Coupling of an aldehyde or ketone to pyridine mediated by a tungsten imido complex

Article abstract of DOI:10.1021/ic0511367

The reactivity of W(NPh)(o-(Me₃SiN)₂C ₆H₄)(py)₂ and W(NPh)(o-(Me₃SiN) ₂C₆H₄)(pic)₂ (py = pyridine; pic = 4-picoline) with unsaturated substrates has been investigated. Treatment of W(NPh)(o-(Me₃SiN)₂C₆H₄)(py) ₂ with diphenylacetylene or 2,3-dimethyl-1,3-butadiene generates W(NPh)(o-(Me₃SiN)₂C₆H₄) (η²-PhC≡CPh) (1) and W(NPh)(o-(Me₃SiN) ₂C₆H₄)-(η⁴-CH ₂=C(Me)C(Me)=CH₂) (3), respectively, while the addition of ethylene to W(NPh)(o-(Me₃SiN)₂C₆H ₄)(py)₂ generates the known metallacycle W(NPh)(o-(Me ₃SiN)₂C₆H₄)(CH₂CH ₂CH₂CH₂). The addition of 2 equiv of acetone to W(NPh)(o-(Me₃SiN)₂C₆H₄)(pic) ₂ provides the azaoxymetallacycle W(NPh)(o-(Me₃SiN) ₂C₆H₄)(OCH(Me)₂)(OC(Me) ₂-o-C₅H₃N-p-Me) (4), the result of acetone insertion into the ortho C-H bond of picoline. Similarily, the addition of 2 equiv of RC(O)H [R = Ph, ^tBu] to W(NPh)(o-(Me₃SiN) ₂C₆H₄)(py)₂ generates W(NPh)(o-(Me₃SiN)₂C₆H₄)(OCH ₂R)-(OCH(R)-o-C₅H₄N) [R = Ph, 5; ^tBu, 6]. In contrast, reaction between W(NPh)(o-(Me ₃SiN)₂C₆H₄)(py)₂ and 2-pyridine carboxaldehyde yields the diolate W(NPh)(o-(Me₃SiN) ₂C₆H₄)(OCH(C₅H₄N) CH(C₅H₄N)O) (7). The synthesis of W(NPh)-(o-(Me ₃SiN)₂C₆H₄)(PMe₃)(py) (η²-OC(H)C₆H₄-p-Me) (9), formed by the addition of p-tolualdehyde to a mixture of W(NPh)(o-(Me₃SiN) ₂C₆H₄)(py)₂ and PMe₃, suggests that an η²-aldehyde intermediate is involved in the formation of the azaoxymetallacycle, while the isolation of W(NPh)(o-(Me ₃SiN)₂C₆H₄)(Cl)(OC(Me)(CMe ₃)-o-C₅H₄N) (10), formed by the reaction of pinacolone with W(NPh)(o-(Me₃SiN)₂C₆H ₄)(py)₂, in the presence of adventitious CH ₂Cl₂, suggests that the reaction proceeds via the hydride W(NPh)(o-(Me₃SiN)₂C₆H₄)(H)(OC(Me) (CMe₃)-o-C₅H₄N).

Full text of DOI:10.1021/ic0511367

Inorg. Chem. 2005, 44, 9506−9517
Coupling of an Aldehyde or Ketone to Pyridine Mediated by a Tungsten
Imido Complex
Trevor W. Hayton,† James M. Boncella,*,† Brian L. Scott,† Khalil A. Abboud,‡ and Ryan C. Mills‡
Chemistry DiVision, Los Alamos National Laboratory, P.O. Box 1663, MS J582, Los Alamos, New
Mexico 87545, and Department of Chemistry and Center for Catalysis, UniVersity of Florida,
GainesVille, Florida 32611-7200
Received July 8, 2005
The reactivity of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and W(NPh)(o-(Me3SiN)2C6H4)(pic)2 (py
with unsaturated substrates has been investigated. Treatment of W(NPh)(o-(Me3SiN)2C6H4)(py)2 with diphenylacetylene
or 2,3-dimethyl-1,3-butadiene generates W(NPh)(o-(Me3SiN)2C6H4)( CPh) (1) and W(NPh)(o-(Me3SiN)2C6H4)-
2-PhC
4-CH2dC(Me)C(Me)
CH2) (3), respectively, while the addition of ethylene to W(NPh)(o-(Me3SiN)2C6H4)(py)2
) pyridine; pic ) 4-picoline)
η
t
(
η
d
generates the known metallacycle W(NPh)(o-(Me3SiN)2C6H4)(CH2CH2CH2CH2). The addition of 2 equiv of acetone
to W(NPh)(o-(Me3SiN)2C6H4)(pic)2 provides the azaoxymetallacycle W(NPh)(o-(Me3SiN)2C6H4)(OCH(Me)2)(OC(Me)2-
o-C5H3N-p-Me) (4), the result of acetone insertion into the ortho C
−
H bond of picoline. Similarily, the addition of
t
2 equiv of RC(O)H [R
(OCH(R)-o-C5H4N) [R
)
)
Ph, Bu] to W(NPh)(o-(Me3SiN)2C6H4)(py)2 generates W(NPh)(o-(Me3SiN)2C6H4)(OCH2R)-
Ph, 5; Bu, 6]. In contrast, reaction between W(NPh)(o-(Me3SiN)2C6H4)(py)2 and 2-pyridine
t
carboxaldehyde yields the diolate W(NPh)(o-(Me3SiN)2C6H4)(OCH(C5H4N)CH(C5H4N)O) (7). The synthesis of W(NPh)-
(o-(Me3SiN)2C6H4)(PMe3)(py)(
2-OC(H)C6H4-p-Me) (9), formed by the addition of p-tolualdehyde to a mixture of
W(NPh)(o-(Me3SiN)2C6H4)(py)2 and PMe3, suggests that an
2-aldehyde intermediate is involved in the formation
η
η
of the azaoxymetallacycle, while the isolation of W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)(CMe3)-o-C5H4N) (10), formed
by the reaction of pinacolone with W(NPh)(o-(Me3SiN)2C6H4)(py)2, in the presence of adventitious CH2Cl2, suggests
that the reaction proceeds via the hydride W(NPh)(o-(Me3SiN)2C6H4)(H)(OC(Me)(CMe3)-o-C5H4N).
Introduction
cleavage of the ortho C-H bond of the bipy ligand.4
Rothwell and co-workers have also documented the ortho
C-H activation of a coordinated pyridine.5,6 The zirconocene
complexes studied by Jordan and co-workers have also
yielded interesting results.7,8 For instance, the addition of
alkenes to Cp2Zr(η2-pyridyl)(THF)+ generates five-mem-
bered azazirconcycles such as Cp2Zr{(η2-C,N-CH2CH(Me)-
(2-Me-6-pyridyl)}+.9,10 In the presence of H2, this complex
catalyzes the insertion of propene into the ortho C-H bond
Electrophilic aromatic substitution is generally a very
effective way of functionalizing an aromatic ring.1 However,
with heterocycles such as pyridine, the electron-poor nature
of the ring makes electrophilic aromatic substitution nonvi-
able, and other synthetic strategies must be employed. In
this regard, metal-mediated transformations are particularly
attractive, and a number of metal-based routes for function-
alizing heterocyclic ring systems are known. For instance,
the silaacyl carbon of Cp*TaCl3(η2-CO(SiMe3)(PR3)) inserts
into the C-H bond of pyridine to form Cp*TaCl3(OCH-
(SiMe3)-o-C5H4N).2,3 Similarly, Cp*Lu(bipy)(CH2SiMe3)2
reacts with CO to give an azaoxymetallacycle through
(3) Arnold, J.; Woo, H.-G.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J.
Organometallics 1988, 7, 2045-2049.
(4) Cameron, T. M.; Gordon, J. C.; Scott, B. L.; Tumas, W. J. Chem.
Soc., Chem. Commun. 2004, 1398-1399.
(5) Zambrano, C. H.; McMullen, A. K.; Kobriger, L. M.; Fanwick, P. E.;
Rothwell, I. P. J. Am. Chem. Soc. 1990, 112, 6565-6570.
(6) Fanwick, P. E.; Kobriger, L. M.; McMullen, A. K.; Rothwell, I. P. J.
Am. Chem. Soc. 1986, 108, 8095-8097.
* To whom correspondence should be addressed. E-mail:
boncella@lanl.gov.
† Los Alamos National Laboratory.
‡ University of Florida.
(7) Guram, A. S.; Jordan, R. F. Organometallics 1991, 10, 3470-3479.
(8) Rodewald, S.; Jordan, R. F. J. Am. Chem. Soc. 1994, 116, 4491-
4492.
(1) March, J. AdVance Organic Chemistry, 4th ed.; John Wiley & Sons:
New York, 1992; pp 501-568.
(2) Arnold, J.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J.; Arif, A. M. J.
Am. Chem. Soc. 1989, 111, 149-164.
(9) Bi, S.; Lin, Z.; Jordan, R. F. Organometallics 2004, 23, 4882-4890.
(10) Jordan, R. F.; Taylor, D. F. J. Am. Chem. Soc. 1989, 111, 778-779.
9506 Inorganic Chemistry, Vol. 44, No. 25, 2005
10.1021/ic0511367 CCC: $30.25
© 2005 American Chemical Society
Published on Web 11/15/2005

Coupling of an Aldehyde or Ketone to Pyridine
of 2-picoline to generate 2-methyl-6-isopropylpyridine, a
transformation that mirrors Friedel-Crafts chemistry.
Recent work in our laboratories has focused on the
chemistry of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and W(NPh)-
(o-(Me3SiN)2C6H4)(pic)2 (py ) pyridine; pic ) 4-picoline).
These unique, square-pyramidal imido complexes exhibit
hindered rotation about their W-N(pyridine) bonds. They
also readily react with Lewis bases to generate six-coordinate
compounds. For instance, W(NPh)(o-(Me3SiN)2C6H4)(py)2
forms the carbonyl complex W(NPh)(o-(Me3SiN)2C6H4)(py)2-
(CO) when exposed to carbon monoxide and forms W(NPh)-
(o-(Me3SiN)2C6H4)(py)(PMe3)2 when treated with trimeth-
ylphosphine.11 Furthermore, W(NPh)(o-(Me3SiN)2C6H4)(py)2
inserts into the C-S bond of thiophene upon thermolysis to
produce the six-membered metalathiocycle W(NPh)(o-(Me3-
SiN)2C6H4)(SC4H4).12 Given these interesting results, the
reactivity of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and W(NPh)-
(o-(Me3SiN)2C6H4)(pic)2 with other potential ligands and
substrates was studied.
Figure 1. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(η2-PhCtCPh)
(1) with 50% probability ellipsoids being shown. Selected bond lengths
(Å) and angles (deg): W-N1 ) 1.756(2), W-N2 ) 1.984(2), W-N3 )
2.017(2), W-C19 ) 2.054(3), W-C20 ) 2.054(3), C19-C20 ) 1.332-
(4), C1-N1-W ) 161.8(2).
In this contribution, we describe the reactivity of W(NPh)-
(o-(Me3SiN)2C6H4)(py)2 and W(NPh)(o-(Me3SiN)2C6H4)-
(pic)2 with alkenes, diphenylacetylene, acetone, and alde-
hydes. With alkenes and diphenylacetylene, substitution of
the two heterocyclic ligands occurs to give the corresponding
π-bound olefin or acetylene adducts. With acetone or
aldehydes, however, insertion of the carbonyl group of these
substrates into the ortho C-H bond of pyridine (or picoline)
is observed.
square-pyramidal geometry with the imido ligand in the
apical position. Both the W-N1(imido) distance [1.756(2)
Å] and W-N1(imido)-C1 angle [161.8(2)°] are similar to
those seen in other members of this class of compounds.11
As well, the phenylenediamide ligand exhibits metrical
parameters characteristic of that ligand. In particular, the fold
angle (the angle between the phenylenediamide aryl ring and
the N2-W-N3 plane) is 135°, which is similar to the angle
found in the related molybdenum alkyne complex Mo(NPh)-
(o-(Me3SiN)2C6H4)(η2-(Me3Si)CtC(SiMe3)).13 The W-C19
and W-C20 bond lengths [both 2.054(3) Å] are in the range
of W-C single bonds, while the C19-C20 distance [1.332-
(4) Å] is in the range of a CdC bond. This evidence suggests
that a metallacyclopropene structure best describes the
bonding of the acetylene ligand in 1.
Reactions of W(NPh)(o-(Me3SiN)2C6H4)(py)2 with Ole-
fins. Toluene solutions of W(NPh)(o-(Me3SiN)2C6H4)(py)2
react with ethylene (20 psi) over 30 min, giving yellow-
brown solutions containing the previously known compound
W(NPh)(o-(Me3SiN)2C6H4)(CH2CH2CH2CH2) (2) (Scheme
1).14 Complex 2 can be isolated in 66% yield with this
procedure. The previous synthetic method involved the
reaction of W(NPh)(o-(Me3SiN)2C6H4)Cl2 with BrMg(CH2)4-
MgBr in Et2O.14 Similarly, toluene solutions of W(NPh)(o-
(Me3SiN)2C6H4)(py)2 also react with 1 equiv of 2,3-dimethyl-
1,3-butadiene when heated to 60 °C for 20 h to give red-
brown solutions containing W(NPh)(o-(Me3SiN)2C6H4)(η4-
CH2dC(Me)C(Me)dCH2) (3) (Scheme 1).
Results
Synthesis and Characterization of W(NPh)(o-(Me3SiN)2-
C6H4)(η2-PhCtCPh). Heating a solution containing equimo-
lar amounts of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and diphe-
nylacetylene to 55 °C for 4 h generates a brown-yellow
solution. From this solution, W(NPh)(o-(Me3SiN)2C6H4)(η2-
PhCtCPh) (1) can be isolated in 68% yield as an air- and
moisture-sensitive brown powder (eq 1). The 1H NMR
spectrum of 1 is consistent with the presence of a diphenyl-
acetylene moiety and contains no signals attributable to a
coordinated pyridine, while the 13C{1H} NMR spectrum
exhibits a singlet at 198.5 ppm, which is assigned to the
alkyne carbons of the diphenylacetylene ligand.
Complex 3 can be isolated as a dark brown solid in 73%
yield. This compound exhibits two doublets at 1.31 and 2.17
ppm in its 1H NMR spectrum, which can be assigned to the
two diastereotopic protons attached to the R carbons of the
coordinated butadiene ligand. The resonances of these
carbons are observed at 50.5 ppm in the 13C NMR spectrum
Single crystals of 1 were grown from an Et2O solution
stored at -40 °C for several weeks and were analyzed by
X-ray crystallography. The solid-state molecular structure
of 1 is shown in Figure 1. Compound 1 adopts a distorted
(11) Mills, R. C.; Wang, S. Y. S.; Abboud, K. A.; Boncella, J. M. Inorg.
Chem. 2001, 40, 5077-5082.
(12) Mills, R. C.; Abboud, K. A.; Boncella, J. M. J. Chem. Soc., Chem.
Commun. 2001, 1506-1507.
(13) Ison, E. A.; Cameron, T. M.; Abboud, K. A.; Boncella, J. M.
Organometallics 2004, 23, 4070-4076.
(14) Wang, S.-Y. S.; VanderLende, D. D.; Abboud, K. A.; Boncella, J. M.
Organometallics 1998, 17, 2628-2635.
Inorganic Chemistry, Vol. 44, No. 25, 2005 9507

Hayton et al.
Scheme 1
and exhibit a one-bond 13C-1H coupling constant of 143
Hz. The NMR data suggest that the R carbons of the
butadiene ligand have considerable sp3 character, and
consequently, the σ2π resonance form predominates.15 To
confirm this feature, an X-ray crystallographic study of
complex 3 was undertaken.
Câ bond length is 1.375(7) Å. Furthermore, the W-CR bond
lengths[W-C19 ) 2.183(5) Å, W-C22 ) 2.178(5) Å] are
shorter than the W-Câ bond lengths [W-C20 ) 2.460(4)
Å, W-C21 ) 2.459(5) Å]. These parameters are similar to
those found in Cp2Zr(2,3-dimethylbutadiene), which is often
considered the quintessential example of a σ2π-bound
butadiene complex.16
Single crystals of 3 suitable for X-ray diffraction analysis
were grown from a pentane solution stored at -40 °C.
Complex 3 crystallizes in the triclinic space group P1h with
two independent molecules in the asymmetric unit. The solid-
state molecular structure of one of these is shown in Figure
2. Complex 3 adopts a distorted square-pyramidal geometry
about W with the imido group occupying the apical position.
The metrical parameters of the imido ligand [W-N1 )
1.755(3) Å, W-N1-C1 ) 169.3(3)°] are similar to those
observed in 1. The di(amido) chelate, however, exhibits
slightly longer W-N bond lengths [W-N2 ) 2.040 (3) Å,
W-N3 ) 2.045(3) Å] and a more planar phenylenediamide
ligand (fold angle 149°). The bond distances associated with
the butadiene fragment are consistent with the NMR data
and support the σ2π bonding model. For instance, the CR-
Câ bond lengths are 1.475(7) and 1.472(7) Å, while the Câ-
Synthesis and Characterization of W(NPh)(o-(Me3SiN)2-
C6H4)(OCH(Me)2) (OC(Me)2-o-C5H3N-p-Me). We at-
tempted to extend the substitution chemistry of W(NPh)(o-
(Me3SiN)2C6H4)(py)2 and W(NPh)(o-(Me3SiN)2C6H4)(pic)2
to other unsaturated organic molecules. Thus, W(NPh)(o-
(Me3SiN)2C6H4)(pic)2 rapidly reacts with acetone to form
deep-green solutions, which turn orange-brown upon stand-
ing. Crystallization of the reaction residue from pentane
provides orange crystals of W(NPh)(o-(Me3SiN)2C6H4)-
(OCH(Me)2)(OC(Me)2-o-C5H3N-p-Me) (4) in 18% yield (eq
1
2). The H NMR spectrum of 4 is consistent with the
proposed formulation. For instance, a septet at 4.93 ppm (1H,
JHH ) 6 Hz) and a doublet at 1.11 ppm (6H, JHH ) 6 Hz)
indicates the presence of an isopropoxide ligand, while a
prominent doublet at 8.18 ppm (assignable to the picoline
ring ortho proton) demonstrates that picoline is incorporated
into the final product.
Single crystals of 4 were grown from a concentrated
pentane solution. The solid-state molecular structure of 4 is
shown in Figure 3. Complex 4 adopts an octahedral geometry
about tungsten. Interestingly, one arm of the phenylenedi-
amide ligand is trans to the imido ligand, a rare structural
feature in this class of compounds.17 The imido ligand
[W-N1 ) 1.763(7) Å, W-N1-C1 ) 169.4(6)°] exhibits
parameters similar to those seen in 1 and 3. The two amido
(15) Yasuda, H.; Tatsumi, K.; Okamoto, T.; Mashima, K.; Lee, K.;
Nakamura, A.; Kai, Y.; Kanehisa, N.; Kasai, N. J. Am. Chem. Soc.
1985, 107, 2410-2422.
Figure 2. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(η4-CH2d
C(Me)C(Me)dCH2) (3) with 50% probability ellipsoids being shown.
Selected bond lengths (Å) and angles (deg): W-N1 ) 1.755(3), W-N2
) 2.040(3), W-N3 ) 2.045(3), W-C22 ) 2.178(5), W-C19 ) 2.183-
(5), W-C21 ) 2.459(5), W-C20 ) 2.460(4), C19-C20 ) 1.475(7), C20-
C21 ) 1.375(7), C21-C22 ) 1.472(7), W-N1-C1 ) 169.3(3).
(16) Yasuda, H.; Tatsumi, K.; Nakamura, A. Acc. Chem. Res. 1985, 18,
120-126.
(17) Boncella, J. M.; Wang, S. Y. S.; VanderLende, D. D.; Huff, R. L.;
Abboud, K. A.; Vaughn, W. M. J. Organomet. Chem. 1997, 530, 59-
70.
9508 Inorganic Chemistry, Vol. 44, No. 25, 2005

Coupling of an Aldehyde or Ketone to Pyridine
benzyl alkoxide ligand in 5 appear as two doublets at 5.65
and 5.89 ppm (2JHH ) 14 Hz), while the lone proton attached
to the carbonyl carbon of the metallacycle appears as a singlet
at 6.46 ppm. In 6, the signals for the diastereotopic protons
of the neopentoxide ligand are found at 4.19 and 4.34 ppm
(2JHH ) 11 Hz), and the proton attached to the carbonyl
carbon of the metallacycle appears at 5.20 ppm. As with the
1H NMR spectrum of 4, a prominent multiplet corresponding
to the ortho proton of the pyridine ring is found at a
significantly downfield chemical shift: 8.41 ppm for 5 and
8.32 ppm for 6. Interestingly, the 1H NMR spectra of 5 and
6 are consistent with the presence of only one diastereomer.
Single crystals of 6 suitable for X-ray diffraction analysis
were grown from a saturated pentane solution stored at -30
°C. The solid-state molecular structure of 6 is shown in
Figure 4. Complex 6 crystallizes in the triclinic space group
P1h as the pentane solvate 6‚1/2C5H12. The complex adopts
an octahedral geometry around W, with the imido ligand
trans to the functionalized pyridine. The imido ligand [W1-
N4 ) 1.751(2) Å, W1-N4-C1 ) 172.4(2)°] exhibits the
expected metrical parameters, while the phenylenediamide
W-N distances [W1-N2 ) 2.031(2) Å, W1-N1 ) 2.082-
(2) Å] are similar to those observed for 1 and 3. The two
W-O distances are similar [W1-O1 ) 1.931(2) Å,
W1-O2 ) 1.950(2) Å] and compare favorably to other
W-O(alkoxide) distances.19 The W-N(pyridine) distance
[W1-N3 ) 2.313(2) Å] is similar to that observed in 4,
while the tert-butyl group of the metallacycle is syn to the
alkoxide ligand.
Isolation of W(NPh)(o-(Me3SiN)2C6H4)(OCH(C5H4N)-
CH(C5H4N)O). During an attempt to extend the scope of
this reaction to other aldehydes, a few red crystals were
isolated from the reaction between W(NPh)(o-(Me3SiN)2C6H4)-
(py)2 and 2-pyridine carboxaldehyde. Crystals suitable for
X-ray diffraction were grown from Et2O, and X-ray crystal-
lography revealed these crystals to be W(NPh)(o-(Me3-
SiN)2C6H4)(OCH(C5H4N)CH(C5H4N)O) (7). The solid-state
molecular structure of 7 is shown in Figure 5. Complex 7
evidently results from the displacement of both pyridine
ligands and the subsequent coupling of two aldehyde
fragments to generate the W(VI) diolate complex, 7 (eq 4).
Figure 3. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(OCH(Me)2)-
(OC(Me)2-o-C5H3N-p-Me) (4) with 50% probability ellipsoids being shown.
Selected bond lengths (Å) and angles (deg): W-N1 ) 1.763(7), W-O2
) 1.874(6), W-O1 ) 1.929(5), W-N3 ) 2.005(7), W-N2 ) 2.152(6),
W-N4 ) 2.293(7), W-N1-C1 ) 169.4(6).
groups of the phenylenediamide ligand exhibit different
W-N distances [W-N3 ) 2.005(7) Å, W-N2 ) 2.152(6)
Å], a manifestation of the trans influence as the amide
nitrogen with the longer W-N bond (N2) is trans to the
imido ligand.18 The W-O(isopropoxide) distance [W-O2
) 1.874(6) Å] is similar to those found in related com-
plexes.19
The most interesting structural feature in 3 is the five-
membered azaoxymetallacycle, formed by the coupling of
picoline with acetone. The W-N(picoline) bond length is
2.293(7) Å, much longer than that seen in the parent
compound W(NPh)(o-(Me3SiN)2C6H4)(pic)2 [W-N(picoline)
) 2.083(3) Å and 2.109(3) Å] but consistent with other
W-N(py) bond lengths,20,21 while the W-O1 bond length
of 1.929(5) Å is comparable to those seen in similar
compounds.22
Synthesis and Characterization of W(NPh)(o-(Me3SiN)2-
t
C6H4)(OCH2R)(OCH(R)-o-C5H4N) [R ) Ph, Bu]. The
tungsten(IV) pyridine complex was also found to react with
aldehydes. the addition of 2 equiv of benzaldehyde or
trimethylacetaldehyde to W(NPh)(o-(Me3SiN)2C6H4)(py)2 at
room temperature generates solutions containing W(NPh)-
(o-(Me3SiN)2C6H4)(OCH2R)(OCH(R)-o-C5H4N) [R ) Ph, 5;
tBu, 6] (eq 3). Crystallization from pentane provides 5 and
6 as red crystalline materials in 36% and 21% yields,
respectively.
In addition, one of the 2-pyridine substituents is coordi-
nated to the tungsten to form a unique O2N tridentate ligand.
The W1-N1-C1 angle of the imido ligand is 155.1(4)°,
(18) Coe, B. J.; Glenwright, S. J. Coord. Chem. ReV. 2000, 203, 5-80.
(19) Schrock, R. R.; DePue, R. T.; Feldman, J.; Schaverien, C. J.; Dewan,
J. C.; Liu, A. H. J. Am. Chem. Soc. 1988, 110, 1423-1435.
(20) Kriley, C. E.; Fanwick, P. E.; Rothwell, I. P. J. Am. Chem. Soc. 1994,
116, 5225-5232.
(21) Wesemann, L.; Waldmann, L.; Ruschewitz, U.; Ganter, B.; Wagner,
T. J. Chem. Soc., Dalton Trans. 1997, 1063-1068.
(22) van der Schaaf, P. A.; Abbenhuis, R. A. T. M.; Grove, D. M.; Smeets,
W. J. J.; Spek, A. L.; van Koten, G. J. Chem. Soc., Chem. Commun.
1993, 504-506.
Both 5 and 6 display several characteristic signals in their
respective 1H NMR spectra that support the proposed
formulation. For instance, the diastereotopic protons of the
Inorganic Chemistry, Vol. 44, No. 25, 2005 9509

Hayton et al.
1
The H NMR spectrum of compound 7 at room temper-
ature consists of several broad singlets. However, its 1H NMR
spectrum at -30 °C in toluene-d8 reveals the presence of
two inequivalent trimethylsilyl groups, while two doublets
at 8.40 and 8.51 ppm are assigned to the ortho protons of
the pyridine substituents. There is no indication of the
presence of the anti-diol diastereomer in the 1H NMR
spectrum. Warming a toluene-d8 solution of 7 to 30 °C results
in the coalescence of the inequivalent Me3Si groups. The
fluxionality can be explained by invoking pyridine dissocia-
tion from the metal to give a five-coordinate transition state.
Coordination of the other pyridyl moiety regenerates the
octahedral species (Scheme 2). Using the two-site exchange
q
approximation, the activation barrier (∆GC ) was calculated
to be 15.0 kcal mol-1 for this process.26
Labeling Studies. To understand how 4, 5, and 6 are
formed, we undertook a number of deuterium labeling
studies. Thus, the reaction of W(NPh)(o-(Me3SiN)2C6H4)-
(py-d5)2 with 2 equiv of benzaldehyde generates red solutions
containing W(NPh)(o-(Me3SiN)2C6H4)(OCHDPh)(OCH(Ph)-
o-C5D4N) (5-d5). A 1H NMR spectrum of 5-d5 displays two
singlets at 5.63 and 5.89 ppm, in an 8:1 ratio, and not the
doublet of doublets as was seen with 5. Furthermore, the
Figure 4. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(OCH2CMe3)-
(OCH(CMe3)-o-C5H4N) (6) with 50% probability ellipsoids being shown.
Selected bond lengths (Å) and angles (deg): W1-N4 ) 1.751(2), W1-
O1 ) 1.931(2), W1-O2 ) 1.950(2), W1-N2 ) 2.031(2), W1-N1 )
2.082(2), W1-N3 ) 2.313(2), W1-N4-C1 ) 172.4(2).
1
prominent multiplet observed at 8.41 ppm in the H NMR
1
spectrum of 5 is not observed in the H NMR spectrum of
5-d5. The 2H NMR spectrum of 5-d5 in C6H6 exhibits a broad
singlet at 5.86 ppm and another broad singlet at 8.41 ppm.
This experiment demonstrates that one hydrogen on the
alkoxide ligand originates from the pyridine ortho position
(eq 5). It also reveals that the addition of the hydrogen to
the aldehyde to form the alkoxide occurs in a diastereose-
lective fashion, as only one of the two hydrogen positions R
to the oxygen becomes deuterated to any extent.
Figure 5. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(OCH(C5H4N)-
CH(C5H4N)O) (7) with 50% probability ellipsoids being shown. Selected
bond lengths (Å) and angles (deg): W1-N1 ) 1.775(5), W1-N2 ) 2.007-
(5), W1-O1 ) 2.012(4), W1-O2 ) 2.020(4), W1-N3 ) 2.026(5), W1-
N4 ) 2.262(5), W1-N1-C1 ) 155.1(4).
Similarly, the reaction of W(NPh)(o-(Me3SiN)2C6H4)(py-
d5)2 with 2 equiv of trimethylacetaldehyde generates
W(NPh)(o-(Me3SiN)2C6H4)(OCHDCMe3)(OCH(CMe3)-o-
much smaller than that observed in similar imido complexes,
while the fold angle of the phenylenediamide ligand (139.5°)
is comparable to related compounds. The two W-O bond
lengths [W1-O1 ) 2.012(4) Å, W1-O2 ) 2.020(4) Å] are
identical but are slightly longer than the tungsten-alkoxide
bond lengths observed in 4 and 6. The W-N(pyridine) bond
length is 2.262(5) Å and is close to that observed for 4.
Interestingly, the product is the syn-diol coupling product.
Previously, coupling of benzaldehyde at Ti has yielded the
anti-diolate product,23 or mixtures of both anti and syn,24
while the coupling of benzaldehyde with SmI2/tetraglyme
gives primarily the syn (or meso) diol.25
1
C5D4N) (6-d5). As with the H NMR spectrum of 5-d5, the
1H NMR spectrum of 6-d5 exhibits two singlets at 4.15 and
4.32 ppm, in a ratio of 9:5, respectively, as opposed to the
doublet of doublets seen in the protio analogue. This
experiment is completely consistent with the benzaldehyde
result; however, the reaction proceeds with significantly
lower diastereoselectivity.
Finally, to determine if a kinetic isotope effect is involved
in azaoxymetallacycle formation, W(NPh)(o-(Me3SiN)2C6H4)-
(py-2-d1)2 was synthesized from W(NPh)(o-(Me3SiN)2C6H4)-
Cl2 and py-2-d1. The reaction of W(NPh)(o-(Me3SiN)2C6H4)-
(py-2-d1)2 with 2 equiv of benzaldehyde or trimethylacetalde-
hyde generates W(NPh)(o-(Me3SiN)2C6H4)(OCH(H/D)R)-
(23) Steinhuebel, D. P.; Lippard, S. J. J. Am. Chem. Soc. 1999, 121, 11762-
11772.
(24) Du, G.; Mirafzal, G. A.; Woo, L. K. Organometallics 2004, 23, 4230-
4235.
(25) Aspinall, H. C.; Greeves, N.; Valla, C. Org. Lett. 2005, 7, 1919-
(26) Friebolin, H. Basic One- and Two-Dimensional NMR Spectroscopy;
1922.
VCH Publishers: New York, 1993; p 295.
9510 Inorganic Chemistry, Vol. 44, No. 25, 2005

Coupling of an Aldehyde or Ketone to Pyridine
Scheme 2
(OCH(R)-o-C5H3(H/D)N) (R ) Ph, 5-d1; R ) tBu, 6-d1) (eq
6). In both products, the deuterium label was distributed
equally between the ortho pyridine position and the meth-
ylene group of the alkoxide ligand. This result is consistent
with a rate-determining step that does not inVolVe pyridine
C-H(D) bond cleavage.
C7-O1 bond length is 1.356(4) Å, considerably longer than
the average C-O bond length in uncoordinated aldehydes
(1.20 Å), while the two W-N(amide) bond lengths are W1-
N3 ) 2.108(2) Å and W1-N2 ) 2.138(2) Å.
Isolation of W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)-
(CMe3)-o-C5H4N). More mechanistic information can be
garnered from the reaction between W(NPh)(o-(Me3-
SiN)2C6H4)(py)2 and pinacolone [Me3CC(O)Me]. A red
crystalline material can be isolated from these reaction
mixtures in low yield. The 1H NMR spectrum of this material
revealed the incorporation of only one pinacolone molecule
into the product, and an X-ray crystallographic study proved
these crystals to be W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)-
(CMe3)-o-C5H4N) (10).
The solid-state molecular structure of 10 is shown in
Figure 7. Complex 10 exhibits an octahedral geometry
around W with an essentially linear phenylimido ligand
whose metrical parameters [W1a-N4 ) 1.759(4) Å, W1a-
N4-C1 ) 160.2(4)°] are similar to those observed in 4 and
6. The complex contains an N,O chelate formed by the
coupling of one pyridine and one pinacolone. The W-O
[W1a-O1 ) 1.939(4) Å] and W-N(pyridine) [W1a-N1
) 2.277(5) Å] distances are similar to the related distances
in 4 and 6. The most surprising structural feature of 10 is
the incorporation of a chloride ligand. The W-Cl bond
length [W1a-Cl1 ) 2.466(1) Å] is slightly longer than that
observed for W(NPh)(o-(Me3SiN)2C6H4)Cl2.17 As observed
in the structure of 6, the tert-butyl group of the metallacycle
is syn to the X- ligand (Cl- in this case).
Synthesis of W(NPh)(o-(Me3SiN)2C6H4)(py)(PMe3)(η2-
OC(H)R) [R ) Ph, p-tol]. The reaction of W(NPh)(o-(Me3-
SiN)2C6H4)(py)2 with benzaldehyde or p-tolualdehyde in the
presence of trimethylphosphine does not yield an azaoxy-
metallacycle-containing complex. Instead, W(NPh)(o-(Me3-
SiN)2C6H4)(py)(PMe3)(η2-OC(H)R) (R ) Ph, 8; R ) p-tol
9) are isolated as red powders in moderate yield (eq 7).
Because PMe3 reacts nearly instantaneously with W(NPh)-
(o-(Me3SiN)2C6H4)(py)2 to form W(NPh)(o-(Me3SiN)2C6H4)-
(py)(PMe3)2, it is probable that this species reacts with the
1
aldehyde to form 8 and 9. The H NMR spectrum of 8
exhibits a doublet at 5.91 ppm (3JPH ) 6.9 Hz) assignable
to the aldehyde proton, while the 13C{1H} NMR exhibits a
doublet at 86.2 ppm (2JPC ) 12.8 Hz) assignable to the
1
carbonyl carbon. The H NMR and 13C{1H} NMR spectra
of 9 display similar resonances at similar chemical shifts.
These data suggest that the aldehyde is bound to tungsten in
an η2 fashion in both 8 and 9. Compounds 8 and 9 are air-
and moisture-sensitive, while complex 8 is also temperature-
sensitive, decomposing to a yellow powder within days at
room temperature. It is not clear why 8 is so much more
sensitive than 9, given their similar structures.
A single crystal of 9, suitable for X-ray diffraction, was
grown from a concentrated Et2O solution. The ORTEP
diagram of one of the independent molecules in the asym-
metric unit of 9 is shown in Figure 6. Complex 9 adopts an
octahedral geometry with the η2-aldehyde ligand occupying
a position cis to the imido ligand. In addition, the C-O bond
of the aldehyde is orthogonal to the W1-N1 vector. The
Figure 6. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(PMe3)(py)(η2-
OC(H)C6H4-p-Me) (9) with 50% probability ellipsoids being shown.
Selected bond lengths (Å) and angles (deg): W1-N1 ) 1.784(3), W1-
O1 ) 2.001(2), W1-N3 ) 2.108(2), W1-N2 ) 2.138(2), W1-C7 )
2.208(3), W1-N4 ) 2.281(2), W1-P1 ) 2.5347(8), O1-C7 ) 1.356(4),
C1-N1-W1 ) 177.9(2).
Inorganic Chemistry, Vol. 44, No. 25, 2005 9511

Hayton et al.
Scheme 3. For instance, (a) the reaction could proceed via
the formation of a pyridyl hydride intermediate, which
sequentially inserts 2 equiv of aldehyde, or (b) it could
proceed by the initial formation of a η2-aldehyde complex,
followed by a direct hydride transfer from pyridine to form
a pyridyl alkoxide complex. Alternatively, the carbon of the
η2-aldehyde ligand could act as a nucleophile and attack the
ortho carbon of pyridine to form an N-metalated dihydro-
pyridine intermediate. From there, (c) H transfer to the metal
to form a hydride, followed by insertion, could give the final
product or (d) aldehyde could bind and direct H transfer
could occur, similar to a Meerwein-Pondorf-Verley reduc-
tion.28
Mechanism a is consistent with the isotopic labeling
studies if the C-H bond-breaking step were fast and
reversible and occurred before the rate-determining step. In
addition, there are many examples of pyridyl hydride species
in the chemical literature, and they readily undergo insertion
with unsaturated organics.7 However, if the reaction did occur
via a pyridyl hydride intermediate, one would expect the
insertion of aldehyde into the W-H bond to occur before
insertion into the W-C bond. This makes the formation of
complex 10 harder to explain. Mechanism b is probably not
operative, as it is difficult to imagine that a concerted
hydrogen transfer from pyridine to aldehyde would not be
rate determining and, thus, exhibit no kinetic isotope effect.
Mechanism c is consistent with both the deuterium labeling
studies and the isolation of complexes 8 and 9. It also nicely
accounts for the formation of 10, which could derive from
the reaction of CH2Cl2 with the tungsten hydride. However,
it is possible that 10 forms via a completely different reaction
because it does not appear that W(NPh)(o-(Me3SiN)2C6H4)-
(py)2 reacts with 2 equiv of pinacolone under any circum-
stances. Mechanism d, where hydrogen transfer occurs
directly to a bound aldehyde in a Meerwein-Pondorf-
Verlay-style reduction, is also consistent with the available
experimental evidence, but it does not explain the formation
of 10 as elegantly as mechanism c.
Figure 7. ORTEP diagram of W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)-
(CMe3)-o-C5H4N) (10) with 50% probability ellipsoids being shown.
Selected bond lengths (Å) and angles (deg): W1a-N4 ) 1.759(4), W1a-
O1 ) 1.939(4), W1a-N3 ) 1.991(5), W1a-N2 ) 2.046(3), W1a-N1 )
2.277(5), W1a-Cl1 ) 2.466(1), W1a-N4-C1 ) 160.2(4).
The origin of the chloride ligand in 10 was not im-
mediately clear. However, the addition of pinacolone to a
diethyl ether solution of W(NPh)(o-(Me3SiN)2C6H4)(py)2,
followed by the introduction of excess CH2Cl2, provides a
deep-green solution. This solution slowly turns brown-
yellow, then deep-red. Cooling this mixture gave red crystals
of 10 in 15% yield (eq 8). CHCl3 can be substituted for CH2-
Cl2 with no improvement in yield. Interestingly, when
pinacolone was added to an equimolar mixture of W(NPh)-
(o-(Me3SiN)2C6H4)Cl2 and W(NPh)(o-(Me3SiN)2C6H4)(py)2
in an attempt to generate 10, a maroon powder was isolated
in low yield, which proved to be W(NPh)(o-(Me3SiN)2C6H4)-
Cl2(py) (11), the pyridine adduct of the tungsten dichloride
starting material.27
Given this evidence, we prefer mechanism c for the
reasons stated above, but also because we only see evidence
for pyridyl C-H activation chemistry when there is aldehyde
or ketone is present. With other unsaturated substrates, like
alkenes, we only observed displacement of the pyridine
ligands and not insertion.
The isolation of 10 suggests that the tungsten hydride
complex W(NPh)(o-(Me3SiN)2C6H4)(H)(OC(Me)(CMe3)-o-
C5H4N) is formed as an intermediate. This species then reacts
with CH2Cl2 to form 10 and CH3Cl. When CH2Cl2 is absent,
no tractable products are isolated, possibly because pina-
colone is too bulky to allow for the formation of an alkoxide
ligand and the azaoxymetallacycle on the same metal center.
This result also suggests that the formation of the axaoxy-
metallacycle occurs before the formation of the alkoxide
ligand.
There is literature precedent for nucleophilic attack by an
acyl group at the ortho carbon of bound pyridine, followed
by a 1,2 hydrogen shift.5 The resulting product is similar to
our azaoxymetallacycles. In our case, however, the nucleo-
phile would be an η2-aldehyde, while the hydrogen shift
would be to the metal, as suggested by the deuterium labeling
results. When an unsaturated substrate coordinates to the
W(IV) imido diamide complexes studied here, the structures
are invariably best described as W(VI) metallacycles. Thus,
the butadiene complex reported in this paper is considered
a σ2π butadiene complex. Assuming that a similar interaction
Discussion
The formation of the final double-insertion product can
be explained by a number of mechanisms, as shown in
(27) Complex 11 can be made directly by adding pyridine to a pentane
suspension of W(NPh)(o-(Me3SiN)2C6H4)Cl2 in a much higher yield.
(28) Campbell, E. J.; Zhou, H.; Nguyen, S. T. Org. Lett. 2001, 3, 2391-
2393.
9512 Inorganic Chemistry, Vol. 44, No. 25, 2005

Coupling of an Aldehyde or Ketone to Pyridine
Scheme 3
occurs between the coordinated aldehydes in 8 and 9, the
carbon atom of the aldehyde would be expected to have a
considerable amount of carbanion character, which would
allow it to behave as a nucleophile and attack the coordinated
pyridine.
Further experiments to rule out one mechanism or the other
have not been fruitful. For instance, attempts to observe a
hydride intermediate by adding only 1 equiv of susbstrate
have not worked, as mixtures of starting material and the
double-insertion product are the only species isolated. As
well, attempts to observe any transient species by NMR
spectroscopy have also failed.
Experimental Section
General. All reactions and subsequent manipulations were
performed under anaerobic and anhydrous conditions either under
a high vacuum or an atmosphere of helium or argon. Pentane was
distilled from NaK while toluene was filtered through two columns
of activated alumina. Dichloromethane and pyridine were distilled
from calcium hydride. C6D6 and pyridine-d5 were dried over
activated 4 Å molecular sieves for 24 h before use. py-d1 was
purchased from CDN Isotopes and used as received. Acetone was
distilled from B2O3. Picoline was distilled from Na. Et2O was
distilled from Na/benzophenone. W(NPh)(o-(Me3SiN)2C6H4)(py)2
and W(NPh)(o-(Me3SiN)2C6H4)(picoline)2 were prepared by the
literature method.11 W(NPh)(o-(Me3SiN)2C6H4)(py-d5)2 and W(N-
Ph)(o-(Me3SiN)2C6H4)(py-d1)2 were made in identical fashions to
their unlabeled counterparts. All other reagents were purchased from
commercial suppliers and used as received.
Summary
In this contribution, we have explored the reactivity of
W(NPh)(o-(Me3SiN)2C6H4)(py)2 and W(NPh)(o-(Me3SiN)2-
C6H4)(pic)2 with unsaturated substrates. With diphenylacety-
lene or olefins, displacement of the heterocyclic ligands
occurs to give the simple adducts, or metallacyclic products
in the case of ethylene. With some aldehydes, net substrate
insertion into the ortho C-H bond of pyridine to form
tungsten azaoxymetallacycle complexes is observed. Both
aliphatic and aromatic aldehydes can participate in the
reaction. The exact nature of the C-H bond activation step
is not well understood, but mechanistic studies suggest that
a tungsten pyridine η2-aldehyde complex is formed before
C-H bond activation occurs and the reaction proceeds via
a metal-hydride intermediate. We have also demonstrated
that, with pyridine-2-carboxaldehyde, coupling to form a
diolate complex occurs. The factors that determine which
reaction pathway is followed, either C-H activation or
diolate formation, are not understood. Further investigation
of more substrates will be necessary to reveal the factors
that control this reaction. In addition, the use of new
substrates may allow us to gain more insight into the C-H
activation step during metallacycle formation. New develop-
ments will be reported in due course.
NMR spectra were recorded on a Bruker AVA300, a Varian
Gemini 300, a VXR 300, or a Mercury 300 spectrometer. H and
1
13C{1H} NMR spectra are referenced to external SiMe4 using the
residual protio solvent peaks as internal standards (1H NMR
experiments) or the characteristic resonances of the solvent nuclei
(13C NMR experiments). 31P spectra were referenced to external
85% H3PO4. Mass spectrometry measurements were performed with
a Finnigan MAT95Q hybrid sector mass spectrometer by Dr. David
Powell at the University of Florida or were obtained at the U. C.
Berkeley Mass Spectrometry Facility using a VG ProSpec. El-
emental analyses were performed at the U. C. Berkeley Microana-
lytical Facility, on a Perkin-Elmer Series II 2400 CHNS analyzer.
W(NPh)(o-(Me3SiN)2C6H4)(η2-PhCtCPh) (1). A Young’s
ampule was charged with W(NPh)(o-(Me3SiN)2C6H4)(py)2 (0.50
g, 0.731 mmol) and diphenylacetylene (0.13 g, 0.731 mmol). The
mixture was dissolved in toluene and heated to 55 °C for 4 h, during
which time the solution became yellow-brown in color. Removal
of the reaction solvent in vacuo, followed by extraction with
pentane, yielded a dark-yellow solution. Cannula filtration, followed
by removal of the solvent in vacuo, gave 0.35 g (68% yield) of a
dark-brown powder. 1H NMR (300 MHz, 25 °C, C6D6): δ 0.41 (s,
18H, SiMe3), 6.81 (t, 1H, phenylimido para proton), 6.97 (m, 4H,
phenylimido meta and ortho protons), 7.11 (m, 5H), 7.25 (m, 2H,
phenylene diamine ortho protons), 7.36 (m, 5H), 7.51 (m, 2H,
Inorganic Chemistry, Vol. 44, No. 25, 2005 9513

Hayton et al.
phenylene diamine meta protons). 13C{1H} NMR (75 MHz, 25 °C,
C6D6): δ 2.38 (SiMe3), 123.3, 124.7, 125.7, 128.9, 129.0, 129.2,
129.6, 130.1, 132.3, 143.1, 198.5 (CtC). HRMS (FAB) calcd for
C32H38N3Si2W: 704.2111 [M + H]+. Found: 704.2114.
W(NPh)(o-(Me3SiN)2C6H4)(OCH2Ph)(OCH(Ph)-o-C5H4N) (5).
To a purple solution of W(NPh)(o-(Me3SiN)2C6H4)(py)2 (0.0756
g, 0.11 mmol) dissolved in diethyl ether (2 mL) was added 2 equiv
of benzaldehyde (23.5 µL, 0.23 mmol). The solution quickly turned
forest green and then slowly became deep red. After 10 min of
stirring, the volatile fraction was removed in vacuo, and the resulting
red-brown powder was dissolved in pentane (2 mL) and filtered
through a column of Celite (0.5 cm × 2 cm) supported on glass
wool. The deep-red solution was stored at -30 °C for 24 h, resulting
in the deposition of red crystals (0.0155 g). Further cooling of the
solution resulted in the deposition of more crystals (0.0170 g, 36%
W(NPh)(o-(Me3SiN)2C6H4)(CH2CH2CH2CH2) (2). W(NPh)(o-
(Me3SiN)2C6H4)(py)2 (0.535 g, 0.78 mmol) and toluene were added
to a Young’s ampule. The sample was frozen and the flask
evacuated. Upon warming to room temperature, the flask was
charged with ethylene (20 psi), resulting in a color change from
purple to orange. The solution was stirred for 30 min, during which
time the solution changed to yellow-brown. Removal of the volatile
fraction in vacuo gave a brown solid. This solid was extracted with
several portions of pentane and transferred to a new vessel via a
cannula filtration. Evaporation of this solution under reduced
pressure gave 0.300 g (66% yield) of a yellow-brown powder. This
material was determined to be W(NPh)(o-(Me3SiN)2C6H4)(CH2-
CH2CH2CH2) (2) by its characteristic proton and 13C NMR spectra.14
1
total yield). H NMR (300 MHz, 25 °C, C6D6): δ 0.47 (s, 9H,
SiMe3), 0.67 (s, 9H, SiMe3), 5.65 (d, 1H, JHH ) 13.9 Hz, OCHHPh),
5.89 (d, 1H, JHH ) 14.0 Hz, OCHHPh), 6.24-6.27 (m, 2H), 6.46
[s, 1H, OCH(Ph)-o-C5H4N], 6.50 (t of d, 1H, aromatic CH), 6.67-
7.21 (m, 17H), 7.33 (m, 2H, phenylimido ortho protons), 8.41 (m,
1H, pyridine ring ortho proton). 13C{1H} NMR (75 MHz, 25 °C,
C6D6): δ 2.59 (SiMe3), 3.79 (SiMe3), 76.0 (OCH2), 88.5 [OCH-
(Ph)-o-C5H4N], 118.7 (CH), 118.8 (CH), 119.5 (CH), 119.6 (CH),
120.8 (CH), 121.9 (CH), 126.0 (CH), 126.1 (CH), 126.2 (CH), 126.4
(CH), 128.0 (CH), 128.1 (CH), 128.2 (CH), 128.3 (CH), 128.8 (CH),
137.9 (CH), 144.3, 147.3 (CH, pyridine ring ortho carbon), 149.2,
149.3, 154.6, 164.7. HRMS (EI) calcd for C37H44O2N4Si2W:
816.2513 [M]+. Found: 816.2506. Anal. Calcd for C37H44N4O2-
Si2W: C, 54.41; H, 5.43; N, 6.86. Found: C, 54.34; H, 5.57; N,
6.65.
W(NPh)(o-(Me3SiN)2C6H4)(η4-CH2dC(Me)C(Me)dCH2) (3).
To a purple solution of W(NPh)(o-(Me3SiN)2C6H4)(py)2 (1.00 g,
1.46 mmol) dissolved in toluene was added 2,3-dimethyl-1,3-
butadiene (0.17 mL, 1.46 mmol). This mixture was heated to 60
°C for 20 h, resulting in a color change to red-brown. The volatile
fraction was removed in vacuo, and the resulting brown powder
was extracted with several portions of pentane and transferred to a
new vessel via a filter cannula. The pentane was then removed
under reduced pressure to give 0.65 g (73% yield) of 3 as a dark-
W(NPh)(o-(Me3SiN)2C6H4)(OCHDPh)(OCH(Ph)-o-C5D4N) (5-
d5). 5-d5 was made in a fashion similar to that described for 5. 1H
NMR (300 MHz, 25 °C, C6D6): δ 0.48 (s, 9H, SiMe3), 0.71 (s,
9H, SiMe3), 5.63 (s, OCDHPh), 5.89 (s, OCHDPh), 6.47 [s, 1H,
OCH(Ph)-o-C5H4N], 6.65-7.21 (m, 17H), 7.33 (m, 2H, phe-
nylimido ortho protons). 2H NMR (46 MHz, 25 °C, C6H6): δ 5.86
(br s), 6.27 (br m), 8.41 (br s).
1
brown solid. H NMR (300 MHz, 25 °C, C6D6): δ 0.37 (s, 18H,
SiMe3), 1.24 (s, 6H, diene methyl), 1.31 (d, 2H, JHH ) 8.5 Hz,
R-CHH), 2.17 (d, 2H, JHH ) 8.5 Hz, R-CHH), 6.85 (m, 3H,
aromatic), 7.12-7.20 (m, 4H, aromatic), 7.33 (m, 2H, aromatic).
13C{1H} NMR (75 MHz, 25 °C, C6D6): δ 2.45 (SiMe3), 18.7
(CCH3), 50.5 (R-CH2, JCH ) 143 Hz), 120.2 (CCH3), 120.5, 121.0,
125.3, 127.5, 128.8, 150.0. HRMS (FAB) calcd for C24H38N3-
Si2W: 607.2035 [M]+. Found: 607.2109.
W(NPh)(o-(Me3SiN)2C6H4)(OCH2CMe3)(OCH(CMe3)-o-
C5H4N) (6). To a purple solution of W(NPh)(o-(Me3SiN)2C6H4)-
(py)2 (0.0689 g, 0.10 mmol) dissolved in toluene (1.5 mL) was
added 2 equiv of trimethylacetaldehyde (23.0 µL, 0.21 mmol). The
solution quickly turned red, and after 15 min of stirring, the volatile
fraction was removed in vacuo. The resulting red-brown powder
was dissolved in pentane (2 mL) and filtered through a column of
Celite (0.5 cm × 2 cm) supported on glass wool. The deep-red
solution was stored at -30 °C for 48 h, resulting in the deposition
of red crystals (0.0166 g, 21% yield). 1H NMR (300 MHz, 25 °C,
C6D6): δ 0.40 (s, 9H, SiMe3), 0.66 (s, 9H, SiMe3), 0.86 (s, 9H,
CMe3), 1.12 (s, 9H, CMe3), 4.19 (d, 1H, JHH ) 11 Hz, OCHH-
CMe3), 4.34 (d, 1H, JHH ) 11 Hz, OCHHCMe3), 5.20 (s, 1H,
OCH(CMe3)-o-C5H4N), 6.28 (m, 1H, pyridine ring meta proton),
6.50-6.81 (m, 6H), 7.06 (dd, 1H, JHH ) 8 Hz, JHH ) 1.2 Hz,
diamine ring ortho proton), 7.21 (m, 2H, phenylimido meta protons),
7.37 (m, 2H, phenylimido ortho protons), 8.32 (m, 1H, pyridine
ring ortho proton). 13C{1H} NMR (75 MHz, 25 °C, C6D6): δ 2.51
(SiMe3), 3.47 (SiMe3), 26.9 (CMe3), 27.5 (CMe3), 34.7 (CMe3),
38.1 (CMe3), 84.1 (OCH2), 92.8 [OCH(CMe3)-o-C5H4N], 118.3
(CH), 118.7 (CH), 118.8 (diamine ring ortho carbon), 119.3 (CH),
120.3 (CH), 121.2 (CH, pyridine ring meta carbon), 125.5 (CH),
126.0 (phenylimido ortho carbons), 128.1 (phenylimido meta
carbons), 137.2 (CH), 148.5 (CH, pyridine ring ortho carbon), 149.5,
149.7, 155.1, 163.5. HRMS (EI) calcd for C33H52O2N4Si2W:
776.3166 [M]+. Found: 776.3139. Anal. Calcd for C33H52N4O2-
Si2W: C, 51.02; H, 6.75; N, 7.21. Found: C, 50.84; H, 6.55; N,
6.88.
W(NPh)(o-(Me3SiN)2C6H4)(OCH(Me)2)(OC(Me)2-o-C5H4N-p-
Me) (4). To a purple solution of W(NPh)(o-(Me3SiN)2C6H4)-
(picoline)2 (0.066 g, 0.09 mmol) dissolved in toluene (1.0 mL) was
added 2 equiv of acetone (13.0 µL, 0.18 mmol). The solution
quickly turned green, then slowly changed to orange-brown over
20 min. After this time, the volatile fraction was removed in vacuo,
and the resulting solid was dissolved in pentane (2 mL) and filtered
through a column of Celite (0.5 cm × 2 cm) supported on glass
wool. The resulting red-brown solution was stored at -30 °C for
several hours, resulting in the deposition a brown powder. The
solution was again filtered through a column of Celite and then
stored at -30 °C for several weeks. This resulted in the deposition
of orange crystals (0.0124 g, 18.2%). 1H NMR (300 MHz, 25 °C,
C6D6): δ 0.44 (s, 9H, SiMe3), 0.70 (s, 9H, SiMe3), 1.11 [d, 6H,
JHH ) 6.0 Hz, OCH(Me)2], 1.42 (s, 3H, Me), 1.54 (s, 3H, Me),
1.62 (s, 3H, Me), 4.93 [septet, 1H, OCH(Me)2, JHH ) 5.9 Hz],
6.11 (d, 1H, JHH ) 5.8 Hz, picoline ring meta proton), 6.31 (s, 1H,
picoline ring meta proton), 6.60-7.12 (m, 5H), 7.23 (m, 2H,
phenylimido meta protons), 7.47 (m, 2H, phenylimido ortho
protons), 8.18 (d, 1H, JHH ) 5.7 Hz, picoline ring ortho proton).
13C{1H} NMR (75 MHz, 25 °C, C6D6): δ 2.55 (SiMe3), 3.71
(SiMe3), 20.3 (Me), 26.6 (Me), 26.9 [OCH(Me)2], 34.2 (Me), 75.8
[OCH(Me)2], 118.6 (CH), 118.8 (CH), 119.5 (CH), 119.7 (picoline
ring meta carbon), 119.9 (CH), 123.1 (picoline ring meta carbon),
125.9 (CH), 126.2 (phenylimido ortho carbon), 127.9 (phenylimido
meta carbon), 147.2 (CH, picoline ring ortho carbon), 148.2, 150.2,
151.2, 154.7, 159.4. HRMS (EI) calcd for C30H46O2N4Si2W:
734.2669 [M]+. Found: 734.2608.
W(NPh)(o-(Me3SiN)2C6H4)(OCHDCMe3)(OCH(CMe3)-o-
C5D4N) (6-d5). 6-d5 was made in a fashion similar to that described
9514 Inorganic Chemistry, Vol. 44, No. 25, 2005

Coupling of an Aldehyde or Ketone to Pyridine
1
for 6. H NMR (300 MHz, 25 °C, C6D6): δ 0.41 (s, 9H, SiMe3),
(d, 9H, JPH ) 9.6 Hz, PMe3), 2.12 (s, 3H, CH3), 5.95 (d, 1H, JPH
) 6.6 Hz, OCH), 6.68-7.12 (m, 16 H), 7.35 (d, 2H, JHH ) 8.1
Hz, phenylimido ortho protons). 31P{1H} NMR (121 MHz, 25 °C,
C6D6): δ -3.88 (JPW ) 322 Hz). 13C{1H} NMR (75 MHz, 25 °C,
C6D6): δ 3.45 (SiMe3), 4.33 (SiMe3), 14.7 (d, PMe3, JPC ) 28
Hz), 20.6 (C6H4-p-Me), 87.5 (d, OCH, JPC ) 13.5 Hz), 116.1 (CH),
117.7 (CH), 118.5 (CH), 120.3 (CH), 120.4 (CH), 123.2 (CH), 123.8
(CH), 127.2 (CH), 127.8 (CH), 136.5, 140.0 (CH), 144.4, 150.1,
153.7, 157.2. Anal. Calcd for C34H49N4OPSi2W: C, 51.00; H, 6.17;
N, 7.00. Found: C, 50.92; H, 6.14; N, 6.92.
0.67 (s, 9H, SiMe3), 0.85 (s, 9H, CMe3), 1.13 (s, 9H, CMe3), 4.15
(s, OCDHCMe3), 4.32 (s, OCHDCMe3), 5.21 (s, 1H, OCH(CMe3)-
o-C5H4N), 6.51-7.22 (m, 8H), 7.37 (m, 2H, phenylimido ortho
protons). 2H NMR (46 MHz, 25 °C, C6H6): δ 4.13 (br s), 4.32 (br
s), 6.31-7.00 (br m), 8.31 (br s).
W(NPh)(o-(Me3SiN)2C6H4)(OCH(C5H4N)CH(C5H4N)O) (7).
To a purple solution of W(NPh)(o-(Me3SiN)2C6H4)(py)2 (0.196 g,
0.29 mmol) in Et2O (1 mL) was added 2-pyridine carboxaldehyde
(51 µL, 0.54 mmol). The solution immediately turned deep red and
copious amounts of precipitate formed. The mixture was allowed
to stir for 3 h, at which point it was filtered through a column of
Celite (0.5 cm × 1 cm) supported on glass wool. The Celite was
subsequently rinsed with Et2O (2 mL), and the combined filtrates
were stored at -30 °C for 24 h, resulting in the deposition of red
crystals (0.0174 g, 8.1% yield). 1H NMR (300 MHz, -30 °C,
C7D8): δ 0.38 (SiMe3), 0.52 (SiMe3), 5.91 (d, 1H, JHH ) 3.7 Hz,
OCH), 5.95 (m, 1H, pyridine ring proton), 6.15 (d, 1H, JHH ) 7.6
Hz, pyridine meta proton), 6.32 (m, 1H, pyridine ring proton), 6.66
(d, 1H, JHH ) 3.7 Hz, OCH), 6.81 (t, 1H, JHH ) 10.3 Hz,
phenylimido para proton), 6.93 (m, 1H, pyridine ring proton), 7.19-
7.45 (m, 7H), 8.40 (d, 1H, JHH ) 4.2 Hz, pyridine ortho proton),
8.51 (d, 1H, JHH ) 5.1 Hz, pyridine ortho proton). 13C{1H} NMR
(75 MHz, 0 °C, C7D8): δ 1.44 (SiMe3), 2.40 (SiMe3), 89.9 (OCH),
119.8 (CH), 120.1 (CH), 121.0 (CH), 121.3 (CH), 121.7 (CH), 122.8
(CH), 123.8 (CH), 125.7 (CH), 135.6 (CH), 140.9, 145.3, 147.4
(CH, pyridine ortho carbon), 148.7 (CH, pyridine ortho carbon),
154.5, 164.2, 164.4. Anal. Calcd for C30H37N5O2Si2W: C, 48.71;
H, 5.04; N, 9.47. Found: C, 48.73; H, 5.02; N, 9.16.
W(NPh)(o-(Me3SiN)2C6H4)(PMe3)(py)(η2-OCH(Ph)) (8). To a
solution of W(NPh)(o-(Me3SiN)2C6H4)(py)2 (0.119 g, 0.17 mmol)
in Et2O (2 mL) was added PMe3 dropwise until an orange-brown
color was achieved. Benzaldehyde (45 mg, 0.42 mmol) was added,
and the solution turned deep red concomitant with the deposition
of a red powder. This powder was isolated from the supernatant to
give 17.6 mg of product. Pentane (2 mL) was added to the
supernatant, and this solution was stored at -30 °C for 24 h,
resulting in the deposition of more red powder. Total yield: 51.5
mg, 38%. 1H NMR (300 MHz, 25 °C, C6D6): δ 0.13 (9H, SiMe3),
0.23 (9H, SiMe3), 0.95 (d, 9H, JPH ) 9.5 Hz, PMe3), 5.91 (d, 1H,
JPH ) 6.9 Hz, CHO), 6.59-6.95 (m, 15H), 7.13 (m, 2H, phe-
nylimido meta protons), 7.37 (d, 2H, JHH ) 7.1 Hz, phenylimido
ortho protons). 31P{1H} NMR (121 MHz, 25 °C, C6D6): δ -4.15
(JPW ) 322 Hz). 13C{1H} NMR (75 MHz, 25 °C, C6D6): δ 3.44
(SiMe3), 4.32 (SiMe3), 14.6 (d, JPH ) 27 Hz, PMe3), 86.2 (d, JPH
) 12.8 Hz, CHO), 115.1 (CH), 117.7 (CH), 118.6 (CH), 120.32
(CH), 123.3 (CH), 123.8 (CH), 126.5 (CH), 127.0 (CH), 127.1 (CH),
127.2 (CH), 127.3 (CH), 138.4 (CH), 146.7, 149.5, 153.1, 156.5.
Anal. Calcd for C33H47N4OPSi2W: C, 50.38; H, 6.02; N, 7.17.
Found: C, 48.0; H, 5.61; N, 6.93. It is likely that the temperature
sensitivity of 8 is responsible for the inconsistent analytical results.
W(NPh)(o-(Me3SiN)2C6H4)(PMe3)(py)(η2-OCH(C6H4-p-
Me)) (9). To a toluene solution (2 mL) of W(NPh)(o-(Me3-
SiN)2C6H4)(py)2 (0.214 g, 0.31 mmol) was added PMe3 (0.0396 g,
0.52 mmol). The solution immediately turned color from purple to
brown-orange. The addition of p-tolualdehyde (0.0381 g, 0.31
mmol) dissolved in toluene (1 mL) to this solution resulted in an
immediate color change to red. After 5 min of stirring, the toluene
was removed in vacuo, and the resultant red oil was rinsed with
pentane (5 mL) to give 0.0577 g of red powder. The pentane
washings were stored at -30 °C for 24 h, resulting in the deposition
W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)(CMe3)-o-C5H4N) (10).
Pinacolone (60 µL, 0.48 mmol) was added to an Et2O (2 mL)
solution of W(NPh)(o-(Me3SiN)2C6H4)(py)2 (0.165 g, 0.24 mmol).
The purple solution quickly turned deep green. After 1 min, excess
CH2Cl2 was added. The solution was allowed to stir for 2 h, during
which time it became deep red in color. The Et2O was removed in
vacuo, and the resulting solids were dissolved in pentane (3 mL)
and filtered through a column of Celite (0.5 cm × 1 cm) supported
on glass wool. The deep-red solution was stored at -30 °C for 24
h, resulting in the deposition of red crystals (0.0272 g, 15.3% yield).
1H NMR (300 MHz, 25 °C, C6D6): δ 0.37 (s, 9H, SiMe3), 0.67 (s,
9H, SiMe3), 1.06 (s, 9H, CMe3), 1.41 [s, 3H, C(O)Me], 6.23 (m,
1H, pyridine meta proton), 5.53-6.63 (m, 4H, aryl protons), 6.68
(br t, 1H, JHH ) 7.5 Hz, phenylimido para proton), 6.85 (m, 1H,
o-phenylenediamine ring proton), 7.07 (d, 1H, JHH ) 7.8 Hz,
o-phenylenediamine ring proton), 7.22 (t, 2H, JHH ) 8.2 Hz,
phenylimido meta protons), 7.55 (d, 2H, JHH ) 6.5 Hz, phenylimido
ortho protons), 8.24 (br d, 1H, JHH ) 5.6 Hz, pyridine ortho proton).
13C{1H} NMR (75 MHz, 25 °C, C6D6): δ 3.04 (SiMe3), 3.19
(SiMe3), 17.6 [C(O)Me], 27.2 (CMe3), 34.8 (CMe3), 95.0 [C(O)-
Me], 120.3 (CH), 120.4 (CH), 120.5 (CH), 121.1 (CH), 122.4 (CH),
122.7 (pyridine ring meta carbon), 126.5 (phenylimido ortho
carbon), 127.1 (phenylimido para carbon), 128.1 (phenylimido meta
carbon), 138.1 (CH), 145.9, 149.9 (CH, pyridine ortho carbon),
150.4, 154.1, 159.8. HRMS (EI) calcd for C29H43ClN4OSi2W:
738.2174 [M]+. Found: 738.2149. Anal. Calcd for C29H43ClN4-
OSi2W: C, 47.12; H, 5.86; N, 7.58. Found: C, 47.16; H, 5.60; N,
7.26.
W(NPh)(o-(Me3SiN)2C6H4)Cl2(py) (11). To a suspension of
W(NPh)(o-(Me3SiN)2C6H4)Cl2 (0.106 g, 0.18 mmol) in pentane (1
mL) was added a pentane (1 mL) solution containing pyridine
(0.026 g, 0.33 mmol). The brown suspension quickly turned purple.
After 1 h of stirring, the solid was allowed to settle, and the
supernatant was decanted away from a maroon powder (0.059 g,
1
48% yield). H NMR (300 MHz, 25 °C, C7D8): δ 0.42 (s, 18H,
SiMe3), 6.26 (br t, 2H, JHH ) 5.8 Hz, pyridine meta protons), 6.53
(m, 1H, pyridine para proton), 6.56 (m, 2H, o-phenylenediamine
ring protons), 6.65 (m, 1H, phenylimido para proton), 6.78 (m, 2H,
o-phenylenediamine ring protons), 7.21 (m, 2H, phenylimido meta
protons), 7.60 (d, 2H, JHH ) 7.4 Hz, phenylimido ortho protons),
8.86 (d, 2H, JHH ) 4.9 Hz, pyridine ortho protons). 13C{1H} NMR
(75 MHz, 25 °C, C7D8): δ 1.7 (SiMe3), 120.1 (CH, o-phenylene-
diamine ring carbons), 123.1 (pyridine meta carbons), 123.3 (CH,
o-phenylenediamine ring carbons), 127.0 (CH, phenylimido ortho
carbons), 128.1 (CH, phenylimido meta carbons), 128.5 (CH,
phenylimido para carbon), 137.1 (CH, pyridine para carbon), 147.1,
151.8 (pyridine ortho carbons), 154.1. Anal. Calcd for C23H32N4-
Cl2Si2W: C, 40.90; H, 4.77; N, 8.29. Found: C, 39.51; H, 4.34;
N, 8.13.
X-ray Crystallography. Data for 1, 3, and 4 were collected at
the University of Florida on a Siemens SMART PLATFORM
equipped with a charge-coupled-device (CCD) area detector and a
graphite monochromator utilizing Mo KR radiation at 173(2) K.
1
of more red powder. Total yield 0.0677 g, 27% yield. H NMR
(300 MHz, 25 °C, C6D6): δ 0.137 (SiMe3), 0.238 (SiMe3), 0.98
Inorganic Chemistry, Vol. 44, No. 25, 2005 9515

Hayton et al.
Table 1. X-ray Crystallographic Data for Complexes 1, 3, 4, 6‚1/2C5H12, 7, 9, and 10‚1/2C5H12
crystal data
1
3
4
6‚1/2C5H12
empirical formula
cryst habit, color
cryst size (mm)
cryst syst
space group
vol (Å3)
a (Å)
b (Å)
c (Å)
C32H37N2Si2W
plate, red
0.23 × 0.15 × 0.03
monoclinic
P21/n
3127.3(2)
12.5177(5)
15.6686(7)
15.9709(7)
90
C24H37N3Si2W
plate, brown
0.17 × 0.15 × 0.03
triclinic
C30H46N4O2Si2W
plate, red
0.20 × 0.17 × 0.17
triclinic
C33H52N4O2Si2W‚1/2C5H12
block, red
0.20 × 0.32 × 0.40
triclinic
P1h
P1h
P1h
2619.0(3)
13.1319(8)
14.0221(9)
15.0036(9)
72.410(1)
84.247(1)
89.938(1)
2
1626.3(2)
10.0899(6)
11.8107(8)
14.1959(9)
95.094(1)
97.433(1)
102.417(1)
2
1970.4(3)
10.1728(9)
10.9145(1)
20.648(2)
103.360(1)
93.943(1)
115.795(1)
2
R (deg)
â (deg)
93.285(1)
90
2
γ (deg)
Z
fw (g/mol)
703.68
1.495
3.795
1408
607.60
1.541
4.517
1216
734.74
1.500
3.657
744
819.8
1.370
3.026
834
density (calcd) (Mg/m3)
abs coeff (cm-1
F000
)
radiation
Mo KR, 0.710 73 Å
Mo KR, 0.710 73 Å
Mo KR, 0.710 73 Å
Mo KR, 0.710 73 Å
Data Refinement
R1 ) 0.030,
final R indicesa
R1 ) 0.021,
wR2 ) 0.049
0.51 and -0.33
R1 ) 0.056,
wR2 ) 0.092
1.30 and -1.07
R1 ) 0.025,
wR2 ) 0.068
1.83 and -1.41
wR2 ) 0.066
largest diff. peak
and hole (e-Å-3
0.742 and -0.841
)
crystal data
7
9
10‚1/2C5H12
empirical formula
cryst habit, color
cryst size (mm)
cryst syst
space group
vol (Å3)
a (Å)
b (Å)
c (Å)
C30H37N5O2Si2W
rectangular slab, red
C34H49N4OPSi2W
irregular, red
0.10 × 0.16 × 0.10
monoclinic
P21/n
7231.6(5)
20.1063(9)
12.3263(5)
29.989(1)
90
C29H43ClN4OSi2W‚1/2C5H12
multifaceted block, red
0.04 × 0.08 × 0.14
0.18 × 0.22 × 0.34
tetragonal
I1/a
orthorhombic
Pbc21
12484(1)
30.267(2)
30.267(2)
13.6276(7)
90
90
90
16
7014.7(5)
9.3024(4)
23.567(1)
31.998(1)
90
90
90
8
R (deg)
â (deg)
103.343(1)
90
8
γ (deg)
Z
fw (g/mol)
739.68
1.574
3.813
800.77
1.471
3.337
3248
775.23
1.468
3.467
density (calcd) (Mg/m3)
abs coeff (cm-1
F000
)
5920
3144
radiation
Mo KR, 0.710 73 Å
Mo KR, 0.710 73 Å
Mo KR, 0.710 73 Å
Data Refinement
R1 ) 0.028,
wR2 ) 0.063
1.28 and -1.04
final R indicesb
R1 ) 0.039,
wR2 ) 0.090
2.35 and -0.84
R1 ) 0.039,
wR2 ) 0.078
1.54 and -0.84
largest diff. peak
and hole (e-Å-3
)
2
2
4
2
a Number of observed reflections: For 1, 7161 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.037p)2
2
2
2
2
4
2
+ 0.31p]-1, p ) [Fo + 2Fc ]/3. For 3, 11 758 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.037p)2 +
2
2
2
2
4
2
0.31p]-1, p ) [Fo + 2Fc ]/3. For 4, 7205 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0265p)2]-1, p
) [Fo + 2Fc ]/3. For 6‚1/2C5H12, 8897 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|) |/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0450p)2
+
2
2
2
2
4
2
1.9216p]-1, p ) [Fo + 2Fc ]/3. b Number of observed reflections: For 7, 6060 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/
2
2
2
2
4
2
2
2
2
∑wFo ]1/2, w ) [σ2Fo + (0.0473p)2 + 43.7649p]-1, p ) [Fo + 2Fc ]/3. For 9, 17 910 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|) |/∑|Fo|, wR2 ) [∑w(|Fo|
-
2
4
2
2
2
|Fc| )2/∑wFo ]1/2, w ) [ σ2Fo + (0.0191p)2 + 9.5164p]-1, p ) [Fo + 2Fc ]/3. For 10‚1/2C5H12, 16 526 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 )
2
2
4
2
2
2
[∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0381p)2 + 3.3258p]-1, p ) [Fo + 2Fc ]/3.
For each, a hemisphere of data (1381 frames) was collected using
the ω-scan method (0.3° frame width). The first 50 frames were
remeasured at the end of data collection to monitor the instrument
and crystal stability (maximum correction on I was <1%).
Absorption corrections by integration were applied on the basis of
measured indexed crystal faces. The structures were solved by the
direct methods in SHELXTL529 and refined using full-matrix least
squares on F2. The non-H atoms were treated anisotropically,
whereas the hydrogen atoms were calculated in ideal positions and
were riding on their respective carbon atoms. For 1, a total of 349
parameters were refined in the final cycle of refinement using 7161
reflections with I >2σ(I) to yield R1 and wR2 values of 2.08%
and 4.87%, respectively. For 3, the asymmetric unit consisted of
two independent molecules. A total of 589 parameters were refined
in the final cycle of refinement using 11 758 reflections with I >2σ-
(I) to yield R1 and wR2 values of 3.00% and 6.55%, respectively.
For 4, a total of 367 parameters were refined in the final cycle of
refinement using 7205 reflections with I >2σ(I) to yield R1 and
wR2 values of 5.59% and 9.23%, respectively.
The crystal structures of compounds 6, 7, 9, and 10 were
determined as follows, with exceptions noted in subsequent
paragraphs. The crystal was mounted in a nylon cryoloop from
(29) Sheldrick, G. M. SHELXTL5; Nicolet XRD Corp.: Madison, WI, 1995.
9516 Inorganic Chemistry, Vol. 44, No. 25, 2005

Coupling of an Aldehyde or Ketone to Pyridine
Paratone-N oil under an argon gas flow. The data were collected
on a Bruker SMART APEX II CCD diffractometer, with a KRYO-
FLEX liquid nitrogen vapor cooling device. All data were collected
at 141 K. The instrument was equipped with a graphite monochro-
matized Mo KR X-ray source (λ ) 0.710 73 Å), with MonoCap
X-ray source optics. A hemisphere of data was collected using ω
scans, with 5-s frame exposures and 0.3° frame widths. Data
collection and initial indexing and cell refinement were handled
using APEX II software.30 Frame integration, including Lorentz-
polarization corrections, and final cell parameter calculations were
carried out using SAINT+ software.31 The data were corrected for
absorption using the SADABS program.32 The decay of reflection
intensity was monitored via an analysis of redundant frames. The
structure was solved using direct methods and difference Fourier
techniques. All hydrogen atom positions were idealized and rode
on the atom they were attached to. The final refinement included
anisotropic temperature factors on all non-hydrogen atoms. Structure
solution, refinement, graphics, and creation of publication materials
were performed using SHELXTL.33
For compound 6, a total of 426 parameters were refined in the
final cycle of refinement using 8897 reflections with I >2σ(I) to
yield R1 and wR2 values of 2.53% and 6.76%, respectively. In
addition, an n-pentane molecule was found to occupy an inversion
center in the lattice, with the inversion center lying on the midpoint
between the third and fourth carbon atoms of the n-pentane
molecule. This disorder was modeled as two full occupancy carbon
atom positions (C35 and C36) and one one-half occupancy carbon
atom position (C34). Carbon atoms C34, C35, and C36 were refined
anisotropically, but without their associated hydrogen atom posi-
tions. For 7, a total of 375 parameters were refined in the final
cycle of refinement using 6060 reflections with I >2σ(I) to yield
R1 and wR2 values of 3.91% and 8.97%, respectively. For 9, a
total of 803 parameters were refined in the final cycle of refinement
using 17 910 reflections with I >2σ(I) to yield R1 and wR2 values
of 2.75% and 6.28%, respectively. For compound 10, a total of
761 parameters (with one restraint) were refined in the final cycle
of refinement using 16 526 reflections with I >2σ(I) to yield R1
and wR2 values of 3.91% and 7.78%, respectively. In addition,
after all atomic positions were assigned, and refined anisotropically
to convergence, a significant residual peak (∼15 e-Å-3) remained
approximately 2.1 Å away from the tungsten atom. Since the peak
occurred at a chemically anomalous position, it was assumed to
result from a small twin. This residual peak was observed in each
of the crystallographically independent tungsten molecules in the
structure. The residual peaks were refined as partial occupancy
tungsten atoms, with variable site-occupancy factors. The sum of
the site-occupancy factors for the major and minor tungsten
components was fixed at 1.0 for each independent molecule. In
addition, the occupancies of the major and minor components of
each independent molecule were constrained to be equivalent. This
final refinement resulted in a site occupancy of 6.16(7)% for the
minor twin component. A summary of relevant crystallographic
data is found in Table 1, and full details of all crystallographic
analyses are provided in the Supporting Information.
Acknowledgment. We are grateful to the National
Science Foundation (Grant No. CHE-0094404) and the
LDRD program at Los Alamos National Laboratory for
support of this work. T.W.H. acknowledges NSERC (Canada)
for a postdoctoral fellowship. We also acknowledge Corey
B. Wilder for preliminary studies in this area.
Supporting Information Available: Complete details of the
X-ray crystallographic studies as CIF files. This material is available
free of charge via the Internet at http://pubs.acs.org.
(30) APEX II, version 1.08; Bruker AXS, Inc.: Madison, WI, 2004.
(31) SAINT+, version 7.06; Bruker AXS, Inc.: Madison, WI, 2003.
(32) Sheldrick, G. M. SADABS, version 2.03; University of Go¨ttingen:
Go¨ttingen, Germany, 2001.
(33) SHELXTL, version 5.10; Bruker AXS, Inc.: Madison, WI, 1997.
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