Dihydrobis(pyrazolyl)borate alkylidyne complexes of tungsten

Article abstract of DOI:10.1002/ejic.200300444

[W(≡CR)Br(CO)₂(NC₅H₄Me-4) ₂] (R = C₆H₃Me₂-2,6 1a, C ₆H₂Me₃-2,4,6 1b) react with K[H ₂B(pz)₂] (pz = pyrazol-1-y1) to provide

Full text of DOI:10.1002/ejic.200300444

FULL PAPER
Dihydrobis(pyrazolyl)borate Alkylidyne Complexes of Tungsten[‡]
Anthony F. Hill,*[a,b] John M. Malget,[a] Andrew J. P. White,[a] and David J. Williams[a]
Keywords: Borates / Carbyne ligands / Multiple bonds / N Ligands / Tungsten
[W(ϵCR)Br(CO)2(NC5H4Me-4)2] (R
=
C6H3Me2-2,6 1a,
both combinations provide primarily the thermally unstable
C6H2Me3-2,4,6 1b) react with K[H2B(pz)2] (pz = pyrazol-1- ketenyl complex [W(η2-OCCR)(CO)(CNRЈ)2{H2B(pz)2}] (4).
yl)
to
provide
two
interconverting
isomers
of
The picoline ligand in [W(ϵCR)Br(CO)2(NC5H4Me-
4){H2B(pz)2}] (2) is readily replaced by PMe2Ph to provide
[W(ϵCR)(CO)2(PMe2Ph){H2B(pz)2}] (structurally charac-
terised for R = C6H3Me2-2,6 6a). The reaction of either
[W(ϵCR)(CO)2(NC5H4Me-4){H2B(pz)2}] (2), one isomer hav-
ing been structurally characterised for R = C6H3Me2-2,6 (2a).
The reactions of [W(ϵCR)Br(CO)2(CNRЈ)2] (5: RЈ
C6H3Me2-2,6, CNMe3) with K[H2B(pz)2] or
=
of
[W(ϵCR)(CO)2(PMe2Ph){H2B(pz)2}]
(6)
or
[W(ϵCR)-
[W(ϵCR)Br(CO)2(NC5H4Me-4){H2B(pz)2}] (2) with isocyan-
ides are more complex due to the facile formation of unstable
(CO)2(NC5H4Me-4){H2B(pz)2}] (R = C6H2Me3-2,4,6 2b) with
excess PMe2Ph provides [W(ϵCR)(CO)(PMe2Ph)2{H2B(pz)2}]
ketenyl derivatives. In the absence of light, the reaction of (7). This complex is also obtained from K[H2B(pz)2] and
[W(ϵCR)Br(CO)2(CNRЈ)2] (5) with K[H2B(pz)2] provides
[W(ϵCR)(CO)2(CNRЈ){H2B(pz)2}] (3) in moderate yield, sim-
[W(ϵCR)Br(CO)(PMe2Ph)3] (8), the latter arising from the re-
action of [W(ϵCR)Br(CO)2(NC5H4Me-4)2] (1b) with PMe2Ph.
ilar yields were obtained from [W(ϵCR)(CO)2(NC5H4Me- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
4){H2B(pz)2}] (2) and CNRЈ. Under mild photolytic conditions
Germany, 2004)
Introduction
The chemistry of alkylidyne complexes of tungsten[2] has
been greatly enriched by use of hydrotris(pyrazolyl)borate
ligands and their derivatives,[3] primarily from the works of
Stone,[4] Angelici,[5] and Templeton.[6] The dihydro-
bis(pyrazolyl)borate chelate [H2B(pz)2; pz ϭ pyrazol-1-yl;
Scheme 1][3] is an intriguing ligand in its own right dis-
playing a propensity for η3-coordination through agostic
and potentially hemilabile BϪHϪM interactions.
In the design of alkylidyne complexes for use in both stoi-
chiometric and catalytic bond-forming processes, the incor-
poration of a vacant coordination site cis to the alkylidyne
ligand remains a valuable goal, although this can present a
challenge for low-valent metal centres which are typically
more constrained by adherence to the 18-electron rule.
Stone has described a range of tungsten alkylidyne com-
plexes coligated by the H2B(pz)2 ligand and shown that they
readily enter into bridge-assisted cluster-assembly reactions
Scheme 1. Dihydrobis(pyrazolyl)borate coordination
(Scheme 2).[7]
The
further
observation
that
to provide [Mo(ϵCCMe3)(CO){P(OMe)3}2{H2B(pz)2}][8]
points toward the intermediacy of coordinatively unsatu-
rated species, if an analogy with alkyne metathesis is enter-
tained. However, no direct observation of the operation of
the η3-coordination mode was ever made in these processes.
We considered that the H2B(pz)2 ligand might nevertheless,
under suitably contrived circumstances, enter into η3-coor-
dination and thereby satisfy the above requirements by vir-
tue of the hemilability of the agostic BϪHϪM interaction.
[Mo(ϵCC6H4OMe-2)(CO){P(OMe)3}2{H2B(pz)2}] reacts
stoichiometrically with PϵCCMe3 under mild conditions
[‡]
Poly(azotyl)chelate Chemistry, 11. Part 10: Ref.[1]
[a]
Department of Chemistry, Imperial College London,
South Kensington, SW7 2AZ, U.K.
E-mail: a.hill@rsc.anu.edu.au
[b]
Research School of Chemistry, Institute of Advanced Studies,
Australian National University,
Canberra ACT, Australia
818
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Alkylidyne Complexes of Tungsten
FULL PAPER
viously employed for the preparation of various ‘‘half-sand-
wich’’ alkylidyne complexes, although its synthesis was not
described.[13] The chloro(pyridine)mesitylmethylidyne com-
plex [W(ϵCC6H2Me3-2,4,6)Cl(CO)2(NC5H5)2] has recently
been reported[14] by the Mayr synthesis from the reaction
of Fischer’s pre-isolated aroylate salt [W{C(ϭO)C6H2Me3-
2,4,6}(CO)5][NMe4][17] with oxalyl chloride and pyridine.
Whilst this salt would presumably also serve as a precursor
for the subsequent introduction of the H2B(pz)2 ligand, the
present
high
yielding
‘‘one-pot’’
synthesis
of
[W(ϵCC6H2Me3-2,4,6)Br(CO)2(NC5H4Me-4)2] (1a) is both
more convenient and atom efficient in a ‘‘green’’ sense.
Specifically, by omitting the Li/NMe4 metathesis step in the
original Mayr synthesis, the bromide anion carried through
from the original synthesis of the aryllithium replaces the
trifluoroactetate
ligand
in
the
intermediate
[W(ϵCR)(O2CCF3)(CO)4]. γ-Picoline was chosen to sim-
plify the NMR data. Spectroscopic data for the complexes
are unremarkable and conform to precedent.[2]
Scheme 2. Dihydrobis(pyrazolyl)borate alkylidynes[7,8]
The results described herein arise from an attempt to
broaden the class of alkylidyne-H2B(pz)2 complexes in pur-
suit of such a situation. Although coordination of the
H2B(pz)2 ligand has been structurally confirmed in the
chemistry of chromium,[9] the Cambridge Crystallographic
Data Centre contains no data for mononuclear H2B(pz)2
complexes of either molybdenum[10] or tungsten and ac-
cordingly, two crystallographic studies of complexes with
the H2B(pz)2W motif were undertaken.
Results and Discussion
Stone’s original approach to alkylidyne complexes col-
igated by the H2B(pz)2 ligand, namely [W(ϵCR)(CO)3-
{κ2-H2B(pz)2}] (R ϭ Me, C6H4Me-4; hereafter κ2 implied
unless otherwise indicated),[7] proceeded from Fischer’s
thermolabile precursors trans-[W(ϵCR)Br(CO)4]. Whilst
the instability of the tetracarbonyl precursors did not pre-
clude a detailed study of [W(ϵCR)(CO)3{H2B(pz)2}], we
sought a more convenient entry point. To this end, ther-
Scheme 3. One Pot Synthesis of alkylidyne tungsten precursors
The reactions of 1a or 1b with K[H2B(pz)2] in propanone
mally stable bis(γ-picoline) precursor complexes were em- or dichloromethane provide high yields of the complexes
ployed. We have previously employed the sterically con- formulated as [W(ϵCR)(CO)2(NC5H4Me-4){H2B(pz)2}]
gested xylylmethylidyne ligand to confer kinetic stability on (R ϭ C6H3Me2-2,6 2a, C6H2Me3-2,4,6 2b) on the basis of
alkylidyne complexes.[13] More recently, Berke employed the spectroscopic data and a crystallographic study (vide infra)
mesitylmethylidyne variant and this allowed the obser- of 2a. Infrared (solution and solid-state) and 1H NMR
vation of rare examples of hydrido-alkylidyne complexes.[14] spectroscopic data for both 2a and 2b would appear to sug-
The
complexes
trans,cis,cis-[W(ϵCR)Br(CO)2- gest the formation of one isomer, however, in this instance
(NC5H4Me-4)2] (R ϭ C6H3Me2-2,6 1a, C6H2Me3-2,4,6 1b) 13C{1H} NMR spectroscopic data appear more sensitive to
were readily obtained directly from [W(CO)6] in ‘‘one-pot’’ the coordination environment around tungsten, revealing
reactions by successive treatment with LiBr/LiR (from Li the coexistence of two isomers in solution (Scheme 4). Thus
and RBr), (CF3CO)2O and γ-picoline (Scheme 3), following for 2b, two carbyne associated resonances are observed at
a
modification/combination of Mayr’s syntheses of low field [δ ϭ 294.5 (major), 284.5 (minor) ppm]. Similarly,
[W(ϵCPh)Cl(CO)2(NC5H4)2] and [W(ϵCPh)(O2CCF3)- the carbonyl resonances are observed in similar ratios; how-
(CO)2(tmeda)].[15,16] The 2-xylyl derivative 1a has been pre- ever, these latter data also allow the assignment of the
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A. F. Hill, J. M. Malget, A. J. P. White, D. J. Williams
FULL PAPER
stereochemistry at tungsten. Thus, the major isomer has and picoline groups are comparable. Since this equilibrium
only one carbonyl environment (δ ϭ 225.3 ppm) whilst the operates under mild conditions, it seems most likely that it
minor isomer features two carbonyl resonances (δ ϭ 227.5 occurs through dissociation of the picoline ligand, re-
and 221.5 ppm). Accordingly, the major isomer corre- arrangement of the five-coordinate complex and picoline
sponds to the more symmetric geometry (i.e. with the pico- recoordination, rather than unimolecular rearrangement of
line ligand trans to the alkylidyne substituent) which is also the octahedral complexes. The lability of the picoline ligand
found in the solid state (Scheme 4, Figure 1). Similar behav- in 2 is also implicit in the ligand-substitution reactions dis-
iour was observed for 2b.
cussed below. It might also be inferred that if tridentate
coordination of the H2B(pz)2 ligand occurs to stabilize the
five-coordinate intermediate, then this is easily replaced by
picoline coordination since no spectroscopic evidence was
obtained for such an intermediate.
The reactions of 2 with a range of ligands were investi-
gated. Under ambient conditions neither 2a nor 2b appear
to react with carbon monoxide within spectroscopically
(IR) determinable limits. This is in contrast to the complex
[Mo(ϵCC6H4OMe-2)(CO){P(OMe)3}2{H2B(pz)2}][8] which
equilibrates to a mixture with the complex [Mo(ϵCC6H4-
OMe-2)(CO)2{P(OMe)3}{H2B(pz)2}] under one atmos-
phere of CO in dichloromethane.[18] However, it is not sur-
prising given that introduction of a further carbonyl ligand
would be disfavored by the competitive π-acidity of the two
carbonyl and alkylidyne ligands already present. The com-
plex [W(ϵCC6H4Me-4)(CO)3{H2B(pz)2}][7] has already
been discussed (see above) and the synthesis proceeds in the
absence of other potential donor ligands.
Isonitriles (CNRЈ: RЈ ϭ CMe3, C6H3Me2-2,6) which are
more nucleophilic and less π-acidic ligands than CO do re-
act with 2 by displacement of the picoline ligand. However,
these reactions are complicated by the competitive forma-
tion of the ketenyl species. Thus, treating 2a with either
CNCMe3 or CNC6H3Me2-2,6 leads to complex mixtures.
This was eventually traced to the competition of thermal
and photochemical processes, each leading to thermally
sensitive products. The major identifiable products of the
thermal reaction were the alkylidyne complexes
[W(ϵCC6H3Me2-2,6)(CO)2(CNRЈ){H2B(pz)2}] (3), whilst
the major photo-products were the ketenyl complexes
Scheme 4
[W(η2-OCC6H3Me2-2,6)(CO)(CNRЈ)2{H2B(pz)2}] (RЈ
C6H3Me2-2,6 4a, CMe3 4b).
ϭ
Kreiβl[19] studied the coupling of alkylidyne and carbonyl
ligands to generate mononuclear ketenyl complexes in ther-
mal reactions of [W(ϵCC6H4Me-4)(CO)2(η-C5H5)] with
PMe3, whilst Stone showed similar couplings in dinuclear
systems.[20] Subsequently, Geoffroy demonstrated that such
processes could be photochemically induced.[21] Ketenyl
formation through alkylidyne/carbonyl coupling has since
been reviewed,[22] whilst the synthetic utility of ketenyl com-
plexes has been amply demonstrated by Kreiβl.[23] The
clarification of the processes involved in the reactions of 2
with isocyanides called for selective synthesis of the prod-
ucts since the reactions themselves were not synthetically
useful in that the mixtures obtained required cryostatic
chromatography (Ϫ40 °C) and the purified products were
unstable at room temperature. The purple ketenyl complex
[W(η2-OCC6H3Me2-2,6)(CO)(CNCMe3)2{H2B(pz)2}] (4b)
Figure 1. Molecular geometry of 2a; hydrocarbon hydrogen
atoms omitted
For both isomers to coexist and interconvert in solution, could most easily be obtained in modest yield (40 %) by the
it may be surmised that the donor properties of the pyrazole addition of CNCMe3 to 2a under irradiation (domestic sun
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Alkylidyne Complexes of Tungsten
FULL PAPER
lamp) followed by cryostatic chromatography. Although formulation being confirmed by FAB-MS data. Thus one
they could be retrospectively identified amongst the prod- isocyanide-associated absorption is observed in the infrared
ucts of the reactions of 2 with CNRЈ, the alkylidyne com- spectrum and one albeit broad resonance in the 13C{1H}
plexes
(RЈ ϭ C6H3Me2-2,6 3a, CMe3 3b) could most easily be ob- ment. The observation of a single isocyanide environment
tained through the reactions of preformed would suggest that either inversion of the B(NN)2W boat
[W(ϵCC6H3Me2-2,6)(CO)2(CNRЈ){H2B(pz)2}] NMR spectrum indicating a trans-W(CNCMe3)2 arrange-
[W(ϵCC6H3Me2-2,6)Br(CO)2(CNRЈ)2] (RЈ ϭ CMe3 5a, arrangement is rapid on the NMR timescale or that the
C6H3Me2-2,6 5b; Scheme 5)[24] with K[H2B(pz)2], although BH2 group does not sufficiently closely approach the tert-
exclusion of light was essential throughout their synthesis butyl groups to render these inequivalent. Molecular
and isolation.
models and the related structural studies (vide infra) would
argue for the former interpretation.
In contrast to the reactions with isocyanides, the reac-
tions of 2 with dimethylphenylphosphane are straightfor-
ward and proceed through picoline substitution to provide
a single isomer with no indication of ketenyl formation.
Thus, treating 2 with one equivalent of PMe2Ph in dichloro-
methane provided the complexes [W(ϵCR)(CO)2-
(PMe2Ph){H2B(pz)2}]
(R
ϭ
C6H3Me2-2,6
6a,
C6H2Me3-2,4,6 6b) each in only one isomeric form. The
complex [W(ϵCC6H4Me-4)(CO)3{H2B(pz)2}] has been re-
ported to react with PPh3 or PMe3 to provide the com-
plexes [W(ϵCC6H4Me-4)(CO)2(PR3){H2B(pz)2}] by car-
bonyl substitution with no evidence for ketenyl formation.[7]
The stereochemistry of 6a in solution (Scheme 6, Figure 2)
follows unequivocally from spectroscopic data and was con-
firmed by X-ray crystallography (vide infra). The dia-
stereotopicity of the phosphane methyl groups confirms the
absence of a molecular element of symmetry excluding the
isomer with phosphane trans to the alkylidyne group. This
possibility may also be discounted by the low value of
2JP-C (8.9 Hz) for the alkylidyne 13C resonance. IR data
Scheme 5
The formulation of both the alkylidyne and ketenyl com-
plexes rests upon spectroscopic and FAB-MS data, since
their instability at ambient temperatures prevented us from
obtaining either satisfactory elemental microanalysis or
crystallographic grade crystals. Nevertheless, the spectro-
scopic data strongly support the formulations as do the
unequivocal synthesis from bis(isocyanide) precursors. For
the alkylidyne complex [W(ϵCC6H3Me2-2,6)(CO)2-
1
(CNCMe3){H2B(pz)2}] (3b), both H and 13C{1H} NMR
spectroscopic data confirm two distinct pyrazolyl environ-
ments, the latter also indicating chemically inequivalent car-
bonyl ligands. Taken together, these data are only consistent
with the geometry shown in Scheme 5. Such arguments also
support a similar geometry for 3a. For the ketenyl complex
[W(η2-OCCC6H3Me2-2,6)(CO)(CNCMe3)2{H2B(pz)2}]
(4b) the stereochemistry at tungsten also follows from a
combination of IR and NMR spectroscopic data, the gross Scheme 6
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A. F. Hill, J. M. Malget, A. J. P. White, D. J. Williams
FULL PAPER
indicates a cis-W(CO)2 arrangement whilst 13C NMR spec- 31P{1H} NMR spectroscopic data for the phosphane
troscopic data indicate that both the CO ligands and also groups and the doublet-triplet fine structure of the carbonyl
the two pyrazolyl groups are chemically inequivalent. Simi- and alkylidyne group resonances in the 13C{1H} NMR
lar arguments apply to the stereochemistry of 6b.
spectrum. The complex 8 reacts cleanly with K[H2B(pz)2]
in tetrahydrofuran to provide 7. In this case it is not neces-
sary to invoke ketenyl intermediates.
Crystal Structure of [W(ϵCC6H3Me2-2,6)(CO)2-
(NC5H4Me-4){H2B(pz)2}]·0.5CH2Cl2 (2a·0.5CH2Cl2)
The complex crystallizes from a mixture of dichlorometh-
ane and petroleum ether as a dichloromethane hemisolvate,
however, the solvent of crystallization which is disordered
shows no directional interactions with the complex and ne-
ither are there any notable intermolecular interactions
within the crystal lattice. The molecular geometry of the
complex is depicted in Figure 1 and selected bond lengths
and angles are presented in Table 1. The geometry at tung-
sten is distorted octahedral with angles between adjacent
ligands lying in the range 82.9(2)Ϫ101.2(2)° such that the
pyrazolyl groups bend away from the alkylidyne groups
[C(1)ϪWϪN(15) 100.5(2), C(1)ϪWϪN(10) 101.2(2)°]
whilst the carbonyl ligands bend less markedly towards it
[C(1)ϪWϪC(28) 85.6(3), C(1)ϪWϪC(30) 87.9(3)°]. The
bending of cis ligands away from metalϪelement multiple
bonds is not uncommon and it has been suggested that this
strengthens the multiple bonding.[28] The alkylidyne ligand
is essentially linear at the carbyne carbon [WϪC(1)ϪC(7)
Figure 2. Molecular geometry of 6a; hydrocarbon hydrogen
atoms omitted
Treating the complex 6b with excess PMe2Ph leads to car-
bonyl substitution and formation of the trans-bis(phos-
phane) complex [W(ϵCC6H2Me3-2,4,6)(CO)(PMe2Ph)2-
{H2B(pz)2}] (7). The stereochemistry at tungsten follows
from 1H, 31P and 13C NMR spectroscopic data. The chemi-
cal equivalence of the two phosphorus nuclei is manifest as
a singlet resonance in the 31P{1H} NMR spectrum, whilst
the trans arrangement is suggested by the virtual triplet nat-
ure of the 13C resonance for the phosphane methyl groups.
Notably this stereochemistry is equivalent to that proposed
for [Mo(ϵCR)(CO){P(OMe)3}2{H2B(pz)2}] (R ϭ CMe3,
˚
178.0(5)°] and the WϵC separation of 1.810(6) A falls
within the range typical of alkylidyne tungsten complexes[2]
and is similar to that found in, for example,
[29]
[W(ϵCPh)(CO)2(Ppy3)]ϩ [1.811(7) A].
The xylyl ring
˚
orientation is presumably dictated by steric effects as it
places the ortho substituents between adjacent coligands,
rather than allowing the aromatic π-system to conjugate
with occupied metal t2g orbitals. In a similar manner, the
plane of the picoline ligand is approximately orthogonal
(ca. 79°) to that of the alkylidyne, lying between the pyrazo-
lyl rings of the H2B(pz)2 chelate and approximately bi-
secting the W(CO)2 group. The octahedral γ-picoline com-
C6H4OMe-2).[8] The IR data [ν(CO) ϭ 1992, 1903 cmϪ1
]
for 6b would suggest that the carbonyl ligands are not ther-
mally labile. Accordingly, the facile formation of 7 from 6b
under mild conditions presumably proceeds through ketenyl
formation followed by CO extrusion, as has been demon-
strated in the synthesis of [W(CϵCC6H4Me-4)-
plexes
trans-[WIIICl4(NC5H4Me-4)2]Ϫ,[30]
cis,cis,trans-
[WIIBr2(bipy)(NC5H4Me-4)2][31] and [W0(CO)5(NC5H4Me-
4)][32] have (mean) WϪN bond lengths of 2.166, 2.176, and
(CO)(PMe3)(η-C5H5)]
from [W(ϵCC6H4Me-4)(CO)2-
the reactions of
˚
2.257 A, respectively, with a lengthening of the WϪN bond
(η-C5H5)].[19]
Notably,
on reduction of the metal centre (WIII, WII, and W0). For-
[W(ϵCR)(CO)2{HB(pz)3}] (R ϭ C6H4Me-4, SMe) with
PMe3 or PEt3 stop at the ketenyl stage providing
˚
Table 1. Selected bond lengths (A) and angles (°) for 2a
[W(η2-OCCC6H4Me-4)(CO)(PMe3){HB(pz)3}][7]
and
[W(η2-OCCSMe)(CO)(PEt3){HB(pz)3}],[5a] respectively.
WϪC(1)
1.810(6) WϪC(28)
1.977(9) WϪN(15)
2.204(6) WϪN(26)
1.416(9)
1.975(8)
2.201(6)
2.378(5)
An alternative synthesis of 7 was developed by the reac- WϪC(30)
tion of [W(ϵCC6H2Me3-2,4,6)Br(CO)(PMe2Ph)3] (8) with
K[H2B(pz)2]. The new precursor 8 was obtained from the
reaction of 1b with PMe2Ph. The closely related complex
[W(ϵCPh)Cl(CO)(PMe3)3] has been reported previously
WϪN(10)
C(1)ϪC(7)
C(1)ϪWϪC(28)
85.6(3)
87.6(3)
94.3(3)
101.2(2)
93.6(3)
173.8(2)
88.9(2)
C(1)ϪWϪC(30)
87.9(3)
100.5(2)
171.5(2)
173.1(3)
83.6(2)
88.9(3)
82.88(19)
178.0(5)
C(28)ϪWϪC(30)
C(28)ϪWϪN(15)
C(1)ϪWϪN(10)
C(30)ϪWϪN(10)
C(1)ϪWϪN(26)
C(30)ϪWϪN(26)
N(10)ϪWϪN(26)
C(1)ϪWϪN(15)
C(30)ϪWϪN(15)
C(28)ϪWϪN(10)
N(15)ϪWϪN(10)
C(28)ϪWϪN(26)
N(15)ϪWϪN(26)
by
Mayr,
arising
from
the
reaction
of
[W(ϵCPh)Cl(CO)2(PMe3)2] with PMe3 over a period of 7
days.[27] In the present case however the stoichiometric
amount of phosphane suffices and the reaction is complete
in 15 h. The mer geometry follows from 1H, 13C and
84.30(18) C(7)ϪC(1)ϪW
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Alkylidyne Complexes of Tungsten
FULL PAPER
mal oxidation states have little meaning in compounds with range previously observed and generally attributed to crys-
metalϪcarbon multiple bonding. However, the sensitivity tal-packing effects.[2] The orientation of the xylyl group is
of the WϪN bond lengths to the π-acidity of trans-disposed such as to minimise steric interactions with cis coligands,
ligands has been demonstrated for the bis(pyridine) com- which places the ortho substituents either side of the
plex [W(ϵCPh)Cl(CO)(ma)(py)2][33] where the WϪN bond W(CO)2 unit. The phosphane ligand has a WϪP bond
˚
trans to the strongly π-acidic maleic anhydride (ma) is length of 2.564(1) A which appears somewhat long. Limit-
˚
˚
longer (2.253 A) than that trans to CO (2.233 A). The ing comparison to 6-coordinate tungsten complexes of
WϪN(26) bond length of 2.378(5) A seen here for 2a far PMe2Ph with sterically modest co-ligands[34,35] there ap-
˚
exceeds those discussed above and is consistent with the pears to be no obvious correlation between the oxidation
lability demonstrated in reactions with CNRЈ and PMe2Ph state (d configuration) and the WϪP bond length [d6:
and also its facile isomerism. This lengthening is also con- 2.480Ϫ2.524; d4: 2.484Ϫ2.512; d3: 2.513Ϫ2.561; d2:
˚
sistent with its location trans to an alkylidyne ligand which 2.481Ϫ2.538A]. The dichotomy that clouds the assignment
is generally considered to be strongest of all carbon π-acid of oxidation states for alkylidyne complexes is shared by
ligands.
nitrosyl ligands and accordingly the most suitable structure
The W(pz)2BH2 metallacycle adopts a typical boat for- for comparison is the complex trans,cis,cis-[W(NO)I(C-
mation with both the tungsten and boron atoms lying ca. O)2(PMe2Ph)2] reported by Basolo[35] which also features
˚
˚
0.65 A out of the plane of the four nitrogen atoms which particularly long WϪP bond lengths [2.582(2), 2.554(2) A].
˚
are coplanar to within 0.007 A. This geometry is compara-
The [H2B(NN)2W] chelate once again adopts a shallow
tively shallow and positions the BH2 group well beyond any boat conformation with here the tungsten and boron atoms
˚
˚
interaction with either the metal [BH···W 3.46 A] or co- that lie (0.54 and 0.65 A, respectively) out of the N4 plane
˚
ligands. Thus, although the adopted conformation places which is coplanar to within 0.026 A. The closest BϪH hy-
the BH2 adjacent to the alkylidyne, the BH···C(1) distance drogen atom approach to the metal centre is 3.49 A, too
of 3.10 A is probably too long to invoke any incipient nuc- distant for any interaction. However, this hydrogen atom is
˚
˚
leophilic interaction of the BϪH bond with the carbyne positioned directly above one of the carbonyl ligands, the
˚
carbon atom. The bite of the chelate at 83.6(2)° is somewhat BH···C(23) distance being 2.87 A, indicating a possible
contracted from 90° with the remaining angles within the weak BϪH···π* interaction. In contrast to 2a, the low sym-
chelate close to those expected for trigonal nitrogen metry of 6a allows the chelate to reveal the comparative
[121.7(6)Ϫ125.0(4)°] and tetrahedral boron [107.9(6)°].
trans influences of carbonyl and alkylidyne ligands. Thus
the pyrazolyl group trans to the alkylidyne has a signifi-
˚
Crystal Structure of [W(ϵCC6H3Me2-2,6)(CO)2-
(PMe2Ph){H2B(pz)2}] (6a)
cantly (20σ) longer WϪN bond length [2.292(3) A] than
˚
that trans to the carbonyl [2.233(3) A]. The difference in
trans influence for the pyrazolyl and phosphane ligands is
Yellow solvate-free needles were obtained by cooling a
solution of the complex in a mixture of propanone and
petroleum ether (40:60). The molecular geometry of the
complex is depicted in Figure 2. As for complex 2a, the
tungsten center approximates octahedral geometry with
angles between cis-ligands falling in the range
81.70(8)Ϫ100.00(11)° (Table 2). However, in contrast to 2a,
the H2B(pz)2 and alkylidyne groups assume a meridional
disposition with the phosphane ligand cis to the alkylidyne
group. The alkylidyne ligand displays a characteristically
less obvious in the bonding of the carbonyl ligands with
˚
that trans to phosphorus [WϪC(23) 2.014(5) A], showing a
˚
smaller (7σ) lengthening relative to WϪC(21) [1.980(4) A].
The only intermolecular packing interaction of note is a
parallel πϪπ stacking of the xylyl rings of centrosymmetr-
ically related molecules with mean interplanar and
˚
centroid···centroid separations of 3.46 and 3.74 A, respec-
tively.
˚
short WϵC separation [1.825(4) A] (not significantly differ-
ent from that in 2a) and is slightly bent at the carbyne car- Experimental Section
bon atom [WϪC(1)ϪC(7) 173.5(3)°], which lies within the
General Procedures: All manipulations were carried out under an
˚
atmosphere of prepurified dinitrogen with conventional Schlenk-
tube techniques. Solvents were purified by distillation from an ap-
propriate drying agent [ethers and paraffins from sodium/potass-
ium alloy with benzophenone as indicator; halocarbons from
CaH2]. Light petroleum ether refers to that fraction of boiling point
40Ϫ60 °C. Chromatographic separations were routinely performed
Table 2. Selected bond lengths (A) and angles (°) for 6a
WϪC(1)
WϪC(23)
WϪN(15)
1.825(4) WϪC(21)
2.014(5) WϪN(10)
2.292(3) WϪP(25)
1.451(5)
87.74(15) C(1)ϪWϪC(23)
87.66(17) C(1)ϪWϪN(10)
1.980(4)
2.233(3)
2.5644(10)
C(1)ϪC(7)
C(1)ϪWϪC(21)
C(21)ϪWϪC(23)
1
using a cryostatically cooled column at Ϫ40 °C. H, 13C{1H} and
86.64(16)
99.92(13)
93.91(14)
87.35(14)
31P{1H} NMR spectra were recorded with a Jeol JNM EX270
NMR spectrometer and referenced against internal Me4Si (1H), in-
ternal CDCl3 (13C) or external H3PO4 (31P). Infrared spectra were
recorded with a PerkinϪElmer 1720-X FT-IR spectrometer. FAB-
Mass spectra were measured with an Autospec Q mass spec-
trometer using 3-nitrobenzyl alcohol as matrix (‘pic’ ϭ γ-picoline).
Photolyses were conducted with a domestic sun-lamp in cryo-
C(21)ϪWϪN(10) 172.25(13) C(23)ϪWϪN(10)
C(1)ϪWϪN(15) 174.94(13) C(21)ϪWϪN(15)
C(23)ϪWϪN(15) 91.95(15) N(10)ϪWϪN(15) 85.02(11)
C(1)ϪWϪP(25)
C(23)ϪWϪP(25) 172.69(12) N(10)ϪWϪP(25)
N(15)ϪWϪP(25) 81.70(8) C(7)ϪC(1)ϪW
100.00(11) C(21)ϪWϪP(25)
95.61(12)
82.00(8)
173.5(3)
Eur. J. Inorg. Chem. 2004, 818Ϫ828
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
823

A. F. Hill, J. M. Malget, A. J. P. White, D. J. Williams
FULL PAPER
statically cooled Schlenk-tubes. Commercial reagents were used as
267.3 [WϵC, 1J (WC) ϭ 207.0 Hz], 222.2 [WCO, 1J(WC) ϭ
171.3 Hz], 153.2 [C-2,6 (NC5H4)], 150.6 [C-4 (NC5H4)], 143.8 [C-1
received and the salt K[H2B(pz)2][3] prepared according to the fol-
lowing procedure. The original procedure involves heating K[BH4] (C6H2)], 141.4 [C-2,6 (C6H2)], 137.7 [C-4(C6H2)], 128.1 [C-3,5
and Hpz in a melt, with the progress of the reaction being moni-
tored by the measurement of evolved hydrogen gas. In our labora-
tory, this usually provided samples of K[H2B(pz)2] contaminated
with both pyrazole and K[HB(pz)3]. The following approach em-
ploys a solvent to moderate the reaction temperature and provide
a homogeneous reaction mixture.
(C6H2)], 125.9 [C-3,5(NC5H4)], 21.4 (C6H2CH3-4), 21.3, 20.6
(NC5H4CH3 and C6H2CH3-2,6) ppm. FAB-MS: m/z (%) ϭ 638(29)
[M]ϩ, 610(52) [M Ϫ CO]ϩ, 582(91) [M Ϫ 2CO]ϩ, 557(78)
[M Ϫ Br]ϩ, 545(41) [M Ϫ pic]ϩ, 517(53) [M Ϫ pic-CO]ϩ, 487(63)
[M Ϫ 2CO]ϩ, 464(37) [M Ϫ Br Ϫ pic]ϩ. C24H25BrN2O2W: calcd.
C 45.24, H 3.95, N 4.40; found C 44.6, H 3.7, N 4.3.
Synthesis of Potassium Dihydrobis(pyrazolyl)borate: Potassium
tetrahydroborate (13.50 g, 0.25 mmol) and pyrazole (68.00 g, 1.00
mol), both finely ground, were suspended in toluene (250 mL) and
gradually brought to reflux. After 12Ϫ16 h hydrogen gas evolution
had effectively ceased. The clear solution was filtered whilst hot to
remove any residual traces of unchanged K[BH4]. The filtrate was
allowed to cool with rapid stirring to about 40 °C whereupon a
white precipitate formed that was filtered off. The finely divided
white solid was washed with dichloromethane (3 ϫ 50 mL), to re-
move any traces of unchanged pyrazole followed by diethyl ether
(2 ϫ 30 mL) and then dried in vacuo. Yield 32.60 g (70 % vs.
K[BH4]). The salt was characterised by comparison of spectro-
scopic data with those previously reported[3] and was found to be
free of Hpz or K[HB(pz)3] within spectroscopically determinable
limits (1H NMR, IR).
Synthesis of mer- and fac-[W(ϵCC6H3Me2-2,6)(CO)2(NC5H4-
Me-4){H2B(pz)2}] (2a): The salt K[H2B(pz)2] (1.77 g, 9.50 mmol,
1.1 equiv.) was added to trans,cis,cis-[W(ϵCC6H3Me2-2,6)-
Br(CO)2(NC5H4Me-4)2] (1a, 5.00 g, 8.60 mmol) in propanone
(30 mL) and the mixture was stirred for 12 h. The solution was
concentrated in vacuo to about 10 mL and purified on an alumina-
loaded column (2 ϫ 30 cm) eluting with a mixture of propanone
and hexane (1:2). The major orange fraction was collected, concen-
trated in vacuo to about 10 mL and diluted with n-hexane (50 mL).
After cooling for 12 h at Ϫ10 °C a bright orange crystalline solid
was isolated and dried in vacuo. Yield 4.20 g (87 %). Crystals of
the fac isomer suitable for X-ray analysis were obtained upon
recrystallization from a mixture of light petroleum and dichloro-
methane (4:1) at Ϫ10 °C (vide infra). IR (CH2Cl2): 1978, 1886
[ν(CO)] cmϪ1. IR (nujol): 2437, 2405, 2284 [ν(BH2)]; 1971, 1877
[ν(CO)] cmϪ1 1H NMR (CDCl3, 25 °C): δ ϭ 2.24 [s, 3 H,
.
Synthesis of [W(ϵCC6H3Me2-2,6)Br(CO)2(NC5H4Me-4)2] (1a):
This complex has been used previously for the preparation of vari-
ous 2-xylyl methylidyne complexes, however, neither preparative
details nor spectroscopic data were provided.[13a] Tungsten hexacar-
bonyl (4.25 g, 12 mmol) was suspended in diethyl ether (30 mL) to
which 1.1 equivalents of LiC6H3Me2-2,6·LiBr in 1 mL aliquots over
30 min were subsequently added. The pale yellow solution was co-
oled (dry ice/propanone) and trifluoroacetic anhydride (1.70 mL,
12.0 mmol) slowly added over a 5 min period. The mixture was
NC5H4CH3], 2.34 [s, 6 H, C6H3(CH3)2], 6.14Ϫ6.18 [m, 2 H, H-
4(C3H3N2)], 6.85 [d, 2 H, H-3,5(C6H3)], 7.05 [t, 1 H, H-4(C6H3)],
7.20Ϫ8.00 [m, 10 H, H-3,5(C3H3N2) and H-2,3,5,6(NC5H4)] ppm.
13C{1H} NMR: δ ϭ 294.5 (major WϵC), 284.5 (minor WϵC),
225.3 (major WCO), 227.5 (minor WCO), 221.5 (minor WCO),
150.8 [C-4(NC5H4)], 145.4 [C-3(C3H3N2)], 140.5 [C-4(C6H3)], 136.6
[C-5(C3H3N2)], 127.3 [C-2,6(C6H3)], 127.0 [C-3,5(C6H3)], 125.9 [C-
3,5(NC5H4)], 105.4 [C-4(C3H3N2)], 21.2 [NC5H4CH3], 20.6
[C6H3CH3] ppm. FAB-MS: m/z (%) ϭ 597(33) [M]ϩ, 569(80) [M
Ϫ CO]ϩ, 541(35) [M Ϫ 2CO]ϩ, 503(41) [M Ϫ pic]ϩ, 446(19) [M Ϫ
2CO-pic]ϩ. C23H24BN5O2W: calcd. C 46.26, H 4.05, N 11.73;
found C 45.6, H 3.9, N 10.9.
stirred for 15 min after which γ-picoline (3.0 mL, 0.957 gcmϪ3
,
30 mmol) was added and allowed to warm to room temperature
which resulted in evolution of carbon monoxide (CAUTION).
After 12 h, a bright yellow precipitate was isolated from solution.
This solid was redissolved in dichloromethane (20 mL) and the Synthesis of fac- and mer-[W(ϵCC6H2Me3-2,4,6)(CO)2(NC5H4-
solution filtered under nitrogen through a plug of alumina (2 ϫ
4 cm). The filtrate was diluted with diethyl ether (60 mL) and then
cooled to Ϫ10 °C whereupon the bright orange solid which formed
was isolated by filtration and dried in vacuo. Yield 6.38 g (85 %).
Me-4){H2B(pz)2}]
[WϵCC6H2Me3-2,4,6)Br(CO)2(NC5H4Me-4)2]
(2b):
The
compound
trans,cis,cis-
(1b, 5.00 g,
7.80 mmol) was treated as above to afford an orange powder. Yield
4.20 g (88 %). IR (CH2Cl2): 1975, 1888 [ν(CO)] cmϪ1. IR (nujol):
IR (CH2Cl2): ν(CO) ϭ 1984, 1895 cmϪ1. Nujol: ν(CO) ϭ 1980,
2425, 2351, 2287 [ν(BH2)]; 1971, 1874 [ν(CO)] cmϪ1 1H NMR
.
1
1888 cmϪ1. H NMR (CDCl3, 25 °C): δ ϭ 2.40, 2.45 [s ϫ 2, 6 H (CDCl3, 25 °C): δ ϭ 2.16 (s, 3 H, C6H2CH3-4), 2.29 (s, 3 H,
ϫ 2, C6H3CH3 and NC5H4CH3], 6.90 [d, 2 H, H3,5 (C6H3)], 7.03 NC5H4CH3), 2.32 (s, 6 H, C6H2CH3-2,6), 6.14Ϫ6.17 [m, 2 H, H-
[m, 1 H, H4 (C6H3)], 7.11, 8.97 [(AB)4, 8 H, NC5H4, 3J(AB) ϭ 4(C3H3N2)], 6.67 [s, 2 H, H-3,5(C6H2)], 7.20Ϫ8.00 [m, 8 H, H-
5.5 Hz] ppm. 13C{1H} NMR: δ ϭ 266.4 [WϵC, 1J (WC) ϭ 3,5(C3H3N2) and H-2,3,5,6(NC5H4)] ppm. 13C{1H} NMR: δ ϭ
207 Hz], 221.9 [WCO, 1J (WC) ϭ 171 Hz], 150.5Ϫ127.2 [C6H3 and 295.0 [major WϵC, 1J(WC) ϭ 200 Hz], 284.9 [minor WϵC,
1
NC5H4], 125.8 [C-3,5 (NC5H4)], 21.0, 20.5 (C6H4CH3 and
1J(WC) ϭ 194 Hz], 225.5 [major WCO, J(WC) ϭ 169 Hz], 227.6
NC5H4CH3) ppm. FAB-MS: m/z ϭ 624 [M]ϩ, 596 [M Ϫ CO]ϩ, [minor WCO, 1J(WC) ϭ 169 Hz], 221.9 [minor WCO, 1J(WC) ϭ
568 [M Ϫ 2CO]ϩ, 543 [M Ϫ Br]ϩ, 529 [M Ϫ pic]ϩ, 503 [M Ϫ pic
169 Hz], 150.8 [C-4(NC5H4)], 145.4 [C-3(C3H3N2)], 136.5 [C-
Ϫ CO]ϩ, 473 [M Ϫ pic Ϫ 2CO]ϩ, 450 [M Ϫ pic Ϫ Br]ϩ. 5(C3H3N2)], 127.8 [C-3,5(C6H3)], 125.9 [C-3,5(NC5H4), 125.6 [C-
C23H23BrN2O2W: calcd. C 44.33, H 3.72, N 4.50; found C 44.8, H
3.5, N 4.4.
2,6(C6H2)], 105.4 [C-4(C3H3N2)], 21.2, 20.8 [NC5H4CH3 and
C6H2CH3-4)], 20.6 [C6H2CH3-2,6] ppm. FAB-MS: m/z (%) ϭ 610
(33) [M]ϩ, 583 (41) [M Ϫ CO]ϩ, 555 (24) [M Ϫ 2CO]ϩ, 516 (100)
[M Ϫ pic]ϩ, 488 (20) [M Ϫ CO Ϫ pic]ϩ, 460 (57) [M Ϫ pic Ϫ
2CO]ϩ. C24H26BN5O2W: calcd. C 47.17, H 4.29, N 11.46; found C
47.6, H 4.0, N 11.8.
Synthesis
of
trans,cis,cis-[W(ϵCC6H2Me3-2,4,6)Br(CO)2-
(NC5H4Me-4)2] (1b): The synthesis follows the procedure described
above, providing 6.74 g (88 %) of the desired complex from
[W(CO)6] (4.25 g, 12.0 mmol). IR (CH2Cl2): ν(CO) ϭ 1984, 1895
cmϪ1. IR (nujol): ν(CO) ϭ 1980, 1888 cmϪ1. 1H NMR (CDCl3, 25
Synthesis
of
[W(ϵCC6H3Me2-2,6)(CO)2(CNC6H3Me2-2,6)-
°C): δ ϭ 2.20 [s, 3 H, C6H2CH3-4], 2.40, 2.43 [s ϫ 2, 12 H, {H2B(pz)2}] (3a): The compound trans,cis,cis-[W(ϵCC6H3Me2-
NC5H4CH3 and C6H2CH3-2,6], 6.75 [s, 2 H, C6H2], 7.09, 8.95 2,6)Br(CO)2(CNC6H3Me2-2,6)2] (5a, 0.20 g, 0.30 mmol) was dis-
[(AB)4, 8 H, (NC5H4), 3J(AB) ϭ 5.6 Hz] ppm. 13C{1H} NMR: δ ϭ
solved in a mixture of diethyl ether and petroleum ether (9:1,
824
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 818Ϫ828

Alkylidyne Complexes of Tungsten
FULL PAPER
30 mL) to which 1.1 equivalents of K[H2B(pz)2] (0.06 g, 0.33 mmol)
was subsequently added. The mixture was stirred for 4 h in the
absence of light. The resulting red solution was concentrated under
reduced pressure and purified on a silica-gel loaded column (2 ϫ
137.1, 135.9 [C-5(C3H3N2)], 127.1 [C-3,5(C6H3)], 126.2 [C-
2,6(C6H3)], 104.8, 106.1 [C-4(C3H3N2)], 58.0 (CMe3), 29.9
[C(CH3)3], 21.1 [C6H3(CH3)2] ppm. FAB-MS: m/z (%) ϭ 671 (21)
[M]ϩ, 641 (20) [M Ϫ CO]ϩ, 614 (100) [M Ϫ 2CO]ϩ, 588 (14) [M
30 cm, Ϫ40 °C) eluting with a mixture of dichloromethane and Ϫ CNRЈ]ϩ, 559 (56) [M Ϫ CO Ϫ CNRЈ]ϩ, 531 (16) [M Ϫ 2CO Ϫ
light petroleum (1:1). The red fraction was collected and the solvent
removed in vacuo under the exclusion of light, to provide a glassy
CNRЈ]ϩ. Satisfactory elemental data were not obtained due to the
thermal instability. C27H35BN6O2W: calcd. C 48.38, H 5.26, N
thermally sensitive red solid. Yield 0.16 g (84 %). IR (CH2Cl2): 12.54; found 45.5, H 4.4, N 11.3.
2141 [ν(CN)]; 1998, 1923 [ν(CO)] cmϪ1. 1H NMR (CDCl3, 25 °C):
Synthesis of [W(ϵCC6H3Me2-2,6)Br(CO)2(CNC6H3Me2-2,6)2]
δ ϭ 2.14 [s, 6 H, NC6H3(CH3)2], 2.66, 2.68 (s ϫ 2, 6 H,
CC6H3CH3), 6.17 [m, 2 H, H-4(C3H3N2)], 6.96 [d, 2 H, H-
3,5(CC6H3)], 7.00 [m, 3 H, H-3,5(NC6H3)], 7.09 [t, 1 H, H-
4(C6H3)], 7.58Ϫ7.80 [m, 4 H, H-3,5(C3H3N2)] ppm. 13C{1H}
NMR: δ ϭ 287.5 (WϵC), 221.7, 210.6 (WCO), 168.0 (WCN), 146.8
[C-1(CC6H3)], 145.4 [C-1(NC6H3)], 145.0, 143.8 [C-5(C3H3N2)],
136.1, 135.2 [C-3(C3H3N2)], 127.9 [C-3,5(CC6H3)], 127.2 [C-
3,5(NC6H3)], 105.2, 104.9 [C-4(C3H3N2)], 18.7, 18.2 [NC6H3(CH3)2
and C6H3(CH3)2] ppm. Satisfactory elemental and FAB-MS data
not obtained due to thermal and photolytic lability.
(5a): 2,6-Dimethylphenyl isocyanide (0.45 g, 3.4 mmol) was added
to trans,cis,cis-[W(ϵCC6H3Me2-2,6)Br(CO)2(NC5H4Me-4)2] (1a,
1.00 g, 1.70 mmol) in diethyl ether (30 mL) and the mixture stirred
for 15 h after which time the solvent was removed in vacuo. The
resulting pale yellow solid was redissolved in n-hexane (10 mL) and
filtered through diatomaceous earth. The filtrate was further di-
luted with hexane (15 mL) and cooled to Ϫ10 °C for 2 days during
which time fine yellow needles formed which were isolated by de-
cantation and dried in vacuo. Yield 0.98 g (89 %). IR (CH2Cl2):
2159, 2134 [ν(CN)]; 2021, 1974 [ν(CO)] cmϪ1. IR (nujol): 2162,
2135 [ν(CN)]; 2005, 1959 [ν(CO)] cmϪ1. 1H NMR (CDCl3, 25 °C):
δ ϭ 2.48 [s, 12 H, NC6H3(CH3)2], 2.58 [s, 6 H, CC6H3(CH3)2], 6.90,
6.92 [d ϫ 2 H, H-3,5(C6H3)], 7.1 [m, 1 H, H-4(C6H3)] ppm.
13C{1H} NMR: δ ϭ 269.7 [WϵC, 1J(WC) ϭ 189 Hz], 205.0 [WCO,
1J(WC) ϭ 136 Hz], 167.7 (br., CϵN), 161.8 (br., N-C), 150Ϫ124
(NC6H3 and CC6H3), 21.2 [CC6H3(CH3)2], 18.8 [NC6H3(CH3)2]
ppm. FAB- MS: m/z (%) ϭ 700 (12) [M]ϩ, 672 (58) [M Ϫ CO]ϩ,
644 (46) [M Ϫ 2CO] ϩ. Calcd for C29H27BrO2N2W: calcd. C 49.81,
H 3.89, N 4.01; found C 50.0, H 4.1, N 3.9.
Synthesis of [W(ϵCC6H3Me2-2,6)(CO)2(CNCMe3){H2B(pz)2}]
(3b): The salt K[H2B(pz)2] (0.06 g, 0.33 mmol, 1.1 equiv.) was
added to trans,cis,cis-[W(ϵCC6H3Me2-2,6)Br(CO)2(CNCMe3)2]
(5c, 0.20 g, 0.30 mmol) in a mixture of diethyl ether and petroleum
ether (9:1, 30 mL). The suspension was stirred for 4 h. under the
exclusion of light. The resulting claret solution was concentrated
under reduced pressure and purified on a silica gel loaded column
(2 ϫ 30 cm, Ϫ40 °C) eluting with a mixture of CH2Cl2 and light
petroleum (1:1). The red fraction was collected and the solvent re-
moved in vacuo (still in the absence of light). An amorphous red
solid was obtained. Yield 0.12 g (67 %). IR (CH2Cl2): 2175 [ν(CN)];
Synthesis of [W(ϵCC6H2Me3-2,4,6)Br(CO)2(CNC6H3Me2-2,6)2]
(5b): 2,6-Dimethylphenyl isocyanide (0.45 g, 3.40 mmol) was added
to trans,cis,cis-[W(ϵCC6H2Me3-2,4,6)Br(CO)2(NC5H4Me-4)2] (1b,
1.00 g, 1.70 mmol) in diethyl ether (30 mL). The mixture was
stirred for 15 h, after which time the solvent and γ-picoline were
removed in vacuo. The resulting pale yellow solid was redissolved
in hexane (10 mL) and filtered through diatomaceous earth. Light
petroleum ether (15 mL) was added to the yellow filtrate and the
mixture stored at Ϫ10 °C for 2 days, whereupon fine yellow crystal-
line needles were obtained and dried in vacuo. Yield 1.00 g (88 %).
IR (CH2Cl2): 2158, 2132 [ν(CN)]; 2018, 1972 [ν(CO)] cmϪ1. IR
1
1998, 1918 [ν(CO)] cmϪ1. H NMR (CDCl3, 25 °C): δ ϭ 1.16 (s, 9
H, CMe3), 2.50 (s, 6 H, C6H3CH3), 5.99 [dd, 1 H, H-4(C3H3N2),
3
3JH,H ϭ 2 Hz], 6.02 [dd, 1 H, H-4(C3H3N2), JH,H ϭ 2 Hz], 6.80
(m ϫ 2, 3 H, C6H3), 7.40Ϫ8.80 [m, 4 H, H-3,5(C3H3N2)] ppm.
13C{1H} NMR: δ ϭ 285.6 (WϵC), 222.1, 211.2 (WCO), 144.3,
143.2 [C-5(C3H3N2)], 136.1, 135.5 [C-3(C3H3N2)], 126.9 [C-
2,6(C6H3)], 126.6 [C-3,5(C6H3)], 147.8 [C-1(C6H3)], 139.6 [C-
4(C6H3)], 104.8, 104.5 [C-4(C3H3N2)], 56.2 [C(CH3)3], 29.9
[C(CH3)3], 20.4 [C6H3(CH3)2] ppm. Satisfactory elemental analyti-
cal data not obtained due to thermal and photochemical lability.
(nujol): 2162, 2134 [ν(CN)]; 2006, 1955 [ν(CO)] cmϪ1 1H NMR
.
(CDCl3, 25 °C): δ ϭ 2.18 (s, 3 H, CC6H2CH3-4), 2.50 [s, 12 H,
NC6H3(CH3)2], 2.56 [s, 6 H CC6H2(CH3)2-2,6] ppm. 13C{1H}
NMR: δ ϭ 270.5 [WϵC, 1J(WC) ϭ 189 Hz], 204.9 [WCO,
1J(WC) ϭ 136 Hz], 162.2 (br., WCN), 147.2 [C-1(C6H2)], 140.6 [C-
2,6(C6H3)], 138.5[C-2,6(C6H2)], 135.6 [C-3,5(C6H2)], 129.3 [C-
4(C6H3)], 128.0 [C-3,5(C6H3)], 126.6 [C-4(C6H2)], 21.6 [C6H2CH3-
4], 21.1, 19.0 [NC6H3(CH3)2-2,6 and CC6H2(CH3)2-2,6] ppm. FAB-
MS: m/z (%) ϭ 658 (100) [M Ϫ 2CO]ϩ. C30H29BrN2O2W: calcd. C
50.51, H 4.10, N 3.93; found C 50.2, H 4.0, N 3.9.
Synthesis of [W(η2-OCCC6H3Me2-2,6)(CO)(CNCMe3)2{H2B-
(pz)2}] (4b): tert-Butyl isocyanide (0.40, mL, 0.735 gcmϪ3, 0.54 g,
6.50 mmol) was added to [W(ϵCC6H3Me2-2,6)(CO)2(NC5H4Me-
4){H2B(pz)2}] (2a, 0.50 g, 0.84 mmol) in dichloromethane (30 mL).
The mixture was then irradiated for 3 h with stirring at 0 °C (ice
bath). The resulting purple solution was concentrated to about
10 mL and purified on a silica-gel loaded column (2 ϫ 30 cm,
Ϫ40 °C) eluting initially with a mixture of CH2Cl2 and light
petroleum (1:1) to remove orange [W(ϵCC6H3Me2-2,6)-
(CO)2(CNCMe3){H2B(pz)2}] (3b, vide supra). The purple fraction
containing 4b was then eluted with tetrahydrofuran. The resulting
eluate was concentrated under reduced pressure to about 2 mL,
diluted with light petroleum (10 mL) and stored at Ϫ10 °C where-
upon purple thermally sensitive microcrystals were obtained over-
Synthesis of [W(ϵCC6H3Me2-2,6)Br(CO)2(CNCMe3)2] (5c): tert-
Butyl isocyanide (0.40 mL, 0.795 gmolϪ1, 0.50 g, 6.0 mmol, excess)
was
added
to
trans,cis,cis-[W(ϵCC6H3Me2-2,6)Br-
(CO)2(NC5H4Me-4)2] (1a, 1.00 g, 1.70 mmol) in diethyl ether
(30 mL) and the mixture stirred for 15 h. The resulting pale yellow
night. Yield 0.23 g (41 %). IR (CH2Cl2): 2162 [ν(CN)]; 1912 solution was reduced to dryness in vacuo and light petroleum
[ν(CϵO)]; 1699 [ν(CϭO)] cmϪ1. IR (nujol): 2405 [ν(BH)]; 2160
(50 mL) was added to the residue. The resulting solution was co-
1
[ν(CN)]; 1917 [ν(CϵO)]; 1708 [ν(CϭO)] cmϪ1. H NMR (CDCl3, oled to Ϫ10 °C for 12 h whereupon a bright yellow crystalline solid
25 °C): δ ϭ 1.27 (s, 18 H, CMe3), 2.02 [s, 6 H, C6H3(CH3)2], 6.02, was isolated and dried in vacuo. Further crops were obtained by
3
6.27 [dd ϫ 2, 2 H, H-4(C3H3N2), JH,H ϭ 2, 2 Hz], 7.00 [m, 3 H, concentrating the supernatant liquor, though these were generally
C6H3], 7.58, 7.59, 7.64, 8.08 [d ϫ 4, 4 H, H-3,5(C3H3N2)] ppm.
less pure. Yield 0.70 g (73 %). IR (CH2Cl2): 2158, 2132 [ν(CN)];
13C{1H} NMR: 247.3 (WCO), 217.2 (WϭCCO), 208.8 (WϭCCO), 2018, 1972 [ν(CO)] cmϪ1. IR (nujol): 2162, 2134 [ν(CN)]; 2006,
153.0 (WCN), 144.9 [C-1(C6H3)], 147.0, 144.3 [C-3(C3H3N2)], 1955 [ν(CO)] cmϪ1. H NMR (CDCl3, 25 °C): δ ϭ 1.57 [s, 18 H,
1
Eur. J. Inorg. Chem. 2004, 818Ϫ828
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
825

A. F. Hill, J. M. Malget, A. J. P. White, D. J. Williams
FULL PAPER
CMe3], 2.52 [s, 6 H, C6H3(CH3)2], 6.90 [d, 2 H, H-3,5(C6H3)], 7.10
24 Hz] ppm. 31P{1H} NMR: δ ϭ Ϫ4.2 ppm [1JW, P ϭ 230.6 Hz].
[t, 1 H, H-4(C6H3)] ppm. 13C{1H} NMR: δ ϭ 267.1 [WϵC, 1J FAB-MS: m/z (%) ϭ 641 (8) [M]ϩ, 614 (75) [M Ϫ CO]ϩ, 584 (11)
(WC) ϭ 189 Hz], 206.8 [WCO, 1J (WC) ϭ 135 Hz], 147.0 (br., [M Ϫ 2CO]ϩ. Elemental microanalytical data not acquired.
WCϵN), 146.1 [C-1(C6H3)], 140.3 [C-4(C6H3)], 127.4 [C-
Synthesis of cis,trans,cis-[W(ϵCC6H2Me3-2,4,6)(CO)(PMe2Ph)2-
2,6(C6H3)], 127.2 [C-3,5(C6H3)], 57.4 [CMe3], 30.5 [C(CH3)3], 20.8
{H2B(pz)2}] (7): (a) Dimethylphenylphosphane (0.24 g, 1.60 mmol)
[C6H3(CH3)2] ppm. FAB-MS: m/z ϭ 606 [M]ϩ, 576 [M Ϫ CO]ϩ,
was added to mer/fac-[W(ϵCC6H2Me3-2,4,6)(CO)2(NC5H4Me-
548 [M Ϫ 2CO]ϩ, 523 [M Ϫ CNR]ϩ, 492 [M Ϫ CO Ϫ CNR]ϩ.
4){H2B(pz)2}] (2b, 0.50 g, 0.82 mmol) in dichloromethane (30 mL).
C21H27BrN2O2W: calcd. C 41.81, H 4.51, N 4.64; found C 41.7, H
4.4, N 4.5.
The mixture was stirred for 12 h and the resulting red solution was
then concentrated to about 10 mL under reduced pressure and
purified on silica-gel (2 ϫ 30 cm, Ϫ30 °C) eluting with a dichloro-
Synthesis of fac-[W(ϵCC6H3Me2-2,6)(CO)2(PMe2Ph){H2B(pz)2}]
methane/light petroleum (1:1) mixture. The red eluate was concen-
trated in vacuo to about 10 mL and diluted with diethyl ether
(50 mL). This solution was cooled to Ϫ10 °C whereupon a red
crystalline solid was obtained, isolated by decantation and dried in
(6a): Dimethylphenylphosphane (0.12 mL, 0.97 gmLϪ1, 0.12 g,
0.87 mmol) was added to mer/fac-[W(ϵCC6H3Me2-2,6)-
(CO)2(NC5H4Me-4){H2B(pz)2}] (2a, 0.50 g, 0.84 mmol) in di-
chloromethane (30 mL) and the mixture stirred for 12 h. The re-
vacuo. Yield 0.60 g (95 %). (b)
A
mixture of mer-
sulting orange solution was concentrated to about 10 mL and chro-
matographed on a silica-gel loaded column (2 ϫ 30 cm, Ϫ30 °C)
eluting with a mixture of dichloromethane and light petroleum
ether (1:1). The major orange fraction was collected and concen-
trated under reduced pressure to about 10 mL and then diluted
with diethyl ether (50 mL). This solution was cooled to Ϫ10 °C
whereupon an orange microcrystalline solid was obtained. Yield
0.52 g (95 %). Crystals suitable for X-ray analysis were obtained
upon recrystallization from hexane/propanone (4:1) at Ϫ10 °C. NB:
The reaction is sufficiently clean that for most practical purposes
the chromatography step may be omitted in which case, the solvent
is simply removed and the resulting orange powder washed with
light petroleum (10 mL) and dried thoroughly under high vacuum
to remove liberated γ-picoline and unchanged phosphane. IR
(CH2Cl2): 1992, 1903 [ν(CO)] cmϪ1. IR (nujol): 2407, 2345, 2288
[W(ϵCC6H2Me3-2,4,6)Br(CO)(PMe2Ph)3] (8, 0.50 g, 0.60 mmol)
and K[H2B(pz)2] (0.12 g, 0.65 mmol) in dichloromethane (30 mL)
was stirred for 1 h. The mixture was then purified as described in
(a) (see above) to provide 7. Yield 0.46 g (93 %). IR (CH2Cl2): 1860
[ν(CO)] cmϪ1. IR (nujol): 2424, 2390, 2353, 2284 [ν(BH2)]; 1857
[ν(CO)] cmϪ1
.
1H NMR (CDCl3, 25 °C): δ ϭ 1.40, 1.47 [vt ϫ 2,
2,4
12 H, trans-(PMe2)2,
J
P,H
ca. 3 Hz], 2.19 [s, 3 H, C6H2CH3-4],
2.49 [s, 6 H, C6H2(CH3)2-2,6], 5.98, 6.11 [dd ϫ 2, 2 H, H-
3
4(C3H3N2), JH,H ϭ 2, 2 Hz], 6.69 (s, 2 H, C6H2), 7.08Ϫ7.26 (m,
10 H, C6H5), 7.36, 7.44, 7.58, 7.85 [d ϫ 4, 4 H, H-3,5(C3H3N2),
2
3JH,H ϭ 2 Hz] ppm. 13C{1H} NMR: δ ϭ 278.2 (t, WϵC, JP,C
11 Hz), 249.9 (t, WCO, JP,C
ϭ
2
ϭ 5.3 Hz), 144.9, 143.6 [C-
3(C3H3N2)], 136.5, 136.1 [C-5(C3H3N2)], 135.7 [C-1(C6H5), 1JP,C ϭ
36.0 Hz], 130.6 [C-3,5(C6H2)], 130.5Ϫ127.5 [C-3,5(C6H5)], 104.9,
104.6 [C-4(C3H3N2)], 21.6 [C6H2CH3-4)], 20.6 [C6H2(CH3)2-2,6],
17.9 [vt, P(CH3)2, 1,3JP,C ϭ 13.4 Hz] ppm. 31P{1H} NMR: δ ϭ 0.28
[1JW, P ϭ 281.4 Hz] ppm. FAB-MS: m/z (%) [assignment] ϭ 766 (12)
[M]ϩ, 738 (4) [M Ϫ CO]ϩ, 628 (100) [M Ϫ PMe2Ph]ϩ, 598 (35) [M
1
[ν(BH2)]; 1974, 1885 [ν(CO)] cmϪ1. H NMR (CDCl3, 25 °C): δ ϭ
2
1.21, 1.31 [d ϫ 2, 6 H, JP,H ϭ 7.3 Hz, diastereotopic-PMe2], 2.63
(s, 6 H, C6H3CH3), 3.55 (br, BH2), 6.12, 6.16 [dd ϫ 2, 2 H, H-
3
4(C3H3N2), JH,H ϭ 2, 2 Hz], 6.96Ϫ7.10 [m, 3 H, H-4(C6H3)],
Ϫ
PMe2Ph Ϫ Ϫ 2PMe2Ph Ϫ
CO]ϩ, 459 (10) [M CO]ϩ.
7.24Ϫ7.28 (m, 5 H, C6H5), 7.36, 7.56, 7.66, 7.89 [d ϫ 4, 4 H, H-
C33H41BN4OP2W: calcd. C 51.72, H 5.39, N 7.31; found C 52.1, H
5.7, N 6.8.
3
3,5(C3H3N2), JH,H ϭ 2 Hz] ppm. 13C{1H} NMR: δ ϭ 285.1 (d,
2
2
WϵC, JP,C ϭ 8.9 Hz), 227.0 (d, WCO, JP,C ϭ 3.6 Hz), 213.4 (d,
2
Synthesis of mer-[W(ϵCC6H2Me3-2,4,6)Br(CO)(PMe2Ph)3] (8):
NB Ϫ the related complex mer-[W(ϵCPh)Cl(CO)(PMe3)3] has
been described previously by Mayr.[27] Dimethylphenylphosphane
(0.70 g, 5.10 mmol) was added to trans,cis,cis-[W(ϵCC6H2Me3-
2,4,6)Br(CO)2(NC5H4Me-4)2] (1b, 1.00 g, 1.70 mmol) in diethyl
ether (30 mL) and the mixture stirred for 15 h. The resulting pale
yellow solution was filtered though diatomaceous earth (20 ϫ
30 mm). The yellow filtrate was then diluted with light petroleum
(15 mL) and cooled to Ϫ10 °C for 2 days, whereupon a fine yellow
powder was obtained which was isolated by decantation and dried
WCO, JP,C ϭ 53.5 Hz), 144.9, 143.6 [C-3(C3H3N2)], 137.0, 136.8
[C-5(C3H3N2)], 135.7 [C-1(C6H5)], 130.8, 130.6 [C-2,6(C6H5)],
129.6Ϫ127.3 [C6H5 and C6H3], 105.4, 105.1 [C-4(C3H3N2)], 20.9
1
[C6H3(CH3)2], 15.7, 14.5 [d ϫ 2, JP,C ϭ 24 Hz, diastereotopic-
P(CH3)2] ppm. 31P{1H} NMR: δ ϭ Ϫ4.1 ppm [1J(WP) ϭ 230.6 Hz]
ppm. FAB-MS: m/z (%) ϭ 641 (14) [M Ϫ H]ϩ, 614 (90) [M Ϫ
CO]ϩ, 584 (21) [M Ϫ 2CO]ϩ, 503 (11) [M
Ϫ
PMe2Ph]ϩ.
C25H28BN4O2PW: calcd. C 46.76, H 4.40, N 8.72; found C 46.2, H
4.2, N, 8.5.
Synthesis
of
fac-[W(ϵCC6H3Me3-2,4,6)(CO)2(PMe2Ph)- in vacuo. Subsequent recrystallisation from a mixture of dichloro-
{H2B(pz)2}] (6b): This complex was prepared as described for 6a
methane/petroleum ether (Ϫ20 °C) afforded bright yellow needles.
(see above) from mer/fac-[WϵCC6H2Me3-2,4,6)(CO)2(NC5H4Me- Yield 1.01 g (90 %). IR (CH2Cl2): 1905 [ν(CO)] cmϪ1. IR (nujol):
1
4){H2B(pz)2}] (2b, 0.51 g, 0.84 mmol). Yield 0.53 g (95 %). IR
1900 [ν(CO)] cmϪ1. H NMR (CDCl3, 25 °C): δ ϭ 1.34Ϫ2.14 [m,
(CH2Cl2): 1993, 1905 [ν(CO)]. IR (nujol): 2407, 2345, 2288 21 H, PMe2 and C6H2CH3-4], 2.19 [s, 6 H, C6H2(CH3)2-2,6], 6.68
1
[ν(BH2)]; 1976, 1882 [ν(CO)] cmϪ1. H NMR (CDCl3, 25 °C): δ ϭ [s, 2 H, H-3,5(C6H2)], 6.85Ϫ7.55 [m, 15 H, C6H5] ppm. 13C{1H}
2
2
1.19, 1.34 [d ϫ 2, 6 H, diastereotopic-PMe2, JP,H ϭ 7.1 Hz], 2.23
NMR: δ ϭ 267.7 (dt, WϵC, JP,C ϭ 7, 12 Hz), 233.3 [dt, WCO,
2
[s, 3 H, C6H2CH3-4], 2.60 [s, 6 H, C6H2(CH3)2-2,6], 6.12, 6.16 [dd
ϫ 2, 2 H, H-4(C3H3N2), JH,H ϭ 2, 2 Hz], 6.78 [s, 2 H, H-
trans- JP,C ϭ 27, cis- 2J(P2C) ϭ 7 Hz], 134.5Ϫ127.9 (C6H5 and,
C6H2), 22.75 [vt, trans-diastereotopic-W(PMe2)2, 1,3J(P2C)
ϭ
3
3,5(C6H2)], 7.28 (m, 5 H, C6H5), 7.34, 7.56, 7.66, 7.79 [d ϫ 4, 4 H, 15.1 Hz], 21.91 [C6H2(CH3)2-2,6], 21.41 (C6H2CH3-4), 17.63 [vt,
H-3,5(C3H3N2), 3JH,H ϭ 2 Hz] ppm. 13C{1H} NMR: δ ϭ 284.4 [d, trans-diastereotopic-W(PMe2)2, 1,3J(P2C) ϭ 13.4 Hz], 16.89 [d, un-
2
2
1
WϵC, JP,C ϭ 8.6 Hz], 227.1 [WCO, JP,C ϭ 3.6 Hz], 213.4 [d,
ique-PMe2, JP,C ϭ 25.0 Hz] ppm. 31P{1H} NMR: δ ϭ Ϫ15.0 [d,
2
WCO, JP,C ϭ 53.1 Hz], 144.9, 143.6 [C-3(C3H3N2)], 137.0, 136.8 1J(WP) ϭ 268, 2JP,P ϭ 20], Ϫ22.5 [t, 1J(WP) ϭ 230, 2JP,P ϭ 20 Hz]
1
[C-5(C3H3N2)], 135.7 [C-1(C6H5), JP,C ϭ 36 Hz], 130.7, 130.6 [C-
2,6(C6H5)], 128.4, 128.2 [C-3,5(C6H5)], 127.7 [C-2,6(C6H2)], 127.3
ppm. FAB-MS: m/z (%) ϭ 700 (44) [M Ϫ PMe2Ph]ϩ, 672 (100) [M
Ϫ CO Ϫ Ϫ CO Ϫ
PMe2Ph]ϩ, 532 (14) [M 2PMe2Ph]ϩ.
[C-3,5(C6H3)], 105.4, 105.1 [C-4(C3H3N2)], 21.5 (C6H2CH3-4), 20.9 C35H44BrOP3W·0.5CH2Cl2: calcd. C 48.46, H 5.16; found C 48.6,
1
[C6H3(CH3)2-2,6], 15.5, 14.5 [diastereotopic-P(CH3)2, JP,C
ϭ
H 5.0.
826
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 818Ϫ828

Alkylidyne Complexes of Tungsten
FULL PAPER
James, A. N. De M. Jelfs, C. M. Nunn, F. G. A. Stone, Chem.
Commun. 1984, 1623.
Crystal Data, X-ray Data Collection and Structural Determination
(a) [W(ϵCC6H3Me2-2,6)(CO)2(NC5H4Me-4){H2B(pz)2}]·0.5CH2Cl2
(2a·0.5CH2Cl2): Orange/red blocks were grown by prolonged cool-
ing of a saturated solution of the complex in a mixture of dichloro-
methane and petroleum ether (bp. 40Ϫ60 °C). Crystal data for 2a:
C23H24BN5O2W·0.5CH2Cl2, Mr ϭ 639.6 g·molϪ1, monoclinic, P21/
[5] [5a]
H. P. Kim, S. Kim, R. A. Jacobson, R. J. Angelici, Or-
[5b]
ganometallics 1986, 5, 2481.
H. P. Kim, R. J. Angelici, Or-
R. A. Doyle, R. J. Angelici, J.
[5c]
ganometallics 1986, 5, 2489.
Am. Chem. Soc. 1990, 112, 194. [5d] R. A. Doyle, R. J. Angelici,
F. G. A. Stone, J. Organomet. Chem. 1989, 378, 81.
Doyle, R. J. Angelici, J. Organomet. Chem. 1989, 375, 73.
W. W. Greaves, R. J. Angelici, Inorg. Chem. 1981, 20, 2983.
[5e]
R. A.
˚
c (no. 14), a ϭ 9.463(3), b ϭ 19.153(2), c ϭ 16.228(3) A, β ϭ
[5f]
3
105.41(2)°, V ϭ 2835.6(10) A , Z ϭ 4, Dc ϭ 1.498 g cmϪ3, µ(Mo-
˚
Kα) ϭ 4.19 mmϪ1, T ϭ 293 K, 3673 independent measured reflec-
tions, F2 refinement, R1 ϭ 0.032, wR2 ϭ 0.087, 3081 independent
observed absorption corrected reflections [|Fo| Ͼ 4σ(|Fo|), 2θ Յ 45°],
329 parameters.
[6] [6a]
A. E. Enriquez, J. L. Templeton, Organometallics 2002, 21,
[6b]
852.
K. C. Stone, G. M. Jamison, P. S. White, J. L. Tem-
pleton, Inorg. Chim. Acta 2002, 330 161. [6c] A. E. Enriquez, P.
S. White, J. L. Templeton, J. Am. Chem. Soc. 2001, 123, 4992.
[6d]
D. S. Frohnapfel, P. S. White, J. L. Templeton, Organomet-
(b) [W(ϵCC6H3Me2-2,6)(CO)2(PMe2Ph){H2B(pz)2}] (6a): Yellow
needles were grown by cooling (Ϫ10 °C) a saturated solution of the
complex in a mixture of propanone and light petroleum. Crystal
data for 6a: C25H28BN4O2PW, Mr ϭ 642.1 g·molϪ1, monoclinic,
[6e]
allics 2000, 19, 1497.
B. E. Woodworth, P. S. White, J. L.
Templeton, J. Am. Chem. Soc. 1998, 120, 9028. [6f] B. E. Wood-
worth, D. S. Frohnapfel, P. S. White, J. L. Templeton, Or-
ganometallics 1998, 17, 1655. [6g] B. E. Woodworth, P. S. White,
˚
P21/n (no. 14), a ϭ 9.982(1), b ϭ 16.952(2), c ϭ 15.970(2) A, β ϭ
[6h]
J. L. Templeton, J. Am. Chem. Soc. 1997, 119, 828.
B. E.
3
103.31(1)°, V ϭ 2629.6(5) A , Z ϭ 4, Dc ϭ 1.622 g cmϪ3, µ(Cu-
˚
Woodworth, J. L. Templeton, J. Am. Chem. Soc. 1996, 118,
Kα) ϭ 8.94 mmϪ1, T ϭ 293 K, 3664 independent measured reflec-
tions, F2 refinement, R1 ϭ 0.022, wR2 ϭ 0.054, 3385 independent
observed absorption corrected reflections [|Fo| Ͼ 4σ(|Fo|), 2θ Յ
116°], 298 parameters. CCDC-219536 (2a) and Ϫ219537 (6a) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge via internet at http://
www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; Fax (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
[6i]
7418.
G. M. Jamison, A. E. Bruce, P. S. White, J. L. Tem-
[6j]
pleton, J. Am. Chem. Soc. 1991, 113, 5057.
G. M. Jamison,
P. S. White, J. L. Templeton, Organometallics 1991, 10, 1954.
[6k] M. Etienne, P. S. White, J. L. Templeton, J. Am. Chem. Soc.
[6l]
1991, 113, 2324.
S. G. Feng, P. S. White, J. L. Templeton,
[6m]
Organometallics 1993, 12, 2131.
S. G. Feng, J. L. Tem-
[6n]
pleton, Organometallics 1992, 11, 2168.
S. G. Feng, P. S.
White, J. L. Templeton, J. Am. Chem. Soc. 1992, 114, 2951. [6o]
G. M. Jamison, A. E. Bruce, P. S. White, J. L. Templeton, J.
[6p]
Am. Chem. Soc. 1991, 113, 5057.
G. M. Jamison, P. S.
White, J. L. Templeton, Organometallics 1991, 10, 1954. [6q] M.
Etienne, P. S. White, J. L. Templeton, J. Am. Chem. Soc. 1991,
[6r]
113, 2324.
A. S. Gamble, P. S. White, J. L. Templeton, Or-
[6s]
ganometallics 1991, 10, 693.
D. C. Brower, M. Stoll, J. L.
Acknowledgments
We wish to thank Professor F. G. A. Stone for helpful discussions
and support. We are grateful to the S. E. R. C. (U.K.) for the
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