Osmabenzenes from the reactions of HC≡CCH(OH)C≡CH with OsX 2(PPh3)3 (X = Cl, Br)

Article abstract of DOI:10.1021/ja0486871

Treatment of OsX₂(PPh₃)₃ (X = Cl, Br) with HC≡CCH(OH)C≡CH in THF produces OsX₂(CH=C(PPh₃)CH(OH)C≡CH)(PPh₃)₂, which reacts withPPh₃ to give osmabenzenes [Os(CHC(PPh

Full text of DOI:10.1021/ja0486871

Published on Web 05/14/2004
Osmabenzenes from the Reactions of HC≡CCH(OH)C≡CH with OsX2(PPh3)3
(X ) Cl, Br)
Haiping Xia,*,†,‡ Guomei He,‡ Hong Zhang,‡ Ting Bin Wen,† Herman H. Y. Sung,†
Ian D. Williams,† and Guochen Jia*,†
Department of Chemistry, The Hong Kong UniVersity of Science and Technology, Clear Water Bay, Kowloon,
Hong Kong, and The College of Chemistry and Chemical Engineering, Xiamen UniVersity, Xiamen, P. R. China
Received March 8, 2004; E-mail: chjiag@ust.hk
The chemistry of transition metal containing metallabenzenes1
is attracting increasing attention both experimentally2 and theoretic-
ally.3 Metallabenzenes are interesting because they can display
aromatic properties and they can mediate organometallic reactions.
The isolation and characterization of stable metallabenzenes rep-
resents one of the major issues of metallabenzene chemistry. The
common strategies previously employed to construct stable met-
allabenzene rings include cyclization reactions of alkynes with
metal-thiocarbonyl,2i,4 deprotonation of pentadienediyl iridium
species (derived from the reactions of IrCl(PR3)3 with potassium
3,5-dimethylpentadienide),5 reactions of LnMCl with lithiated
3-vinyl-1-cyclopropenes,2a,d,e,6 and oxidation of bicyclic iridium
complexes derived from the coupling of alkynes.2b During an in-
vestigation of the reactivity of OsCl2(PPh3)3 with terminal alkynes,7
we found a new convenient route to prepare osmabenzenes starting
from readily accessible HCtCCH(OH)CtCH. The investigation
led us to isolate the first phosphonium salts of metallabenzenes.
Treatment of OsCl2(PPh3)3 8 (1) with HCtCCH(OH)CtCH9 in
Figure 1. Molecular structure for the complex cation of 2. The hydrogens
of phenyls are omitted for clarity. Selected bond distances (Å): Os-C1,
dichloromethane produced 2, which can be isolated as a green solid
1.946(12); C1-C2, 1.398(15); C2-C3, 1.373(16); C3-C4, 1.448(17),
in 44% yield (Scheme 1). Compound 2 has been characterized
C4-C5, 1.363(15); C5-Os, 1.971(12).
by solution NMR spectroscopic data and elemental analysis.10 The
31P{1H} NMR spectrum in CD2Cl2 showed two singlets at 20.1
Scheme 1
and -15.5 ppm assignable to CPPh3 and OsPPh3, respectively. The
presence of the metallacycle is clearly indicated by the 1H and 13
C
NMR data. In particular, the 1H NMR spectrum in CD2Cl2 showed
the characteristic OsCH signal at 23.13 ppm and the γ-CH signal
at 8.57 ppm; the 13C{1H} NMR spectrum (in CD2Cl2) showed the
signals of OsCH, CPPh3, and γ-CH at 239.7, 112.7, and 160.5 ppm,
respectively. The structure of 2 has been confirmed by X-ray
diffraction. As shown in Figure 1, the complex contains an essen-
tially planar six-membered metallacycle with two PPh3 substituents.
The maximum deviation from the least-squares plane through
Os(1), C(1), C(2), C(3), C(4), and C(5) is 0.0754 Å for C(1). The
Os-C(1) (1.946 (12) Å) and Os-C(5) (1.971 (12) Å) bond
distances are shorter than the Os-CH distances in osmabenzenes
Os(C(SMe)CHCHC(X)CH)I(CO)(PPh3)2 (X ) NO2, 2.011(7) Å;
X ) Br, 2.039(9) Å).2j The C-C bond distances of the metallacycle
are longer than typical CdC double bonds and shorter than typical
C-C single bonds. The NMR as well as the X-ray diffraction data
indicate that the six-membered metallacycle of the complex cation
of 2 has a delocalized structure with contribution from 2A-2D.
The similarity in P-C(phenyl) and P-C(metallabenzene) bond
distances indicates that 2A and 2B are the dominant resonance
structures.
confirmed by X-ray diffraction (Figure 2). As expected, slight
short-long bond alternations were observed for the Os-C and C-C
distances of the metallacycle. The solid-state structure is fully
supported by the solution NMR spectroscopic data.
A plausible mechanism for the formation of the cationic complex
2 from the reaction of HCtCCH(OH)CtCH with 1 is proposed
in Scheme 2. Complex 1 can initially react with HCtCCH(OH)-
CtCH to give intermediate A, which can react with PPh3 to give
4. 4 may then react with additional PPh3 present in solution to give
intermediate B, which loses an OH- from the γ-carbon to give
compound 2. Addition reactions of phosphines to coordinated
alkynes are known reactions.11 The dissociation of OH- from B is
interesting and can be related to the formation of allenylidene
complexes LnMdCdCdCR2 from the reactions of LnM with
HCtCC(OH)R2.12
Reaction of 2 with PMe3 produced osmabenzene 3 (Scheme 1),
which is closely related to Roper’s osmabenzenes Os(C(SMe)-
CHCHC(X)CH)I(CO)(PPh3)2.2i,j,4 The structure of 3 has also been
One of the intermediates, complex 4, has been isolated as a
yellow solid from the reaction of 1 with HCtCCH(OH)CtCH
carried out in THF. The structure of 4 can be readily assigned on
† The Hong Kong University of Science and Technology.
‡ Xiamen University.
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10.1021/ja0486871 CCC: $27.50 © 2004 American Chemical Society

C O M M U N I C A T I O N S
CD2Cl2 showed a CPPh3 signal at 18.8 and the OsPPh3 signal at
-27.3 ppm. The chemical shift of the CPPh3 is similar to those of
complex 2, indicating that the PPh3 groups are in a similar
environment. The 1H NMR spectrum in CD2Cl2 showed two OsCH
signals at 20.1 (OsCHCI) and 19.0 (OsCHCPPh3) ppm and the
OsCHCICH signal at 8.10 ppm. In the 13C NMR spectrum, the
five carbon signals of the HCC(PPh3)CHCICH chain were observed
at 248.2 (OsCHCI), 220.9 (OsCHCPPh3), 152.6 (OsCHCICH),
112.9 (OsCHCPPh3), and 98.3 (OsCHCI) ppm.
In summary, we found a very convenient route for the preparation
of osmabenzenes starting from readily accessible HCtCCH-
(OH)CtCH. The reactions involve nucleophilic attack of coordi-
nated alkynes by nucleophiles such as PPh3 and I-, followed by
dissociation of OH- at γ-carbon. The isolation of osmabenzenes
2, 7, and 8 is interesting because it demonstrate that metallaben-
zenes, like benzene, can also form phosphonium salts. We are in
the process of extending the chemistry to prepare other metalla-
benzenes and studying the chemistry of our new osmabenzenes.
Figure 2. Molecular structure for the complex cation of 3. The hydrogens
of phenyls and methyls are omitted for clarity. Selected bond dis-
tances (Å): Os-C1, 1.995(3); C1-C2, 1.383(5); C2-C3, 1.426(5);
C3-C4, 1.382(5), C4-C5, 1.429(5); C5-Os, 1.920(4).
Scheme 2
Acknowledgment. This work was supported by the Hong Kong
Research Grant Council.
Supporting Information Available: Experimental procedures and
characterization data (PDF); X-ray crystallographic files (CIF). This
material is available free of charge via the Internet at http://pubs.acs.org.
1
References
the basis of its analytical and spectroscopic data. The H NMR
spectrum (in CD2Cl2) showed OsCH, CHOH, and CtCH sig-
nals at 12.93, 5.39, and 3.75 ppm, respectively. The 13C{1H}
NMR spectrum (in CD2Cl2, 246 K) showed five signals of the
HCdC(PPh3)CH(OH)CtCH chain at 206.5 (OsCH), 111.2
(CPPh3), 85.0 (CtCH), 78.6 (C≡CH), and 77.8 (CHOH) ppm. In
the 31P{1H} NMR spectrum (in CD2Cl2), the signals of CPPh3
appeared at 9.8 ppm and the signals of OsPPh3 appeared at -6.9
and -7.9 ppm. Observation of two signals of OsPPh3 is expected
because of the presence of the CH(OH)CtCH group.
The production of 2 from 4 has been confirmed experimentally.
Thus, treatment of 4 with PPh3 quickly produced 2 in good yield.
Similar chemistry was also observed starting from OsBr2(PPh3)3
(5). Thus treatment of 5 with HCtCCH(OH)CtCH in THF
produced complex 6, which reacted with PPh3 to give 7 after
metathesis with Bu4NBr (eq 1). Complexes 6 and 7 presumably
(1) Bleeke, J. R. Chem. ReV. 2001, 101, 1205.
(2) Examples of recent experimental work: (a) Gilbertson, R. D.; Lau, T. L.
S.; Lanza, S.; Wu, H. P.; Weakley, T. J. R.; Haley, M. M. Organometallics
2003, 22, 3279. (b) Paneque, M.; Posadas, C. M.; Poveda, M. L.; Rendo´n,
N.; Salazar, V.; On˜ate, E.; Mereiter, K. J. Am. Chem. Soc. 2003, 125,
9898. (c) Effertz, U.; Englert, U.; Podewils, F.; Salzer, A.; Wagner, T.;
Kaupp. M. Organometallics 2003, 22, 264. (d) Jacob, V.; Weakley, T. J.
R.; Haley, M. M. Angew. Chem., Int. Ed. 2002, 41, 3470. (e) Wu, H. P.;
Lanza, S.; Weakley, T. J.; Haley, M. M. Organometallics 2002, 21, 2824.
(f) Liu, S. H.; Ng, W. S.; Chu, H. S.; Wen, T. B.; Xia, H. P.; Zhou, Z. Y.;
Lau, C. P. Jia, G. Angew. Chem., Int. Ed. 2002, 41, 1589. (g) Bleeke, J.
R.; Hinkle, P. V.; Rath, N. P. Organometallics 2001, 20, 1939. (h) Bleeke,
J. R.; Blanchard, J. M. B.; Donnay, E. Organometallics 2001, 20, 324.
(i) Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J. J.
Organomet. Chem. 2001, 623, 109. (j) Rickard, C. E. F.; Roper, W. R.;
Woodgate, S. D.; Wright, L. J. Angew. Chem., Int. Ed. Engl. 2000, 39,
750.
(3) Examples of recent theoretical work: (a) Iron, M. A.; Martin, J. M. L.;
van der Boom, M. E. Chem. Commun. 2003, 132. (b) Iron, M. A.; Martin,
J. M. L.; van der Boom, M. E. J. Am. Chem. Soc. 2003, 125, 13020. (c)
Iron, M. A.; Martin, J. M. L.; van der Boom, M. E. J. Am. Chem. Soc.
2003, 125, 11702.
(4) Elliott, G. P.; Roper, W. R.; Waters, J. M. J. Chem. Soc., Chem. Commun.
1982, 811.
(5) (a) Bleeke, J. R.; Xie, Y. F.; Peng, W. J.; Chiang, M. J. Am. Chem. Soc.
1989, 111, 4118. (b) Bleeke, J. R.; Behm, R. J. Am. Chem. Soc. 1997,
119, 8503. (c) Bleeke, J. R.; Behm, R.; Xie, Y. F.; Chiang, M. Y.;
Robinson, K. D.; Beatty, A. M. Organometallics 1997, 16, 606 and
references therein.
(6) Gilbertson, R. D.; Weakley, T. J. R.; Haley, M. M. J. Am. Chem. Soc.
1999, 121, 2597.
(7) (a) Wen, T. B.; Zhou, Z. Y.; Jia, G. Angew. Chem., Int. Ed. 2001, 40,
1951. (b) Wen, T. B.; Yang, S. Y.; Zhou, Z. Y.; Lin, Z.; Lau, C. P.; Jia,
G..Organometallics 2000, 19, 3757. (c) Wen, T. B.; Zhou, Z. Y.; Lo, M.
F.; Willians, I. D.; Jia, G. Organometallics 2003, 22, 5217.
(8) Hoffmann, P. R.; Caulton, K. G. J. Am. Chem. Soc. 1975, 97, 4221.
(9) Jones, E. R. H.; Lee, H. H.; Whiting, M. C. J. Chem. Soc. 1960, 3483.
(10) See Supporting Information for experimental and spectroscopic details
of 2-4 and 6-8 and for X-ray studies of 2 and 3.
have the same structures as 4 and 2 respectively as judged on the
basis of the spectroscopic data. The new osmabenzenes 2, 3, and
7 appear to be air stable in both solid state and in solution for at
least a week.
Preliminary study shows that other nucleophiles can also react
with 4 to give osmabenzenes. For example, treatment of 4 with
NaI in CH2Cl2 produced a brown solid. On the basis of spectro-
scopic data, the major species of the solid can be formulated as
the iodo-osmabenzene 8 (eq 2). The 31P{1H} NMR spectrum in
(11) For example, see: Jung, J. H.; Hoffman, D. M.; Lee, T. R. J. Organomet.
Chem. 2000, 599, 112 and references therein.
(12) Bruce, M. I. Chem. ReV. 1998, 98, 2797.
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