Synthesis and reactivity of tris(imido)rhenium complexes containing rhenium-main group element bonds. Silicon-carbon bond activations of PhSiH 3 by silyl complexes

Article abstract of DOI:10.1021/ic030282e

The synthesis and reactivity of a series of complexes of the (DippN=) ₃Re (Dipp = 2,6-ⁱPr₂C₆H₃) fragment are reported. The anionic, Re(V) complex (THF)₂Li(μ, μ-NDiPP)₂Re(=NDipp) (1), prepared by the reaction of (DippN=) ₃ReCl with (THF)₃LiSi(SiMe₃)₃ or ^tBuLi (2 equiv) in the presence of THF (4 equiv), served as an important starting material for the synthesis of rhenium-element-bonded complexes. For example, treatment of 1 with ClSiR₃ gave the corresponding silyl complexes (DippN=)₃ReSiR₃ (SiR ₃ = SiMe₃ (2a), SiHPh₂ (2b), SiH₂Ph (2c)). Complexes 2a-c are thought to exist in equilibrium between the Re(VII) (DippN=)₃ReSiR₃ and Re(V) (DippN=)₂ReN(SiR ₃)-Dipp isomers. Complexes 2a,b reacted with PhSiH₃ to give reaction mixtures that included 2c, Ph₂SiH₂, SiH ₄, and C₆H₆. The silane and organic products arise from Si-C bond formation and cleavage. Treatment of 2a with CO gave (DippN=)₂Re[N(SiMe₃)Dipp](CO) (3), which appears to result from trapping of the reactive Re(V) isomer of 2a by CO. Complex 1 reacted with the main group halides Mel, Ph₃GeCl, Me₃SnCl, Ph ₂PCl, and PhSeCl to give the corresponding rhenium complexes (DippN=)₃ReER_n (ER_n = Me (4), GePh₃ (5), SnMe₃ (6), PPh₂ (7), SePh (8)) in high yields. X-ray diffraction data for 5 indicate that the germyl ligand is bonded to rhenium, but positional disorder of the phenyl and Dipp groups prevented refinement of accurate metric parameters.

Full text of DOI:10.1021/ic030282e

Inorg. Chem. 2004, 43, 4353−4362
Synthesis and Reactivity of Tris(imido)rhenium Complexes Containing
Rhenium−Main Group Element Bonds. Silicon−Carbon Bond Activations
of PhSiH by Silyl Complexes
3
John Gavenonis and T. Don Tilley*
Department of Chemistry, UniVersity of California at Berkeley, Berkeley, California 94720-1460
Received September 22, 2003
i
The synthesis and reactivity of a series of complexes of the (DippNd)3Re (Dipp ) 2,6-Pr2C H ) fragment are
6
3
reported. The anionic, Re(V) complex (THF)2Li(µ,µ-NDipp)2Re(dNDipp) (1), prepared by the reaction of
(DippNd)3ReCl with (THF)3LiSi(SiMe3)3 or tBuLi (2 equiv) in the presence of THF (4 equiv), served as an important
starting material for the synthesis of rhenium−element-bonded complexes. For example, treatment of 1 with ClSiR
3
gave the corresponding silyl complexes (DippNd)3ReSiR (SiR ) SiMe (2a), SiHPh (2b), SiH Ph (2c)). Complexes
3
3
3
2
2
2a−c are thought to exist in equilibrium between the Re(VII) (DippNd)3ReSiR and Re(V) (DippNd)2ReN(SiR )-
3
3
Dipp isomers. Complexes 2a,b reacted with PhSiH to give reaction mixtures that included 2c, Ph2SiH , SiH , and
3
2
4
C H . The silane and organic products arise from Si−C bond formation and cleavage. Treatment of 2a with CO
6
6
gave (DippNd)2Re[N(SiMe3)Dipp](CO) (3), which appears to result from trapping of the reactive Re(V) isomer of
2a by CO. Complex 1 reacted with the main group halides MeI, Ph3GeCl, Me3SnCl, Ph2PCl, and PhSeCl to give
the corresponding rhenium complexes (DippNd)3ReER (ER ) Me (4), GePh3 (5), SnMe3 (6), PPh2 (7), SePh
n
n
(8)) in high yields. X-ray diffraction data for 5 indicate that the germyl ligand is bonded to rhenium, but positional
disorder of the phenyl and Dipp groups prevented refinement of accurate metric parameters.
Introduction
silicon chemistry has been extensively studied (especially
for reactions such as σ-bond metathesis),1,12 comparatively
fewer complexes containing germyl,3,13,14 stannyl,3,4,14-16
phosphido,17,18 and selenido2 ligands have been described.
In a search for new reactivity for σ-bonds involving d0
transition metals, we have investigated complexes containing
silyl12,14,19 and stannyl14,15 ligands. Much of this chemistry
is derived from complexes containing a bis(cyclopentadienyl)
The chemistry of compounds containing a bond between
a d0 transition metal and a heavy main group element (from
the third period and beyond) is relatively unexplored.1-7 Such
compounds are of interest for their potential to display new
structures and bonding modes and because they are expected
to be highly reactive.8 For example, thermochemical data
reported by Marks and co-workers indicate that σ-bonds
between lanthanides and main group element ligands are
relatively weak9,10 and should readily participate in reactions
such as σ-bond metathesis.11 While d0 transition metal-
(9) Nolan, S. P.; Porchia, M.; Marks, T. J. Organometallics 1991, 10,
1450.
(10) Nolan, S. P.; Stern, D.; Marks, T. J. J. Am. Chem. Soc. 1989, 111,
7844.
(11) Forsyth, C. M.; Nolan, S. P.; Marks, T. J. Organometallics 1991, 10,
2543.
(12) Tilley, T. D. Acc. Chem. Res. 1993, 26, 22.
(13) Nikonov, G. I.; Churakov, A. V.; Antipin, M. Y. Organometallics
2003, 22, 2178.
* Author to whom correspondence should be addressed. E-mail: tdtilley@
socrates.berkeley.edu.
(1) Corey, J.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175.
(2) Arnold, J. Prog. Inorg. Chem. 1995, 43, 353.
(3) Sharma, H. K.; Haiduc, I.; Pannell, K. H. In Chemistry of Organic
Germanium, Tin and Lead Compounds; Rappoport, Z., Ed.; John Wiley
& Sons Ltd.: Chichester, U.K., 2002; Vol. 2, p 1241.
(4) Holt, M. S.; Wilson, W. L.; Nelson, J. H. Chem. ReV. 1989, 89, 11.
(5) Huttner, G.; Evertz, K. Acc. Chem. Res. 1986, 19, 406.
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2002, 102, 1851.
(14) Woo, H.-G.; Freeman, W. P.; Tilley, T. D. Organometallics 1992,
11, 2198.
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J. Inorg. Chem. 1999, 825.
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Chem. 2000, 608, 21.
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Chem. 1995, 34, 2461.
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10.1021/ic030282e CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/09/2004
Inorganic Chemistry, Vol. 43, No. 14, 2004 4353

Gavenonis and Tilley
ancillary ligand framework. Given the formal 1σ, 2π donor
analogy between cyclopentadienyl and imido ligands,20,21 and
the robust nature of the early metal imido bond,22,23
complexes that possess both imido and main group element
ligands are interesting candidates for exploration. Generally,
however, complexes containing both imido ligands and
reactive σ-bonds are rare. Examples of d0 silyl complexes
that contain imido ligands have been reported for hafnium,24
niobium,25-28 tantalum,26-36 molybdenum,37,38 and tungsten.37
Few d0 complexes containing both imido ligands and
reactive σ-bonds (e.g., M-H and M-Si) have been reported
for rhenium, although the chemistry of rhenium imido
complexes has been extensively investigated.39 In 1981, La
Monica et al. reported the Re(V) (d2) complexes (p-
MeC6H4Nd)Re(PPh3)2(H)(Cl)(X) (X ) Cl, OMe, OEt), the
first examples of compounds containing both imido and
hydride ligands.40 More recently, Schrock and co-workers
described the Re(V) imido hydride complex (DippNd)2ReH-
(PMe2Ph)2 (Dipp ) 2,6-iPr2C6H3) and the high oxidation state
(Re(VII)) complex (DippNd)3ReH, though some uncertainty
remains regarding the structure of the latter compound.41
Herein we report complexes of the (DippNd)3Re fragment
containing silyl and other main group element ligands and
the reactivity of the silyl complexes toward silane substrates.
Figure 1. ORTEP diagram of (THF)2Li(µ,µ-NDipp)2Re(dNDipp) (1).
thesis of silyl derivatives via salt metathesis reactions
of this compound. However, when (DippNd)3ReCl was
treated with (THF)3LiSi(SiMe3)3, (THF)2LiSi(tBu)Ph2, or
(THF)2LiSiHMes2, the corresponding silyl complexes were
not obtained. Instead, the reduced Re(V) compound (THF)2Li-
(µ,µ-NDipp)2Re(dNDipp) (1) was formed in high yield (74%
isolated yield for the reaction with (THF)3LiSi(SiMe3)3) along
with the corresponding chlorosilane (eq 1). In an NMR tube
scale reaction of (DippNd)3ReCl with KSi(SiMe3)3 (benzene-
d6, room temperature, <1 min), an insoluble precipitate was
obtained and ClSi(SiMe3)3 was the only product observed
by 1H NMR spectroscopy. Thus, the precipitate in the
reaction mixture is likely due to an insoluble, reduced
complex that might be the potassium analogue of 1. When
THF-d8 was used as the reaction solvent, multiple products
Results and Discussion
Preparation of an Anionic Re(V) Complex. The tris-
(imido)rhenium chloride complex (DippNd)3ReCl (Dipp )
2,6-iPr2C6H3), reported by Schrock and Williams,41 appeared
to be a convenient starting material for the preparation of
imido silyl complexes. Initial efforts focused on the syn-
(20) Gibson, V. C. J. Chem. Soc., Dalton Trans. 1994, 1607.
(21) Gibson, V. C.; Poole, A. D.; Siemeling, U.; Williams, D. N.; Clegg,
W.; Hockless, D. C. R. J. Organomet. Chem. 1993, 462, C12.
(22) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; John Wiley
& Sons: New York, 1988.
(23) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.
(24) Castillo, I.; Tilley, T. D. J. Organomet. Chem. 2002, 643-644, 431.
(25) Nikonov, G. I.; Mountford, P.; Dubberley, S. R. Inorg. Chem. 2003,
42, 258.
1
were observed in the reaction mixture (by H NMR spec-
troscopy), indicating that the reduced potassium complex did
not form cleanly.
(26) Nikonov, G. I.; Mountford, P.; Ignatov, S. K.; Green, J. C.; Leech,
M. A.; Kuzmina, L. G.; Razuvaev, A. G.; Rees, N. H.; Blake, A. J.;
Howard, J. A. K.; Lemenovskii, D. A. J. Chem. Soc., Dalton Trans.
2001, 2903.
(27) Nikonov, G. I. J. Organomet. Chem. 2001, 635, 24.
(28) Nikonov, G. I.; Mountford, P.; Green, J. C.; Cooke, P. A.; Leech, M.
A.; Blake, A. J.; Howard, J. A. K.; Lemenovskii, D. A. Eur. J. Inorg.
Chem. 2000, 1917.
(29) Gavenonis, J.; Tilley, T. D. J. Am. Chem. Soc. 2002, 124, 8536.
(30) Gavenonis, J.; Tilley, T. D. Organometallics 2002, 21, 5549.
(31) Burckhardt, U.; Casty, G. L.; Gavenonis, J.; Tilley, T. D. Organo-
metallics 2002, 21, 3108.
While reactions with silyl anions did not yield the desired
products containing Re-Si bonds, complex 1 was envisioned
as a precursor to silyl complexes via salt metathesis reactions
with halosilanes. Therefore, a more readily available reducing
agent was desired for the preparation of 1. Fortunately,
(DippNd)3ReCl was found to react with tBuLi (2 equiv) in
the presence of THF (4 equiv) in toluene to afford 1 in 70%
yield (eq 1). Thus, this reaction is approximately as efficient
as the analogous reaction with (THF)3LiSi(SiMe3)3, but tBuLi
is much preferred as the reagent to employ in the synthesis
of 1, as it is commercially available.
(32) Burckhardt, U.; Casty, G. L.; Tilley, T. D.; Woo, T. K.; Rothlisberger,
U. Organometallics 2000, 19, 3830.
(33) Gountchev, T. I.; Tilley, T. D. J. Am. Chem. Soc. 1997, 119, 12831.
(34) Gavenonis, J.; Tilley, T. D. Organometallics 2004, 23, 31.
(35) Wu, Z.; Xue, Z. Organometallics 2000, 19, 4191.
(36) Dubberley, S. R.; Ignatov, S. K.; Rees, N. H.; Razuvaev, A. G.;
Mountford, P.; Nikonov, G. I. J. Am. Chem. Soc. 2003, 125, 642.
(37) Casty, G. L.; Tilley, T. D.; Yap, G. P. A.; Rheingold, A. L.
Organometallics 1997, 16, 4746.
(38) Chen, T.; Sorasaenee, K. R.; Wu, Z.; Diminnie, J. B.; Xue, Z. Inorg.
Chem. Acta 2003, 345, 113.
X-ray-quality crystals of 1 were obtained by cooling a
concentrated pentane solution of complex 1 to -35 °C. The
molecular structure is shown in Figure 1, and important bond
distances and angles are listed in Table 1. One of the imido
(39) Roma˜o, C. C.; Ku¨hn, F. E.; Herrmann, W. A. Chem. ReV. 1997, 97,
3197.
(40) La Monica, G.; Cenini, S.; Porta, F. Inorg. Chem. Acta 1981, 48, 91.
(41) Williams, D. S.; Schrock, R. R. Organometallics 1993, 12, 1148.
4354 Inorganic Chemistry, Vol. 43, No. 14, 2004

Tris(imido)rhenium Complexes
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
(THF)2Li(µ,µ-NDipp)2Re(dNDipp) (1)
Bond Lengths
Re(1)-N(1)
Re(1)-N(2)
Re(1)‚‚‚Li(1)
Li(1)-O(1)
1.737(5)
1.794(3)
2.81(1)
N(1)-C(1)
N(2)-C(8)
N(2)-Li(1)
1.410(8)
1.397(5)
2.297(10)
1.978(8)
Bond Angles
Re(1)-N(1)-C(1)
Re(1)-N(2)-C(8)
N(1)-Re(1)-N(2)
N(2)-Re(1)-N(2)
Re(1)-N(2)-Li(1)
180.0
Li(1)-N(2)-C(8)
N(2)-Li(1)-N(2)
O(1)-Li(1)-O(1)
O(1)-Li(1)-N(2)
O(1)-Li(1)-N(2)
120.6(3)
79.0(4)
103.8(6)
98.0(2)
153.4(3)
125.5(1)
109.0(2)
86.0(2)
Cooling a toluene-d8 solution of 2a to -95 °C revealed
only one set of broadened imido ligand resonances by H
144.4(2)
1
NMR spectroscopy, which suggests the presence of a
rhenium-bound silyl ligand (A, eq 2). However, given the
observed behavior of 1, it is also possible that 2a is highly
fluxional, with the silyl group migrating rapidly between the
nitrogen atoms. In this case, complex 2a might be described
as having a ground-state structure with a nitrogen-bound silyl
group and a Re(V) metal center (B). A third possibility
involves an equilibrium between structures A and B in which
the silyl group rapidly migrates between the rhenium and
nitrogen atoms. This type of transformation is thought to
occur as the initial step in the thermal decomposition
of Cp*(DippNd)Ta[Si(SiMe3)3]H to Cp*(DippNd)Ta-
[CH2Si(SiMe3)2SiMe2H]H,31 in which the hydride ligand
migrates to the imido nitrogen to give the Ta(III) compound
Cp*Ta[N(H)Dipp]Si(SiMe3)3. Schrock and Williams have
suggested a related dynamic process for the hydride complex
(DippNd)3ReH.41 The latter compound features a 1H NMR
resonance at 7.22 ppm (which is reasonable for either a
Re-H or N-H group), but no νReH or νNH stretches were
observed in the IR spectrum. Attempts to obtain X-ray-
quality crystals of 2a have been complicated by the high
solubility of this compound in common organic solvents and
the associated difficulty in growing single crystals. However,
the X-ray crystal structures of (DippNd)3ReMe44 and
(DippNd)3ReGePh3 (5, vide infra) reveal rhenium-bound
one-electron ligands, and this suggests that 2a-c possess
ground-state structures with Re-Si bonds (structure A).
The 29Si NMR data for complexes 2a-c do not allow a
distinction between either structure type. While the 29Si NMR
shift of 2a (34.31 ppm) is somewhat downfield from the
values for the nitrogen-bound silyl groups in (DippNd)2Re-
[N(SiMe3)Dipp](CO) (24.36 ppm, 3, vide infra), DippN-
(SiMe3)H (3.70 ppm), and [DippN(SiMe3)Li]2 (-11.52 ppm),
these differences do not appear to be significant enough to
draw a meaningful conclusion regarding the ground-state
structure of 2a. Furthermore, the 29Si NMR chemical shift
of complex 2b (14.97 ppm) appears in the range of
complexes that contain nitrogen-bound silyl groups, and the
value for 2c (-16.52 ppm) appears upfield of all the values
listed.
ligands is terminal, with a RedN bond length of 1.737(5) Å
and a Re(1)-N(1)-C(1) bond angle of 180.0°. Two of the
imido ligands bridge the Re and Li atoms, the latter of which
is bonded to two THF ligands. This structure type has
previously been observed for the rhenium imido complex
(tmeda)Li(µ,µ-NtBu)2Re(dNtBu)2 (tmeda ) tetramethyl-
ethylenediamine).42 In contrast, the related complex [N(PPh3)2]-
[Re(dNDipp)3] contains well-separated ion pairs.41
Even though the X-ray crystal structure of 1 reveals imido
ligands that bridge a Li(THF)2 group, only one set of imido
1
ligand resonances were found in the H NMR spectrum of
1, indicating approximate C3V symmetry. This observation
suggests the presence of separated ion pairs in solution, or
a rapid exchange between equivalent structures via migration
of the Li(THF)2 group between equivalent pairs of imido
ligands. However, cooling a pentane-d12 solution to -105
°C revealed only one set of broadened imido ligand
resonances, implying that the exchange process is still rapid
at -105 °C. While the 1H NMR spectrum of the analogous
complex (tmeda)Li(µ,µ-NtBu)2Re(dNtBu)2 also contains
only one set of ligand resonances at room temperature,
cooling a toluene-d8 solution of this compound to -50 °C
revealed two distinct sets of resonances for the bridging and
terminal imido groups.43
Synthesis and Reactivity of Silyl Complexes. Since
reactions of lithium and potassium silyl reagents with
(DippNd)3ReCl did not provide the desired complexes
containing Re-Si bonds, silyl complexes were prepared via
salt metathesis reactions of 1 with chlorosilanes. Compound
1 cleanly reacted with ClSiMe3, ClSiHPh2, and ClSiH2Ph in
toluene to provide the corresponding silyl complexes
(DippNd)3ReSiR3 (SiR3 ) SiMe3 (2a), SiHPh2 (2b), SiH2Ph
(2c)) in 99%, 61%, and 59% yields, respectively (eq 2).
Alternatively, Me3Si(OSO2CF3) can be used to synthesize
1
2a. The H NMR spectra for all three compounds 2a-c
contain only one set of imido ligand resonances, indicating
pseudo-3-fold symmetry. The 29Si NMR resonances for 2a-c
appear at 34.31, 14.97, and -16.52 ppm, respectively, and
1
compounds 2b,c possess JSiH values of 199 and 201 Hz.
No reaction was observed between 1 and the more hindered
chlorosilanes ClSiPh3 (5 days) and ClSiHMes2 (2 days) in
benzene-d6 at room temperature.
In some cases, chemical reactivity may provide a useful
indication of structure. For example, a compound of structure
type A is expected to possess a nucleophilic silyl group with
(42) Danopoulos, A. A.; Wilkinson, G.; Hussain, B.; Hursthouse, M. B. J.
Chem. Soc., Chem. Commun. 1989, 896.
(43) Danopoulos, A. A.; Longley, C. J.; Wilkinson, G.; Hussain, B.;
Hursthouse, M. B. Polyhedron 1989, 8, 2657.
(44) Herrmann, W. A.; Ding, H.; Ku¨hn, F. E.; Scherer, W. Organometallics
1998, 17, 2751.
Inorganic Chemistry, Vol. 43, No. 14, 2004 4355

Gavenonis and Tilley
silyl anion character.45-47 Such compounds should react with
an alcohol to yield the corresponding silane HSiR3 and a
rhenium alkoxide. However, a compound of structure type
B would be expected to contain an electrophilic silyl group,
which should react with an alcohol to yield a silyl ether as
the organic product. Treatment of 2a with MeOH (1 equiv)
in benzene-d6 (room temperature, 30 min) gave rise to a
1
complex reaction mixture that contained MeOSiMe3 by H
NMR spectroscopy and GCMS. The formation of MeOSiMe3
suggests the presence of an electrophilic silyl group in 2a,
which is consistent with a ground-state, nitrogen-bound
structure (B) or with the rapid equilibrium of eq 2, where
isomer B is much more reactive than A toward MeOH. Given
the spectroscopic, reactivity, and structural data described
above, we favor the latter possibility.
Figure 2. ORTEP diagram of (DippNd)2Re[N(SiMe3)Dipp](CO) (3).
Compound 2a reacted cleanly with CO (1 atm) at room
temperature to provide the Re(V) complex (DippNd)2Re-
[N(SiMe3)Dipp](CO) (3) as a red-brown crystalline solid in
69% yield (eq 3). The νCO stretch at 1927 cm-1 and 13C NMR
resonance at 260.6 ppm are consistent with a rhenium-bound
carbonyl ligand, and multiple Dipp resonances indicate the
loss of apparent C3V symmetry. The result of this reaction
with CO is consistent with both structures A and B for the
starting rhenium complex, assuming an equilibrium between
the rhenium- and nitrogen-bound silyl group structures. A
complex reaction mixture was obtained upon treating a
benzene-d6 solution of 2a with (2,6-Me2C6H3)NtC (room
temperature, 25 min) or DMAP (room temperature, 6 days).
No reaction was observed with the donor ligands PPh3,
OdPPh3, and 4-tBuC5H4N (benzene-d6, 55 °C, 4 h).
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
(DippNd)2Re(DippNSiMe3)(CO) (3)
Bond Lengths
Re(1)-N(1)
Re(1)-N(2)
Re(1)-N(3)
N(2)-C(17)
N(3)-C(29)
2.004(4)
1.759(4)
1.781(4)
1.391(6)
1.371(6)
Re(1)-C(1)
O(1)-C(1)
N(1)-Si(1)
N(1)-C(5)
1.905(5)
1.174(6)
1.741(4)
1.450(6)
Bond Angles
126.5(2)
Re(1)-N(1)-Si(1)
Re(1)-N(1)-C(5)
Re(1)-N(2)-C(17)
Re(1)-N(3)-C(29)
Re(1)-C(1)-O(1)
Si(1)-N(1)-C(5)
N(1)-Re(1)-N(2)
N(1)-Re(1)-N(3)
N(2)-Re(1)-N(3)
C(1)-Re(1)-N(1)
C(1)-Re(1)-N(2)
C(1)-Re(1)-N(3)
116.4(2)
109.4(2)
121.2(2)
98.5(2)
99.3(2)
108.5(2)
114.7(3)
164.0(4)
161.0(4)
169.0(5)
118.8(3)
The reactivity of complexes 2a,b toward substrates
containing H-H and Si-H bonds was evaluated by ex-
posing these complexes to H2 and PhSiH3. A Re(VII) silyl
complex (A) might be expected to react with H2 through a
concerted, four-membered transition state to give HSiMe3
and (DippNd)3ReH.50,51 A Re(V) silylamido complex (B),
on the other hand, should add H2 to give the dihydride
(DippNd)2Re[N(SiR3)Dipp](H)2. This compound could be
a stable product of the reaction, or could eliminate HSiMe3
to yield (DippNd)3ReH. Tilley and Gountchev have ob-
served a related silane elimination that forms a Ta(V) imido
complex.33 However, no reaction was observed between 2a
and H2 (1 atm) at room temperature (benzene-d6), and heating
to 50 °C (12 days) resulted only in the thermal decomposition
of 2a. Hydrogen was not involved in the reaction, as
indicated by the observation of identical 1H NMR resonances
when 2a was heated to 50 °C in the absence of H2 (benzene-
d6, 12 days). Similarly, no reaction was observed between
2b and H2 (1 atm) at 60 °C (5 h, benzene-d6), and heating
to 100 °C resulted in a complex reaction mixture.
X-ray-quality crystals were obtained by cooling a con-
centrated pentane solution of complex 3 to -35 °C. The
molecular structure is shown in Figure 2, and important bond
distances and angles are listed in Table 2. Due to the steric
demands of the imido and amido ligands, the compound
adopts an approximate tetrahedral geometry that is highly
distorted toward a trigonal pyramid. The Re(1)-N(2) and
Re(1)-N(3) bond lengths of 1.759(4) and 1.781(4) Å,
respectively, are well within the expected region for rhenium
imido bonds.22,23,48,49 The Re(1)-N(1) bond length of
2.004(4) and the sum of the angles around the amido nitrogen
(N(1), 360°) are reasonable for a rhenium amido com-
plex.22,23,48,49
Treatment of 2a with PhSiH3 (1 equiv) in benzene-d6
(46 h) gave rise to HSiMe3 (0.70 equiv) and (DippNd)3Re-
SiH2Ph (2c, 0.58 equiv). Only a trace amount of unreacted
PhSiH3 was observed in the reaction mixture. In cyclohexane-
(45) Arnold, J.; Tilley, T. D. J. Am. Chem. Soc. 1987, 109, 3318.
(46) Arnold, J.; Shina, D. N.; Tilley, T. D. Organometallics 1986, 5, 2037.
(47) Tilley, T. D. Organometallics 1985, 4, 1452.
(48) Chisholm, M. H.; Rothwell, I. P. In ComprehensiVe Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;
Pergamon: Oxford, U.K., 1987; Vol. 2, p 161.
(50) Woo, H.-G.; Walzer, J. F.; Tilley, T. D. J. Am. Chem. Soc. 1992,
114, 7047.
(51) Campion, B. K.; Falk, J.; Tilley, T. D. J. Am. Chem. Soc. 1987, 109,
(49) Nugent, W. A.; Haymore, B. L. Coord. Chem. ReV. 1980, 31, 123.
2049.
4356 Inorganic Chemistry, Vol. 43, No. 14, 2004

Tris(imido)rhenium Complexes
Scheme 1
d12, this reaction was observed to produce C6H6 (0.14 equiv;
in benzene-d6 the C6H6 resonance was obscured by the
solvent resonance). After 16 days at room temperature, the
reaction had not gone to completion. With excess PhSiH3
(10 equiv), 3.00 equiv of PhSiH3 were consumed after 47 h
at room temperature, and HSiMe3 (0.71 equiv), SiH4 (0.14
equiv in solution), and Ph2SiH2 (0.94 equiv) were produced.
Under these conditions, 2c was not found among the mixture
of products. After 16 days at room temperature (for the
reaction of 2a with 10 equiv of PhSiH3), 4.71 equiv of
PhSiH3 were consumed, and increased yields of HSiMe3
(0.97 equiv), SiH4 (0.15 equiv in solution), and Ph2SiH2 (1.49
equiv) were observed. When cyclohexane-d12 was used as
the solvent in the reaction of 2a with PhSiH3 (10 equiv, room
temperature, 17 days), 6.17 equiv of PhSiH3 were consumed
and HSiMe3 (1.00 equiv), SiH4 (0.30 equiv in solution),
Ph2SiH2 (2.26 equiv), and C6H6 (0.60 equiv) were formed
(eq 4). The greater observed yields of the silane and organic
products in cyclohexane-d12 (versus benzene-d6) suggest that
the reaction proceeds slightly faster in this solvent, although
the apparent higher yields of some products (such as SiH4)
may be attributed to enhanced solubility. The formation of
SiH4, Ph2SiH2, and C6H6 in the reactions of 2a with PhSiH3
indicates that some type of Si-C bond activation has
occurred. Furthermore, the observation of more than 1 equiv
of Ph2SiH2 shows that this reaction is catalytic with regard
to rhenium. However, none of the Re-containing products
1
could be identified in the reaction mixture (by H NMR
spectroscopy). Similar product distributions have been
observed in the reactions of [Cp*2Ln(µ-H)]2 (Ln ) Sm, Lu)
with PhSiH3.52-54 In these systems, mechanistic studies
indicate that σ-bond metathesis reactions via concerted, four-
membered transition states are responsible for the formation
of products.52
days at room temperature, a total of 6.34 equiv of PhSiH3
was consumed, while Ph2SiH2 (1.60 equiv) and SiH4 (0.07
equiv in solution) formed. Benzene was also formed during
the course of this reaction, but it was not quantified due to
1
the overlap of its H NMR resonance with that of the
benzene-d6 solvent.
The mechanism for the formation of 2c and HSiMe3 in
the reaction of 2a with PhSiH3 is not apparent, and no
intermediate species could be identified by monitoring the
When compound 2b was treated with PhSiH3 (1 equiv)
in benzene-d6 at room temperature, some of the rhenium
complex (0.60 equiv) and most of the PhSiH3 (0.96 equiv)
were consumed, and compound 2c (0.28 equiv) and Ph2SiH2
(0.39 equiv) were observed as products by 1H NMR
spectroscopy (after 29 h). After 19 days at room temperature,
complex 2c was completely consumed, a small amount of
Ph2SiH2 (0.12 equiv) remained, and the amount of 2b had
increased (0.62 equiv present). Thus, the Ph2SiH2 that is
produced in this reaction is eventually converted back to 2b.
When 2b was treated with excess PhSiH3 (10 equiv) at room
temperature (benzene-d6), the rhenium complex and 2.57
equiv of PhSiH3 were completely consumed within 10 h.
Diphenylsilane (0.80 equiv) and SiH4 (0.06 equiv in solution)
were observed as products in the reaction mixture. Over 19
1
reaction progress by H NMR spectroscopy. Possible path-
ways for this reaction are outlined in Scheme 1. In mecha-
nism I, the Re(VII) isomer of 2a (A) reacts with PhSiH3
through a concerted, four-membered transition state to yield
2c and HSiMe3. The exchange of silyl groups via this
concerted σ-bond metathesis pathway is a well-precedented
transformation for high-oxidation state, d0 metal-silyl
complexes50,55,56 in the presence of imido ligands.34 Another
possibility (mechanism II) involves the oxidative addition
of PhSiH3 to the Re(V) isomer (DippNd)2ReN(SiMe3)Dipp
(B) to give the Re(VII) complex (DippNd)2Re[N(SiMe3)-
Dipp](H)(SiH2Ph). This compound could then undergo a 1,2-
elimination of HSiMe3 to produce 2c. The formation of a
metal-imido bond by silane elimination from d0 complexes
(52) Castillo, I.; Tilley, T. D. J. Am. Chem. Soc. 2001, 123, 10526.
(53) Castillo, I.; Tilley, T. D. Organometallics 2001, 20, 5598.
(54) Castillo, I.; Tilley, T. D. Organometallics 2000, 19, 4733.
(55) Woo, H.-G.; Heyn, R. H.; Tilley, T. D. J. Am. Chem. Soc. 1992, 114,
5698.
(56) Woo, H.-G.; Tilley, T. D. J. Am. Chem. Soc. 1989, 111, 3757.
Inorganic Chemistry, Vol. 43, No. 14, 2004 4357

Gavenonis and Tilley
has been previously observed in a tantalum system.33 A third
possibility (mechanism III) involves addition of PhSiH3
across a RedN double bond of the Re(VII) isomer (A) to
generate the bis(imido) complex (DippNd)2Re[N(SiH2Ph)-
Dipp](H)(SiMe3). The addition of silanes across a d0 metal-
imido bond to give a product with silylamido and hydride
ligands has been previously observed.33 This Re(VII) com-
pound could then reductively eliminate HSiMe3 to give
(DippNd)2ReN(SiH2Ph)Dipp, which is expected to exist in
equilibrium with (DippNd)3ReSiH2Ph (2c). A related mech-
anism involving addition of PhSiH3 to a RedN double bond
of the Re(V) isomer (B), followed by 1,2-elimination of
Me3SiH from the resulting DippNdRe[N(SiMe3)Dipp]-
[N(SiH2Ph)Dipp](H) complex is also possible.
solution to -35 °C. Although the structure and connectivity
(including the rhenium-bound germyl ligand) of complex 5
were confirmed by X-ray crystallography, the refinement of
accurate metric parameters was not possible due to severe
positional disorder of the phenyl and Dipp groups.
Benzene-d6 solutions of complex 5 did not react with H2
(1 atm, 140 °C, 2 days), PhSiH3 (1 equiv, 140 °C, 2 days),
CO (1 atm, 140 °C, 2 days), or (2,6-Me2C6H3)NtC (1 equiv,
145 °C, 18 h). Similarly, the trimethylstannyl complex
(DippNd)3ReSnMe3 (6) did not react with H2 (1 atm, 145
°C, 2 days), PhSiH3 (1 equiv, 140 °C, 2 days), CO (1 atm,
125 °C, 27 h), or (2,6-Me2C6H3)NtC (1 equiv, 135 °C, 2
days). In addition, heating benzene-d6 solutions of 6 with
nBu2SnH2 and MesSnH3 (Mes ) 2,4,6-Me3C6H2) to 125 °C
(18 h) and 60 °C (5 days), respectively, resulted in
decomposition of the stannanes without any change to
complex 6. Cooling a toluene-d8 solution of 6 to -92 °C
revealed only one set of broadened ligand resonances (by
1H NMR spectroscopy), which suggests a rhenium-bound
stannyl ligand. However, recall that one set of imido ligand
While the equilibrium between the Re(VII) and Re(V)
isomers of 2a and the lack of identifiable intermediate species
1
in the reaction mixture (by H NMR spectroscopy) cause
difficulty in distinguishing among mechanisms I-III, some
insight is gained by considering the reactions of 2a,b with
H2. Hydrogen can react with d0 metal-silyl complexes
through a concerted, four-membered transition state (as in
mechanism I) and with lower oxidation state compounds by
oxidative addition to the metal center (as in mechanism II).
However, since neither 2a nor 2b reacted with H2 (vide
supra), and since silanes and hydrogen often display similar
reactivity patterns toward transition metal complexes, mech-
anisms I and II seem less likely than mechanism III. While
a silane may undergo nucleophilic attack (mechanism III),
this type of reaction is very difficult for H2.
1
resonances was also observed by H NMR spectroscopy at
low temperature for compounds 1 and 2a.
The diphenylphosphido complex (DippNd)3RePPh2 (7)
is related to the rhenium phosphido compounds
(tBuNd)3RePR2 (R2 ) Ph2, (SiMe3)2, Mes(H)) reported
previously by Wilkinson and co-workers.57 The crystal
structure of the (tBuNd)3RePPh2 complex revealed a rhe-
nium-bound phosphido ligand with a pyramidal geometry
about phosphorus. Furthermore, the 31P{1H} NMR resonance
of this compound at -8.78 ppm (R2 ) Ph2) is indicative of
a pyramidal phosphorus and a Re-P single bond. Complex
7 possesses a low-frequency 31P{1H} NMR chemical shift
at 28.33 ppm, which suggests that this complex also features
pyramidal phosphorus and a Re-P single bond.58,59 No
reaction was observed for benzene-d6 solutions of complex
7 with H2 (1 atm, 145 °C, 2 days), PhSiH3 (1 equiv, 140 °C,
2 days), CO (1 atm, 125 °C, 27 h), or (2,6-Me2C6H3)NtC
(1 equiv, 135 °C, 2 days). In contrast, some early metal (d0)
phosphido complexes have been found to insert unsaturated
substrates such as CO and C6H11NtC. Bercaw and co-
workers reported the reaction of Cp*HfCl2(PtBu2) with CO
to give Cp*HfCl2[η2-C(O)PtBu2],18 and Hey-Hawkins and
co-workers described the reaction of Cp°2ZrCl(PHC6H11)
with C6H11NtC to yield Cp°2ZrCl[η2-C(NC6H11)P(H)(C6H11)]
(Cp° ) η5-C5EtMe4).17
Preparation of Tris(imido) Complexes Containing Rhe-
nium-Main Group Element Bonds. Complex 1 reacted
cleanly with a series of main group halides, MeI, Ph3GeCl,
Me3SnCl, Ph2PCl, and PhSeCl, to give the corresponding
rhenium imido complexes (DippNd)3ReERn (ERn ) Me (4,
97%), GePh3 (5, 83%), SnMe3 (6, 76%), PPh2 (7, 88%), SePh
(8, 87%); eq 5). To the best of our knowledge, compounds
5 and 6 are the first rhenium imido compounds containing
1
germyl and stannyl ligands. The H NMR spectrum of 4 is
consistent with the data previously reported for this com-
pound by Schrock and Williams.41 No reaction was observed
between 4 and PhSiH3 (8.68 equiv) at temperatures as high
as 100 °C (benzene-d6, 17 h). After the reaction mixture was
heated to 145 °C for 5 days, 0.77 equiv of PhSiH3 and 0.11
equiv of 4 were consumed, while trace amounts of Ph2SiH2
(0.42 equiv) were formed. Thus, the Re-C bond of 4 does
not appear to be very reactive in σ-bond metathesis processes.
The phenylselenido complex (DippNd)3ReSePh (8) ap-
pears to be the first example of a rhenium compound that
contains both terminal imido and terminal selenido ligands.
However, Batail and co-workers have previously described
rhenium clusters that contain bridging imido and selenido
groups.60 The 77Se{1H} NMR spectrum of 8 contains a single
(57) Saboonchian, V.; Danopoulos, A. A.; Gutierrez, A.; Wilkinson, G.;
Williams, D. J. Polyhedron 1991, 10, 2241.
(58) Handler, A.; Peringer, P.; Mu¨ller, E. P. J. Chem. Soc., Dalton Trans.
1990, 3725.
(59) Jo¨rg, K.; Malisch, W.; Reich, W.; Meyer, A.; Schubert, U. Angew.
Chem., Int. Ed. Engl. 1986, 25, 92.
(60) Uriel, S.; Boubekeur, K.; Batail, P.; Orduna, J. Angew. Chem., Int.
Ed. Engl. 1996, 35, 1544.
X-ray diffraction data were collected for the triphenyl-
germyl complex (DippNd)3ReGePh3 (5). Crystals of com-
plex 5 were obtained by cooling a concentrated pentane
4358 Inorganic Chemistry, Vol. 43, No. 14, 2004

Tris(imido)rhenium Complexes
resonance at 245.8 ppm (relative to SeMe261). Complex 8
did not react with PhSiH3 (1 equiv, 140 °C, 2 days, benzene-
d6).
Vacuum Atmospheres drybox unless otherwise noted. Dry, oxygen-
free solvents were used unless otherwise indicated. Olefin impurities
were removed from pentane by treatment with concentrated H2SO4,
0.5 N KMnO4 in 3 M H2SO4, and saturated NaHCO3. Pentane was
then dried over MgSO4, stored over activated 4 Å molecular sieves,
and distilled from potassium benzophenone ketyl under a nitrogen
atmosphere. Thiophene impurities were removed from toluene and
benzene by treatment with H2SO4 and saturated NaHCO3. Toluene
and benzene were then dried over MgSO4 and distilled from
potassium under a nitrogen atmosphere. Tetrahydrofuran was
distilled from sodium benzophenone ketyl under a nitrogen
atmosphere. Benezene-d6 was purified and dried by vacuum
distillation from sodium/potassium alloy.
Concluding Remarks
In an effort to develop highly reactive reagents and
catalysts for new chemical processes, we have explored the
synthesis and reactivity of rhenium imido complexes con-
taining rhenium-main group element bonds. These com-
pounds are readily prepared in high yield by the treatment
of (THF)2Li(µ,µ-NDipp)2Re(dNDipp) (1) with main group
element halides. Spectroscopic and chemical reactivity
studies suggest that 2a-c are Re(VII) silyl complexes that
are in equilibrium with Re(V) (DippNd)2ReN(SiR3)Dipp
isomers. The trapping of isomer B by CO provides support
for the presence of the equilibrium in eq 2. This type of
equilibrium also appears to be operative for the rhenium
hydride complex (DippNd)3ReH reported by Schrock and
Williams.41 In the latter system, spectroscopic data support
formulation of the complex as either the Re(VII) hydride or
Re(V) bis(imido)-amido isomers, and chemical reactivity
indicates that an equilibrium involving these two structures
exists.
The silyl complexes 2a,b exhibit somewhat unusual
reactions with PhSiH3, since these processes involve some
type of Si-C bond activation. Related chemistry has been
observed for lanthanide complexes of the type [Cp*2Ln(µ-
H)]2 (Ln ) Sm, Lu).52-54 Mechanistic studies indicate that
these lanthanide complexes react with PhSiH3 through a
concerted, four-membered transition state to yield SiH4,
Ph2SiH2, and C6H6.52 While a concerted σ-bond metathesis
pathway could occur for the reaction of 2a,b with PhSiH3
to form 2c (Scheme 1, mechanism I), the equilibrium
between A and B raises other mechanistic possibilities.
Alternative mechanisms involve oxidative addition of PhSiH3
to the rhenium metal center of structure B (mechanism II)
or the addition of PhSiH3 across the RedN double bond of
structure A (mechanism III). Considering the lack of reactiv-
ity of 2a,b with H2 (which generally reacts with metal
complexes via a four-membered transition state or oxidative
addition), mechanism III seems more likely than mechanisms
I and II for the formation of 2c and HSiMe3 from 2a (or 2b)
and PhSiH3.
NMR spectra were recorded at 500.132 (1H), 194.371 (7Li),
125.759 (13C), 99.376 (29Si), 202.457 (31P), 95.363 (77Se), or 186.50
(
119Sn) MHz using a Bruker DRX-500 spectrometer. 1H NMR
spectra were referenced internally to the residual solvent signal
relative to tetramethylsilane. 7Li NMR spectra were referenced using
a 10% aqueous LiCl external standard. 13C{1H} NMR spectra were
referenced internally by the 13C NMR signal of the NMR solvent
relative to tetramethylsilane. 29Si NMR spectra were referenced
using a tetramethylsilane external standard. 31P{1H} NMR spectra
were referenced relative to an 85% aqueous H3PO4 external
standard. 77Se{1H} NMR spectra were referenced relative to SeMe2
via a secondary Se2Cl2 external standard.61 119Sn{1H} NMR spectra
were referenced using a tetramethylstannane external standard. In
some cases, distortionless enhancement by polarization transfer
(DEPT) was used to assign the 13C NMR resonances as CH3, CH2,
CH, or C groups, and 1H-coupled and decoupled insensitive nuclei
enhanced by polarization transfer (INEPT) were used to identify
1
29Si resonances and JSiH values. Heteronuclear multiple quantum
1
coherence (HMQC) was used to identify some H,13C and 1H,29Si
couplings, heteronuclear multiple bond correlation (HMBC) was
used to identify some 1H,29Si couplings, and total correlation
spectroscopy (TOCSY) was used to identify some coupled 1H NMR
systems. All spectra were recorded at room temperature (∼22 °C)
unless otherwise indicated. Infrared spectra were recorded as KBr
pellets using a Mattson FTIR spectrometer at a resolution of 4 cm-1
.
Elemental analyses were performed by the College of Chemistry
Microanalytical Laboratory at the University of California, Berkeley.
All chemicals were purchased from Aldrich or Fluka and used
without further purification. Carbon monoxide was purchased from
Scott Specialty Gases. The compounds (2,6-iPr2C6H3Nd)3ReCl,41
64
(THF)3LiSi(SiMe3)3,62 DippN(SiMe3)H,63 and [DippN(SiMe3)Li]2
were prepared as reported in the literature. Phenylsilane was
prepared by the reduction of PhSiCl3 with LiAlH4.
In summary, the tris(imido)rhenium fragment (DippNd)3Re
is capable of supporting an array of main group element
ligands. The bond-activation and redistribution chemistry
observed in the reactions of 2a,b with PhSiH3 provides
further evidence that new stoichiometric and catalytic
processes might be based on reactive silyl complexes
containing imido ligands. Current investigations are directed
toward developing such reactions and expanding the range
of main group element derivatives for this tris(imido)
fragment.
(THF)2Li(µ,µ-DippN)2Re(dNDipp) (1). Method A. A mixture
of (DippNd)3ReCl (1.47 g, 1.97 mmol) and (THF)3LiSi(SiMe3)3
(0.954 g, 2.02 mmol) was dissolved in toluene (100 mL) to give a
dark, yellow-orange reaction mixture. After the reaction mixture
was stirred at room temperature for 2 h, the solvent was removed
in vacuo to produce a red-orange oily solid. The solid was extracted
with pentane (4 × 30 mL) and the extracts were filtered to give a
red-orange solution. The solution was concentrated to ca. 35 mL
and cooled to -35 °C to yield dark, red-orange crystals of 1 (1.26
g, 74%).
Experimental Procedures
(62) Gutekunst, G.; Brook, A. G. J. Organomet. Chem. 1982, 225, 1.
(63) Chao, Y.-W.; Wexler, P. A.; Wigley, D. E. Inorg. Chem. 1989, 28,
3860.
General Procedures. All experiments were conducted under a
nitrogen atmosphere using standard Schlenk techniques or in a
(64) Kennepohl, D. K.; Brooker, S.; Sheldrick, G. M.; Roesky, H. W. Chem.
Ber. 1991, 124, 2223.
(61) Milne, J. B. Can. J. Chem. 1992, 70, 693.
Inorganic Chemistry, Vol. 43, No. 14, 2004 4359

Gavenonis and Tilley
t
Method B. A solution of BuLi in pentane (1.7 M, 1.05 mmol)
1287 (s), 1329 (s), 1360 (m), 1382 (m), 1426 (s), 1459 (s), 1559
(w), 1567 (w), 1585 (w), 1653 (w), 2105 (m, νSiH), 2868 (s), 2924
(s), 2962 (vs), 3021 (w), 3054 (m). Anal. Calcd for C48H62N3ReSi:
C, 64.39; H, 6.98; N, 4.69. Found: C, 64.34; H, 7.04; N, 4.51.
ClSiH2Ph. A solution of PhSiH3 (5.30 g, 49.0 mmol) in benzene
(10 mL) was added to solid Ph3CCl (13.6 g, 48.8 mmol). The
reaction vessel was sealed and heated to 60 °C for 1 week. After
the colorless reaction mixture was cooled to room temperature, large
crystals of Ph3CH formed and were isolated by filtration. Benzene
was removed by distillation under N2 (1 atm), and ClSiH2Ph was
collected as a colorless liquid (3.82 g, 50%) that distilled at ca.
165 °C. The isolated ClSiH2Ph was degassed and stored under
nitrogen. The spectroscopic data for this compound agree with those
reported previously by Ishikawa and co-workers.65
was added via syringe to a stirred solution of (DippNd)3ReCl (0.388
g, 0.519 mmol) and tetrahydrofuran (0.170 mL, 2.10 mmol) in
toluene (20 mL). Upon addition, the reaction mixture appeared dark
red-orange. After the reaction mixture was stirred at room temper-
ature for 1 h, the solvent and volatile byproducts were removed in
vacuo to leave behind a dark red-orange, oily solid. The solid was
extracted with pentane (5 × 10 mL) and the combined extracts
were filtered to give a dark red-orange solution. The solution was
concentrated to ca. 7 mL and cooled to -35 °C to afford dark red-
orange crystals of 1 (0.312 g, 70%). 1H NMR (benzene-d6): δ 1.11
i
(m, 8 H, THF), 1.30 (d, 36 H, J ) 6 Hz, Pr-Me), 3.24 (m, 8 H,
THF), 4.10 (septet, 6 H, J ) 7 Hz, iPr-H), 7.12 (t, 1 H, J ) 5 Hz,
Ar-H), 7.14 (d, 7 H, J ) 4 Hz, Ar-H), 7.16 (d, 1 H, J ) 4 Hz,
Ar-H). 13C{1H} NMR (benzene-d6): δ 24.0 (iPr-Me), 25.6 (THF),
30.0 (iPr-CH), 69.2 (THF), 122.6 (CH), 136.0, 157.6 (aromatic C’s).
7Li NMR (benzene-d6): δ 4.73. IR (KBr, cm-1): 680 (vw), 753
(m), 796 (w), 879 (w), 918 (w), 933 (w), 975 (m), 1036 (m), 1058
(w), 1098 (w), 1115 (w), 1158 (vw), 1178 (vw), 1221 (w), 1281
(s), 1331 (s), 1357 (m), 1380 (m), 1424 (s), 1460 (m), 1547 (vw),
1585 (w), 1917 (vw), 2869 (m), 2886 (m), 2929 (m), 2960 (s),
3055 (w). Anal. Calcd for C44H67LiN3O2Re: C, 61.22; H, 7.82; N,
4.87. Found: C, 61.01; H, 7.87; N, 5.19.
(DippNd)3ReSiH2Ph (2c). Chlorophenylsilane (27 µL, ∼0.17
mmol) was added via syringe to a stirred solution of compound 1
(0.146 g, 0.169 mmol) in toluene (10 mL) to give a red reaction
mixture. After the reaction mixture was stirred at room temperature
for 1 h, the solvent was removed in vacuo to leave behind a red
oily solid. This solid was extracted with pentane (3 × 10 mL) and
the combined extracts were filtered to give a red solution. The
solution was concentrated to ca. 5 mL and cooled to -78 °C for 3
months to yield dark red crystals of compound 2c (0.081 g, 59%).
i
1H NMR (benzene-d6): δ 1.15 (d, 36 H, J ) 7 Hz, Pr-Me), 3.87
(DippNd)3ReSiMe3 (2a). Chlorotrimethylsilane (77 µL, 0.61
mmol) was added via syringe to a stirred solution of compound 1
(0.481 g, 0.557 mmol) in toluene (20 mL) to give a red-purple
reaction mixture. After the reaction mixture was stirred at room
temperature for 1 h, the solvent was removed in vacuo to leave
behind a dark red solid. The solid was extracted with pentane (3 ×
15 mL) and the extracts were filtered to give a red-purple solution.
The solution was concentrated to ca. 10 mL and cooled to -78 °C
to yield three crops of red-purple crystals of 2a (0.437 g, 99%). 1H
NMR (benzene-d6): δ 0.85 (s, 9 H, SiMe3), 1.20 (d, 36 H, J ) 7
Hz, Pr-Me), 3.92 (septet, 6 H, J ) 7 Hz, Pr-H), 7.04 (m, 1 H,
Ar-H), 7.05 (s, 1 H, Ar-H), 7.06 (s, 2 H, Ar-H), 7.07 (s, 2 H, Ar-
H), 7.08 (d, 1 H, J ) 5 Hz, Ar-H). 13C{1H} NMR (benzene-d6):
δ 9.2 (SiMe3), 24.2 (iPr-Me), 28.6 (iPr-H), 123.3, 127.0 (CH’s),
141.8, 154.2 (aromatic C’s). 29Si{1H} NMR (benzene-d6): δ 34.31
(SiMe3). IR (KBr, cm-1): 450 (vw), 541 (vw), 620 (w), 689 (w),
753 (s), 796 (m), 837 (s), 934 (w), 988 (m), 1047 (vw), 1058 (w),
1102 (w), 1113 (w), 1159 (vw), 1178 (vw), 1241 (m), 1290 (s),
1331 (vs), 1360 (m), 1382 (w), 1424 (m), 1459 (m), 1567 (vw),
1928 (vw), 2869 (m), 2888 (m), 2926 (m), 2962 (vs), 3022 (vw),
3056 (w). Anal. Calcd for C39H60N3ReSi: C, 59.66; H, 7.70; N,
5.35. Found: C, 59.68; H, 7.57; N, 5.29.
(septet, 6 H, J ) 7 Hz, iPr-H), 6.59 (s, 2 H, JSiH ) 201 Hz, SiH),
6.96 (d, 1 H, J ) 2 Hz, SiPh), 6.96 (d, 2 H, J ) 2 Hz, SiPh), 7.04
(t, 1 H, J ) 5 Hz, Ar-H), 7.06 (d, 6 H, J ) 4 Hz, Ar-H), 7.08 (d,
2 H, J ) 5 Hz, Ar-H), 7.65 (m, 2 H, SiPh). 13C{1H} NMR (benzene-
d6): δ 24.0 (iPr-Me), 28.9 (iPr-CH), 123.2, 127.8, 128.6, 130.2
(CH’s), 134.9 (aromatic C), 137.0 (CH), 142.5, 154.4 (aromatic
C’s). 29Si NMR (benzene-d6): δ -16.52 (tt, 1JSiH ) 201 Hz, 4JSiH
) 7 Hz, SiH2Ph). IR (KBr, cm-1): 410 (w), 453 (vw), 488 (w),
706 (m), 753 (s), 780 (vs), 914 (m), 932 (m), 988 (m), 1046 (w),
1060 (w), 1102 (m), 1114 (m), 1226 (vw), 1250 (m), 1287 (s),
1328 (vs), 1360 (m), 1382 (m), 1421 (m), 1461 (m), 1549 (vw),
1567 (w), 1585 (w), 2127 (m, νSiH), 2146 (m, νSiH), 2869 (m),
2924 (m), 2962 (vs), 3021 (w), 3056 (m). Anal. Calcd for
C42H58N3ReSi: C, 61.58; H, 7.14; N, 5.13. Found: C, 61.60; H,
7.06; N, 4.99.
i
i
DippN(SiMe3)H. This compound was prepared according to the
method described by Wigley and co-workers.63 29Si{1H} NMR
(benzene-d6): δ 3.70.
[DippN(SiMe3)Li]2. This compound was prepared according to
the method described by Roesky and co-workers.64 29Si{1H} NMR
(benzene-d6): δ -11.52.
(DippNd)3ReSiHPh2 (2b). Chlorodiphenylsilane (73 µL, 0.37
mmol) was added via syringe to a stirred solution of compound 1
(0.308 g, 0.357 mmol) in toluene (10 mL) to give a red-purple
reaction mixture. After the reaction mixture was stirred at room
temperature for 1 h, the solvent was removed in vacuo to leave
behind a red-purple oily solid. The solid was extracted with pentane
(3 × 10 mL) and the combined extracts were filtered to give a
red-purple solution. Evaporation of the solvent gave compound 2b
(DippNd)2Re[N(SiMe3)Dipp](CO) (3). Compound 2a (0.204
g, 0.260 mmol) was dissolved in toluene (10 mL), and the resulting
solution was transferred to a 50 mL reaction vessel. The solution
was degassed, CO (1 atm) was admitted, and the reaction solution
was stirred at room temperature. After 1.5 h, the solvent was
removed in vacuo to leave behind a dark red solid that was ex-
tracted into pentane (3 × 10 mL). The combined extracts were
concentrated to ca. 5 mL and cooled to -35 °C to afford two crops
1
1
as a red-purple sticky solid (0.194 g, 61%). H NMR (benzene-
of red-brown crystals of compound 3 (0.145 g, 69%). H NMR
i
i
d6): δ 1.07 (d, 36 H, J ) 7 Hz, Pr-Me), 3.78 (septet, 6 H, J ) 7
(benzene-d6): δ 0.37 (s, 9 H, SiMe3), 1.04 (broad s, 18 H, Pr-
i
i
Hz, Pr-H), 7.00 (m, 6 H, SiPh2), 7.06 (m, 9 H, Ar-H), 7.62 (s, 1
Me), 1.09 (d, 12 H, J ) 7 Hz, Pr-Me), 1.25 (broad d, 6 H, J ) 7
H, SiH), 7.72 (m, 4 H, SiPh2). 13C{1H} NMR (benzene-d6): δ 24.0
(iPr-Me), 28.9 (iPr-CH), 123.3, 127.6, 128.7, 130.0, 137.4 (CH’s),
137.7, 142.4, 154.4 (aromatic C’s). 29Si NMR (benzene-d6): δ 14.97
i
i
Hz, Pr-Me), 3.40 (broad s, 4 H, Pr-H), 3.76 (septet, 2 H, J ) 7
Hz, iPr-H), 6.97 (d, 4 H, J ) 7.5 Hz, Ar-H), 7.07 (m, 5 H, Ar-H).
13C{1H} NMR (benzene-d6): δ 4.5 (broad, SiMe3), 23.5 (iPr-Me),
24.6 (broad, iPr-Me), 25.9 (iPr-Me), 28.3 (iPr-H), 28.9 (iPr-H), 123.6
1
4
(d of pentets, JSiH ) 199 Hz, JSiH ) 6 Hz, SiHPh2). IR (KBr,
cm-1): 407 (w), 428 (w), 456 (w), 484 (m), 597 (vw), 699 (s),
714 (s), 749 (s), 796 (m), 853 (vw), 933 (w), 987 (m), 1046 (w),
1058 (w), 1101 (m), 1157 (vw), 1178 (w), 1227 (vw), 1250 (m),
(65) Kunai, A.; Kawakami, T.; Toyoda, E.; Ishikawa, M. Organometallics
1992, 11, 2708.
4360 Inorganic Chemistry, Vol. 43, No. 14, 2004

Tris(imido)rhenium Complexes
(CH), 125.1 (broad, CH), 125.9 (CH), 127.7 (CH), 142.6 (aromatic
C), 145.7 (broad, aromatic C), 156.8 (aromatic C), 260.6 (broad,
CO). 29Si{1H} NMR (benzene-d6): δ 24.36 (SiMe3). IR (KBr,
cm-1): 439 (w), 476 (vw), 533 (w), 632 (vw), 679 (vw), 745 (m),
761 (w), 792 (m), 833 (m), 853 (m), 880 (w), 908 (m), 932 (w),
978 (w), 1049 (vw), 1058 (vw), 1101 (w), 1180 (w), 1247 (m),
1274 (w), 1292 (w), 1337 (w), 1360 (w), 1382 (w), 1422 (w), 1430
(w), 1460 (w), 1584 (vw), 1927 (vs, νCO), 2867 (w), 2926 (w),
2963 (s), 3059 (vw). Anal. Calcd for C40H60N3OReSi: C, 59.08;
H, 7.44; N, 5.17. Found: C, 59.33; H, 7.37; N, 5.37.
(s), 2886 (m), 2924 (s), 2961 (s), 3022 (w), 3056 (w). Anal. Calcd
for C39H60N3ReSn: C, 53.48; H, 6.91; N, 4.80. Found: C, 53.43;
H, 7.00; N, 5.12.
(DippNd)3RePPh2 (7). Chlorodiphenylphosphine (61 µL, 0.34
mmol) was added via syringe to a stirred solution of compound 1
(0.292 g, 0.339 mmol) in toluene (10 mL) to give a red-purple
reaction mixture. After the reaction mixture was strirred at room
temperature for 1 h, the solvent was removed in vacuo to leave
behind a red-purple solid. The solid was extracted with pentane (3
× 10 mL) and the combined extracts were filtered to give a red-
purple solution. The solution was concentrated to ca. 5 mL and
cooled to -78 °C to yield red crystals of compound 7 (0.268 g,
88%). 1H NMR (benzene-d6): δ 1.03 (s, 36 H, J ) 7 Hz, iPr-Me),
3.62 (septet, 6 H, J ) 7 Hz, iPr-H), 6.86 (t, 2 H, J ) 8 Hz, PPh2),
6.97 (td, 4 H, J ) 8 Hz, J ) 2 Hz, PPh2), 7.01 (dd, 3 H, J ) 9 Hz,
J ) 6 Hz, Ar-H), 7.04 (s, 4 H, Ar-H), 7.06 (d, 2 H, J ) 2 Hz,
Ar-H), 7.70 (td, 4 H, J ) 8 Hz, J ) 2 Hz, PPh2). 13C{1H} NMR
(benzene-d6): δ 24.2 (iPr-Me), 28.9 (iPr-CH), 123.2, 127.4, 128.7
(DippNd)3ReMe (4). Iodomethane (20 µL, 0.32 mmol) was
added via syringe to a stirred solution of compound 1 (0.256 g,
0.297 mmol) in toluene (10 mL) to give a dark red reaction mixture.
After the reaction mixture was stirred at room temperature for 2 h,
the solvent and excess MeI were removed in vacuo to leave behind
a dark red solid. The solid was extracted with pentane (3 × 10
mL) and the combined extracts were filtered to give a dark red
solution. The solution was concentrated to ca. 5 mL and cooled to
-35 °C to yield two crops of dark red crystals of compound 4
(0.210 g, 97%). The spectroscopic data for this compound agree
with those reported previously by Schrock and co-workers.41
(DippNd)3ReGePh3 (5). Compound 1 (0.368 g, 0.426 mmol)
and Ph3GeCl (0.145 g, 0.427 mmol) were dissolved in toluene (15
mL) to give a red-orange reaction mixture. Over the course of 1
day, the reaction mixture became red-purple in color. After the
reaction mixture was strirred at room temperature for 3 days, the
solvent was removed in vacuo to leave behind a red-purple oily
solid. The solid was extracted with pentane (3 × 10 mL) and the
combined extracts were filtered to give a red-purple solution. The
solution was concentrated to ca. 8-10 mL and cooled to -35 °C
to yield three crops of red crystals of compound 5 (0.361 g, 83%).
3
2
(CH’s), 129.1 (d, JPC ) 6 Hz, m-PPh2), 136.6 (d, JPC ) 18 Hz,
1
o-PPh2), 141.0 (d, JPC ) 28 Hz, aromatic-PPh2), 142.6 (aromatic
C), 154.1 (d, JPC ) 1 Hz, aromatic C). 31P{1H} NMR (benzene-
3
d6): δ 28.33 (s, JPC ) 18 Hz, PPh2). IR (KBr, cm-1): 504 (w),
696 (m), 739 (m), 753 (s), 796 (w), 934 (w), 1046 (vw), 1058 (w),
1102 (w), 1114 (w), 1179 (vw), 1226 (w), 1250 (m), 1285 (vs),
1307 (m), 1328 (vs), 1359 (m), 1382 (m), 1421 (m), 1432 (m),
1460 (m), 1581 (vw), 2801 (vw), 2867 (m), 2924 (m), 2962 (vs),
3022 (vw), 3055 (m). Anal. Calcd for C48H61N3PRe: C, 64.26; H,
6.85; N, 4.68. Found: C, 64.48; H, 6.98; N, 4.62.
(DippNd)3ReSePh (8). Compound 1 (0.182 g, 0.210 mmol) and
PhSeCl (0.041 g, 0.21 mmol) were dissolved in toluene (10 mL)
to give a red-brown reaction mixture. After the reaction mixture
was strirred at room temperature for 1 h, the solvent was removed
in vacuo to leave behind a red-brown solid. The solid was extracted
with pentane (3 × 10 mL) and the combined extracts were filtered
to give a dark, red-brown solution. The solution was concentrated
to ca. 5 mL and cooled to -35 °C to yield two crops of long,
blocklike, brown crystals of compound 8 (0.160 g, 87%). 1H NMR
i
1H NMR (benzene-d6): δ 0.97 (d, 36 H, J ) 7 Hz, Pr-Me), 3.65
(septet, 6 H, J ) 7 Hz, iPr-H), 7.01 (m, 10 H, Ar-H), 7.03 (s, 2 H,
Ar-H), 7.04 (s, 4 H, Ar-H), 7.06 (d, 2 H, J ) 2 Hz, Ar-H), 7.66
(m, 6 H, GePh3). 13C{1H} NMR (benzene-d6): δ 24.0 (iPr-Me),
28.9 (iPr-CH), 123.3, 127.4, 129.0, 129.3, 136.6 (CH’s), 142.2,
142.6, 154.3 (aromatic C’s). IR (KBr, cm-1): 457 (m), 468 (m),
541 (vw), 600 (vw), 670 (w), 699 (s), 736 (s), 751 (s), 795 (m),
933 (w), 988 (m), 1024 (vw), 1046 (w), 1058 (w), 1083 (m), 1104
(w), 1114 (w), 1176 (w), 1186 (w), 1227 (w), 1251 (m), 1287 (vs),
1308 (m), 1329 (vs), 1360 (m), 1382 (m), 1428 (s), 1460 (s), 1482
(w), 2803 (w), 2868 (s), 2885 (m), 2925 (s), 2963 (vs), 3023 (w),
3052 (m). Anal. Calcd for C54H66GeN3Re: C, 63.84; H, 6.55; N,
4.14. Found: 63.97; H, 6.37; N, 4.09.
i
(benzene-d6): δ 1.08 (d, 36 H, J ) 7 Hz, Pr-Me), 3.74 (septet, 6
i
H, J ) 7 Hz, Pr-H), 6.80 (tt, 1 H, J ) 7 Hz, J ) 2 Hz, p-SePh),
6.87 (tt, 2 H, J ) 7 Hz, J ) 2 Hz, SePh), 6.99 (dd, 3 H, J ) 9 Hz,
J ) 6 Hz, Ar-H), 7.03 (s, 4 H, Ar-H), 7.05 (d, 2 H, J ) 2 Hz,
Ar-H), 7.87 (dq, 2 H, J ) 8 Hz, J ) 1 Hz, SePh). 13C{1H} NMR
(benzene-d6): δ 24.0 (iPr-Me), 29.2 (iPr-CH), 123.1, 127.0, 127.6,
129.7 (CH’s), 131.6 (aromatic C), 135.4 (CH), 142.6, 154.0
(aromatic C’s). 77Se{1H} NMR (benzene-d6): δ 245.8 (SePh). IR
(KBr, cm-1): 429 (vw), 445 (vw), 460 (vw), 540 (vw), 597 (vw),
665 (vw), 690 (w), 738 (m), 753 (s), 797 (m), 934 (m), 987 (m),
1021 (w), 1046 (w), 1061 (m), 1102 (m), 1116 (w), 1159 (vw),
1178 (w), 1227 (w), 1251 (m), 1287 (vs), 1328 (vs), 1360 (m),
1382 (m), 1420 (m), 1438 (m), 1460 (m), 1574 (m), 1926 (vw),
1942 (vw), 2711 (vw), 2722 (vw), 2754 (vw), 2801 (vw), 2867
(m), 2924 (m), 2960 (vs), 3023 (vw), 3057 (w). Anal. Calcd for
C42H56N3ReSe: C, 58.11; H, 6.50; N, 4.84. Found: C, 58.33; H,
6.69; N, 4.69.
(DippNd)3ReSnMe3 (6). Compound 1 (0.270 g, 0.313 mmol)
and Me3SnCl (0.0624 g, 0.313 mmol) were dissolved in toluene
(10 mL) to give a red-purple reaction mixture. After the reaction
mixture was strirred at room temperature for 1 h, the solvent was
removed in vacuo to leave behind a red-purple oily solid. The solid
was extracted with pentane (3 × 10 mL) and the combined extracts
were filtered to give a red-purple solution. The solution was
concentrated to ca. 3 mL and cooled to -35 °C to yield two crops
of red crystals of compound 6 (0.207 g, 76%). 1H NMR (benzene-
d6): δ 0.73 (s, 9 H, JSnH ) 50 Hz, SnMe3), 1.20 (d, 36 H, J ) 7
i
i
Hz, Pr-Me), 3.86 (septet, 6 H, J ) 7 Hz, Pr-H), 7.03 (m, 1 H,
Ar-H), 7.05 (s, 2 H, Ar-H), 7.06 (s, 4 H, Ar-H), 7.07 (d, 2 H, J )
5 Hz, Ar-H). 13C{1H} NMR (benzene-d6): δ -0.9 (SnMe3), 24.0
(iPr-Me), 28.8 (iPr-CH), 123.2, 126.9 (CH’s), 141.5, 154.3
(aromatic C’s). 119Sn{1H} NMR (benzene-d6): δ 69.54. IR (KBr,
cm-1): 448 (vw), 507 (w), 524 (m), 753 (s), 795 (m), 933 (w),
989 (s), 1046 (w), 1058 (w), 1103 (w), 1112 (w), 1159 (vw), 1178
(w), 1227 (w), 1250 (m), 1291 (s), 1332 (s), 1360 (m), 1382 (m),
1423 (s), 1459 (s), 2706 (w), 2722 (w), 2753 (w), 2803 (w), 2868
X-ray Structure Determinations. X-ray diffraction measure-
ments were made on a Siemens SMART diffractometer with a CCD
area detector, using graphite-monochromated Mo KR radiation. The
crystal was mounted on a glass fiber using Paratone N hydrocarbon
oil. A hemisphere of data was collected using ω scans of 0.3°. Cell
constants and an orientation matrix for data collection were obtained
from a least-squares refinement using the measured positions of
reflections in the range 4° (or 3.5°) < 2θ < 45°. The frame data
were integrated using the program SAINT.66 An empirical absorp-
Inorganic Chemistry, Vol. 43, No. 14, 2004 4361

Gavenonis and Tilley
Table 3. Crystallographic Data for Compounds 1 and 3
structures were solved using the teXsan crystallographic software
package of the Molecular Structure Corp., using direct methods,
and expanded with Fourier techniques. All non-hydrogen atoms
were refined anisotropically, and the hydrogen atoms were included
in calculated positions but not refined unless otherwise noted. The
function minimized in the full-matrix least-squares refinement was
Σw(|Fo| - |Fc|)2. The weighting scheme was based on counting
statistics and included a p-factor to downweight the intense
reflections. Crystallographic data are summarized in Table 3.
Compound 1. Crystals suitable for X-ray diffraction were
obtained by cooling a concentrated pentane solution of 1 to -35
°C. An orientation matrix gave a C-centered, monoclinic cell with
dimensions described in Table 3. Data were collected for 10 s
frames. The raw data were integrated using SAINT,66 and an
empirical absorption correction was applied using SADABS.67 In
addition, XPREP68 clearly indicated the space group was C2/c (No.
15). The structure was solved using direct methods (SIR92) and
was found to contain one molecule of the rhenium complex/
asymmetric unit. The molecule lies on a 2-fold axis at [0, y, 0.25],
and as such, half of the atoms are related by symmetry. All non-
hydrogen atoms were refined anisotropically. All hydrogen atoms
were refined isotropically in geometrically calculated positions.
Compound 3. Crystals suitable for X-ray diffraction were
obtained by cooling a concentrated pentane solution of 3 to -35
°C. An orientation matrix gave a primitive, triclinic cell with
dimensions described in Table 3. Data were collected for 10 s
frames. The raw data were integrated using SAINT,66 and an
empirical absorption correction was applied using SADABS.67 In
addition, XPREP68 clearly indicated the space group was P1h (No.
2). The structure was solved using direct methods (SIR92) and was
found to contain one molecule of the rhenium complex/asymmetric
unit. All non-hydrogen atoms were refined anisotropically. All
hydrogen atoms were refined isotropically in geometrically calcu-
lated positions.
param
1
3
empirical formula
fw
C44H67N3O2LiRe
863.18
C40H60N3OReSi
813.23
cryst color, habit
cryst size (mm)
cryst system
space group
a (Å)
red plate
red block
0.22 × 0.20 × 0.12 0.35 × 0.35 × 0.30
monoclinic
C2/c (No. 15)
17.9687(4)
13.1938(4)
18.5450(5)
triclinic
P1h (No. 2)
9.8121(5)
11.4850(6)
18.3071(9)
96.247(1)
92.516(1)
101.806(1)
2002.8(2)
b (Å)
c (Å)
R (deg)
â (deg)
100.643(1)
γ (deg)
V (Å3)
4320.9(2)
orientatn reflcns
(2θ range (deg))
Z value
6169 (3.5-49.3)
7919 (4.487-49.509)
4
2
D
F000
calc (g/cm3)
1.327
1784.00
28.50
SMART
1.348
836.00
30.97
SMART
µ(Mo KR) (cm-1
diffractometer
)
graphite-monochromated
radiatn (λ (Å))
Mo KR (0.710 69) Mo KR (0.710 69)
temp (°C)
-124.0
-112
scan type (0.3°/frame)
scan rate (s/frame)
2θmax (deg)
ω
ω
10.0
10.0
49.3
49.5
reflcns measd
tot.: 9610
unique: 3709
0.042
tot.: 10 132
unique: 6352
0.032
Rint
transm factors
Tmax ) 0.71
Tmin ) 0.48
direct methods
(SIR92)
Tmax ) 0.395
Tmin ) 0.338
direct methods
(SIR92)
struct soln
no. of observns
no. of variables
3001 (I > 3.00σ(I)) 5483 (I > 3.00σ(I))
233
415
reflcns/param ratio
residuals: R; Rw; Rall
goodness of fit
12.88
13.21
0.029; 0.033; 0.036 0.033; 0.038; 0.037
1.13
1.25
max shift/error in final cycle 0.00
0.00
max and min peaks in
1.22, -1.38
1.60, -2.25
Acknowledgment. Acknowledgment is made to the
National Science Foundation for their support of this work.
We thank Dr. Frederick J. Hollander and Dr. Allen G. Oliver
for assistance with the X-ray structure determinations and
Dr. Herman van Halbeek for assistance with NMR experi-
ments.
final diff map (e-/Å3)
tion correction based on measurements of multiply redundant data
was performed using the program SADABS.67 XPREP68 clearly
indicated the space group. Equivalent reflections were merged. The
data were corrected for Lorentz and polarization effects. A
secondary extinction correction was applied if appropriate. The
Supporting Information Available: Tables of crystal, data
collection, and refinement parameters, atomic coordinates, bond
distances, bond angles, and anisotropic displacement parameters
for complexes 1 and 3. This material is available free of charge
via the Internet at http://pubs.acs.org.
(66) SAX Area-Detector Integration Program, V4.024; Siemens Industrial
Automation, Inc.: Madison, WI, 1995.
(67) Sheldrick, G. M. Siemens Area Detector Absorption Corrections;
Siemens Industrial Automation, Inc.: Madison, WI, 1996.
(68) SHELXTL Crystal Structure Determination Package; Siemens Indus-
trial Automation, Inc.: Madison, WI, 1995.
IC030282E
4362 Inorganic Chemistry, Vol. 43, No. 14, 2004