Bis(3,5-dimethylpyrazol-1-yl)acyl and bis(3,5-dimethylpyrazol-1-yl)methide carbonyl tungsten derivatives

Article abstract of DOI:10.1021/om800603p

Reaction of (isopropyl)diphenylstannylbis(3,5-dimethylpyrazol-1-yl)methane [(i-Pr)Ph₂SnCH(3,5-Me₂Pz)₂] and tricyclohexylstannylbis(3,5-dimethylpyrazol-1-yl)mediane [Cy₃SnCH(3, 5-Me₂Pz)₂] with W(CO)₅THF in refluxing THF yields heterobimetallic complexes (i-Pr)Ph₂SnCH(3,5-Me ₂Pz)₂W(CO)₄ and Cy₃SnCH(3,5-Me ₂Pz)₂W(CO)₄, respectively. Treatment of these heterobimetallic complexes, R₃SnCH(3,5-Me₂Pz) ₂W(CO)₄ (R₃ = (i-Pr)Ph₂, Cy ₃, Et₃), with I₂ results in the formation of a novel η¹-bis(pyrazol-1-yl)acyl complex CHC(O)(3,5-Me ₂Pz)₂W(CO)₃I, with the loss of the organotin group from the methine carbon. In addition, the reaction of R ₃SnCH(3,5-Me₂Pz)₂W(CO)₄ with SnCl₄ in a 1:1 molar ratio gives heterotrimetallic complexes R ₃SnCH(3,5-Me₂Pz)₂W(Cl)(CO)₃SnCl ₃ (R = Cy, Et). It is unexpected that these heterotrimetallic complexes are also reactive in solution. They change to a novel four-membered heterometallacyclic complex CH(3,5-Me₂Pz)₂W(CO) ₃Cl in dichloromethane solution at room temperature. Furthermore, this complex can also be obtained by the selective cleavage of the W-Sn bond in complexes CH(3,5-Me₂Pz)₂W(CO)₃SnAr₃ with SnCl₄.

Full text of DOI:10.1021/om800603p

5684
Organometallics 2008, 27, 5684–5690
Bis(3,5-dimethylpyrazol-1-yl)acyl and
Bis(3,5-dimethylpyrazol-1-yl)methide Carbonyl Tungsten Derivatives
Yun-Fu Xie, Zhen-Kang Wen, Run-Yu Tan, Juan Hong, Shu-Bin Zhao, and Liang-Fu Tang*
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed June 29, 2008
Reaction of (isopropyl)diphenylstannylbis(3,5-dimethylpyrazol-1-yl)methane [(i-Pr)Ph2SnCH(3,5-
Me2Pz)2] and tricyclohexylstannylbis(3,5-dimethylpyrazol-1-yl)methane [Cy3SnCH(3,5-Me2Pz)2] with
W(CO)5THF in refluxing THF yields heterobimetallic complexes (i-Pr)Ph2SnCH(3,5-Me2Pz)2W(CO)4
and Cy3SnCH(3,5-Me2Pz)2W(CO)4, respectively. Treatment of these heterobimetallic complexes, R3SnCH(3,5-
Me2Pz)2W(CO)4 (R3 ) (i-Pr)Ph2, Cy3, Et3), with I2 results in the formation of a novel η1-bis(pyrazol-
1-yl)acyl complex CHC(O)(3,5-Me2Pz)2W(CO)3I, with the loss of the organotin group from the methine
carbon. In addition, the reaction of R3SnCH(3,5-Me2Pz)2W(CO)4 with SnCl4 in a 1:1 molar ratio gives
heterotrimetallic complexes R3SnCH(3,5-Me2Pz)2W(Cl)(CO)3SnCl3 (R ) Cy, Et). It is unexpected that
these heterotrimetallic complexes are also reactive in solution. They change to a novel four-membered
heterometallacyclic complex CH(3,5-Me2Pz)2W(CO)3Cl in dichloromethane solution at room temperature.
Furthermore, this complex can also be obtained by the selective cleavage of the W-Sn bond in complexes
CH(3,5-Me2Pz)2W(CO)3SnAr3 with SnCl4.
complexes R3SnCH(3,5-Me2Pz)2W(CO)4 (R ) alkyl).6b These
facts suggest that the electronic and steric effects of substitutions
Introduction
Bis(pyrazol-1-yl)methane, modified by organic functional
groups on the bridging carbon atom to form heteroscorpionate
ligands, is currently drawing extensive attention,1,2 and its
application has also been increasingly exploited in recent
years.3-5 Our recent investigations on bis(pyrazol-1-yl)methane
indicate that the modification of this ligand with organometallic
groups on the methine carbon atom can provide unusual
reactivity.6 For example, the reaction of triarylstannylbis(3,5-
dimethylpyrazol-1-yl)methane with W(CO)5THF results in the
oxidative addition of the Sn-Csp3 bond to the tungsten(0) atom
to give the novel four-membered metallacyclic complex, while
the analogous reaction of di(tert-butyl)phenylstannylbis(3,5-
dimethylpyrazol-1-yl)methane results in the oxidative addition
of the Sn-Csp2 bond to the tungsten(0) atom. Interestingly, the
similar reaction of trialkylstannylbis(3,5-dimethylpyrazol-1-
yl)methane with W(CO)5THF gives only heterobimetallic
on the tin atom play a key role in these reactions. To gain further
(3) For heteroscorpionate ligands with N2O coordination environments,
see: (a) Otero, A.; Fern´andez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-
Sa´nchez, A.; Sa´nchez-Barba, L. F.; Sa´nchez-Molina, M.; Franco, S.; Lo´pez-
Solera, M. I.; Rodr´ıguez, A. M. Inorg. Chem. 2007, 46, 8475. (b) Hu¨bner,
E.; Tu¨rkoglu, G.; Wolf, M.; Zenneck, U.; Burzlaff, N. Eur. J. Inorg. Chem.
2008, 1226. (c) Milione, S.; Grisi, F.; Centore, R.; Tuzi, A. Organometallics
2006, 25, 266. (d) Hoffman, J. T.; Tran, Ba, L.; Carrano, C. J. Dalton Trans.
2006, 3822. (e) Mohr, F.; Cerrada, E.; Laguna, M. Dalton Trans. 2006,
5567. (f) Alegria, E. C. B.; Martins, L. M.; D, R. S.; Haukka, M.; Pombeiro,
A. J. L. Dalton Trans. 2006, 4954. (g) Hu¨bner, E.; Haas, T.; Burzlaff, N.
Eur. J. Inorg. Chem. 2006, 4989. (h) Papish, E. T.; Taylor, M. T.; Jernigan,
F. E., III; Rodig, M. J.; Shawhan, R. R.; Yap, G. P. A.; Jove´, F. A. Inorg.
Chem. 2006, 45, 2242. (i) Milione, S.; Bertolasi, V.; Cuenca, T.; Grassi,
A. Organometallics 2005, 24, 4915. (j) Porchia, M.; Papini, G.; Santini,
C.; Lobbia, G. G.; Pellei, M.; Tisato, F.; Bandoli, G.; Dolmella, A. Inorg.
Chem. 2005, 44, 4045. (k) Hammes, B. S.; Chohan, B. S.; Hoffman, J. T.;
Einwa¨chter, S.; Carrano, C. J. Inorg. Chem. 2004, 43, 7800.
(4) For heteroscorpionate ligands with N2S coordination environments,
see: (a) Hammes, B. S.; Carrano, C. J. J. Chem. Soc., Dalton Trans. 2000,
3304. (b) Hammes, B. J.; Carrano, C. J. Inorg. Chem. 2001, 40, 919. (c)
Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Carrillo-Hermosilla, F.; Tejeda,
J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Ferna´ndez-Lo´pez, M.; Rodr´ıguez,
A. M.; Lo´pez-Solera, I. Inorg. Chem. 2002, 41, 5193. (d) Otero, A.;
Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.; Sa´nchez-
Barba, L.; Sa´nchez-Molina, M.; Franco, S.; Lo´pez-Solera, I.; Rodr´ıguez,
A. M. Dalton Trans. 2006, 4359. (e) Tan, R.-Y.; Song, H.-B.; Tang, L.-F.
J. Organomet. Chem. 2006, 691, 5964. (f) Pellei, M.; Alidori, S.; Camalli,
M.; Campi, G.; Lobbia, G. G.; Mancini, M.; Papini, G.; Spagna, R.; Santini,
C. Inorg. Chim. Acta 2008, 361, 1456.
(5) For heteroscorpionate ligands with N2N′ coordination environments,
see: (a) Alonso-Moreno, C.; Garce´s, A.; Sa´nchez-Barba, L. F.; Fajardo,
M.; Ferna´ndez-Baeza, J.; Otero, A.; Lara-Sa´nchez, A.; Antin˜olo, A.;
Broomfield, L.; Lo´pez-Solera, M. I.; Rodr´ıguez, A. M. Organometallics
2008, 27, 1310. (b) Sa´nchez-Barba, L. F.; Garce´s, A.; Fajardo, M.; Alonso-
Moreno, C.; Ferna´ndez-Baeza, J.; Otero, A.; Antin˜olo, A.; Tejeda, J.; Lara-
Sa´nchez, A.; Lo´pez-Solera, M. I. Organometallics 2007, 26, 6403. (c) Otero,
A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.;
Sa´nchez-Barba, L. F.; Lo´pez-Solera, I.; Rodr´ıguez, A. M. Inorg. Chem.
2007, 46, 1760. (d) Adhikari, D.; Zhao, G.; Basuli, F.; Tomaszewski, J.;
Huffman, J. C.; Mindiola, D. J. Inorg. Chem. 2006, 45, 1604. (e) Reger,
D. L.; Semeniuc, R. F.; Gardinier, J. R.; O’Neal, J.; Reinecke, B.; Smith,
M. D. Inorg. Chem. 2006, 45, 4337.
* Corresponding author. E-mail: lftang@nankai.edu.cn. Fax: 86-22-
23502458.
(1) For reviews, see: (a) Pettinari, C.; Pettinari, R. Coord. Chem. ReV.
2005, 249, 663, and references therein. (b) Otero, A.; Ferna´ndez-Baeza, J.;
Antin˜olo, A.; Tejeda, J.; Lara-Sanchez, A. Dalton Trans. 2004, 1499.
references cited therein.
(2) For some recent examples, see: (a) Otero, A.; Fern˜andez-Baeza, J.;
Antin˜olo, A.; Lara-Sa´nchez, A.; Mart´ınez-Caballero, E.; Tejeda, J.; Sa´nchez-
Barba, L. F.; Alonso-Moreno, C.; Lo´pez-Solera, I. Organometallics 2008,
27, 976. (b) Santillan, G. A.; Carrano, C. J. Inorg. Chem. 2008, 47, 930.
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Tetrahedron 1983, 39, 4133.
10.1021/om800603p CCC: $40.75
2008 American Chemical Society
Publication on Web 10/03/2008

Carbonyl Tungsten DeriVatiVes
Organometallics, Vol. 27, No. 21, 2008 5685
Scheme 1. Synthesis of Bis(3,5-dimethylpyrazol-1-yl)acyl
Tungsten Derivative
Figure 1. Molecular structure of 3. The thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths (Å) and angles
(deg): Sn(1)-C(41) 2.236(9), Sn(1)-C(18) 2.151(9), N(4)-C(41)
1.452(11), N(2)-C(41) 1.441(11), W(1)-N(1) 2.289(8), W(1)-N(3)
2.260(8); C(24)-Sn(1)-C(16) 119.6(4), C(18)-Sn(1)-C(41) 93.3(3),
N(4)-C(41)-Sn(1) 123.9(6), O(4)-C(4)-W(1) 166.5(9), O(2)-C-
(2)-W(1) 169.5(10), N(3)-W(1)-N(1) 80.3(3), N(2)-C(41)-N(4)
110.8(7), C(4)-W(1)-C(2) 163.4(4), C(1)-W(1)-N(3) 174.0(4).
understanding of the influence of the nature of substitutions on
the tin atom on these reactions, in this paper we synthesize
bis(3,5-methylpyrazol-1-yl)methanes modified with the bulky
(isopropyl)diphenyltin and tricyclohexyltin groups on the me-
thine carbon and study their related reactivities. Some novel
bis(3,5-dimethylpyrazol-1-yl)acyl and bis(3,5-dimethylpyrazol-
1-yl)methide carbonyl tungsten derivatives are obtained by the
reaction of heterobimetallic complexes R3SnCH(3,5-Me2Pz)2W-
(CO)4 with I2 and SnCl4.
organotin halide.7 In addition, the oxidation of group 6 metal
carbonyl derivatives of poly(pyrazol-1-yl)methane by halogen,
forming six- and seven-coordinate group 6 metal (0-VI) halides
of poly(pyrazol-1-yl)methane, has also been reported in the
literature.8 Although no oxidative addition reaction of the
Sn-Csp3 or Sn-Csp2 bond to the tungsten(0) atom takes place
during the reaction of ligands 1 and 2 with W(CO)5THF,
the products 3 and 4 are fascinating owing to their having two
reactive centers as described above. Thus these two complexes
are expected to display some markedly different reactivities
compared with the corresponding mononuclear complexes
possibly owing to the cooperative effects of two different metal
centers.9
It is interesting that treatment of complexes 3 and 4 with I2
leads to the novel η1-bis(pyrazol-1-yl)acyl complex CHC(O)(3,5-
Me2Pz)2W(CO)3I (5) (Scheme 1), with the loss of the organotin
group from the methine carbon. To investigate if the bulky
substituents on the tin atom are necessary for the novel reaction,
Et3SnCH(3,5-Me2Pz)2W(CO)4 is also treated with I2 under the
same conditions, which yields the same complex 5. The IR
spectrum of 5 clearly shows that this complex has a η1-acyl
coordinate mode with the characteristic carbonyl absorption at
1676.6 cm-1. The structure of 5 is further confirmed by X-ray
single-crystal diffraction, as shown in Figure 2. The carbonyl
group is bound to the tungsten in an η1-fashion, resulting in
bis(pyrazol-1-yl)acyl acting as a novel tridentate κ3-[N,C,N]
chelating ligand. The C(6)-C(9) bond length of 1.608(10) Å
is somewhat longer than other η1-acyl complexes of tungsten,10
possibly owing to the large strain originating from the chelating
Results and Discussion
Synthesis of Bis(3,5-dimethylpyrazol-1-yl)acyl Tungsten
Derivative. Treatment of (isopropyl)diphenylstannylbis(3,5-
dimethylpyrazol-1-yl)methane (1) and tricyclohexylstannyl-
bis(3,5-dimethylpyrazol-1-yl)methane (2), prepared by the
reactions of bis(3,5-dimethylpyrazol-1-yl)methyl lithium with
the corresponding organotin halide, with W(CO)5THF in re-
fluxing THF yields heterobimetallic complexes 3 and 4 (Scheme
1). No oxidative addition of the Sn-Csp3 or Sn-Csp2 bond to
the tungsten(0) atom is observed. These two complexes have
been characterized by spectroscopic methods. Their 119Sn{1H}
NMR signals are very similar to those in free ligands 1 and 2,
consistent with the reaction position away from the tin atom.
In addition, their IR spectra also display a typical cis-
tetracarbonyl arrangement around the tungsten atom.
The structure of complex 3, presented in Figure 1, has been
further confirmed by X-ray crystallography. As shown in Figure
1, the organotin group is still connected to the methine carbon
and lies in the axial position of the ligand. The fundamental
molecular framework is similar to that in (p-MeC6H4)3SnCH(3,5-
Me2Pz)2W(CO)4.6b It is worth noting that two cis-carbonyl
groups are markedly distorted with the O(4)-C(4)-W(1) angle
of 166.5(9)° and O(2)-C(2)-W(1) angle of 169.5(10)°, and
some angles around the Sn(1) and C(41) atoms (such as the
C(18)-Sn(1)-C(41) angle of 93.3(3)° and N(4)-C(41)-Sn(1)
angle of 123.9(6)°) significantly deviate from the tetrahedral
geometry of the sp3-hybridized Sn(1) and C(41). These geo-
metric parameters suggest a large steric repulsion in this
complex, as expected.
(7) (a) Thoonen, S. H. L.; Deelman, B. J.; von Koten, G. J. Organomet.
Chem. 2004, 689, 2145. (b) Ingham, R. K.; Rosenberg, S. D.; Gilman, H.
Chem. ReV. 1960, 60, 459.
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S.-L.; Wei, S.-C. Organometallics 1990, 9, 669. (c) Dhawan, I. K.; Bruck,
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(10) Ipaktschi, J.; Kooshenas, P.; Du¨lmer, A. Organometallics 2005,
24, 6239.
It is known that the reaction of tetraorganotin derivatives with
halogen leads to the cleavage of the Sn-C bond to give
(6) (a) Tang, L.-F.; Jia, W.-L.; Song, D.-T.; Wang, Z.-H.; Chai, J.-F.;
Wang, J.-T. Organometallics 2002, 21, 445. (b) Tang, L.-F.; Zhao, S.-B.;
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L.-F. J. Organomet. Chem. 2008, 693, 1359.

5686 Organometallics, Vol. 27, No. 21, 2008
Xie et al.
the W-Sn bond in CH(3,5-Me2Pz)2W(CO)3SnPh3 with I2.
However, no migratory insertion reaction is observed when the
solution of 6 is treated with CO under similar experimental
conditions in which 5 is formed. Thus an alternative mechanism
is suggested to interpret the formation of the bridging carbonyl.
It is known that the carbonyl group in cationic carbonyl metal
complexes is strongly activated toward nucleophilic attack owing
to the positive charge on the metal.13 The nucleophilic attack
at the carbonyl carbon in cationic carbonyl tungsten complexes
has been observed.14 In addition, the oxidative addition of
carbonyl tungsten derivatives of poly(pyrazol-1-yl)methane with
I2 yielding cationic carbonyl tungsten complexes is also
known.15 Taking into consideration the above facts, the initial
reaction to form complex 5 is more likely to take place on the
tungsten(0) atom to yield cationic intermediate C. Subsequently
the iodide anion attacks the tin atom to lead to the cleavage of
the Sn-Csp3 bond, and the nucleophilic attack of the resulting
anion on the carbonyl carbon atom gives complex 5.
Figure 2. Molecular structure of 5. The thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths (Å) and angles
(deg): W(1)-C(9) 2.231(7), W(1)-I(1) 2.8732(7), W(1)-N(1)
2.253(4), O(3)-C(9) 1.169(9), C(6)-C(9) 1.608(10), N(2)-C(6)
1.430(5); C(6)-C(9)-W(1) 101.6(4), O(3)-C(9)-C(6) 117.6(7),
N(1)-W(1)-N(1A) 84.7(2), N(2A)-C(6)-N(2) 112.9(6) (sym-
metric code A: x, -y + 1/2, z).
Synthesis of Bis(3,5-dimethylpyrazol-1-yl)methide Tung-
sten Derivative. The above novel reaction mode of heterobi-
metallic complexes R3SnCH(3,5-Me2Pz)2W(CO)4 with I2 in-
spires us to expand the investigations on reactivities of these
complexes. The oxidative addition of the tin(IV)-halogen bond
to low-valent group 6 metals has been well-established.16 Our
previous investigations indicated that the reaction with SnCl4
of group 6 metal carbonyl complexes with bis(pyrazol-1-yl)-
methane gives heterobimetallic M-Sn complexes in good
yields.17 Herein, treatment of heterobimetallic complexes
R3SnCH(3,5-Me2Pz)2W(CO)4 (R ) Cy or Et) with SnCl4 in a
1:1 molar ratio similarly gives the oxidative addition products
7 and 8 (Scheme 3), as expected. What is beyond expectation
is that these two complexes are also reactive in solution.
Complex 7 slowly converts to four-membered heterometalla-
cyclic complex 9 in CH2Cl2 solution at room temperature. We
are unable to obtain 8 in pure form because it exhibits a higher
reactivity compared with 7 in solution. In addition, when the
reaction of 4 with SnCl4 is carried out in a 1:2 molar ratio,
complex 9 is yielded directly. At the same time, complex 9 is
also obtained by the selective cleavage of the W-Sn bond in
CH(3,5-Me2Pz)2W(CO)3SnAr3 (Ar ) C6H5 or p-CH3C6H4) with
SnCl4.
effect of the bis(pyrazol-1-yl)acyl ligand. In addition, the
C(6)-C(9)-W(1) angle of 101.6(4)° significantly deviates from
the trigonal and planar C(9) atom of the sp2 hybridization,
probably influenced by the same factor. The long C(6)-C(9)
bond distance as well as the large strain makes this complex
unstable, which slowly loses the acyl group to yield four-
membered heterometallacyclic complex 6.
The M-acyl complexes are key intermediates in many
catalytic carbonylation reactions. Capturing these key species
and obtaining their structural parameters play an important role
in understanding the catalytic mechanism and improving the
activity of the catalyst. Although there are some examples of
η1-acyl tungsten complexes of scorpionate ligands in the
literature,11 the related acyl complexes of anionic heteroscor-
pionate ligands prior to our work are unknown. Herein we
present a case of the novel acyl complex of the heteroscorpionate
ligand.
Possible Pathways of the Formation of 5. The high reaction
rate, even at -50 °C, prevents us from obtaining any intermedi-
ate as the direct evidence for supporting the reaction pathways,
though several possible pathways to form complex 5 are
reasoned (Scheme 2). According to the known knowledge, the
initial reaction possibly takes place on the tin atom to form
intermediate A;7 subsequently the oxidative addition of the C-I
bond to the tungsten(0) atom gives 6.12 In the alternative possible
pathway, 6 is yielded via intermediate B,8b formed from the
initial reaction of R3SnCH(3,5-Me2Pz)2W(CO)4 with I2. The
lone electron pair on the iodine atom in B attacks the tin atom
to facilitate the cleavage of the Sn-Csp3 bond, and subsequently
the resulting anion attacks the tungsten atom to result in the
cleavage of this W-I bond, yielding 6. Although 6 cannot be
obtained from the reaction of R3SnCH(3,5-Me2Pz)2W(CO)4 with
I2, fortunately it can be prepared by the selective cleavage of
1
Complexes 7 and 9 have been characterized by IR and H
NMR spectroscopy, and their structures have been further
confirmed by X-ray structural analyses. The proton signal of
the CH group in complex 9 (5.55 ppm) is markedly shifted to
higher field, compared with those in 7 (6.08 ppm) and 4 (6.18),
but similar to that in 6 (5.41 ppm). Furthermore, complexes 6
and 9 have very similar IR spectra, indicating that they possibly
have analogous structures.
The crystal structure of complex 7 is presented in Figure 3.
One chlorine-bridged W-Sn bond is observed in this complex,
which is similar to other W(Mo)-Sn systems, such as
(L2)W(Cl)(CO)3(SnCl3) (L ) CH3CN, PPh3, dppe, and bipy)18
(13) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals, 3rd ed.; John Wiley & Sons, Inc.: New York, 2001; p 200.
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Organometallics 1986, 5, 158. (b) Treichel, P. M.; Shubkin, R. L. Inorg.
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(17) (a) Chai, J.-F.; Tang, L.-F.; Jia, W.-L.; Wang, Z.-H.; Wang, J.-T.;
Leng, X.-B.; Wang, H.-G. Polyhedron 2001, 20, 3249. (b) Tang, L.-F.;
Wang, Z.-H.; Xu, Y.-M.; Wang, J.-T.; Wang, H.-G.; Yao, X.-K. Polyhedron
1998, 17, 3765.
(18) (a) Szyman´ska-Buzar, T.; Głowiak, T. Polyhedron 1997, 16, 1599.
(b) Szyman´ska-Buzar, T.; Głowiak, T. Polyhedron 1998, 17, 3419.

Carbonyl Tungsten DeriVatiVes
Organometallics, Vol. 27, No. 21, 2008 5687
Scheme 2. Possible Pathways of the Formation of 5
Me3Pz)2W(CO)3SnPh3 and CH(3,5-iPr2Pz)2W(CO)3SnPh3.6b
6a
Scheme 3. Reaction of R3SnCH(3,5-Me2Pz)2W(CO)4 (R ) Cy,
Et) with SnCl4
The average W-N distance is 2.2345 Å, similar to those in
CH(3,5-iPr2Pz)2W(CO)3SnPh3 (2.217 Å) and CH(3,4,5-Me3Pz)2-
W(CO)3SnPh3 (2.2325 Å). The W-Csp3 bond distance is
2.296(13) Å, comparable to the corresponding bonds in CH(3,5-
iPr2Pz)2W(CO)3SnPh3 (2.343(6) Å) and CH(3,4,5-Me3Pz)2W-
(CO)3SnPh3 (2.326(5) Å). In addition, the W-Cl bond distance is
2.462(4) Å, slightly shorter than that in complex 7 (2.545(2) Å).
Although the chlorine bridge repels the SnCl3 group away
from the SnCy3 group in the solid 7, the approach of the chlorine
atom on the SnCl3 group to the tin atom of the SnCy3 group
should be possible in solution by the dissociation of this bridge
owing to the weak Sn(1) · · · Cl(1) interactions. Furthermore, in
the nonbridged W-SnCl3 complexes with bis(pyrazol-1-yl)-
methane ligands,17 the SnCl3 group close to the bridging carbon
has been observed. Thus, the possible formation pathway of 9
from 7 and 8 may be similar to that of the formation of 6 from
and CH2(4-BrPz)2Mo(CO)3(Cl)(SnCl2Ph).17a The Sn(1)-Cl(1)
distance (2.831(2) Å) is markedly longer than the terminal
Sn-Cl bond lengths (2.324(2)-2.336(2) Å), indicating that this
bond is relatively weak and possibly dissociates in solution. It
is also noted that the Sn(2)-C(9) bond length is longer than
those of the other three Sn-C bonds. In addition, some angles
around the Sn(2) and C(9) atoms (such as the C(9)-Sn(2)-C(21)
angle of 97.1(3)° and N(2)-C(9)-Sn(2) angle of 125.8(5)°)
significantly deviate from the tetrahedral geometry of the sp3-
hybridized Sn(2) and C(9), suggesting a large steric repulsion
in this complex. These structural parameters should be in favor
of the intramolecular redistribution reaction of the tricyclohexyl-
tin group with the SnCl3 group to yield complex 9.
The X-ray crystal structure of complex 9 consists of two
crystallographically independent molecules with similar struc-
tural parameters. One of them is presented in Figure 4, which
clearly shows that the bridging carbon of bis(pyrazol-1-
yl)methide is integrated with the tungsten atom to form two
four-membered heterometallacyclyes, as in complexes CH(3,4,5-
Figure 3. Molecular structure of 7. The thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths (Å) and angles
(deg): W(1)-N(1) 2.241(5), W(1)-N(4) 2.253(5), W(1)-Cl(1)
2.545(2),W(1)-Sn(1)2.7187(7),Sn(1) · · · Cl(1)2.831(2),Sn(1)-Cl(2)
2.336(2), Sn(1)-Cl(3) 2.324(2), Sn(1)-Cl(4) 2.369(2), Sn(2)-C(9)
2.264(7), Sn(2)-C(15) 2.125(8), N(2)-C(9) 1.447(8), N(3)-C(9)
1.459(9); N(1)-W(1)-N(4) 81.6(2), Cl(1)-W(1)-Sn(1) 64.96(4),
N(2)-C(9)-N(3) 110.1(5), N(2)-C(9)-Sn(2) 125.8(5), C(15)-Sn-
(2)-C(27)117.6(4),C(9)-Sn(2)-C(21)97.1(3),C(21)-Sn(2)-C(27)
106.4(3), Cl(2)-Sn(1)-Cl(4) 98.13(10), Cl(3)-Sn(1)-W(1)
121.15(6), Cl(3)-Sn(1)-Cl(2) 101.74(10).

5688 Organometallics, Vol. 27, No. 21, 2008
Xie et al.
Synthesis of (i-Pr)Ph2SnCH(3,5-Me2Pz)2 (1). To a solution of
bis(3,5-dimethylpyrazol-1-yl)methane (0.41 g, 2.0 mmol) in THF
(30 mL) was added a hexane solution of n-BuLi (2.5 M, 0.80 mL)
at -70 °C, and the mixture was stirred for 1 h at that temperature.
To the mixture was added a solution of the (i-Pr)Ph2SnI (0.89 g,
2.0 mmol) in THF (10 mL). The reaction mixture was stirred at
-70 °C for 1 h, allowed to slowly reach room temperature, and
stirred overnight. The solvent was removed under reduced pressure,
and the residual solid was recrystallized from hexane to yield white
crystals of 1. Yield: 0.65 g, 63%, mp 69-71 °C. 1H NMR: δ 1.29
(d, J ) 7.5 Hz, 6H, (CH3)2CH), 1.91 (m, 1H, (CH3)2CH), 1.81,
2.11 (s, s, 6H, 6H, CH3), 5.65 (s, 2H, 4-position hydrogen of
pyrazole ring), 6.34 (s, 1H, CHN), 7.18-7.33 (m, 10H, C6H5).
13C{1H} NMR: δ 11.0, 13.5 (3 and 5-CH3), 20.8 ((CH3)2CH), 21.6
((CH3)2CH), 70.2 (CHN), 106.9 (4-position carbon of pyrazole ring),
141.7, 147.0 (3- or 5-position carbon of pyrazole ring), 128.0, 128.3,
137.6, 139.7 (C6H5). 119Sn{1H} NMR: δ -128.1. Anal. Found: C,
60.35; H, 6.04; N, 10.97. Calcd for C26H32N4Sn: C, 60.14; H, 6.21;
N, 10.79.
Synthesis of Cy3SnCH(3,5-Me2Pz)2 (2). This ligand was
similarly obtained as above-mentioned for 1, but (i-Pr)Ph2SnI was
replaced by Cy3SnCl. Yield: 53%, mp 73-75 °C. 1H NMR: δ
1.36-1.78 (m, 33H, C6H11), 1.96, 2.09 (s, s, 6H, 6H, CH3), 5.61
(s, 2H, 4-position hydrogen of pyrazole ring), 6.18 (s, 1H, CH).
13C{1H} NMR: δ 11.1, 13.4 (3 and 5-CH3), 27.3, 29.5, 30.3, 31.8
(C6H11), 67.9 (CHN), 106.4 (4-position carbon of pyrazole ring),
138.9, 146.1 (3- or 5-position carbon of pyrazole ring). 119Sn{1H}
NMR: δ -85.9. Anal. Found: C, 60.80; H, 8.68; N, 9.46. Calcd
for C29H48N4Sn: C, 60.95; H, 8.47; N, 9.80.
Figure 4. Molecular structure of 9. The thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths (Å) and angles
(deg): W(1)-C(12) 2.296(13), W(1)-Cl(1) 2.462(4), W(1)-N(1)
2.242(10), W(1)-N(3) 2.227(11), N(2)-C(12) 1.450(15), N(4)-
C(12) 1.433(14); N(1)-W(1)-N(3) 87.9(4), N(1)-W(1)-C(12)
60.2(4), N(3)-W(1)-C(12) 60.2(4), N(2)-C(12)-N(4) 109.5(10),
N(4)-C(12)-W(1) 92.4(8), N(2)-C(12)-W(1) 92.4(7).
the intermediate B in Scheme 2, with the attack by the chlorine
atom on the SnCl3 group instead of the iodine atom. Namely,
the lone electron pair on one chlorine atom connected to the
Sn(1) atom attacks the Sn(2) atom to lead to the cleavage of
the Sn(2)-C(9) bond. Subsequently, the resulting anion attacks
the tungsten atom to result in the cleavage of the W-Sn bond
to complete the related reactions. Intermediate D is possibly
formed when 4 reacts with SnCl4 in a 1:2 molar ratio.19 The
stronger Lewis acidity of the tin atom on the methine atom in
intermediate D, compared with the corresponding tin atom in
4, possibly favors the attack of the chlorine atom on W-SnCl3,
which leads to quick formation of complex 9.
In conclusion, novel bis(3,5-dimethylpyrazol-1-yl)acyl and
bis(3,5-dimethylpyrazol-1-yl)methide carbonyl tungsten deriva-
tives can be easily synthesized by treatment of heterobimetallic
complexes R3SnCH(3,5-Me2Pz)2W(CO)4 with I2 or SnCl4.
Although strains exist in four-membered metallacycles of
complexes CH(3,5-Me2Pz)2W(CO)3X (X ) Cl or I), these
complexes are easily obtained and stable. The strong W-Csp3
bond possibly plays the key role in the formation of these four-
membered metallacycles.
Reaction of 1 and 2 with W(CO)5THF. Ligand 1 or 2 (0.3
mmol) was added to a solution of W(CO)5THF in THF, prepared
in situ by the irradiation of a solution of W(CO)6 (0.11 g, 0.30
mmol) in THF (20 mL) for 8 h, and the mixture was stirred and
heated at reflux for 5 h. After the reaction was complete, the solvent
was removed under reduced pressure. The residual solid was
purified by column chromatography on silica using CH2Cl2/hexane
(1:1 v/v) as eluent. The eluate was concentrated to dryness again,
and the residual solid was recrystallized from CH2Cl2/hexane to
give yellow-green crystals.
Synthesis of (i-Pr)Ph2SnCH(3,5-Me2Pz)2W(CO)4 (3). This
complex was obtained by the reaction of 1 with W(CO)5THF. Yield:
1
55%. H NMR: δ 1.21 (d, J ) 7.5 Hz, 6H, (CH3)2CH), 2.20 (m,
1H, (CH3)2CH), 2.15, 2.52 (s, s, 6H, 6H, CH3), 6.02 (s, 2H,
4-position hydrogen of pyrazole ring), 6.56 (s, 1H, CHN), 7.12-7.36
(m, 10H, C6H5). 13C{1H} NMR: δ 11.8, 17.1 (3 and 5-CH3), 21.4
((CH3)2CH), 24.3 ((CH3)2CH), 64.7 (CHN), 107.8 (4-position
carbon of pyrazole ring), 140.1, 157.8 (3- or 5-position carbon of
pyrazole ring), 128.6, 129.3, 136.6, 139.1 (C6H5), 206.8, 211.2
(CO). 119Sn{1H} NMR: δ -124.2. IR (cm-1): νCO ) 1997.6 vs,
1886.1 vs, 1844.8 vs, 1829.7 vs. Anal. Found: C, 44.39; H, 3.75;
N, 6.68. Calcd for C30H32N4O4SnW: C, 44.20; H, 3.96; N, 6.87.
Synthesis of Cy3SnCH(3,5-Me2Pz)2W(CO)4 (4). This complex
was obtained by the reaction of 2 with W(CO)5THF. Yield: 62%.
1H NMR: δ 1.24-1.29, 1.52-1.61, 1.64-1.89 (m, m, m, 15H,
12H, 6H, C6H11), 1.97, 2.10 (s, s, 6H, 6H, CH3), 5.69 (s, 2H,
4-position hydrogen of pyrazole ring), 6.18 (s, 1H, CHN). 13C{1H}
NMR: δ 11.2, 13.4 (3- and 5-CH3), 27.3, 29.4, 30.4, 31.7 (C6H11),
67.9 (CHN), 106.3 (4-position carbon of pyrazole ring), 139.0, 146.0
(3- or 5-position carbon of pyrazole ring), 201.8, 206.1, 211.4 (CO).
119Sn{1H} NMR: δ -86.0. IR (cm-1): νCO ) 1996.2, 1873.7,
1831.0 (br, vs). Anal. Found: C, 45.48; H, 5.74; N, 6.58. Calcd for
C33H48N4O4SnW: C, 45.70; H, 5.58; N, 6.46.
Experimental Section
General Considerations. All reactions were carried out under
an atmosphere of argon. Solvents were dried and distilled prior to
use according to standard procedures. NMR spectra were recorded
on a Bruker AV300 or Mercury 400BB spectrometer using CDCl3
as solvent unless otherwise noted, and the chemical shifts are
reported in ppm with respect to the reference (internal SiMe4 for
1H NMR and 13C{1H} NMR spectra, external SnMe4 for 119Sn{1H}
NMR). IR spectra were recorded as KBr pellets on a Bruker
Equinox55 spectrometer. Elemental analyses were carried out on
an Elementar Vairo EL analyzer. CH(3,5-Me2Pz)2W(CO)3SnAr3
(Ar ) Ph (10) and p-CH3C6H4 (11)),6b Et3SnCH(3,5-Me2Pz)2-
W(CO)4,6b and (i-Pr)Ph2SnI20 were prepared according to the
literature methods. Melting points were measured with an X-4
digital micro melting-point apparatus and are uncorrected.
Reaction of 3 and 4 as well as Et3SnCH(3,5-Me2Pz)2W-
(CO)4 with I2. To a stirred solution of 3, 4, or Et3SnCH(3,5-
Me2Pz)2W(CO)4 (0.058 mmol) in CH2Cl2 (15 mL) was added
dropwise at room temperature a CH2Cl2 solution (15 mL) of I2
(0.058 mmol). After addition was complete, the reaction mixture
(19) Elhamzaoui, H.; Jousseaume, B.; Toupance, T.; Allouchi, H.
Organometallics 2007, 26, 3908.
(20) Abel, E. W.; Brady, D. B. J. Chem. Soc. 1965, 1192.

Carbonyl Tungsten DeriVatiVes
Organometallics, Vol. 27, No. 21, 2008 5689
Table 1. Crystallographic Data for Complexes 3, 5, 7, and 9
3
5
7
9
formula
fw
C30H32N4O4SnW
815.14
C15H15IN4O4W
626.06
C32H48Cl4N4O3Sn2W
1099.77
C14H15ClN4O3W
506.60
cryst size, mm
cryst syst
space group
0.30 × 0.10 × 0.10
0.20 × 0.18 × 0.14
monoclinic
P21/m
0.18 × 0.16 × 0.14
0.14 × 0.10 × 0.08
triclinic
triclinic
triclinic
j
P1
j
P1
j
P1
cell params
a, Å
b, Å
c, Å
8.607(6)
10.833(8)
17.866(12)
93.782(11)
92.825(12)
112.388(11)
1531.9(18)
2
7.1875(13)
14.160(3)
9.0408(16)
90
97.959(3)
90
10.6878(16)
12.4245(18)
17.410(3)
74.486(3)
75.947(3)
65.769(2)
2008.0(5)
2
9.196(2)
14.033(3)
14.305(3)
81.941(5)
81.338(4)
73.698(4)
1742.3(7)
4
R, deg
ꢀ, deg
γ, deg
V, Å3
911.2(3)
2
Z
T, K
293(2)
1.767
792
4.606
7526/5181
(0.0578)
3179
294(2)
2.282
584
294(2)
1.819
1068
4.393
10 282/7037
(0.0338)
5005
294(2)
1.931
968
6.801
9929/7025
(0.0708)
3162
calcd density, Mg/m-3
F(000)
µ, mm-1
no. of rflns collcd/unique
8.059
5927/2498
(0.0336)
2003
(Rint
)
no. of rflns obsd with (I g 2σ(I))
no. of params
367
126
419
423
R, Rw (I g 2σ(I))
0.0516, 0.0806
0.925
0.0354, 0.0693
1.025
0.0398, 0.0787
0.984
0.0566, 0.0850
0.891
goodness-of-fit on F2
was stirred for an additional 1 h. The solvent was removed under
reduced pressure, and the residual solid was recrystallized from
CH2Cl2/hexane at -18 °C to give yellow crystals of CH(CO)(3,5-
Me2Pz)2W(CO)3I (5). Yield: 45% from 3, 40% from 4, and 50%
-18 °C to give red crystals of Cy3SnCH(3,5-Me2Pz)2W(CO)3-
(Cl)SnCl3 (7). Yield: 32 mg, 58%. 1H NMR: δ 1.62-1.97 (m, 33H,
C6H11), 2.35, 2.70 (s, s, 6H, 6H, 3- or 5-CH3), 6.08 (s, 2H, 4-position
hydrogen of pyrazole ring), 6.37 (s, 1H, CH). 13C{1H} NMR: δ
12.2, 17.5 (3- or 5-CH3), 26.9, 29.2, 32.3, 33.8 (C6H11), 59.3 (CH),
110.0 (4-position carbon of pyrazole ring), 140.3, 155.1 (3- or
5-position carbon of pyrazole ring). The carbonyl carbon signals
are not observed possibly due to the lower signal intensity and the
low solubility of complex 7. IR (cm-1): νCO ) 2020.7 s, 1996.5
vs, 1899.6 vs. Anal. Found: C, 34.61; H, 4.55; N, 4.92. Calcd for
C32H48Cl4N4O3Sn2W: C, 34.95; H, 4.40; N, 5.09. In addition, when
stirring the CH2Cl2 solution of 7 for 24 h at room temperature, this
complex slowly transformed to complex CH(3,5-Me2Pz)2W(CO)3Cl
1
from Et3SnCH(3,5-Me2Pz)2W(CO)4. H NMR: δ 2.44, 2.73 (s, s,
6H, 6H, CH3), 5.82 (s, 1H, CH), 6.05 (s, 2H, 4-position hydrogen
of pyrazole ring). IR (cm-1): νCO ) 2019.1 vs, 1919.2 vs; νCdO
)
1676.6 s. Anal. Found: C, 28.96; H, 2.25; N, 9.11. Calcd for
C15H15IN4O4W: C, 28.78; H, 2.42; N, 8.95. In addition, this reaction
was also carried out at -50 °C; only complex 5 was obtained.
During storage, this complex slowly lost the acyl group to yield
CH(3,5-Me2Pz)2W(CO)3I (6), which also can be obtained as
follows.
1
Reaction of CH(3,5-Me2Pz)2W(CO)3SnPh3 (10) with I2 to
Yield 6. To a stirred solution of 10 (110 mg, 0.134 mmol) in CH2Cl2
(15 mL) at 10 °C was dropwise added a solution of I2 (34.0 mg,
0.134 mmol) in CH2Cl2 (10 mL). After addition was complete, the
reaction mixture was stirred for an additional 2 h at room
temperature. The solvent was removed under reduced pressure, and
the residual solid was recrystallized from CH2Cl2/hexane to yield
(9). H NMR: δ 2.29, 2.47 (s, s, 6H, 6H, 3- or 5-CH3), 5.55 (s,
1H, CH), 5.76 (s, 2H, 4-position hydrogen of pyrazole ring). IR
(cm-1): νCO ) 2028.0 s, 1929.0 vs, 1892.0 s. Anal. Found: C, 32.86;
H, 2.60; N, 10.80. Calcd for C14H15ClN4O3W: C, 33.19; H, 2.98;
N, 11.06.
Reaction of Et3SnCH(3,5-Me2Pz)2W(CO)4 with SnCl4. To a
vigorously stirred solution of Et3SnCH(3,5-Me2Pz)2W(CO)4 (57 mg,
0.080 mmol) in CH2Cl2 (20 mL) cooled to 0 °C was slowly added
dropwise a solution of SnCl4 (0.080 mmol) in CH2Cl2 (5 mL). After
addition was complete, the reaction mixture was stirred for an
additional 1 h to 0 °C. The solvent was removed under reduced
pressure, and the residue was analyzed by 1H NMR spectroscopy,
indicating that no starting material was observed, and complexes
Et3SnCH(3,5-Me2Pz)2W(CO)3(Cl)SnCl3 (8) and 9 were formed. The
ratio was estimated to be ca. 3:1 (8:9) according to the integration
of the CH resonance. Unfortunately, we were unable to isolate
complex 8 in pure form owing to its instability in solution. In fact,
when the reaction mixture was stirred overnight, only complex 9
was observed by 1H NMR spectroscopy, and it was isolated in ca.
21% yield by silica column chromatography. 1H NMR data for 8:
δ 1.08-1.15 (m, 15H, C2H5), 2.29, 2.61 (s, s, 6H, 6H, 3- or 5-CH3),
6.06 (s, 2H, 4-position hydrogen of pyrazole ring), 6.33 (s, 1H,
CH).
1
52 mg (65%) of 6 as orange-red crystals. H NMR: δ 2.20, 2.43
(s, s, 6H, 6H, CH3), 5.67 (s, 2H, 4-position hydrogen of pyrazole
ring), 5.41 (s, 1H, CH). 13C{1H} NMR: δ 9.0, 13.0 (3- or 5-CH3),
40.3 (CH), 106.3 (4-position carbon of pyrazole ring), 141.9, 152.4
(3- or 5-position carbon of pyrazole ring), 220.5, 240.0 (CO). IR
(cm-1): νCO ) 2023.4 s, 1926.1 vs, 1898.8 vs. Anal. Found: C,
28.16; H, 2.52; N, 9.51. Calcd for C14H15IN4O3W: C, 28.12; H,
2.53; N, 9.37.
Attempted Reaction of 6 with CO. In a Schlenk flask, the
solution of 6 (20 mg, 0.033 mmol) in CH2Cl2 (10 mL) was degassed
by multiple freeze-pump-thaw cycles. The flask was refilled with
CO. The reaction mixture was warmed to room temperature and
stirred for additional 5 h under a CO atmosphere. After the solvent
was removed under reduced pressure, the residue was analyzed by
1H NMR spectroscopy, indicating that no reaction took place; only
starting material 6 was observed.
Reaction of 4 with SnCl4 in 1:1 Molar Ratio. To a vigorously
stirred solution of Cy3SnCH(3,5-Me2Pz)2W(CO)4 (43 mg, 0.050
mmol) in CH2Cl2 (15 mL) at room temperature was added dropwise
a solution of SnCl4 (0.050 mmol) in CH2Cl2 (5 mL). The color of
the solution changed from green-yellow to orange-red. After
addition was complete, the reaction mixture was stirred for an
additional 1 h. The solvent was removed under reduced pressure,
and the residual solid was recrystallized from CH2Cl2/hexane at
Reaction of 4 with SnCl4 in 1:2 Molar Ratio. This reaction
was carried out similarly to that described above for the reaction
in 1:1 molar ratio, using SnCl4 (0.10 mmol) instead. During the
reaction, some white solids precipitated. After the reaction was
complete, the solution was filtered off. With a similar workup, red
crystals of 9 were obtained. Yield: 45%.
In addition, this complex can also be obtained by the reaction
of CH(3,5-Me2Pz)2W(CO)3SnAr3 (Ar ) C6H5 (10) or p-CH3C6H4

5690 Organometallics, Vol. 27, No. 21, 2008
Xie et al.
(11)) with SnCl4 as follows. To a stirred solution of 10 or 11 (0.05
mmol) in CH2Cl2 (10 mL) at 10 °C was added dropwise a solution
of SnCl4 (0.05 mmol) in CH2Cl2 (5 mL). After addition was
complete, the reaction mixture was stirred for an additional 2 h at
room temperature. The solvent was removed under reduced
pressure, and the residual solid was purified by short column
chromatography on silica using CH2Cl2 as eluent. After removing
the solvent, the residual solid was recrystallized from CH2Cl2/
hexane to yield 9 as red crystals. Yield: 60% from 10 and 48%
from 11, respectively.
were resolved by the direct method and refined by full-matrix least-
squares on F2. All non-hydrogen atoms were refined anisotropically.
A summary of the fundamental crystal data for these complexes is
listed in Table 1.
Acknowledgment. This work is supported by the National
Natural Science Foundation of China (Nos. 20672059 and
20721062) and the Ministry of Education of China (NCET-
04-0227).
X-ray Crystallographic Determinations of 3, 5, 7, and 9.
Green-yellow crystals of 3 as well as red crystals of 5, 7, and 9
suitable for X-ray analyses were grown by diffusion of hexane into
their CH2Cl2 solutions at -18 °C. All intensity data were collected
with a Bruker SMART CCD diffractometer, using graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). The structures
Supporting Information Available: Tables of crystallographic
data, atom coordinates, thermal parameters, and bond distances and
angles for 3, 5, 7, and 9. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800603P