An unprecedented κ3-[N,C,N] coordination mode of the bis(3,4,5-trimethylpyrazol-1-yl)methide ligand

Article abstract of DOI:10.1021/om0109307

The coordination modes of the bis(3,4,5-trimethylpyrazol-1-yl) methide ligand were investigated. The treatment of ligand with W(CO)₅THF resulted in the oxidative addition of tin-carbon bonds. The addition reaction yielded the heterodinuclear co

Full text of DOI:10.1021/om0109307

© Copyright 2002
Volume 21, Number 3, February 4, 2002
American Chemical Society
Communications
An Un p r eced en ted K3-[N,C,N] Coor d in a tion Mod e of th e
Bis(3,4,5-tr im eth ylp yr a zol-1-yl)m eth id e Liga n d
Liang-Fu Tang,*,† Wen-Li J ia,† Da-Tong Song,† Zhi-Hong Wang,†
J ian-Fang Chai,† and J i-Tao Wang‡
Department of Chemistry and State Key Laboratory of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, People’s Republic of China
Received October 26, 2001
Summary: Treatment of triarylstannyl-bis(3,4,5-trim-
ethylpyrazol-1-yl)methane, Ar3SnCH(3,4,5-Me3Pz)2 (Ar
) phenyl or p-tolyl), with W(CO)5THF results in the
oxidative addition of the tin-carbon(sp3) bond to the
tungsten(0) center to yield the heterodinuclear complexes
CH(3,4,5-Me3Pz)2(CO)3W-SnAr3, in which four-mem-
bered metallacycles are found and bis(3,4,5-trimeth-
ylpyrazol-1-yl)methide acts as a tridentate monoanionic
κ3-[N,C,N] chelating ligand.
purity synthetic methods for poly(pyrazol-1-yl)alkanes
have been explored.5b,7 In recent years, modification of
the central carbon atom by the organic functional groups
to form heteroscorpionate ligands has also been suc-
cessful. These new heteroscorpionate ligands usually
have asymmetric N2O,8 N2S,9 or N3O10 coordination
environments. Recently, replacement of the central
carbon atom by the silicon atom to form poly(pyrazol-
(5) For some recent examples see: (a) Tang, L. F.; Wang, Z. H.; J ia,
W. L.; Xu Y. M.; Wang, J . T. Polyhedron 2000, 19, 381. (b) Pettinari,
C.; Pellei, M.; Cingolani, A.; Martini, D.; Drozdov, A.; Troyanov, S.;
Panzeri, W.; Mele, A. Inorg. Chem. 1999, 38, 5777. (c) Reger, D. L.;
Collins, J . E.; Mattews, M. A.; Rheingold, A. L.; Liable-Sands, L. M.;
Guzei, I. A. Inorg. Chem. 1997, 36, 6266. (d) Reger, D. L.; Collins, J .
E.; Rheingold, A. L.; Liable-Sands, L. M.; Yap, G. P. A. Inorg. Chem.
1997, 36, 345. (e) Reger, D. L.; Collins, J . E.; Lovland, R.; Adams, R.
D. Inorg. Chem. 1996, 35, 1372. (f) Pettinari, C.; Lorenzotti, A.; Sclavi,
G.; Cingolani, A.; Rivarola, E.; Colapietro, M.; Cassetta, A. J . Orga-
nomet. Chem. 1995, 496, 69.
(6) For some recent examples see: (a) Arroyo, N.; Go´mez-de la Torre,
F.; J alo´n, F. A.; Manzano, B. R.; Moreno-Lara, B.; Rodr´ıguez, A. M. J .
Organomet. Chem. 2000, 603, 174. (b) Tsuji, S.; Swenson, D. C.; J ordan,
R. F. Organometallics 1999, 18, 4758. (c) Reger, D. L.; Collins, J . E.;
Rheingold, A. L.; Liable-Sands, L. M. Inorg. Chem. 1999, 38, 3235. (d)
Reger, D. L.; Collins, J . E.; Rheingold, A. L.; Liable-Sands, L. M.; Yap,
G. P. A. Organometallics 1997, 16, 349. (e) Reger, D. L.; Collins, J . E.;
Rheingold, A. L.; Liabble-Sands, L. M. Organometallics 1996, 15, 2029.
(f) Dhawan, I. K.; Bruck, M. A.; Schilling, B.; Grittini, C.; Enemark, J .
H. Inorg. Chem. 1995, 34, 3801.
Poly(pyrazol-1-yl)alkanes were first reported to form
transition-metal complexes by Trofimenko in 1970.1
After that, and especially after an improved synthetic
method was developed by J ulia et al.,2 the coordination
chemistry of these ligands has received increasing
attention.3,4 A number of main-group5 and transition-
metal6 complexes containing poly(pyrazol-1-yl)alkanes
have been synthesized and characterized in recent
years. To advance the development of poly(pyrazol-1-
yl)alkane chemistry, some new higher yield and higher
* To whom correspondence should be addressed. E-mail: tanglf@
eyou.com. Fax: 0086-22-23502458.
† Department of Chemistry.
‡ State Key Laboratory of Elemento-Organic Chemistry.
(1) Trofimenko, S. J . Am. Chem. Soc. 1970, 92, 5118.
(2) J ulia, S.; del Mazo, J . M.; Avila, L.; Elguero, J . Org. Prep. Proced.
Int. 1984, 16, 299.
(7) (a) Reger, D. L.; Grattan, T. C.; Brown, K. J .; Little, C. A.; Lamba,
J . J . S.; Rheingold, A. L.; Sommer, R. D. J . Organomet. Chem. 2000,
607, 120. (b) Reger, D. L.; Collins, J . E.; J ameson, D. L.; Castellano,
R. K. Inorg. Synth. 1998, 32, 63. (c) Titze, C.; Hermann, J .; Vahren-
kamp, H. Chem. Ber. 1995, 128, 1095.
(3) Byers, P. K.; Canty, A. J .; Honeyman, R. T. Adv. Organomet.
Chem. 1992, 34, 1.
(4) Trofimenko, S. Prog. Inorg. Chem. 1986, 34, 115.
10.1021/om0109307 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 01/09/2002

446 Organometallics, Vol. 21, No. 3, 2002
Communications
1-yl)silanes has been reported.11 However, the modifica-
tion of poly(pyrazol-1-yl)alkanes by substitution of
organometallic groups on the central carbon atom is
rare.12 Such poly(pyrazol-1-yl)alkanes are expected to
have unusual reactivity, owing to the introduction of the
organometallic groups. In this paper we report the
synthesis of two new poly(pyrazol-1-yl)alkanes modified
by introduction of organotin groups on the central
carbon atom and their reaction with W(CO)5THF to
yield heterodinuclear complexes containing four-mem-
bered metallacycles, in which bis(3,4,5-trimethylpyrazol-
1-yl)methide acts as an unprecedented tridentate
monoanionic κ3-[N,C,N] chelating ligand.
signal of the CH group in 1 is remarkably different from
that in 2, which appears at 6.50 ppm for 1a and 6.70
ppm for 1b, respectively, but is considerably shifted to
higher field in 2, appearing at 4.34 ppm for 2a and 2b.
The smaller electronegativity of tungsten compared with
that of tin may be responsible for this upfield shift.
Three strong ν(CO) bands in the range 1970-1840 cm-1
are observed in the IR spectrum of 2, which is consistent
with the tricarbonyltungsten species.
The structures of 2 have also been confirmed by X-ray
crystallography.15 The crystal structure of 2a (Figure
1) is similar to that of 2b (Figure 2, in the Supporting
Information). They clearly show that the triarylstannyl
groups have been transferred to the tungsten center and
that new tungsten-saturated carbon and tungsten-tin
bonds have been formed. The seven-coordinate tungsten
atom in 2a or 2b is best described as a capped octahe-
dron with the triarylstannyl groups in the capping
position. The capped face is made up of C(1), C(2), and
C(4) atoms for 2a and C(1), C(2), and C(10) atoms for
2b. The W-Sn distance is 2.7795(4) Å in 2a and 2.7845-
(15) Å in 2b, which is within the normal range for W-Sn
bonds.16 The most interesting structural feature of 2 is
that bis(3,4,5-trimethylpyrazol-1-yl)methide acts as a
tridentate, monoanionic κ3-[N,C,N] chelating ligand,
resulting in formation of two novel four-membered
metallaheterocycles. This coordination mode has not
been reported previously for poly(pyrazol-1-yl)alkane
The modification of bis(3,4,5-trimethylpyrazol-1-yl)-
methane by substitution of organotin groups on the
central carbon atom was readily carried out by reaction
of (bis(3,4,5-trimethylpyrazol-1-yl)methyl)lithium13 with
a triaryltin chloride as shown in eq 1. Treatment of 1a
(13) To a solution of bis(3,4,5-trimethylpyrazol-1-yl)methane (2
mmol) in THF (40 mL) under Ar was added a hexane solution of n-BuLi
(2 M, 1.0 mL) at -78 °C, and the mixture was stirred for 1 h at that
temperature. To the mixture was added a solution of the triaryltin
chloride (2 mmol) in THF (10 mL). The reaction mixture was stirred
at -78 °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. Physical and spectroscopic data for 1a are as follows. Yield:
49%. Mp: 132-134 °C. Anal. Found: C, 64.05; H, 5.88; N, 9.57. Calcd
for C31H34N4Sn: C, 64.03; H, 5.85; N, 9.64. IR (KBr, cm-1): 1577.7 s
(ν(pyrazole ring)). 1H NMR (CDCl3, 200 MHz): δ 1.77, 1.80, 2.11 (s, s,
s, 6H, 6H, 6H, CH3), 6.50 (s, 1H, CH), 7.38-7.65 (m, 15H, C6H5).
Physical and spectroscopic data for 1b are as follows. Yield: 51%. Mp:
150-152 °C. Anal. Found: C, 65.40; H, 6.38; N, 9.01. Calcd for
and 1b with W(CO)5THF in refluxing THF resulted in
3
the oxidative addition of the Sn-Csp bond to the
C
34H40N4Sn: C, 65.49; H, 6.42; N, 8.99. IR (KBr, cm-1): 1584.3 s
tungsten(0) center to yield the novel four-membered
(ν(pyrazole ring)). 1H NMR (CDCl3, 200 MHz): δ 1.76, 2.12 (s, s, 12H,
6H, CH3), 2.30 (s, 9H, p-CH3C6H4), 6.70 (s, 1H, CH), 7.23, 7.43 (d, d,
6H, 6H, p-CH3C6H4).
metallacyclic complexes 2,14 which were characterized
1
by H NMR spectroscopy, their IR spectra, and elemen-
(14) Compounds 1 (0.3 mmol) were added to a solution of W(CO)5THF
in THF, prepared in situ by the irradiation of a solution of W(CO)6
(0.3 mmol) in THF (20 mL) for 8 h, and the mixture was stirred and
heated at reflux for 2 h. After the reaction was complete, the solvent
was removed under reduced pressure, and the residual solid was
purified by column chromatography on alumina using CH2Cl2/hexane
(1/2 v/v) as eluent. The eluate was concentrated to dryness under
reduced pressure, and the residual solid was recrystallized from CH2-
Cl2/hexane to give orange-red crystals. Spectroscopic data for 2a are
as follows. Yield: 41%. Anal. Found: C, 47.10; H, 3.59; N, 6.30. Calcd
for C34H34N4O3SnW‚0.25CH2Cl2: C, 47.23; H, 3.96; N, 6.43. IR (KBr,
cm-1): 1970.0 s, 1876.0 s, 1843.0 s (ν(CO)). 1H NMR (CDCl3, 200
MHz): δ 1.73, 1.83, 2.24 (s, s, s, 6H, 6H, 6H, CH3), 4.34 (s, 1H, CH),
5.29 (s, 0.5H, CH2Cl2), 7.23-7.44 (m, 15H, C6H5). Spectroscopic data
for 2b are as follows. Yield: 33%. Anal. Found: C, 46.46; H, 4.27; N,
5.92. Calcd for C37H40N4O3SnW‚CH2Cl2: C, 46.71; H, 4.30; N, 5.74. IR
(KBr, cm-1): 1969.9 s, 1878.3 s, 1839.7 s (ν(CO)). 1H NMR (CDCl3,
200 MHz): δ 1.73, 1.82, 2.22 (s, s, s, 6H, 6H, 6H, CH3), 2.27 (s, 9H,
p-CH3C6H4), 4.34 (s, 1H, CH), 5.28 (s, 2H, CH2Cl2), 7.03, 7.23 (d, d,
6H, 6H, p-CH3C6H4).
tal analyses, as well as X-ray structure analyses of 2a
and 2b.
Complexes 2 are air-stable in the solid state, and even
their solutions could be manipulated in air. The proton
(8) (a) Hammes, B. S.; Carrano, C. J . Inorg. Chem. 1999, 38, 3562.
(b) Higgs, T. C.; Carrano, C. J . Inorg. Chem. 1997, 36, 298. (c) Otero,
A.; Ferna´ndez-Baeza, J .; Tejeda, J .; Antin˜olo, A.; Carrillo-Hermosilla,
F.; D´ıez-Barra, E.; Lara-Sa´nchez, A.; Ferna´ndez-Lo´pez, M. J . Chem.
Soc., Dalton Trans. 2000, 2367. (d) Beck, A.; Weibert, B.; Burzlaff, N.
Eur. J . Inorg. Chem. 2001, 521.
(9) (a) Hammes, B. S.; Carrano, C. J . J . Chem. Soc., Dalton Trans.
2000, 3304. (b) Hammes, B. S.; Carrano, C. J . J . Chem. Soc., Chem.
Commun. 2000, 1635. (c) Astley, T.; Hitchman, M. A.; Skelton, B. W.;
White, A. H. Aust. J . Chem. 1997, 50, 145. (d) Alsfasser, R.; Vahren-
kamp, H. Inorg. Chim. Acta 1993, 209, 19.
(10) Kla¨ui, W.; Berghahn, M.; Rheinwald, G.; Lang, H. Angew.
Chem., Int. Ed. 2000, 39, 2464.
(11) (a) Pullen, E. E.; Rabinovich, D.; Incarvito, C. D.; Concolino, T.
E.; Rheingold, A. L. Inorg. Chem. 2000, 39, 1561. (b) Richburg, L. M.;
Farouq, J . A.; Incarvito, C. D.; Rheingold, A. L.; Rabinovich, D.
Polyhedron 2000, 19, 1815. (c) Stibrany, R. T.; Knapp, S.; Potenza, J .
A.; Schugar, H. J . Inorg. Chem. 1999, 38, 132.
(15) Crystallographic data for 2a : triclinic, P1h, a ) 9.6379(7) Å, b
) 13.684(1) Å, c ) 13.876(1) Å, R ) 97.379(1)°, â ) 94.724(1)°, γ )
94.196(1)°, V ) 1802.2(2) Å3, Z ) 2, Dcalcd ) 1.604 g cm-3, T ) 298 K,
6326 unique reflections, 5623 with I > 2σ(I), R (Rw) ) 0.0294 (0.0848).
Crystallographic data for 2b: monoclinic, P21/n, a ) 10.541(5) Å, b )
22.32(1) Å, c ) 17.059(9) Å, â ) 93.928(9)°, V ) 4004(3) Å3, Z ) 4,
Dcalcd ) 1.619 g cm-3, T ) 293 K, 16 397 collected reflections, 7005
with I > 2σ(I), R (Rw) ) 0.0436 (0.0791).
(12) (a) Antin˜olo, A.; Carrillo-Hermosilla, F.; D´ıez-Barra, E.; Ferna´n-
dez-Baeza, J .; Ferna´ndez-Lo´pez, M.; Lara-Sa´nchez, A.; Moreno, A.;
Otero, A.; Rodriguez, A. M.; Tejeda, J . J . Chem. Soc., Dalton Trans.
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11.

Communications
Organometallics, Vol. 21, No. 3, 2002 447
The oxidative addition of a tin-phenyl carbon bond
to a tungsten(0) center to yield W-Sn bonded complexes
with a κ3-[C,N,N′] ligand has been reported,17 but there
is no prior report of tungsten complexes containing sp3-
hybridized carbon in κ3-[N,C,N] ligands.18 The present
report also exhibits a novel coordination mode for poly-
(pyrazol-1-yl)alkanes. The other interesting aspect of the
present report is that stable metallacyclic complexes
having an M-M′ bond can be formed under mild
conditions. In view of known catalytic processes involv-
ing the formation of metallacyclic fragments, and the
potential catalytic activity of heterobimetallic com-
plexes, the present results are of some interest. Fur-
thermore, the present results suggest that poly(pyrazol-
1-yl)alkanes with organometallic groups on the central
carbon may have distinctive reactivity, and modification
of the central carbon using a more extensive range of
organometallic groups is in progress.
Ack n ow led gm en t. This work was supported by the
National Natural Science Foundation of China (No.
20172029) and State Key Laboratory of Elemento-
Organic Institute of Nankai University.
F igu r e 1. Molecular structure of 2a . The thermal el-
lipsoids are drawn at the 30% probability level. Selected
bond distances (Å) and angles (deg): W(1)-N(1) ) 2.222-
(4), W(1)-N(4) ) 2.243(4), W(1)-C(4) ) 2.326(5), W(1)-
Sn(1) ) 2.7795(4), N(3)-C(4) ) 1.462(6), N(2)-C(4) )
1.458(6); N(1)-W(1)-N(4) ) 82.00(16), C(3)-W(1)-C(4) )
155.6(2), N(1)-W(1)-C(4) ) 60.63(16), N(4)-W(1)-C(4) )
60.51(15), N(2)-C(4)-N(3) ) 109.2(4), N(2)-C(4)-W(1) )
91.1(3), N(3)-C(4)-W(1) ) 91.2(3).
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data, atom coordinates, thermal parameters, and
bond distances and angles for 2a and 2b and an ORTEP plot
of 2b. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM0109307
(17) Buffin, B. P.; Poss, M. J .; Arif, A. M.; Richmond, T. G. Inorg.
Chem. 1993, 32, 3805.
(18) (a) van Koten, G. Pure Appl. Chem. 1989, 61, 1681. (b) Rietveld,
M. H. P.; Grove, D. M.; van Koten, G. New J . Chem. 1997, 21, 751.
ligands. It is also noteworthy that in the four-membered
metallaheterocycles the angles N-C-W are very close
to 90°.