has the same character as the analogous Mo system.
Table 8 presents a population analysis of the frontier molecular
Conclusions
A simple, one-pot synthesis of [WBr(dppe)(h-C
7
H )] from
7
10
orbitals of 6-H alongside equivalent data for the Mo analogue
shown in parentheses). The degree of similarity is striking and
MO plots for the HOMO-1 and HOMO-2 of 6-H (see ESI†)
ring and the
[WBr(CO)
istry of the electron-rich, d , cycloheptatrienyl tungsten auxiliary
W(dppe)(h-C ). The reactions of [WBr(dppe)(h-C )] with
2
(h-C
7
H
7
)] has opened up investigations into the chem-
6
(
7
H
7
7
H
7
confirm strong d interactions between the C
7
H
7
terminal alkynes in refluxing methanol proceed with alkyne to
vinylidene isomerisation to afford oxacyclocarbene and vinylidene
tungsten dxy and dx2 -y2 orbitals, identical to the Mo analogue and
key to the establishment of a HOMO with substantial metal dz2
complexes of general formulation [W{(C)
= CR
}(dppe)(h-
n
2
10
+
character.
C
7
H
7
)] (n = 0 or 1). An X-ray structural study on the
+
For the 17-electron radical cation [6-H] , spin density distribu-
tion is again dominated by the metal dz2 orbital with B3LYP/Def2-
SVP computed Mulliken spin densities revealing significant local-
phenylvinylidene complex [W(C CHPh)(dppe)(h-C
7
H
7
)][PF ],
6
reveals that, in common with the Mo analogue, the vinylidene
ligand adopts a vertical orientation consistent with a strong
interaction between a filled metal dz2 orbital and the vacant
isation of spin density at the W centre (W: 0.980, C
a
: -0.123,
C
b
: 0.234, see ESI†). Finally the shift in the alkynyl n(C C)
p orbital on C
a
of the vinylidene ligand. Variable temperature
1
stretching frequency resulting from one-electron oxidation of
H NMR investigations on [W(C CH )(dppe)(h-C )][PF
demonstrate that the energy barrier to rotation about the W
2
7
H
7
6
]
+
-1
6
-H to [6-H] was examined. We find n(C C) = 2039 cm
C
a
-
1
-1
-1
(
BP86)/2126 cm (B3LYP) in 6-H and n(C C) = 2000 cm
bond is approximately 10 kJ mol larger than for the analo-
gous molybdenum complex. Deprotonation of the vinylidenes
[W(C CHR)(dppe)(h-C
[W(C CR)(dppe)(h-C
the 17-electron radicals [W(C CR)(dppe)(h-C
tion of Mo by its 5d counterpart W in the alkynyl complexes
[M(C CR)(dppe)(h-C
the electronic properties of the system with the key parameter
Dn(C C) (the shift in the alkynyl stretching frequency resulting
from one-electron oxidation) essentially identical for Mo and
W analogues. Electronic structure calculations confirm the dz2
-
1
+
(
-
BP86)/2091 cm (B3LYP) in [6-H] , giving a shift, Dn(C C) =
39 cm- (BP86)/-35 cm (B3LYP). Both levels of calculation
1
-1
7
H
7
)][PF
6
] yields the alkynyl complexes
slightly exaggerate the shift but obtain the correct trend. The
BP86 functional gives better agreement with experiment for the
position of the stretching wavenumber but the B3LYP functional
is slightly better at predicting the magnitude of the shift. The
small experimental shift in n(C C) resulting from one-electron
oxidation of 6 to [6] is therefore consistent with the highly metal-
based frontier orbital character found in the calculated electronic
structures of these systems.
7
H
7
)] which can be reversibly oxidised to
+
7
H )] . Substitu-
7
n+
7
H )] has a relatively small effect on
7
+
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1267–1278 | 1275

View Online
character of the HOMO in the W(dppe)(h-C
7
H
7
) fragment and
Preparation of [WBr(dppe)(g-C
7
7
H )], 1
successfully model the increase in activation energy to metal-
3
3
+
A mixture of xylene (50 cm ) and toluene (50 cm ) was heated
C
a
bond rotation in [W(C CH
attributed to the stronger M C p-bonding interactions in the
HOMO-1]. The alkynyl complexes [W(C CR)(dppe)(h-C )]
2
)(dppe)(h-C
7
H )] , which can be
7
to reflux point then dppe (1.21 g, 3.04 mmol) and [WBr(CO)
2
(h-
C
7
H
7
)] (2.50 g, 6.08 mmol) were added to the solution as a mixture
of solids. After 1 h the reaction mixture was treated with additional
dppe (1.21 g, 3.04 mmol) and reflux continued for 3 h. The resulting
[
7
H
7
also feature a strongly metal-based dz2 HOMO, in common
with their Mo counterparts and this can account for the very
similar spectroscopic properties of the two series of complexes.
solution was filtered hot to remove [W(CO)(dppe)(h-C
then evaporated to dryness. The green–brown residue, dissolved in
CH Cl was transferred to an alumina/n-hexane chromatography
column. A yellow band, [W(CO) (dppe)], was eluted first using
n-hexane–CH Cl (1 : 1) followed by a red band. The required
product eluted as a green band using n-hexane–CH Cl /acetone
2 : 2 : 1) solvent mixture as eluant. The green band was collected,
solvent removed, and the residue recrystallised from CH Cl –n-
hexane to give [WBr(dppe)(h-C )] as a green solid, yield 0.97 g
7
H
7
)]Br,
Fundamentally, the exchange of W in place of Mo in the vinylidene
+
2
2
complexes [M(C CHR)(dppe)(h-C
7
H
7
)] and alkynyl complexes
n+
4
[
M(C CR)(dppe)(h-C
7
H )] results in limited effects only. The
7
2
2
dominant feature which controls the electronic structure and
chemical properties of these systems is the strong d bonding
2
2
(
between the metal and the e
2
level of the C
7
7
H ring leading
2
2
to substantial metal dz2 character in frontier orbitals and this
overrides the more subtle effects resulting from replacement of the
7
H
7
+
(
21%). Cyclic voltammetry: E
Calcd. (%) for C33
.0. Mass (MALDI): m/z 753 (M ), 673 (M - Br).
1
= -0.77 V vs. FeCp
2
/FeCp . Anal.
2
4
d orbital set of Mo with the 5d set of W.
2
H
31WP Br: C, 52.6; H, 4.1. Found: C, 52.3; H,
2
+
+
4
Experimental
Preparation of
A mixture of [WBr(dppe)(h-C
2
General procedures
7
H
7
)] (0.40 g, 0.53 mmol), 3-butyn-
The preparation, purification and reactions of the complexes
described were carried out under dry nitrogen. All solvents were
dried by standard methods, distilled and deoxygenated before use.
1-ol (0.19 g, 2.71 mmol) and K[PF ] (0.20 g, 1.09 mmol) in AR
methanol (40 cm ) was heated at reflux for 3 h and the resulting
deep orange solution was evaporated to dryness. The residue
6
3
The complex [W(CO)
procedure. NMR spectra were recorded on a Varian Inova 400
3
(h-C
7
H
7
)][PF
6
] was prepared by a published
was recrystallised from CH
orange solid washed with toluene. A further recrystallisation from
acetone–diethyl ether gave 2 as an orange solid; yield 0.07 g (15%).
2
Cl -diethyl ether and the resulting
2
20
1
13
1
31
1
(
400 MHz H, 100 MHz C{ H}, 162 MHz P{ H}) spectrometer.
Infrared spectra were obtained on a Perkin Elmer FT RX1
spectrometer and MALDI mass spectra were recorded using a
Micromass/Waters TOF Spec 2E instrument. Microanalyses were
conducted by the staff of the Microanalytical Service of the School
of Chemistry, University of Manchester. Cyclic voltammograms
Anal. Calcd. (%) for C37
49.6; H, 3.8. Mass (MALDI): m/z 744 (M + H), 673 (M
CCH CH CH O).
H
37WOP
3
F : C, 50.0; H, 4.2. Found: C,
6
+
+
-
2
2
2
Preparation of [W(C CH )(dppe)(g-C H )][PF ], 3
2
7
7
6
-
1
were recorded (n = 100 mV s ) from 0.2 M [NBu
4
][PF
6
], CH
2
Cl
2
-
4
A mixture of [WBr(dppe)(h-C
7
H
7
)] (0.49 g, 0.65 mmol),
] (0.24 g, 1.30 mmol)
solutions ca. 1 ¥ 10 M in analyte using a three-electrode
cell equipped with a glassy carbon working electrode, Pt wire
counter electrode and Ag/AgCl reference electrode. All redox
potentials are reported with reference to an internal standard of
the ferrocene/ferrocenium couple (FeCp
visible and IR spectroelectrochemical experiments were performed
at room temperature with an air-tight OTTLE cell equipped with
Pt minigrid working and counter electrodes, a Ag wire reference
HC CSiMe
3
(0.21 g, 2.14 mmol) and K[PF
6
3
in AR methanol (40 cm ) was heated at reflux for 2 h and the
resulting orange solution was evaporated to dryness. The orange
+
residue, dissolved in CH
chromatography column, and the product eluted as an orange
band using n-hexane–CH Cl (1 : 1) solvent mixture as eluant.
The orange band was collected, solvent removed, the residue was
recrystallised from CH Cl -diethyl ether and the resulting solid
2
Cl
2
was transferred to a Celite/n-hexane
2
/FeCp
2
= 0.00 V). UV-
2
2
47
2
2
electrode and CaF windows using either a Nicolet Avatar
2
washed with toluene. A further recrystallisation from acetone–
diethyl ether gave 3 as a yellow solid; yield 0.33 g (60%).
Mass (MALDI): m/z 699 (M ). HR ES+-MS (m/z): 699.1588
spectrometer or a Perkin Elmer Lambda 900 spectrophotometer.
EPR experiments were conducted on a Bruker BioSPin EMX
microspectrometer at X-band (9 GHz); spectra are the average of
+
(
WC35
H
33
P
2
requires 699.1561).
1
6 scans. Spectral analysis and simulation was carried out using
Bruker WinEPR software (Bruker Biospin Ltd.).
Preparation of [W(C CHPh)(dppe)(g-C
7
H
7
)][PF ], 4
6
A mixture of [WBr(dppe)(h-C
7
H
7
)] (0.55 g, 0.73 mmol), HC CPh
] (0.28 g, 1.52 mmol) in AR
Preparation of [WBr(CO)
2
(g-C
7
H
7
)]
(
0.42 g, 4.12 mmol) and K[PF
6
3
A solution of [W(CO) (h-C
3
7
H
7
)][PF
6
] (4.76 g, 9.44 mmol) in AR
methanol (40 cm ) was heated at reflux for 2 h and the resulting
deep orange solution was evaporated to dryness. The residue
3
acetone (70 cm ) was treated with NaBr (1.41 g, 13.69 mmol)
and the reaction mixture stirred for 1 h to give a green solution
was recrystallised from CH Cl–diethyl ether and the resulting
2
before the solvent was removed in vacuo over a period of 30 min.
orange solid washed with toluene. A further recrystallisation from
acetone–diethyl ether gave 4 as an orange solid; yield 0.54 g (80%).
3
The residue was extracted with CH
2
Cl
2
(50 cm ) and the resulting
solution filtered, treated with hexane and the volume reduced to
yield [WBr(CO) (h-C )] as a dark green solid; yield 3.17 g (82%).
Anal. Calcd. (%) for C41
H, 3.7. Mass (MALDI): m/z 775 (M ), 673 (M - C CHPh).
H
37WP
3
F : C, 53.5; H, 4.0. Found: C, 53.5;
6
+
+
2
7
H
7
1
276 | Dalton Trans., 2011, 40, 1267–1278
This journal is © The Royal Society of Chemistry 2011

View Online
Preparation of [W(C CHC
6
H
4
-4-Me)(dppe)(g-C
7
H
7
)][PF
6
], 5
Table 9 Crystal data and refinement parameters
A mixture of [WBr(dppe)(h-C
7
H
7
)] (0.81 g, 1.08 mmol),
] (0.39 g,
.12 mmol) in AR methanol (80 cm ) was heated at reflux for
h and the resulting orange solution was evaporated to dryness.
Cl was transferred to a
Celite/n-hexane chromatography column, and the product eluted
as an orange band using n-hexane–CH Cl (1 : 1) solvent mixture
as eluant. The orange band was collected, solvent removed, the
residue was recrystallised from CH Cl -diethyl ether and the
Formula
C H P BrCl W, C H P F W, 4[PF ]
34
33
2
2
41
37
3
6
6
1
·CH
2 2
Cl
HC CC -4-Me (0.62 g, 5.35 mmol) and K[PF
6
H
4
6
3
Mass
T/K
Crystal system
838.20
100(2)
920.47
100(2)
2
2
Orthorhombic
Pcab
23.3121(10)
9.3925(4)
27.8933(15)
90.00
Monoclinic
P2 /c
The orange residue, dissolved in CH
2
2
Space group
1
a/A˚
33.250(5)
12.061(5)
18.645(5)
104.641(5)
7234(4); 8
3.388
b/A˚
c/A˚
2
2
◦
b ( )
V/ A˚ ; Z
3
6107.5(5); 8
5.395
2
2
-1
Absorption coefficient/mm
q range ( )
Limiting indices (h,k,l)
resulting solid washed with toluene. A further recrystallisation
from acetone–diethyl ether gave 5 as an orange solid; yield 0.82 g
◦
3.15–28.54
-30/30,
-12/12,-35/36
7189
1.27–26.42
-38/41; -15/8;
-22/23
(
82%). Anal. Calcd. (%) for C42
C, 53.5; H, 4.0. Mass (MALDI): m/z 789 (M ), 673 (M
C(H)C -4-Me).
H
39WP
3
F
6
: C, 54.0; H, 4.2. Found:
+
+
Total reflections
Independent reflections,
I > 2s(I)
40504
-
4653
14741
C
6
H
4
R
1
0.0731
0.2155
99.3
0.0512
0.0954
99.3
wR
Completeness to theta (%)
2
Preparation of [W(C CPh)(dppe)(g-C
7
7
H )], 6
A
mixture of [W(C CHPh)(dppe)(h-C
7
H
7
)][PF
6
] (0.27 g,
t
3
0
.29 mmol) and KOBu (0.33 g, 2.95 mmol) in thf (50 cm ) was
˚
Diffractometer using monochromated Mo-Ka (l = 0.7103 A)
radiation and w scans; an absorption correction was applied
stirred at room temperature for 40 min then the resulting red–
brown solution was evaporated to dryness. The residue, dissolved
48
with the aid of the SADABS program. Both structures were
solved by direct methods with refinement by full-matrix least
squares based on F against all reflections; SHELXS-97, was
employed for the computing structure solutions and SHELXL-
in CH
column, and the product eluted as a red band using n-hexane–
CH Cl (1 : 1) as eluant. The red band was collected, solvent
2
2
Cl was transferred to a Celite/n-hexane chromatography
2
49
2
2
removed, and the residue, dissolved in diethyl ether, was filtered
through a Celite covered sinter. The volume of solvent was reduced
50
9
7, for the computing structure refinements. In the structure of
1·CH
2
Cl , the anisotropic displacement parameters of the atoms
2
◦
and the solution left in the freezer overnight at -20 C leading to
C(1)–C(7) of the cycloheptatrienyl ring, C(29)–C(34) of the dppe
ligand, and Br(1) were disordered and restrained since they tended
to become unrealistic (NPD). Constraints were applied to the
cycloheptatrienyl ring, Br(1) and C(29)–C(34), all non-hydrogen
atoms were refined anisotropically and hydrogen atoms were
precipitation of the product. The mother liquors were removed
by syringe and the remaining solid dried in vacuo to give 6 as
a red–brown solid; yield 0.13 g, (58%). Mass (MALDI): m/z 774
+
+
(
M ), 673 (M - C
2
Ph). HR ES+-MS (m/z): 774.1801 (C41
H
36
2
P W
requires 774.1796).
included in calculated positions. The asymmetric unit of 4[PF ]
6
contains two molecules; in one of the cations the cycloheptatrienyl
ring is disordered over two sites, the occupancy of which was
constrained to sum to unity with restraints applied to the geometry
of the two disordered components. All non-hydrogen atoms were
refined anisotropically with constraints applied to the disordered
cycloheptatrienyl ring described above; hydrogen atoms were
included in calculated positions.
Preparation of [W(C CC
6
H
4
-4-Me)(dppe)(g-C
7
H
7
)], 7
Complex 7 was prepared as a red–brown solid by an identical
procedure to that described for 6 starting from [W(C CHC -4-
] (0.40 g, 0.43 mmol) and KOBu (0.48 g,
.29 mmol); yield 0.24 g, (71%). HR ES+-MS (m/z): 788.1962
W requires 788.1953).
6
H
4
t
Me)(dppe)(h-C
7
H
7
)][PF
6
4
(
C
42
H
39
P
2
Acknowledgements
X-Ray crystal structures of [WBr(dppe)(g-C
·CH Cl and [W(C CHPh)(dppe)(g-C
7
H
7
)]·CH
2
Cl ,
2
1
2
2
7
H
7
)][PF ], 4[PF ].
6
6
We thank the EPSRC for support of this work through grants
EP/E025544/1 and EP/E02582X/1 and for a DTA studentship
The majority of details of the structure analyses carried out on
complexes 1·CH Cl and 4[PF ] are given in Table 9. Single crystals
of 1·CH Cl were obtained by vapour diffusion of diethyl ether
into a CH Cl solution of the complex to give green needles;
single crystals of 4[PF ] were obtained by vapour diffusion of
diethyl ether into a CH Cl solution of the complex to give
Cl were collected with an
(
to H.N.L). We are also grateful to the Nuffield Foundation
2
2
6
for an Undergraduate Research Bursary (URB/34287) (to Mark
Holden). P.J.L. holds an EPSRC Leadership Fellowship.
2
2
2
2
6
2
2
References
orange plates. X-ray data for 1·CH
2
2
1
2
3
P. J. Low and M. I. Bruce, Adv. Organomet. Chem., 2001, 48, 71.
M. I. Bruce and P. J. Low, Adv. Organomet. Chem., 2004, 50, 179.
(a) N. Gauthier, G. Argouarch, F. Paul, M. G. Humphrey, L. Toupet, S.
Ababou-Girad, H. Sabbah, P. Hapiot and B. Fabre, Adv. Mater., 2008,
20, 1952; (b) P. J. Low, Dalton Trans., 2005, 2821; (c) B. Kim, J. M.
Beebe, C. Olivier, S. Rigaut, D. Touchard, J. G. Kushmerick, X. Y. Zhu
and C. D. Frisbie, J. Phys. Chem. C, 2007, 111, 7521.
Oxford Diffraction X-Calibur 2 Diffractometer equipped with
an Oxford-Cryosystems low-temperature device, by means of
˚
Mo-Ka (l = 0.7103 A) radiation and w scans. Data were
corrected for Lorentz, polarisation and absorption factors. Data
collection, cell refinement and data reduction were carried out
with Oxford Diffraction Ltd., CrysAlis CCD and CrysAlis RED
4
(a) C. Lapinte, J. Organomet. Chem., 2008, 693, 793; (b) F. Paul
and C. Lapinte, in Unusual Structures and Physical Properties in
software. X-Ray data for 4[PF
6
] was collected with a Bruker AXS
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1267–1278 | 1277

View Online
Organometallic Chemistry, M. Gielen, R. Willem, B. Wrackmeyer,
Eds), (John Wiley and Sons Ltd., New York, 2002.
29 N. M. Kosti c´ and R. F. Fenske, Organometallics, 1982, 1, 974.
(
30 (a) K. R. Birdwhistell, S. J. Nieter Burgmayer and J. L. Templeton,
J. Am. Chem. Soc., 1983, 105, 7789; (b) P. N. Nickias, J. P. Selegue and
B. A. Young, Organometallics, 1988, 7, 2248.
5
(a) M. Samoc, G. T. Dalton, J. A. Gladysz, Q. Zheng, Y. Velkov, H.
A˚ gren, P. Norman and M. G. Humphrey, Inorg. Chem., 2008, 47, 9946;
(
b) M. Samoc, N. Gauthier, M. P. Cifuentes, F. Paul, C. Lapinte, M. G.
31 P. Kub a´ cˇ ek, R. Hoffmann and Z. Havias, Organometallics, 1982, 1,
180.
Humphrey and G. T. Dalton, Angew. Chem., Int. Ed., 2008, 47, 629;
(
c) J. P. Morrall, G. T. Dalton, M. G. Humphrey and M. Samoc, Adv.
32 M. Brookhart, J. R. Tucker, T. C. Flood and J. Jensen, J. Am. Chem.
Organomet. Chem., 2007, 55, 61.
Soc., 1980, 102, 1203.
6
7
8
J. S. Adams, C. Bitcon, J. R. Brown, D. Collison, M. Cunningham and
M. W. Whiteley, J. Chem. Soc., Dalton Trans., 1987, 3049.
R. L. Beddoes, C. Bitcon, R. W. Grime, A. Ricalton and M. W. Whiteley,
J. Chem. Soc., Dalton Trans., 1995, 2873.
(a) H. N. Lancashire, R. Ahmed, T. L. Hague, M. Helliwell, G. A.
Hopgood, L. Sharp and M. W. Whiteley, J. Organomet. Chem., 2006,
33 W. B. Studabaker and M. Brookhart, J. Organomet. Chem., 1986, 310,
C39.
34 S. E. Kegley, M. Brookhart and G. R. Husk, Organometallics, 1982, 1,
760.
35 G. Consiglio and F. Morandini, Inorg. Chim. Acta, 1987, 127, 79.
36 F. Paul, L. Toupet, T. Roisnel, P. Hamon and C. Lapinte, C. R. Chim.,
2005, 8, 1174.
37 M. I. Bruce, K. Costuas, T. Davin, J.-F. Halet, K. A. Kramarczuk, P. J.
Low, B. K. Nicholson, G. J. Perkins, R. L. Roberts, B. W. Skelton, M. E.
Smith and A. H. White, Dalton Trans., 2007, 5387.
6
91, 3617; (b) N. J. Brown, D. Collison, R. Edge, E. C. Fitzgerald, P. J.
Low, M. Helliwell, Y. T. Ta and M. W. Whiteley, Chem. Commun., 2010,
6, 2253.
4
9
R. W. Grime, M. Helliwell, Z. I. Hussain, H. N. Lancashire, C. R.
Mason, J. J. W. McDouall, C. M. Mydlowski and M. W. Whiteley,
Organometallics, 2008, 27, 857.
38 F. Paul, J.-Y. Mevellec and C. Lapinte, J. Chem. Soc., Dalton Trans.,
2002, 1783.
1
1
1
0 N. J. Brown, D. Collison, R. Edge, E. C. Fitzgerald, M. Helliwell,
J. A. K. Howard, H. N. Lancashire, P. J. Low, J. J. W. McDouall, J.
Raftery, C. A. Smith, D. S. Yufit and M. W. Whiteley, Organometallics,
39 G. M. Aston, S. Badriya, R. D. Farley, R. W. Grime, S. J. Ledger, F. E.
Mabbs, E. J. L. McInnes, H. W. Morris, A. Ricalton, C. C. Rowlands,
K. Wagner and M. W. Whiteley, J. Chem. Soc., Dalton Trans., 1999,
4379.
40 C. J. Adams, I. M. Bartlett, S. Carlton, N. G. Connelly, D. J. Harding,
O. D. Hayward, A. G. Orpen, E. Patron, C. D. Ray and P. H. Rieger,
Dalton Trans., 2007, 62.
2
010, 29, 1261.
1 (a) F. Paul, L. Toupet, J.-Y. Thepot, K. Costuas, J.-F. Halet and C.
Lapinte, Organometallics, 2005, 24, 5464; (b) F. Paul, G. da Costa, A.
Bondon, N. Gauthier, S. Sinbandhit, L. Toupet, K. Costuas, J.-F. Halet
and C. Lapinte, Organometallics, 2007, 26, 874.
2 (a) F. Paul, B. G. Ellis, M. I. Bruce, L. Toupet, T. Roisnel, K. Costuas,
J.-F. Halet and C. Lapinte, Organometallics, 2006, 25, 649; (b) M. A.
Fox, R. L. Roberts, W. M. Khairul, F. Hartl and P. J. Low, J. Organomet.
Chem., 2007, 692, 3277.
3 D. W. Clack and K. D. Warren, Theor. Chim. Acta, 1977, 46, 313.
4 M. Tamm, A. Kunst, T. Bannenberg, E. Herdtweck and R. Schmid,
Organometallics, 2005, 24, 3163.
5 C. Bitcon, R. Breeze, P. F. Miller and M. W. Whiteley, J. Organomet.
Chem., 1989, 364, 181.
41 Gaussian 03, Revision D.02, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr.,
T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V.
Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C.
Gonzalez and J. A. Pople, Gaussian, Inc., Wallingford CT, 2004.
42 F. Weigend and R. Ahlrichs, Phys. Chem. Chem. Phys., 2005, 7, 3297.
43 http://bases.turbo-forum.com/TURBOMOLE_BASISSET_LIBRARY/
tbl.html.
1
1
1
1
6 M. L. H. Green, D. K. P. Ng and H.-V. Wong, J. Chem. Soc., Dalton
Trans., 1993, 3213.
1
1
7 R. B. King and A. Fronzaglia, Inorg. Chem., 1966, 5, 1837.
8 G. Hoch, R. Panter and M. L. Ziegler, Z. Naturforsch. B, 1976, 31B,
2
94.
9 R. W. Grime and M. W. Whiteley, J. Chem. Soc., Dalton Trans., 1994,
671.
1
1
2
2
0 A. Roberts and M. W. Whiteley, J. Organomet. Chem., 1993, 458, 131.
1 R. Breeze, S. Endud and M. W. Whiteley, J. Organomet. Chem., 1986,
3
02, 371.
2
2
2 C. L. Hyde and D. J. Darensbourg, Inorg. Chem., 1973, 12, 1075.
3 G. Consiglio, F. Bangerter, C. Darpin, F. Morandini and V. Lucchini,
Organometallics, 1984, 3, 1446.
44 D. Andrae, U. Haeussermann, M. Dolg, H. Stoll and H. Preuss, Theor.
Chim. Acta, 1990, 77, 123.
45 (a) A. D. Becke, Phys. Rev. A: At., Mol., Opt. Phys., 1988, 38, 3098;
(b) J. P. Perdew, Phys. Rev. B: Condens. Matter, 1986, 33, 8822.
46 A. D. Becke, J. Chem. Phys., 1993, 98, 5648.
2
4 N. G. Connelly, M. P. Gamasa, G. Gimeno, C. Lapinte, E. Lastra, J. P.
Maher, N. Le Narvor, A. L. Rieger and P. H. Rieger, J. Chem. Soc.,
Dalton Trans., 1993, 2575.
5 R. L. Beddoes, R. W. Grime, Z. I. Hussain and M. W. Whiteley,
J. Organomet. Chem., 1996, 526, 371.
6 M. I. Bruce and R. C. Wallis, Aust. J. Chem., 1979, 32, 1471.
7 R. L. Beddoes, R. W. Grime, Z. I. Hussain and M. W. Whiteley, J. Chem.
Soc., Dalton Trans., 1996, 3893.
8 G. Argouarch, P. Thominot, F. Paul, L. Toupet and C. Lapinte,
C. R. Chim., 2003, 6, 209.
47 M. Krejeik, M. Danek and F. Hartl, J. Electroanal. Chem., 1991, 317,
179.
2
48 G. M. Sheldrick, SADABS, an Empirical Absorption Corrections
2
2
Program, Universit a¨ t G o¨ ttingen, Germany, 1997.
49 G. M. Sheldrick, SHELXS-97, Program for Crystal Structure Solution,
Universit a¨ t G o¨ ttingen, Germany, 1997.
2
50 G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, Universit a¨ t G o¨ ttingen, Germany, 1997.
1
278 | Dalton Trans., 2011, 40, 1267–1278
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