Reactivity of the four-membered heterometallacycles CH(3,5-Me 2Pz)2(CO)3WSnAr3 (Pz = Pyrazol-1-yl) with P(OR)3: Unexpected P-O/C exchange reactions in phosphite

Article abstract of DOI:10.1021/om7003332

Reactions of CH(3,5-Me₂Pz)₂(CO)₃WSnAr ₃ (Pz = pyrazol-1-yl; Ar = phenyl, p-tolyl) with P(OR)₃ (R = methyl, isopropyl) under solvent-free conditions give the decarbonylated complexes CH(3,5-Me₂Pz)₂-(CO)₂(P(OR) ₃)WSnAr₃. However, treatment of CH(3,5-Me_{2 2}Pz)₂(CO)₃WSnAr₃ with P(OMe) ₃ at elevated temperature results in unexpected P-O/C exchange reactions with the cleavage of the W-C bond to give the novel reductive elimination product (MeO)₂PCH(3,5-Me₂Pz) ₂W(CO)₃. Furthermore, even at low temperature, the reaction of CH(3,5-Me₂Pz)₂(CO)₃WSnAr ₃ with P(OAr)₃ only yields the similar reductive elimination products (ArO)₂PCH(3,5-Me₂Pz) ₂W(CO)₂. In these novel tungsten(0) complexes, the newly formed diaryl or dialkyl bis(3,5-dimethylpyrazol-1-yl)methylphosphonite acts as a neutral tridentate κ³-[N,N,P] chelating ligand.

Full text of DOI:10.1021/om7003332

4038
Organometallics 2007, 26, 4038-4041
Reactivity of the Four-Membered Heterometallacycles
CH(3,5-Me2Pz)2(CO)3WSnAr3 (Pz ) Pyrazol-1-yl) with P(OR)3:
Unexpected P-O/C Exchange Reactions in Phosphite
Xiao-Yan Zhang, Juan Hong, Hai-Bin Song, and Liang-Fu Tang*
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed April 4, 2007
Reactions of CH(3,5-Me2Pz)2(CO)3WSnAr3 (Pz ) pyrazol-1-yl; Ar ) phenyl, p-tolyl) with P(OR)3 (R
) methyl, isopropyl) under solvent-free conditions give the decarbonylated complexes CH(3,5-Me2Pz)2-
(CO)2(P(OR)3)WSnAr3. However, treatment of CH(3,5-Me2Pz)2(CO)3WSnAr3 with P(OMe)3 at elevated
temperature results in unexpected P-O/C exchange reactions with the cleavage of the W-C bond to
give the novel reductive elimination product (MeO)2PCH(3,5-Me2Pz)2W(CO)3. Furthermore, even at low
temperature, the reaction of CH(3,5-Me2Pz)2(CO)3WSnAr3 with P(OAr)3 only yields the similar reductive
elimination products (ArO)2PCH(3,5-Me2Pz)2W(CO)3. In these novel tungsten(0) complexes, the newly
formed diaryl or dialkyl bis(3,5-dimethylpyrazol-1-yl)methylphosphonite acts as a neutral tridentate κ3-
[N,N,P] chelating ligand.
tions on whether the reaction of these complexes with nucleo-
philic reagents also leads to novel reactivity modes. In this paper,
we report the distinctive reaction of 1 with P(OR)3, which leads
to an unexpected P-O/C exchange reaction with the cleavage
Introduction
Metallacycles have been extensively investigated for a long
time, due to the important roles they play in many catalytic
transformations. Furthermore, they are key intermediates in a
variety of catalytic C-C bond formation as well as C-C and
C-H bond activation reactions.1 Due to their ring strain, small
metallacycles such as metallacyclopropanes2 and metallacy-
clobutanes3 usually have high activity. For example, they
undergo easy ring expansion by the insertion of unsaturated
small molecules into the M-C bonds. The oxidative addition
of the C-C bond to the low-valent transition-metal centers is
one of the classic methods for the synthesis of metallacycles.1
Our recent investigations introduced the reaction of (triaryl-
stannyl)bis(pyrazol-1-yl)methane with W(CO)5THF, which leads
3
of the W-Csp bond instead of the simple carbonyl substitution
reaction, supplementing the common knowledge that the nu-
cleophilic attack of phosphorus ligands at metal carbonyl
complexes results in a carbonyl substitution reaction.
Results and Discussion
Reaction of 1 with P(OR)3 (R ) Me, i-Pr, Ph, p-MePh).
Upon treatment of 1 with trialkyl phosphite under solvent-free
conditions and at low temperature, only one carbonyl is
displaced to give complexes 2 (eq 2). However, when the
3
to the oxidative addition of the Sn-Csp bond to the tungsten-
(0) atom, yielding the novel heterodinuclear four-membered
heterometallacyclic complexes CH(3,5-Me2Pz)2(CO)3WSnAr3
(1) (eq 1).4 Upon treatment of 1 with electrophilic reagents such
3
as HX (X ) Cl, Br), the W-Csp bond in the small four-
membered metallacycles of 1 shows unusual reactivity, owing
to the ring strain and the high polarity of the metal-carbon
bond.5 This result has inspired us to carry out further investiga-
reaction of 1 with P(OMe)3 is carried out at elevated temper-
ature, the novel reductive elimination product (MeO)2PCH(3,5-
Me2Pz)2W(CO)3(3a) is obtained with an unexpected P-O/C
exchange reaction. Furthermore, even at low temperature the
reaction of 1 with P(OAr)3 yields only the reductive elimination
products (ArO)2PCH(3,5-Me2Pz)2W(CO)3. On the other hand,
even at elevated temperature, treatment of 1 with stronger
nucleophiles PR3 (R ) phenyl, n-butyl) under similar conditions
* To whom correspondence should be addressed. E-mail: lftang@
nankai.edu.cn. Fax: 0086-22-23502458.
(1) For reviews, see: (a) Jennings, P. W.; Johnson, L. L. Chem. ReV.
1994, 94, 2241. (b) Mashima, K. J. Synth. Org. Chem. Jpn. 1998, 56, 171.
(c) Ca´mpora, J.; Palma, P.; Carmona, E. Coord. Chem. ReV. 1999, 193-
195, 207. (d) Nakamura, I.; Yamamoto, Y. AdV. Synth. Catal. 2002, 344,
111.
10.1021/om7003332 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 06/29/2007

P-O/C Exchange Reactions in Phosphite
Organometallics, Vol. 26, No. 16, 2007 4039
only yields the decarbonylation products CH(3,5-Me2Pz)2(CO)2-
(PR3)WSnAr3 (see the Supporting Information), with no similar
P-C/C exchange reactions taking place.
Complexes 2 and 3 are air-stable in the solid state, and even
their solutions can be manipulated in the air without notable
decomposition. They have been characterized by elemental
analyses and IR and NMR spectroscopy. Complexes 2 and 3
display markedly different IR and NMR spectra. For example,
complexes 2 show two strong ν(CO) bands in the range of
1781-1880 cm-1, while complexes 3 have three such absorption
peaks in the range of 1781-2004 cm-1. The proton signal of
the CH group in 3 is markedly shifted to lower field in
comparison to the signals for 1 and 2 but is very close to those
in the ligands Ph3SnCH(3,5-Me2Pz)2 and (p-MePh)3SnCH(3,5-
Me2Pz)2.4a At the same time, the 13C NMR signals of the CH
group in complexes 3a and 3b are accordingly shifted to lower
field, in comparison with the signal for complex 2c. All of these
complexes display the expected 31P coupling to the proton and
carbon of the CH group. In addition, the 31P NMR signal in 3a
(204.36 ppm) is also markedly shifted to lower field in
comparison with those for complexes 2a (158.69 ppm) and 2b
(159.75 ppm) as well as for the free P(OMe)3 ligand (130.23
ppm). Furthermore, the 31P NMR signals of 3b (182.81 ppm)
and 3c (181.78 ppm) are also markedly different from those
for the free ligands P(OPh)3 (127.55 ppm) and P(OPhMe-p)
(127.57 ppm). These results are consistent with the fact that
the CH group in complexes 3 has linked to the phosphorus atom.
Figure 1. Molecular structure of 3b. The thermal ellipsoids
are drawn at the 30% probability level. Selected bond distances
(Å) and angles (deg): W(1)-C(1) ) 1.961(3), W(1)-C(2) ) 1.950-
(3), W(1)-C(3) ) 1.973(3), W(1)-N(1) ) 2.287(3), W(1)-N(3)
) 2.262(2), W(1)-P(1) ) 2.4269(8), P(1)-O(4) ) 1.618(2), P(1)-
C(9) ) 1.876(3), C(9)-N(2) ) 1.451(4), C(9)-N(4) ) 1.445(4),
C(1)-O(1) ) 1.173(4), C(2)-O(2) ) 1.166(4), C(3)-O(3) )
1.174(4); N(2)-C(9)-N(4) ) 110.7(2), N(4)-C(9)-P(1) ) 105.5-
(2), N(2)-C(9)-P(1) ) 103.9(1), C(21)-O(5)-P(1) ) 122.3(1),
O(5)-P(1)-O(4)
) 100.5(1), O(5)-P(1)-C(9) ) 96.0(1),
The molecular structure of 3b, presented in Figure 1, has been
confirmed further by X-ray single-crystal diffraction analyses,
which clearly show that the phosphorus atom is integrated with
the bridging carbon of bis(pyrazol-1-yl)methide and the newly
formed diphenyl bis(3,5-dimethylpyrazol-1-yl)methylphospho-
nite acts as a neutral tridentate κ3-[N,N,P] chelating ligand. The
tungsten atom adopts a six-coordinate distorted-octahedral
geometry. The average W-N distance is 2.275 Å, comparable
to the corresponding values found in other octahedral W(0)
complexes with poly(pyrazol-1-yl)alkanes or poly(pyrazol-1-
yl)silane (such as the average values 2.25 Å in Ph3GeCH(3,5-
Me2Pz)2W(CO)4,6 2.269 Å in Me3SiCH(3,5-Me2Pz)2W(CO)4,6
2.2915 Å in (CH2dCH)3SnCH(3,5-Me2Pz)2W(CO)3,4b 2.285 Å
O(5)-P(1)-W(1) ) 129.47(9), C(9)-P(1)-W(1) ) 93.65(9),
N(1)-W(1)-N(3) ) 77.81(9), C(1)-W(1)-N(3) ) 173.7(1),
C(3)-W(1)-P(1) ) 169.56(9), C(1)-W(1)-N(1) ) 98.6(1),
C(1)-W(1)-C(2) ) 88.1(1), W(1)-C(1)-O(1) ) 177.0(3),
W(1)-C(2)-O(2) ) 179.1(3), W(1)-C(3)-O(3) ) 175.8(3).
shorter than that reported in other W(0) complexes with
9
phosphorus ligands (such as 2.484(1) Å in (PNN)W(CO)3 ).
Possible Pathways of the Formation of 3. The P-C/X (X
) aryl, alkyl, N- or O-base group) exchange reactions in
transition-metal-phosphine complexes have been extensively
observed.10 In addition, the P-O/C exchange, through the
nucleophilic substitution reaction of triphenyl phosphite with
carbanions, has already been widely used in the synthesis of
phosphines, phosphinites, and phosphonites.11 In combination
with these known facts, a plausible mechanism for the formation
of 3 is depicted as in Scheme 1. Initially, the phosphorus electron
lone pair attacks the tungsten atom, leading to the cleavage of
the W-C bond. The resulting anion subsequently attacks the
phosphorus atom to complete the P-O/C exchange reaction.
Finally, the nucleophilic attack of the phenoxide or alkoxide
leaving group at the tin atom breaks the Sn-W bond to give
the reductive elimination products 3. In spite of the fact that
breaking of the W-C bond can release the ring strain of the
four-membered metallacycle in 1 as well as the decarbonylation
products CH(3,5-Me2Pz)2(CO)2(PR3)WSnAr3 (see the Support-
ing Information) and decrease the steric pressure at the tungsten
center of the decarbonylation products and the fact that triaryl-
7
in MeSi(3,5-Me2Pz)3W(CO)3 and 2.265 Å in PhP(3,5-Me2-
8
Pz)2W(CO)3 ). The W-P distance is 2.4269(8) Å, slightly
(2) For some recent examples, see: (a) Tsuchiya, K.; Kondo, H.;
Nagashima, H. Organometallics 2007, 26, 1044. (b) Okazaki, M.; Jung, K.
A.; Tobita, H. Organometallics 2005, 24, 659. (c) Lim, P. J.; Slizys, D. A.;
White, J. M.; Young, C. G.; Tiekink, E. R. T. Organometallics 2003, 22,
4853. (d) Bennett, M. A.; Castro, J.; Edwards, A. J.; Kopp, M. R.; Wenger,
E.; Willis, A. C. Organometallics 2001, 20, 980. (e) Ipaktschi, J.; Klotzbach,
T.; Du¨lmer, A. Organometallics 2000, 19, 5281. (f) Debad, J. D.; Legzdins,
P.; Lumb, S. A.; Rettig, S. J.; Batchelor, R. J.; Einstein, F. W. B.
Organometallics 1999, 18, 3414. (g) Wick, D. D.; Northcutt, T. O.;
Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484.
(3) For some recent examples, see: (a) Romero, P. E.; Piers, W. E. J.
Am. Chem. Soc. 2007, 129, 1698. (b) Suresh, C. H. J. Organomet. Chem.
2006, 691, 5366. (c) Bochkarev, L. N.; Begantsova, Y. E.; Bochkarev, A.
L.; Stolyarova, N. E.; Grigorieva, I. K.; Malysheva, I. P.; Basova, G. V.;
Platonova, E. O.; Fukin, G. K.; Baranov, E. V.; Kurskii, Y. A.; Abakumov,
G. A. J. Organomet. Chem. 2006, 691, 5240. (d) Harvey, B. G.; Mayne, C.
L; Arif, A. M.; Ernst, R. D. J. Am. Chem. Soc. 2005, 127, 16426. (e) Tsang,
W. C. P.; Hultzsch, K. C.; Alexander, J. B.; Bonitatebus, P, J., Jr.; Schrock,
R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2003, 125, 2652. (f) Slugovc, C.;
Mereiter, K.; Schmid, R.; Kirchner, K. Eur. J. Inorg. Chem. 1999, 1141.
(4) (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.;
Jia, W. L.; Yang, Z.; Song, D. T.; Wang, J. T. Organometallics 2003, 22,
3290.
(7) Pullen, E. E.; Rabinovich, D.; Incarvito, C. D.; Concolino, T. E.;
Rheingold, A. L. Inorg. Chem. 2000, 39, 1561.
(8) Cobbledick, R. E.; Dowdell, L. R. J.; Einstein, F. W. B.; Hoyano, J.
K.; Petrson, L. K. Can. J. Chem. 1979, 57, 2285.
(9) Yang, C. C.; Yeh, W. Y.; Lee, G. H.; Peng, S. M. J. Organomet.
Chem. 2000, 598, 353.
(10) Macgregor, S. A. Chem. Soc. ReV. 2007, 36, 67.
(5) Tang, L. F.; Hong, J.; Wen, Z. K. Organometallics 2005, 24, 4451.
(6) Tang, L. F.; Jia, W. L.; Zhao, X. M.; Yang, P. Wang, J. T. J.
Organomet. Chem. 2002, 658, 198.
(11) (a) Keller, J.; Schlierf, C.; Nolte, C.; Mayer, P.; Straub, B. F.
Synthesis 2006, 354 and references therein. (b) Albrow, V. E.; Blake, A.
J.; Fryatt, R.; Wilson, C.; Woodward, S. Eur. J. Org. Chem. 2006, 2549.

4040 Organometallics, Vol. 26, No. 16, 2007
Zhang et al.
1
Scheme 1. Possible Pathways of the Formation of 3
Yield: 45%. H NMR: δ 1.79, 2.41 (s, s, 6H, 6H, CH3), 2.28 (s,
3
9H, CH3C6H4), 3.56 (d, 9H, JPH ) 8.7 Hz, OCH3), 4.35 (d, 1H,
3JPH ) 2.1 Hz, CH), 5.60 (s, 2H, hydrogen in 4-position of
pyrazole), 6.98, 7.27 (d, d, JHH ) 5.4 Hz, 6H, 6H, C6H4). 31P
3
NMR: δ 159.75. IR (cm-1): νCO 1806.1 vs, 1877.3 s. Anal. Calcd
for C37H45N4O5PSnW‚CH2Cl2: C, 43.71; H, 4.54; N, 5.37. Found:
C, 44.14; H, 4.70; N, 5.61.
Synthesis of 2c. This complex was obtained by the reaction of
1a with P(O-i-Pr)3 at 80 °C for 3 h. The reaction mixture was
purified by column chromatography using CH2Cl2/hexane (1/1 v/v)
1
3
as eluent. Yield: 40%. H NMR: δ 1.19 (d, JHH ) 4.5 Hz, 18H,
3
OCH(CH3)2), 1.78, 2.47 (s, s, 6H, 6H, CH3), 4.36 (d, 1H, JPH
)
1.8 Hz, CH), 4.41-4.45 (m, 3H, OCH(CH3)2), 5.56 (s, 2H,
hydrogen in 4-position of pyrazole), 7.17-7.20, 7.41-7.44 (m, m,
9H, 6H, C6H5). 13C NMR: δ 8.71, 13.30 (carbons of 3- or 5-CH3),
24.26 (OCH(CH3)2), 52.12 (d, 2JPC ) 50.9 Hz, CH), 69.91 (d, 2JPC
) 8.5 Hz, OCH(CH3)2), 104.58 (carbon of 4-position of pyrazole),
127.31, 127.55, 137.15, 141.19 (C6H5), 146.21, 150.81 (carbons
of 3- and 5-positions of pyrazole), 228.79, 229.08 (CO). The 31P
coupling with carbonyl carbons is not observed, due to the lower
signal intensity. 31P NMR: δ 143.84. IR (cm-1): νCO 1797.1 vs,
1875.6 s. Anal. Calcd for C40H51N4O5PSnW: C, 47.98; H, 5.13;
N, 5.99. Found: C, 47.88; H, 5.26; N, 6.23.
or trialkylphosphines have stronger nucleophilicities in com-
parison with triaryl or trialkyl phosphites,12 no similar P-Caryl
/
C
alkyl exchange reactions10 take place upon treatment of 1 with
Synthesis of 2d. This complex was obtained by the reaction of
1b with P(O-i-Pr)3 at 80 °C for 3 h. The reaction mixture was
purified by column chromatography using CH2Cl2/hexane (1/1 v/v)
PR3. On the other hand, the reaction of 1 with triphenyl
phosphite, with a good phenoxide leaving group, only gives
the reductive elimination products 3, even at low temperature.
These facts indicate that the P-O/C exchange reaction may play
a decisive role in the formation process of 3.
1
3
as eluent. Yield: 36%. H NMR: δ 1.19 (d, JHH ) 4.5 Hz, 18H,
OCH(CH3)2), 1.78, 2.46 (s, s, 6H, 6H, CH3), 2.27 (s, 9H, CH3C6H4),
4.37 (d, 1H, 3JPH ) 2.4 Hz, CH), 4.39-4.45 (m, 3H, OCH(CH3)2),
5.56 (s, 2H, hydrogen in 4-position of pyrazole), 6.70, 7.30 (d, d,
3JHH ) 5.7 Hz, 6H, 6H, C6H4). 31P NMR: δ 144.45. IR (cm-1):
Experimental Section
νCO 1794.5 vs, 1875.7 s. Anal. Calcd for C43H57N4O5PSnW‚0.5CH2-
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 (1H, 13C, and
31P) were recorded on a Bruker AV300 spectrometer, and the
chemical shifts were reported in ppm with respect to reference
standards (internal SiMe4 for 1H NMR and 13C NMR spectra,
external 85% H3PO4 aqueous solution for 31P NMR spectra) using
CDCl3 as solvent unless otherwise noted. IR spectra were recorded
as KBr pellets on a Bruker Equinox55 spectrometer. Elemental
analyses were carried out on an Elementar Vairo EL analyzer.
Complexes 1 were prepared according to the literature methods.4b
Reaction of 1 with P(OR)3 (R ) Me, i-Pr) To Give Complexes
2. The mixture of complex 1a or 1b (0.5 mmol) and P(OR)3
(4 mmol) was stirred and heated at a suitable temperature for 4 h.
After it was cooled to room temperature, the reaction mixture was
washed with hexane to remove the excess P(OR)3, and the residue
was purified by column chromatography on silica using CH2Cl2/
hexane or ethyl acetate/hexane as eluent. The eluate was concen-
trated to dryness under reduced pressure, and the residual solid was
recrystallized from CH2Cl2/hexane to give yellow-green crystals.
Synthesis of 2a. This complex was obtained by the reaction of
1a with P(OMe)3 at 100 °C. The reaction mixture was purified by
column chromatography using CH2Cl2/hexane (3/2 v/v) as eluent.
Cl2: C, 48.07; H, 5.39; N, 5.16. Found: C, 48.53; H, 5.96;
N, 5.53.
Reaction of 1 with P(OR)3 (R ) Me, Ph, p-MePh) To Give
Complexes 3. The reaction was carried out as detailed above for
complexes 2. The reaction temperature was higher for P(OMe)3.
After a similar workup, yellow-green crystals of 3 were obtained.
Synthesis of 3a. This complex was obtained by the reaction of
1a or 1b with P(OMe)3 at 120 °C for 3 h. The reaction mixture
was purified by column chromatography using ethyl acetate as
eluent. Yield: 49% from 1a and 44% from 1b. 1H NMR: δ 2.36,
3
2.40 (s, s, 6H, 6H, CH3), 3.48 (d, 6H, JPH ) 13.2 Hz, OCH3),
5.93 (s, 2H, hydrogen in 4-position of pyrazole), 6.00 (d, 1H, 2JPH
) 4.5 Hz, CH). 13C NMR: δ 11.63, 16.11 (carbons of 3- or 5-CH3),
2
57.23 (d, JPC ) 12.5 Hz, OCH3), 71.74 (d, JPC ) 38.3 Hz, CH),
107.46 (carbon of 4-position of pyrazole), 139.05, 154.33 (carbons
of 3- and 5-positions of pyrazole), 214.99, 220.55, 220.66 (CO).
31P NMR: δ 204.36. IR (cm-1): νCO 1781.4 vs, 1805.7 sh, 1908.8
vs. Anal. Calcd for C16H21N4O5PW: C, 34.06; H, 3.75; N, 9.93.
Found: C, 34.04; H, 3.27; N, 9.48.
Synthesis of 3b. This complex was obtained by the reaction of
1a or 1b with P(OPh)3 at 80 °C for 4 h. The reaction mixture was
purified by column chromatography using ethyl acetate/hexane (1/1
1
v/v) as eluent. Yield: 46% from 1a and 45% from 1b. H NMR:
1
Yield: 53%. H NMR: δ 1.71, 2.34 (s, s, 6H, 6H, CH3), 3.49 (d,
δ 2.31, 2.39 (s, s, 6H, 6H, CH3), 5.98 (s, 2H, hydrogen in 4-position
9H, 3JPH ) 11.4 Hz, OCH3), 4.28 (d, 1H, 3JPH ) 3.3 Hz, CH), 5.54
(s, 2H, hydrogen in 4-position of pyrazole), 7.10-7.12, 7.32-7.35
(m, m, 9H, 6H, C6H5). 31P NMR: δ 158.69. IR (cm-1): νCO 1797.9
vs, 1879.0 s. Anal. Calcd for C34H39N4O5PSnW: C, 44.52; H, 4.29;
N, 6.11. Found: C, 44.44; H, 4.45; N, 6.02.
2
of pyrazole), 6.37 (d, 1H, JPH ) 4.2 Hz, CH), 6.65-6.68, 7.11-
7.14, 7.22-7.25 (m, m, m, 4H, 2H, 4H, C6H5). 13C NMR: δ 11.52,
15.87 (carbons of 3- or 5-CH3), 71.58 (d, JPC ) 46.1 Hz, CH),
107.45 (carbon of 4-position of pyrazole), 120.93, 125.60, 130.03,
152.20 (C6H5), 139.11, 154.57 (carbons of 3- and 5-positions of
pyrazole), 218.70, 218.81, 228.01 (CO). 31P NMR: δ 182.81. IR
(cm-1): νCO 1794.4 vs, 1814.5 vs, 1916.6 vs. Anal. Calcd for
C26H25N4O5PW: C, 45.37; H, 3.66; N, 8.14. Found: C, 45.51; H,
3.48; N, 8.36. In addition, this reaction was also carried out at
60 °C; only 3b was isolated. At temperatures lower than 60 °C, no
evident reaction was observed.
Synthesis of 2b. This complex was obtained by the reaction of
1b with P(OMe)3 at 80 °C. The reaction mixture was purified by
column chromatography using CH2Cl2/hexane (2/1 v/v) as eluent.
(12) (a) Rahman, M. M.; Liu, H. Y.; Eriks, K.; Prock, A.; Giering, W.
P. Organometallics 1989, 8, 1. (b) Kempf, B.; Mayr, H. Chem. Eur. J.
2005, 11, 917.

P-O/C Exchange Reactions in Phosphite
Organometallics, Vol. 26, No. 16, 2007 4041
Synthesis of 3c. This complex was obtained by the reaction of
1a or 1b with P(O-p-MePh)3 at 100 °C for 4 h. The reaction mixture
was purified by column chromatography using ethyl acetate/hexane
(1/1 v/v) as eluent. Yield: 39% from 1a and 42% from 1b,
respectively. 1H NMR: δ 2.29 (s, 6H, CH3C6H4), 2.39, 2.43 (s, s,
6H, 6H, CH3), 6.03 (s, 2H, hydrogen in 4-position of pyrazole),
(3) Å, â ) 95.225(2)o, V ) 2546.1(7) Å3, Z ) 4, Dcalcd ) 1.796 g
cm-3, T ) 113(2) K, A total of 6071 unique reflections was used
for refinement (Rint ) 0.0410); final R indices (I g 2σ(I)) were R1
) 0.0253 and wR2 ) 0.0611.
Acknowledgment. This work was supported by the National
Natural Science Foundation of China (Nos. 20672059 and
20421202) and the Ministry of Education of China (No. NCET-
04-0227).
6.38 (d, 1H, 2JPH ) 3.0 Hz, CH), 6.60, 7.05 (d, d, 4H, 4H, 3JHH
)
6.0 Hz, C6H4). 31P NMR: δ 181.78. IR (cm-1): νCO 1800.8 vs,
1854.9 vs, 2003.8 vs. Anal. Calcd for C28H29N4O5PW: C, 46.95;
H, 4.08; N, 7.82. Found: C, 47.28; H, 4.16; N, 7.86.
X-ray Crystallographic Determination of 3b. Yellow-green
crystals of 3b suitable for X-ray analyses were grown by slow
diffusion of hexane into its CH2Cl2 solution at -10 °C. All intensity
data were collected with a Rigaku Saturn CCD diffractometer, using
graphite monochromated Mo KR radiation (λ ) 0.710 70 Å). The
structure was resolved by direct methods and refined by full-matrix
least squares on F2. All non-hydrogen atoms were refined aniso-
tropically. Crystal data: C26H25N4O5PW, Mr ) 688.32, monoclinic,
space group P21/c, a ) 15.739(3) Å, b ) 9.6644(14) Å, c ) 16.808-
Supporting Information Available: Text, figures, and tables
giving details of the reaction of 1 with PR3 (R ) Ph, n-Bu),
crystallographic data, atom coordinates, thermal parameters, and
bond distances and angles for 3b and the decarbonylation products
CH(3,5-Me2Pz)2(CO)2(PR3)WSnAr3, and two ORTEP plots of the
decarbonylation products. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM7003332