Organoimido complexes of tungsten-(VI) and -(V): Correlation between relative orientation of π-donor ligands and electron configuration of the metal

Article abstract of DOI:10.1039/a606644e

The high-yield synthesis of the monomeric five-co-ordinate arylimido complex [WCl₃(NPh)(OC₆H₃Prⁱ ₂-2,6)] was achieved starting from [{WCl₃(NPh)}₂(μ-Cl)₂]. The adducts [WCl₃(NPh)(OC₆H₃Prⁱ ₂-2,6)L] (L = tetrahydrofuran, pyridine (py) or 4-tert-butylpyridine) of the monoalkoxide have been synthesized and the constitution of the pyridine adduct determined by X-ray crystallography. The reduction of the monoalkoxide with 1 equivalent of sodium amalgam in the presence of pyridine or triethylphosphine leads to the paramagnetic adducts [WCl₂(NPh)(OC₆H₃Prⁱ ₂-2,6)L₂] (L = py or PEt3) which were characterized. A trans configuration was found for the two chlorine atoms and the two σ-donor ligands in the structure analysis. Reorganization of the two π-donor ligands (aryloxide and NPh) from a cis arrangement in the complex with d⁰ electron configuration to a trans arrangement in the d¹ configurated complexes is found and verified by X-ray diffraction analyses.

Full text of DOI:10.1039/a606644e

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Organoimido complexes of tungsten-(VI) and -(V): correlation
between relative orientation of ð-donor ligands and electron
configuration of the metal‡
Lars Wesemann,*,† Ludger Waldmann, Uwe Ruschewitz, Beate Ganter and Trixie Wagner
Institut für Anorganische Chemie, Technische Hochschule Aachen, D-52056 Aachen, Germany
The high-yield synthesis of the monomeric five-co-ordinate arylimido complex [WCl3(NPh)(OC6H3Pri2-2,6)] was
achieved starting from [{WCl3(NPh)}2(µ-Cl)2]. The adducts [WCl3(NPh)(OC6H3Pri2-2,6)L] (L = tetrahydrofuran,
pyridine (py) or 4-tert-butylpyridine) of the monoalkoxide have been synthesized and the constitution of the
pyridine adduct determined by X-ray crystallography. The reduction of the monoalkoxide with 1 equivalent of
sodium amalgam in the presence of pyridine or triethylphosphine leads to the paramagnetic adducts
[WCl2(NPh)(OC6H3Pri2-2,6)L2] (L = py or PEt3) which were characterized. A trans configuration was found for the
two chlorine atoms and the two σ-donor ligands in the structure analysis. Reorganization of the two π-donor
ligands (aryloxide and NPh) from a cis arrangement in the complex with d0 electron configuration to a trans
arrangement in the d1 configurated complexes is found and verified by X-ray diffraction analyses.
The correlation between the relative orientation of two π-donor
ligands in octahedrally co-ordinated complexes and the electron
configuration of the metal centre is well established by several
theoretical and preparative studies.1–4 Mingos1 had discussed in
1979 the cis preference of the MO2 moiety in d0 L4MO2 octa-
hedra and the trans preference in d2 L4MO2 octahedra using the
[MoO2(PH3)4]n+ (n = 2 or 0) system on the basis of extended-
Hückel molecular orbital calculations. Similar arguments hold
for the alkylimide ligand which is isoelectronic to the oxide
ligand and acts as a 4e π donor exhibiting a M᎐N᎐C angle of
ca. 180Њ. Several examples for the cis-M(NR)2 preference in d0
complexes are known.3,5–8 In 1989 Wigley and co-workers3
presented an example of the confirmation of this phenomenon
in a tantalum() phenylimidoaryloxide. That work clearly
shows the cis orientation of the aryloxide and phenylimide
ligands in the d0 complex [TaCl2(NR)(OC6H3Pri2-2,6)(py)2]
(R = 2,6-Pri2C6H3, py = pyridine) and the trans stereochemistry
complexes, [WCl2(NPh)(OC6H3Pri2-2,6)L2] (L = py or PEt3),
is described. The solid-state structure of the d0 complex [WCl3-
(NPh)(OC6H3Pri2-2,6)(py)] and of the d1 complex [WCl2(NPh)-
(OC6H3Pri2-2,6)(py)2] are also discussed.
Results and Discussion
Syntheses
The tungsten() phenoxide [WCl3(NPh)(OC6H3Pri2-2,6)] 2 can
be prepared straightforwardly in 85% yield starting from
[{WCl3(NPh)}2(µ-Cl)2], which is converted quantitatively into
[W(NPh)(OC6H3Pri2-2,6)4] 1 in hexane using a mixture of 2,6-
,14
diisopropylphenol and diethylamine (Scheme 1).§
The
diethylamine hydrochloride was filtered off and the solvent
was changed to toluene. Owing to the high solubility of the
tetraaryloxide even in hexane, crystallization at Ϫ30 ЊC affords
crystals of 1 in only 28% yield. Therefore we developed a
method to use the crude reaction product, which is pure on the
2
i
᎐
in the reduced d complex [Ta(NR)(OC H Pr -2,6)(EtC᎐CEt)-
᎐
6
3
2
(py)2]. The cis configuration of two π donors in complexes with
d0 electron configuration allows all three metal dπ orbitals to
accept π donation from the π-donor ligands. In complexes with
d1 and d2 electron configuration the π-donor ligands prefer the
trans configuration because the electrons can reside in the lone
dπ orbital which is not destabilized by the π donation.
1
basis of H NMR spectroscopy. The crude toluene solution of
the tetraaryloxide 1 was treated with 1.5 equivalents of
[{WCl3(NPh)}2(µ-Cl)2] resulting in a redistribution to give the
monoaryloxide [WCl3(NPh)(OC6H3Pri2-2,6)] 2. Redistribution
reactions have previously been shown to be a versatile method
for the syntheses of phenylimidoaryloxides.15
We are interested in the synthesis and reduction of tung-
sten() phenylimidoaryloxides which are known to react to-
gether with SnR3H as catalysts for ring-opening metathesis
polymerization of cyclic alkenes.9 The organoimide ligand,
which has become very popular in the last years, provides elec-
tronic flexibility and steric control. The structures of organo-
imido complexes in the solid state and solution have been
studied very extensively.8 Mono- as well as di-meric complexes
are known.8,10 In comparison to the many organoimido
complexes of tungsten(), there are few of tungsten(). Nearly
all the latter are of the general composition [WCl3(NR)L2], with
L being a σ-donor ligand.11–13
The monomeric five-co-ordinate compound 2 reacts with σ
donors like thf, pyridine or 4-tert-butylpyridine to form the six-
co-ordinate complexes [WCl3(NPh)(OC6H3Pri2-2,6)L] (L = thf
3, py 4 or bpy 5) (Scheme 2).16 The monoaryloxide 2 is readily
reduced by 1 equivalent of sodium amalgam in the presence of
2 equivalents of the desired σ-donor ligand (L = py or PEt3)
using toluene–tetrahydrofuran (3:1) as solvent. The pyridine
NPh
W
Cl
W
Cl
Cl
W
Cl
NPh
W
Cl
PhN
NPh
Cl
Cl
Cl
( i )
(ii )
8Cl
Cl
OR
2RO
RO
OR
–8NEt2H•HCl
Cl
OR
In this work another example of the dependence of the rela-
tive orientation of two π-donor ligands on the electronic con-
figuration is presented. The synthesis of three tungsten()
complexes, [WCl3(NPh)(OC6H3Pri2-2,6)L] [L = tetrahydrofuran
(thf), py or 4-tert-butylpyridine (bpy)], and two tungsten()
1
2
Scheme 1 R = 2,6-Pri2C6H3. (i) 8ROH, 8NEt2H; (ii) 3[{WCl3(NPh)}2-
(µ-Cl)2]
§ Proposed monomeric structure of 1, in the case of the analogue
oxoaryloxide complex [WO(OC6H3Pri2-2,6)4] the monomeric square-
pyramidal structure has been demonstrated by a crystal structure
analysis.14
† E-Mail: lars.wesemann@ac.rwth-aachen.de
‡ Non-SI units employed: µB ≈ 9.27 × 10Ϫ24 J TϪ1; G = 10Ϫ4 T.
J. Chem. Soc., Dalton Trans., 1997, Pages 1063–1068
1063

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NPh
W
( )
i
Cl
Cl
Cl
OR
Table 1 Selected bond lengths (Å) for compounds 4* and 6
[WCl3(NPh)(OC6H3-
Pri2-2,6)(py)] 4
[WCl2(NPh)(OC6H3-
L
Pri2-2,6)(py)2] 6
W᎐Cl(1)
3-5
W(1a)᎐Cl(1a)
W(1b)᎐Cl(1b)
W(1a)᎐Cl(2a)
W(1b)᎐Cl(2b)
W(1a)᎐Cl(3a)
W(1b)᎐Cl(3b)
W(1a)᎐O(1a)
W(1b)᎐O(1b)
W(1a)᎐N(1a)
W(1b)᎐N(1b)
W(1a)᎐N(2a)
W(1b)᎐N(2b)
2.325(5)
2.358(6)
2.350(6)
2.337(6)
2.381(5)
2.365(6)
1.85(1)
1.82(1)
1.78(1)
1.70(2)
2.32(2)
2.31(2)
2.400(3)
2.406(3)
NPh
W
(
)
iii
W᎐Cl(2)
Cl
Cl
OR
Cl
2
NPh
W
W᎐O
1.969(8)
1.75(1)
2.18(1)
Cl
(ii)
L′
Cl
L′
W᎐N(1)
W᎐N(2)
OR
6,7
Scheme 2 R = 2,6-Pri2-C6H3. (i) L = thf, py or bpy; (ii) Na–Hg, 2LЈ
W᎐N(3)
2.18(1)
1.38(1)
(LЈ = py or PEt3); (iii) Na–Hg, L = LЈ = py
N(1a)᎐C(11a)
N(1b)᎐C(11b)
N(1b)᎐C(11b*)
O(1a)᎐C(1a)
O(1a)᎐C(1a*)
O(1b)᎐C(1b)
N(2a)᎐C(21a)
N(2b)᎐C(21b)
1.34(2)
1.62(5)
1.24(5)
1.53(5)
1.26(5)
1.40(2)
1.30(3)
1.33(3)
N(1)᎐C(11)
O᎐C(1)
1.33(1)
N(2)᎐C(21)
N(3)᎐C(31)
1.34(1)
1.34(2)
* Indices a and b indicate the two independent molecules A and B, an
asterix the second different position of the disordered groups.
Table 2 Selected bond angles (Њ) for compounds 4 and 6
4
6
Cl(1a)᎐W(1a)᎐Cl(2a)
Cl(1b)᎐W(1b)᎐Cl(2b)
Cl(1a)᎐W(1a)᎐Cl(3a)
Cl(1b)᎐W(1b)᎐Cl(3b)
Cl(2a)᎐W(1a)᎐Cl(3a)
Cl(2b)᎐W(1b)᎐Cl(3b)
Cl(1a)᎐W(1a)᎐O(1a)
Cl(1b)᎐W(1b)᎐O(1b)
Cl(2a)᎐W(1a)᎐O(1a)
Cl(2b)᎐W(1b)᎐O(1b)
Cl(3a)᎐W(1a)᎐O(1a)
Cl(3b)᎐W(1b)᎐O(1b)
Cl(1a)᎐W(1a)᎐N(1a)
Cl(1b)᎐W(1b)᎐N(1b)
Cl(1a)᎐W(1a)᎐N(2a)
Cl(1b)᎐W(1b)᎐N(2b)
Cl(2a)᎐W(1a)᎐N(1a)
Cl(2b)᎐W(1b)᎐N(1b)
Cl(2a)᎐W(1a)᎐N(2a)
Cl(2b)᎐W(1b)᎐N(2b)
Cl(3a)᎐W(1a)᎐N(1a)
Cl(3b)᎐W(1b)᎐N(1b)
Cl(3a)᎐W(1a)᎐N(2a)
Cl(3b)᎐W(1b)᎐N(2b)
168.2(2)
168.2(2)
87.0(2)
85.7(2)
87.8(2)
87.7(2)
91.7(4)
89.7(4)
91.0(4)
93.9(3)
167.3(4)
163.5(4)
98.6(5)
94.4(6)
85.1(4)
84.8(4)
92.2(4)
95.7(6)
83.8(5)
84.6(4)
92.8(4)
94.1(7)
83.9(4)
81.9(4)
Cl(1)᎐W᎐Cl(2)
174.1(1)
Cl(1)᎐W᎐O
Cl(2)᎐W᎐O
87.6(3)
86.5(2)
Cl(1)᎐W᎐N(1)
Cl(1)᎐W᎐N(2)
Cl(2)᎐W᎐N(1)
Cl(2)᎐W᎐N(2)
94.6(3)
89.7(3)
91.3(3)
90.4(3)
Fig. 1 A SCHAKAL plot of [WCl3(NPh)(OC6H3Pri2-2,6)(py)] 4
adduct [WCl2(NPh)(OC6H3Pri2-2,6)(py)2] 6 was obtained as
dark green crystals in 77% yield and the triethylphosphine
adduct [WCl2(NPh)(OC6H3Pri2-2,6)(PEt3)2] 7 as red crystals in
62% yield. The reduction of [WCl3(NPh)(OC6H3Pri2-2,6)(py)] 4
with 1 equivalent of sodium amalgam in the presence of
pyridine also leads to the paramagnetic pyridine adduct 6.
Cl(1)᎐W᎐N(3)
Cl(2)᎐W᎐N(3)
O᎐W᎐N(1)
85.9(3)
93.5(3)
177.8(4)
O(1a)᎐W(1a)᎐N(1a)
O(1b)᎐W(1b)᎐N(1b)
O(1a)᎐W(1a)᎐N(2a)
O(1b)᎐W(1b)᎐N(2b)
99.9(5)
102.1(8)
83.4(6)
81.9(5)
Crystal structures
O᎐W᎐N(2)
88.0(3)
Brown single crystals of [WCl3(NPh)(OC6H3Pri2-2,6)(py)] 4
suitable for structure analysis were grown from benzene–
hexane–diethyl ether (1:2:2) at Ϫ6 ЊC. Compound 4 crystal-
lizes in the monoclinic space group P21/c with two independent
molecules (named A and B). Both have a disordered group: in
molecule A the OC6H3Pri2 and in B the NPh group have two
alternative positions. A SCHAKAL 17 plot of A is shown in Fig.
1; the disordered moiety was omitted for clarity. Selected bond
lengths and angles are compiled in Tables 1 and 2. Obviously the
disorder of the two groups is correlated, otherwise short inter-
molecular distances would occur (shortest C᎐C distance ca. 2.8
Å). The disorder in molecule A shows for the important angles
of the OC6H3Pri2 part [W(1a)᎐O(1a)᎐C(1a) 142(2) and
W(1a)᎐O(1a)᎐C(1a*) 161(3)Њ] a difference of 19(5)Њ. In the
other disordered group, the NPh in molecule B, the difference is
O᎐W᎐N(3)
N(1)᎐W᎐N(2)
86.6(3)
91.8(4)
N(1a)᎐W(1a)᎐N(2a)
N(1b)᎐W(1b)᎐N(2b)
174.9(6)
176.0(8)
N(1)᎐W᎐N(3)
N(2)᎐W᎐N(3)
W᎐O᎐C(1)
93.8(4)
173.1(4)
168.3(7)
W(1a)᎐O(1a)᎐C(1a)
W(1a)᎐O(1a)᎐C(1a*)
W(1b)᎐O(1b)᎐C(1b)
W(1a)᎐O(1a)᎐C(11a)
W(1b)᎐N(1b)᎐C(11b)
W(1b)᎐N(1b)᎐C(11b*)
142(2)
161(3)
151(1)
175(2)
172(2)
153(3)
W᎐N(1)᎐C(11)
175.7(9)
19(5)Њ too [W(1b)᎐N(1b)᎐C(11b) 172(2) and W(1b)᎐N(1b)᎐
C(11b*) 153(3)Њ]. It seems likely that the two moieties avoid
each other. There is a meridional arrangement of the three
1064
J. Chem. Soc., Dalton Trans., 1997, Pages 1063–1068

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NR′
NR′
Ta
Et
Et
py
Cl
Cl
OR
py
py
Ta
py
d0
OR
d2
NPh
W
NPh
W
Cl
Cl
Cl
Cl
OR
py
Cl
py
py
d0
OR
d1
Scheme 3 R = RЈ = 2,6-Pri2C6H3
reduction product with a trans arrangement of the respective
π-donor ligands.
These preparative and structural results are consistent with
the theoretical studies of Mingos and co-workers1,2 on the MO2
moiety. In octahedrally co-ordinated d0 complexes a cis
arrangement of the π-donor ligands is preferred because all
three dπ orbitals are allowed to accept π donation from these
ligands. A trans configuration is favoured by the π-donor lig-
ands in complexes with d1 and d2 electron configuration because
the valence electrons can reside in the lone dπ orbital which is
not destabilized by π donation.
Fig. 2 A PLATON 18 drawing of [WCl2(NPh)(OC6H3Pri2-2,6)(py)2] 6
chloride ligands and a cis arrangement of the phenylimide and
aryloxide π-donor ligands at the tungsten centre.
Green single crystals of [WCl2(NPh)(OC6H3Pri2-2,6)(py)2] 6
were grown from a benzene–hexane solution at room tempera-
ture. The molecular structure is shown in Fig. 2. Selected bond
lengths and angles are in Tables 1 and 2. The tungsten atom
Spectroscopy
The 1H NMR spectra of complexes 4 and 5 show a significant
low-field shift of δ 9.46 and 9.16 for the Hα protons of the co-
ordinated pyridine. Three bands are observed in the IR spectra
for the W᎐Cl stretches which is characteristic for a meridional
arrangement of the chlorine substituents.15a In the case of the
reduction products 6 and 7 only one W᎐Cl stretch at 297 and
282 cmϪ1 can be observed, which is consistent with the trans
arrangement of the chloride ligands.25
The magnetic susceptibility of complex 6 was measured over
a temperature range (2–300 K) and the Curie–Weiss relation
was obeyed within a small value of θ (5 K). The magnetic
moment of 1.58 µB (room temperature) is appreciable less than
the spin-only value. Apparently spin–orbit coupling is respon-
sible for the low magnetic moment.26
adopts a distorted-octahedral configuration with
a trans
arrangement of the arylimide and aryloxide ligands. A trans
arrangement is also found for the two chlorine atoms and two
pyridine ligands.
The short W᎐N(1) distance [1.75(1) Å] and the almost linear
W᎐N(1)᎐C(11) angle [175.7(9)Њ] clearly indicate that the
organoimido group functions as a four-electron donor.19 The
W᎐O distance of the aryloxide moiety is 1.969(8) Å, which is
in the middle of the range for other known aryloxide W᎐O
distances, e.g. 2.129(8) Å in [WH3(OPh)(PMe3)4],20 1.966(4)
Å in [WCl2(OR)2(PMe2Ph)2] (R = 2,6-Ph2C6H3),21 1.849(5)–
1.866(5) Å in [W(OC6H3Pri2-2,6)4]22 and 1.853(4) and 1.877(4)
Å in [WCl3(OR)2(PMe2Ph)].21 The large W᎐O᎐C(1) angle of
168.3(7)Њ together with the W᎐O distance indicate a weak π-
donor character of the aryloxide ligand. Steric interactions
between the isopropyl groups of the aryloxide and the equa-
torial ligands (py, Cl) have also to be taken into consideration
for the W᎐O᎐C(1) angle enlargement.
Cyclic voltammograms of complexes 6 and 7 were recorded
in thf. The voltammogram of ferrocene was used for calibration
purposes. Both complexes show
a quasi-reversible one-
₁
₁
electron reduction (6, E = Ϫ1.68 V; 7, E = Ϫ1.64 V, vs.
₂

₂

ferrocene–ferrocenium)¶ which can be assigned to the couple
WV᎐WIV.
Owing to poor crystal quality the data set for the structure
determination of [WCl2(NPh)(OC6H3Pri2-2,6)(PEt3)2] 7 did not
allow an anisotropic refinement of all non-hydrogen atoms.
Therefore the bond lengths and angles will not be discussed.
However the trans arrangement of the arylimide and aryloxide
ligands at the octahedrally co-ordinated tungsten centre was
unambiguously demonstrated. The cis arrangement in d0 and
the trans arrangement in dn transition-metal complexes (n = 1 or
2) of two π-donor ligands has been observed in several
examples (Table 3).
Our structural studies of compounds 4 and 6 together with
the direct transformation of the diamagnetic adduct 4 to the
paramagnetic product 6 (Scheme 3) by reduction clearly shows
that the reorganization of the ligands depends on the electron
configuration at the transition-metal centre. Wigley8 found
another example for this dependence during his studies of the
chemistry of tantalum() phenylimidoaryloxides (Scheme 3).
The reduction of the tantalum() complex [TaCl2(NRЈ)(OC6H3-
Pri2-2,6)(py)2] (RЈ = 2,6-Pri2C6H3) with cis arrangement of the
π-donor ligands (NRЈ and OC6H3Pri2) leads to a reorganized
The new compounds 6 and 7 were also characterized by their
X-band EPR spectra. The fluid solution spectrum of 6 [Fig.
3(a)] shows an intense peak centred at g = 1.86 along with two
satellite peaks characteristic of the coupling of a single
unpaired electron with the 183W nucleus (I = ¹, natural abun-
¯
²
dance = 14.4%, A = 60 × 10Ϫ4 cmϪ1). In the frozen-solution
spectrum of 6 [Fig. 3(b)] three different g values were expected
due to the C2v symmetry. The spectrum shows only two signals;
obviously two g values are not resolvable (g1, g2 = 1.88,
g3 = 1.80). Again the hyperfine splitting for the 183W isotope can
be observed as satellites around the main peak. The fluid-
solution EPR spectrum of 7 [Fig. 3(c)] exhibits a triplet centred
at g = 1.89, with hyperfine coupling to two equivalent 31P nuclei
¶ The reference electrode was a saturated calomel electrode (SCE). A
platinum-inlay electrode was used as the working electrode and the
counter electrode was also platinum. Test solutions contained 1 × 10Ϫ3
mol dmϪ3 analyte and 0.1 mol dmϪ3 [NBun4][PF6] supporting electro-
₁
lyte. The E values are reported vs. ferrocene–ferrocenium as internal
₂

standard.
J. Chem. Soc., Dalton Trans., 1997, Pages 1063–1068
1065

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Table 3 Examples of the relative orientation of two π-donor ligands in octahedral complexes
Electron
Complex
configuration
Orientation
Ref.
[WCl3(NPh)(OC6H3Pri2-2,6)(py)]
[TaCl2(NC6H3Pri2-2,6)(OC6H3Pri2-2,6)(py)2]
[ReCl3(Me)(NC6H3Me2-2,6)2]Ϫ
[WCl2(NPh)2(bipy)]
d0
d0
d0
d0
d1
d1
d1
d2
d2
d2
d2
cis
cis
cis
cis
trans
trans
trans
trans
trans
trans
trans
This work
3
5
6
This work
This work
21
3
23
24
4
[WCl2(NPh)(OC6H3Pri2-2,6)(py)2]
[WCl2(NPh)(OC6H3Pri2-2,6)(PEt3)2]
[WCl3(OC6H3Ph2-2,6)2(PMe2Ph)]
i
i
᎐
[Ta(NC6H3Pr 2-2,6)(OC6H3Pr 2-2,6)(EtC᎐CEt)(py)2]
[Re(NC6H4Me-4)(OEt)(S2CNMe2)2]
[ReCl2O(OEt)(py)2]
᎐
[WCl2(OCH2Cf3)2(PMe2Ph3)2]
bipy = 2,2Ј-Bipyridine.
and treated with a mixture of diethylamine (6.36 g, 87 mmol)
and 2,6-diisopropylphenol (15.5 g, 87.0 mmol). The reaction
mixture was stirred for 15 h at room temperature. Diethylamine
hydrochloride was separated by filtration, the hexane solution
was concentrated in vacuo (removal of hexane in vacuo results in
a highly viscous red oil, у95% pure according to 1H NMR
spectroscopy) and cooled to Ϫ30 ЊC to give red crystals which
were filtered off (5.95 g, 28%). NMR (CDCl3): 1H (300 MHz), δ
7.47 (m, 2 H, NPh), 7.12–7.02 (m, 3 H, NPh), 7.01 [d, 8 H,
3
3J(HH) = 7.4, H3,5 of aryloxide], 6.85 [dd, 4 H, J(HH) = 7.1,
8.1, H4 of aryloxide], 3.52 [spt, 8 H, 3J(HH) = 6.7, CHCH3] and
0.92 [d, 48 H, 3J(HH) = 6.7 Hz, CHCH3]; 13C-{1H} (75.4 MHz),
δ 159.1 (Cipso of aryloxide), 153.5 (Cipso of NPh), 138.1 (C2,6 of
aryloxide), 127.7, 127.6, 127.0, 123.3, 123.1 (NPh, aryloxide),
26.5 (CHCH3) and 23.9 (CHCH3). Mass spectrum (SIMS): m/z
806 [M+ Ϫ OC6H3Pri2] (Found: C, 65.8; H, 7.75. Calc. for
C54H73NO4W: C, 65.9; H, 7.5%).
Fig. 3 The EPR spectra (X-band) of (a) complex 6 in toluene at room
temperature (first derivative), (b) 6 in toluene at 136 K (first derivative)
and (c) 7 in toluene at room temperature
(A = 28 × 10Ϫ4 cmϪ1) which is in the range found for other
complexes.27
[WCl3(NPh)(OC6H3Pri2-2,6)] 2. The red viscous oil of com-
plex 1 (21.4 g, 21.7 mmol) (not crystallized from hexane for this
preparation) was dissolved in toluene and treated with
[{WCl3(NPh)}2(µ-Cl)2] (27.2 g, 32.6 mmol) at room temperature.
The mixture was stirred overnight, concentrated in vacuo,
cooled to Ϫ30 ЊC and the brown microcrystals filtered off (41.3
g, 85%). NMR: 1H (250 MHz, CDCl3), δ 7.9–7.1 (m, 8 H, NPh,
Experimental
Materials
2,6-Diisopropylphenol, bpy and py were obtained from Aldrich.
Triethylphosphine28 and [{WCl3(NPh)}2(µ-Cl)2]15b were pre-
pared according to literature procedures. Hexane was distilled
from potassium, benzene and thf from sodium–benzophenone
and toluene from sodium. All distillations and bench-top
manipulations were carried out under nitrogen.
3
aryloxide), 3.45 [spt, 2 H, J(HH) = 6.8, CHCH3] and 1.29 [d,
3
12 H, J(HH) = 6.8 Hz, CHCH3]. Mass spectrum (SIMS): m/z
557 (M+). Molecular weight determination (vapour-pressure
osmometry, 32.35 mg in 1.1870 g CH2Cl2): M = 555. Calc.
558.59 (Found: C, 38.45; H, 4.05; N, 2.5. Calc. for
C18H22Cl3NOW: C, 38.7; H, 3.95; N, 2.5%).
Physical measurements
Infrared spectra were recorded on a Perkin-Elmer FT-IR 1720
X spectrometer, NMR spectra with Bruker WP 80 PFT (1H, 80
MHz), WH-250 PFT (1H, 250; 13C, 62.9 MHz) and Varian VXR
300 (1H, 300; 13C, 75.4 MHz) spectrometers. Cyclic voltam-
metry was performed using an EG&G 173 potentiostat and a
175 programmer with a normal three-electrode configuration.
The EPR spectra were obtained with a Bruker ER 200D/ESP
3220 spectrometer. Samples were prepared as ≈1 mmol dmϪ3
solutions in toluene (using diphenylpicrylhydrazyl for calibra-
tion). A gaseous nitrogen cryostat was used for low-temperature
(136 K) studies. Magnetic measurements on a polycrystalline
sample were carried out with a SQUID magnetometer (Quan-
tum design). Liquid secondary ion mass spectra were obtained
with a Finnigan MAT 95 instrument. Elemental analyses were
performed by Mikroanalytisches Labor Pascher (D 53424
Remagen) and for complexes 2, 3 and 5 with a Carlo-Erba
Elemental Analyzer.
[WCl3(NPh)(OC6H3Pri2-2,6)(thf)] 3. A solution of complex 2
(0.5 g, 0.4 mmol) in thf (10 cm3) was stirred overnight at room
temperature. The solvent was removed in vacuo. Slow diffusion
from hexane into a diethyl ether solution of 2 gave the product
as a dark red microcrystalline powder (0.5 g, 96%). NMR
(CDCl3): 1H (80 MHz), δ 7.6–6.8 (m, 8 H, aryloxide, NPh), 4.5–
4.0 (br s, 4 H, Hα of thf), 3.84 [spt, 2 H, 3J(HH) = 6.8, CHCH3],
2.2–1.8 (m, 4 H, Hβ of thf) and 1.23 [d, 12 H, 3J(HH) = 6.8 Hz,
CHCH3]; 13C-{1H} (62.9 MHz), δ 160.0 (Cipso of aryloxide),
151.0 (Cipso of NPh), 138.3 (C2,6 of aryloxide), 131.9, 129.6,
127.4, 126.2, 123.7 (NPh, aryloxide), 70.0 (br, Cα of thf), 26.1
(CHCH3), 25.6 (Cβ of thf) and 24.5 (CHCH3) (Found: C, 41.2;
H, 4.85; N, 2.25. Calc. for C22H30Cl3NO2W: C, 41.9; H, 4.8; N,
2.2%).
[WCl3(NPh)(OC6H3Pri2-2,6)(py)] 4. A solution of complex 2
(1.45 g, 1.3 mmol) in thf (10 cm3) was treated with pyridine
(0.21 cm3, 2.6 mmol) and stirred for 30 min at room temper-
ature. The solvent was removed in vacuo. Recrystallization from
benzene–hexane–diethyl ether (1:2:2) gave the complex as dark
brown crystals (1.27 g, 77%). IR: νmax/cmϪ1 (CsI) 337, 322 and
Syntheses
[W(NPh)(OC6H3Pri2-2,6)4] 1.
[{WCl3(NPh)}2(µ-Cl)2] (9.06 g, 10.9 mmol) was cooled to 0 ЊC
A hexane suspension of
1066
J. Chem. Soc., Dalton Trans., 1997, Pages 1063–1068

View Article Online
Table 4 Crystallographic data for complexes 4 and 6*
4
6
Formula
M
C23H27Cl3N2OW
637.69
C28H32Cl2N3OW
681.34
Crystal size/mm
a/Å
b/Å
c/Å
0.20 × 0.20 × 0.20
15.483(8)
17.886(8)
18.315(9)
93.42(5)
5063(8)
1.673
0.25 × 0.20 × 0.15
9.815(2)
15.965(3)
11.7752(5)
92.09(2)
2780(2)
1.628
β/Њ
U/Å3
Dc/g cmϪ3
Z
8
50.0
203
4
44.6
253
µ(Mo-Kα)/cmϪ1
T/K
Scan mode
ω–2θ
ω
Scan range/Њ
Total data
3 < θ < 25
9579
3 < θ < 28
5278
No. unique observed data
[I > 1.0σ(I)]
No. variables
R, RЈ
4386
523
0.084, 0.062
1.189
2709
316
0.046, 0.048
1.113
0.96 (0.96 Å from W)
Goodness of fit
Maximum residual density/e ÅϪ3
2.01 [1.02 Å from W(1a)]
* Details in common: monoclinic, space group P21/c; weighting scheme w = 1/σ2(Fo).
288 (WCl). NMR (C6D6): 1H (250 MHz), δ 9.46 [dd, 2 H,
3J(HH) = 6.5, 4J(HH) = 1.5, Hα of py], 7.15–6.35 (m, 11 H, aryl-
oxide, NPh, py), 3.72 [spt, 2 H, 3J(HH) = 6.8, CHCH3] and 1.03
Mass spectrum (SIMS): m/z 758 (M+), 724 (M+ Ϫ Cl), 642
(M+ Ϫ PEt3) and 583 (M+ Ϫ OC6H3Pri2) (Found: C, 47.6; H,
6.9. Calc. for C30H52Cl2NOP2W: C, 47.45; H, 6.9%).
3
[d, 12 H, J(HH) = 6.8 Hz, CHCH3]; 13C-{1H} (62.9 MHz), δ
159.8 (Cipso of aryloxide), 151.5 (Cα of py), 150.9 (Cipso of NPh),
139.2 (C2,6 of aryloxide), 138.8 (Cγ of py), 131.6, 130.0, 128.5,
126.5, 124.4, 124.3 (NPh, aryloxide, Cγ of py), 26.3 (CHCH3)
and 24.7 (CHCH3) (Found: C, 43.95; H, 4.45. Calc. for
C23H27Cl3N2OW: C, 43.3; H, 4.25%).
Crystallography
Crystals of complexes 4 and 6 were mounted on a glass fibre
under a stream of nitrogen. Geometry and intensity data were
collected on an Enraf-Nonius CAD4 diffractometer with
graphite-monochromatized Mo-Kα radiation (λ = 0.710 73 Å).
Crystal data and the parameters of data collection and struc-
ture refinement29 are compiled in Table 4. Structure 4 was
solved by direct methods30 and 6 by the Patterson method. The
remaining atom positions resulted from subsequent refinement
cycles and Fourier-difference syntheses. In the final least-
squares full-matrix refinement (based on F) all non-hydrogen
atoms were refined with anisotropic thermal displacement
parameters except for the disordered parts of structure 4 which
were refined isotropically. All hydrogen atoms of both struc-
tures were treated as riding atoms with an idealized geometry
(C᎐H 0.98 Å, BH = 1.3BC). For 4 an empirical absorption
correction was applied (ψ scans).31
[WCl3(NPh)(OC6H3Pri2-2,6)(bpy)] 5. This complex was pre-
pared in the same manner as for 4 using 2 (1.30 g, 2.3 mmol).
Yield 1.31 g (81%). IR: νmax/cmϪ1 (CsI) 339, 325 and 288 (WCl).
1
3
NMR (CDCl3): H (250 MHz), δ 9.16 [dd, 2 H, J(HH) = 5.4,
4J(HH) = 1.3, Hα of bpy], 7.5–6.9 (m, 10 H, aryloxide, NPh,
bpy), 3.27 [spt, 2 H, 3J(HH) = 6.8, CHCH3], 1.26 (s, 9 H, CCH3)
3
and 0.85 [d, 12 H, J(HH) = 6.8 Hz, CHCH3]; 13C-{1H} (62.9
MHz), δ 164.3, 159.4, 150.5 (Cipso of aryloxide, NPh, bpy), 151.0
(Cα of bpy), 138.8 (C2,6 of aryloxide), 131.8, 130.0, 127.5, 126.2,
123.8, 121.8 (aryloxide, NPh, Cβ of bpy), 35.4 [C(CH3)3], 30.3
[C(CH3)3], 26.0 (CHCH3) and 24.5 (CHCH3) (Found: C, 46.2;
H, 5.4, N, 3.95. Calc. for C27H35Cl3N2OW: C, 46.75; H, 5.1; N,
4.05%).
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 186/368.
[WCl2(NPh)(OC6H3Pri2-2,6)(py)2] 6. A solution of complex 2
(6.49 g, 5.81 mmol) in thf (10 cm3) and toluene (30 cm3) was
cooled to 0 ЊC and treated with pyridine (1.84 g, 2.23 mmol).
After 5 min sodium amalgam (Na, 267 mg, 11.6 mmol; Hg, 52
g) was added. The mixture was stirred vigorously overnight at
room temperature, filtered and the solvent removed in vacuo.
Recrystallization from benzene–hexane gave the complex as
dark green crystals (6.1 g, 77%). IR: νmax/cmϪ1 (CsI) 297 (WCl).
Mass spectrum (SIMS): m/z 683 (M+), 646 (M+ Ϫ Cl), 604
(M+ Ϫ py) and 505 (M+ Ϫ OC6H3Pri2) (Found: C, 49.35; H,
4.75. Calc. for C28H32Cl2N3OW: C, 49.35; H, 4.75%).
Acknowledgements
We thank Professor Dr. G. E. Herberich for his support.
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Received 27th September 1996; Paper 6/06644E
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J. Chem. Soc., Dalton Trans., 1997, Pages 1063–1068