The dihydride-osmium(IV) complex [OsH2(/c2-O2CCH3)(H2O)(PiPr3)2]BF4 as a precursor for carbon-carbon coupling reactions

Article abstract of DOI:10.1021/om000475z

The dihydride-osmium(IV) complex [OsH2(/c2-O2CCH3)(H2O)(PiPr3)2]BF4 (1) reacts with acetylene (1 atm) at 0 °C to give polyacetylene and the vinyl-carbyne derivative [Os(CH= CH2)(2-02CCH3)(=CCH3)(PiPr3)2]BF4 (2). Both polyacetylene and 2 can also be obtained by reaction of [OsH(K2-O2CCH3XCCH3XPiPr3)2]BF4 (3) with acetylene. Under an acetylene atmosphere, complex 2 yields polyacetylene in a slow but constant manner. Complex 2 reacts with carbon monoxide to give initially the carbene derivative [Os(/t2-O2CCH3){=C(CH= CH2)CH3}(CO)(PiPr3)2]BF4 (4), by migratory insertion of the carbyne ligand of 2 into the Os-vinyl bond. Under a carbon monoxide atmosphere, complex 2 is unstable and evolves into [Os(K2-O2CCH3)(CO)2(PiPr3)2]BF4 (5). Treatment of 2 with KOH in methanol produces the deprotonation of the carbyne ligand and the formation of the vinyl-vinylidene derivative Os(CH=CH2)(/c2-O2CCH3)(=C=CH2)(PiPr3)2 (6), which reacts with carbon monoxide to give the butadienyl compound Os{C(CH=CH2)=CH2}{1-OC(O)CH3}(CO)2(PiPr3)2 (7) by migratory insertion of the vinylidene ligand into the Os-vinyl bond. The structure of 7 has been determined by X-ray diffraction analysis. The geometry around the osmium atom can be rationalized as a distorted octahedron with the phosphine ligands occupying opposite positions. The remaining perpendicular plane is formed by the butadienyl ligand, the acetate, and the carbonyl groups mutually cis disposed. The Os-butadienyl distance is 2.195(5) A, whereas the torsion angle in the diene is 50.7(8)°. The butadienyl ligand of 7 acts as a diene in Diels-Alder reactions. Thus, the addition of dimethyl acetylenedicarboxylate and maleic anhydride to benzene solutions of 7 affords the corresponding cycloaddition products Os-{C=CHCH2C(CO2Me)=C(C02Me)CH2{1-OC(O)CH3}(CO)2(PiPr3)2 (8) and Os{C=CHCH2CH-[C(O)OC(0)]CHCH2}{1-OC(O)CH3}(CO)2(PiPr3)2 (9). Treatment of 8 with HBF4-OEt2 gives i 5 and dimethyl l,4-cyclohexadiene-l,2-dicarboxylate.

Full text of DOI:10.1021/om000475z

5098
Organometallics 2000, 19, 5098-5106
Th e Dih yd r id e-Osm iu m (IV) Com p lex
[OsH2(K2-O2CCH3)(H2O)(P iP r 3)2]BF 4 a s a P r ecu r sor for
Ca r bon -Ca r bon Cou p lin g Rea ction s
Miguel A. Esteruelas,* Cristina Garc´ıa-Yebra, Montserrat Oliva´n,
Enrique On˜ate, and Mar´ıa A. Tajada
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received J une 5, 2000
The dihydride-osmium(IV) complex [OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4 (1) reacts with
acetylene (1 atm) at 0 °C to give polyacetylene and the vinyl-carbyne derivative [Os(CHd
CH2)(κ2-O2CCH3)(tCCH3)(PiPr3)2]BF4 (2). Both polyacetylene and 2 can also be obtained by
reaction of [OsH(κ2-O2CCH3)(tCCH3)(PiPr3)2]BF4 (3) with acetylene. Under an acetylene
atmosphere, complex 2 yields polyacetylene in a slow but constant manner. Complex 2 reacts
with carbon monoxide to give initially the carbene derivative [Os(κ2-O2CCH3){dC(CHd
CH2)CH3}(CO)(PiPr3)2]BF4 (4), by migratory insertion of the carbyne ligand of 2 into the
Os-vinyl bond. Under a carbon monoxide atmosphere, complex 2 is unstable and evolves
into [Os(κ2-O2CCH3)(CO)2(PiPr3)2]BF4 (5). Treatment of 2 with KOH in methanol produces
the deprotonation of the carbyne ligand and the formation of the vinyl-vinylidene derivative
Os(CHdCH2)(κ2-O2CCH3)(dCdCH2)(PiPr3)2 (6), which reacts with carbon monoxide to give
the butadienyl compound Os{C(CHdCH2)dCH2}{κ1-OC(O)CH3}(CO)2(PiPr3)2 (7) by migratory
insertion of the vinylidene ligand into the Os-vinyl bond. The structure of 7 has been
determined by X-ray diffraction analysis. The geometry around the osmium atom can be
rationalized as a distorted octahedron with the phosphine ligands occupying opposite
positions. The remaining perpendicular plane is formed by the butadienyl ligand, the acetate,
and the carbonyl groups mutually cis disposed. The Os-butadienyl distance is 2.195(5) Å,
whereas the torsion angle in the diene is 50.7(8)°. The butadienyl ligand of 7 acts as a diene
in Diels-Alder reactions. Thus, the addition of dimethyl acetylenedicarboxylate and maleic
anhydride to benzene solutions of 7 affords the corresponding cycloaddition products Os-
{CdCHCH2C(CO2Me)dC(CO2Me)CH2{κ1-OC(O)CH3}(CO)2(PiPr3)2 (8) and Os{CdCHCH2CH-
[C(O)OC(O)]CHCH2}{κ1-OC(O)CH3}(CO)2(PiPr3)2 (9). Treatment of 8 with HBF4‚OEt2 gives
5 and dimethyl 1,4-cyclohexadiene-1,2-dicarboxylate.
In tr od u ction
Among the group of organic molecules most frequently
studied in metal-assisted carbon-carbon bond-forming
reactions, alkynes play a prominent role, as is evident
from their participation in numerous transformations
of both fundamental and industrial relevance.2,3 In this
respect, monohydride,4 hydride-dihydrogen,5 trihy-
dride,6 and dihydride-dihydrogen7 derivatives of os-
mium have shown to be the usual precursors for the
stoichiometric and/or catalytic coupling of terminal
alkynes. However, the capacity of the dihydride com-
plexes for coupling has not been investigated.
The formation of carbon-carbon bonds mediated by
transition-metal compounds has emerged in its own
right over the past decades as an important step in
organic synthesis. These reactions can involve migratory
cis-ligand insertion, the coupling of adjacent carbon-
carbon bonds, or the attack of a reagent to unsaturated
organic ligands without metal-reagent bond formation.1
(1) (a) Stille, J . K. In Chemistry of the Metal-Carbon Bond; Hartley,
F. R., Patai, S., Eds.; Wiley: Chichester, U.K., 1985; Vol. 2. (b) Hagashi,
T.; Kumada, M. In Asymmetric Synthesis; Morrison, J . D., Ed.;
Academic Press: New York; Vol. 5. (c) Yamamoto, A. Organotransition
Metal Chemistry; Wiley: New York, 1986. (d) Collman, J . P.; Hegedus,
L. J .; Norton, J . R.; Fink, R. G. Principles and Applications of
Organotransition Metal Chemistry; University Science Books: Mill
Valley, CA, 1987. (e) Brown, J . M.; Cooley, N. A. Chem. Rev. 1988, 88,
1031. (f) Brookhart, M.; Volpe, A. F., J r.; Yoon, I. In Comprehensive
Organic Synthesis; Trost, B. M., Fleming, V., Eds.; Pergamon Press:
Tarrytown, NY, 1991; Vol. 4. (g) Schmalz, H. G. Angew. Chem., Int.
Ed. Engl. 1995, 34, 1833. (h) Barluenga, J . Pure Appl. Chem. 1996,
68, 543. (i) Weyershausen, B.; Do¨tz, K. H. Eur. J . Inorg. Chem. 1999,
1057.
The reactivity of osmium compounds containing two
hydrogen atoms bonded to the metallic center toward
terminal alkynes is a little-studied field and is difficult
to rationalize. The main problem comes from the fact
that the four dihydride complexes studied so far lead
to four different types of organometallic compounds, all
of them different from the usual alkenyl derivatives.
In 1993, we reported that the six-coordinate os-
mium(IV) complex OsH2Cl2(PiPr3)2 reacted with phen-
10.1021/om000475z CCC: $19.00 © 2000 American Chemical Society
Publication on Web 10/27/2000

[OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4
Organometallics, Vol. 19, No. 24, 2000 5099
ylacetylene, cyclohexylacetylene, 1-(trimethylsilyl)-1,4-
pentadiyne, or (trimethylsilyl)acetylene to give the
hydride-carbyne derivatives OsHCl2(tCCH2R)(PiPr3)2.8
Subsequently, we observed that the reaction of the
osmium(II) complex OsCl2(η2-H2)(CO)(PiPr3)2, contain-
ing an elongated dihydrogen ligand instead of two
hydride ligands, with phenylacetylene leads to the
carbene compound OsCl2(dCHCH2Ph)(CO)(PiPr3)2.9
Recently, as part of our study on the chemical proper-
ties of OsH2Cl2(PiPr3)2,10 we have described the synthe-
sis of the acetate derivatives OsH2(κ2-O2CCH3){κ1-OC-
(O)CH3}(PiPr3)211 and [OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]-
BF4.12 In the presence of alkynes, the behavior of the
bis(acetate) complex differs from that previously men-
tioned for OsH2Cl2(PiPr3)2 and OsCl2(η2-H2)(CO)(PiPr3)2.
Thus, the reaction of OsH2(κ2-O2CCH3){κ1-OC(O)CH3}-
(PiPr3)2 with 2-methyl-1-buten-3-yne affords the hy-
dride-vinylidene complex OsH(κ2-O2CCH3){dCdCHC-
(CH3)dCH2}(PiPr3)2.11 The monoacetate neither shows
the same reactivity as the bis(acetate) nor follows a
behavior similar to that for OsH2Cl2(PiPr3)2 or OsCl2-
(η2-H2)(CO)(PiPr3)2. The complex [OsH2(κ2-O2CCH3)(H2O)-
(PiPr3)2]BF4 reacts with phenylacetylene and 1,1-di-
phenyl-2-propyn-1-ol to give the hydride-osmacyclo-
propene derivatives [OsH(κ2-O2CCH3){C(R)CH2}(PiPr3)2]-
BF4 (R ) Ph, C(OH)Ph2) and with tert-butylacetylene
or (trimethylsilyl)acetylene to afford the hydride-car-
byne compounds [OsH(κ2-O2CCH3)(tCR)(PiPr3)2]BF4 (R
) CH2CMe3, CH3),12 whereas the reactions with 2-phen-
yl-3-butyn-2-ol and 2-methyl-3-butyn-2-ol give mixtures
of the corresponding hydride-osmacyclopropene and
hydride-carbyne species.13
The reactions previously mentioned suggest that the
nature of the obtained products depends on both factors
related to the electronic nature of the starting complexes
and the nature of the substituent of the alkyne.
In the search for new information about the influence
of the alkyne in these types of reactions, we have now
studied the reactivity of [OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]-
BF4 toward acetylene. In this paper, we report the
formation of[Os(CHdCH2)(κ2-O2CCH3)(tCCH3)(PiPr3)2]-
BF4 and its potential as a precursor of carbon-carbon
coupling reactions.
(2) (a) O’Connor, J . M.; Pu, L.; Rheingold, A. L. J . Am. Chem. Soc.
1990, 112, 6232. (b) Albertin, G.; Amendola, P.; Antoniutti, S.; Ianelli,
S.; Pellizzi, G.; Bordignon, E. Organometallics 1991, 10, 2876. (c) J ia,
G.; Meek, D. W. Organometallics 1991, 10, 1444. (d) Fryzuk, M. D.;
Huang, L.; McManus, N. T.; Paglia, P.; Rettig, S. J .; White, G. S.
Organometallics 1992, 11, 2979. (e) Trost, B. M.; Flygare, J . A. J . Am.
Chem. Soc. 1992, 114, 5476. (f) Field, L. D.; George, A. V.; Purches, G.
R.; Slip, I. H. M. Organometallics 1992, 11, 3019. (g) Santos, A.; Lo´pez,
J .; Matas, L.; Ros, J .; Gala´n, A.; Echavarren, A. M. Organometallics
1993, 12, 4215. (h) Scha¨fer, M.; Mahr, N.; Wolf, J .; Werner, H. Angew.
Chem., Int. Ed. Engl. 1993, 32, 1315. (i) Werner, H. J . Organomet.
Chem. 1994, 475, 45. (j) Trost, B. M.; Flygare, J . A. Tetrahedron Lett.
1994, 35, 4059. (k) Bianchini, C.; Caulton, K. G.; J ohnson, T. J .; Meli,
A.; Peruzzini, M.; Vizza, F. Organometallics 1995, 14, 933. (l) Werner,
H.; Scha¨fer, M.; Wolf, J .; Peters, K.; von Schnering, H. G. Angew.
Chem., Int. Ed. Engl. 1995, 34, 191. (m) Wiedemann, R.; Wolf, J .;
Werner, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 1244. (n) Bianchini,
C.; Innocenti, P.; Peruzzini, M.; Romerosa, A.; Zanobini, F. Organo-
metallics 1996, 15, 272. (o) Wiedemann, R.; Steinert, P.; Gevert, O.;
Werner, H. J . Am. Chem. Soc. 1996, 118, 2495. (p) Esteruelas, M. A.;
Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez, L. Organometallics 1996,
15, 823. (q) Braun, T.; Meuer, P.; Werner, H. Organometallics 1996,
15, 4075. (r) Ting, P.-C.; Lin, Y.-C.; Lee, G.-H.; Cheng, M.-C.; Wang,
Y. J . Am. Chem. Soc. 1996, 118, 6433. (s) Merlic, C. A.; Pauly, M. E.
J . Am. Chem. Soc. 1996, 118, 11319. (t) Lee, H. M.; Yao, J .; J ia, G.
Organometallics 1997, 16, 3927. (u) Werner, H.; Wiedemann, R.;
Steinert, P.; Wolf, J . Chem. Eur. J . 1997, 3, 127. (v) Esteruelas, M. A.;
Liu, F.; On˜ate, E.; Sola, E.; Zeier, B. Organometallics 1997, 16, 2919.
(x) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego, J .; On˜ate,
E. Organometallics 1997, 16, 5826. (y) Spivak, G. J .; Caulton, K. G.
Organometallics 1998, 17, 5260. (z) Esteruelas, M. A.; Go´mez, A. V.;
Lo´pez, A. M.; On˜ate, E.; Ruiz, N. Organometallics 1998, 17, 2297.
(3) (a) Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa,
J . I. Organometallics 1998, 17, 3479. (b) Esteruelas, M. A.; Go´mez, A.
V.; Lo´pez, A. M.; Puerta, M. C.; Valerga, P. Organometallics 1998, 17,
4959. (c) Bruce, M. I. Chem. Rev. 1998, 98, 2797. (d) Touchard, D.;
Dixneuf, P. H. Coord. Chem. Rev. 1998, 178, 409. (e) Noata, T.; Takaya,
H.; Murahashi, S.-I. Chem. Rev. 1998, 98, 2599. (f) Bruneau, C.;
Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311. (g) Slugovc, C.; Mereiter,
K.; Schmid, R.; Kirchner, K. Eur. J . Inorg. Chem. 1999, 1141. (h)
Slugovc, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organometallics
1999, 18, 1011. (i) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; On˜ate,
E.; Ruiz, N. Organometallics 1999, 18, 1606. (j) Esteruelas, M. A.;
Go´mez, A. V.; Lo´pez, A. M.; Oliva´n, M.; On˜ate, E.; Ruiz, N. Organo-
metallics 2000, 19, 4.
Resu lts a n d Discu ssion
1. Rea ction of [OsH2(K2-O2CCH3)(H2O)(P iP r 3)2]-
BF 4 w ith Acetylen e. At 0 °C, under 1 atm of acetylene,
dichloromethane solutions of [OsH2(κ2-O2CCH3)(H2O)-
(PiPr3)2]BF4 (1) give a dark blue, intractable, air-
sensitive solid and a yellow solution. According to the
UV/vis spectrum of the solid, which shows an unstruc-
tured absorption at about 700 nm and a weak, very
broad band at about 590 nm, the dark material is trans-
polyacetylene with a minor amount of the cis isomer.14
From the yellow solution, the vinyl-carbyne complex
[Os(CHdCH2)(κ2-O2CCH3)(tCCH3)(PiPr3)2]BF4 (2) was
isolated by addition of diethyl ether, as a yellow solid
in 75% yield.
The formed amount of polyacetylene increases by
increasing the exposure time of 1 to acetylene, in a slow
but constant manner. This suggests that complex 1 is
a catalyst precursor for the polymerization of acetylene.
The active species should be 2 or a derivative of this
compound. In fact, the stirring of dichloromethane
solutions of 2 under 1 atm of acetylene affords poly-
acetylene and a yellow solution, from which complex 2
is recovered in high yield.
(4) (a) Werner, H.; Esteruelas, M. A.; Otto, H. Organometallics 1986,
5, 2295. (b) Bohanna, C.; Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.;
Oro, L. A.; Sola, E. Organometallics 1995, 14, 4825. (c) Esteruelas, M.
A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Sola, E. J . Am. Chem. Soc. 1996,
118, 89.
(5) (a) Barbaro, P.; Bianchini, C.; Peruzzini, M.; Polo, A.; Zanobini,
F.; Frediani, P. Inorg. Chim. Acta 1994, 220, 5. (b) Bohanna, C.;
Callejas, B.; Edwards, A. J .; Esteruelas, M. A.; Lahoz, F. J .; Oro, L.
A.; Ruiz, N.; Valero, C. Organometallics 1998, 17, 373.
(6) (a) Esteruelas, M. A.; Oro, L. A.; Ruiz, N. Organometallics 1994,
13, 1507. (b) Huang, D.; Oliva´n, M.; Huffman, J . C.; Eisenstein, O.;
Caulton, K. G. Organometallics 1998, 17, 4700.
(7) (a) Buil, M. L.; Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.
Organometallics 1997, 16, 3169. (b) Bohanna, C.; Buil, M. L.; Esteru-
elas, M. A.; On˜ate, E.; Valero, C. Organometallics 1999, 18, 5176.
(8) Espuelas, J .; Esteruelas, M. A.; Lahoz, F. J .; Oro, L. A.; Ruiz, N.
J . Am. Chem. Soc. 1993, 115, 4683.
The catalytic formation of polyacetylene and the
stoichiometric formation of 2 is also observed when
dichloromethane solutions of the previously described
hydride-carbyne complex [OsH(κ2-O2CCH3)(tCCH3)-
(PiPr3)2]BF4 (3) are stirred under 1 atm of acetylene at
(9) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Valero, C.;
Zeier, B. J . Am. Chem. Soc. 1995, 117, 7935.
(10) Castarlenas, R.; Esteruelas, M. A.; Gutie´rrez-Puebla, E.; J ean,
Y.; Lledo´s, A.; Mart´ın, M.; On˜ate, E.; Toma`s, J . Organometallics 2000,
19, 3100 and references therein.
(11) Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.; Mart´ınez, M.-P.;
Oliva´n, M.; On˜ate, E.; Ruiz, N. Organometallics 1998, 17, 4500.
(12) Buil, M. L.; Eisenstein, O.; Esteruelas, M. A.; Garc´ıa-Yebra,
C.; Gutie´rrez-Puebla, E.; Oliva´n, M.; On˜ate, E.; Ruiz, N.; Tajada, M.
A. Organometallics 1999, 18, 4949.
(13) Buil, M. L.; Esteruelas, M. A.; Garc´ıa-Yebra, C.; Gutie´rrez-
Puebla, E.; Oliva´n, M. Organometallics 2000, 19, 2184.
(14) Wegner, G. Angew. Chem., Int. Ed. Engl. 1981, 20, 361.

5100 Organometallics, Vol. 19, No. 24, 2000
Esteruelas et al.
Sch em e 1
Sch em e 2
0 °C. This suggests that the reaction of 1 with acetylene
to give 2 is a two-step process which involves the initial
formation of 3 and subsequent insertion of the alkyne
into the Os-H bond of this intermediate (Scheme 1).
Once complex 2 has been formed, the migratory inser-
tion of the carbyne ligand into the Os-vinyl bond should
afford a carbene derivative, which could be the active
species of the catalysis. The polymerization of alkynes
in a living manner via alkylidene compounds is a well-
known process.15 In favor of the formation of an alkyl-
idene species from 2 under an acetylene atmosphere,
we have observed that, under a carbon monoxide
atmosphere, complex 2 evolves into [Os(κ2-O2CCH3)-
{dC(CHdCH2)CH3}(CO)(PiPr3)2]BF4 (4), which is un-
stable under these conditions and affords, finally, the
known compound [Os(κ2-O2CCH3)(CO)2(PiPr3)2]BF4 (5).11
Complex 2 was characterized by MS, elemental
analysis, and IR and 1H, 13C{1H}, and 31P{1H} NMR
spectroscopy. In the 1H NMR spectrum, the most
noticeable resonances are a triplet at 1.84 ppm with an
H-P coupling constant of 0.9 Hz, due to the methyl
group of the carbyne ligand, two doublets at 5.87 and
4.69 ppm with H-H coupling constants of 10.5 and 16.2
Hz, respectively, and a doublet of doublets at 7.55 ppm
with the same H-H coupling constants, corresponding
to the vinyl ligand. In the 13C{1H} NMR spectrum, the
OstC resonance appears as a triplet at 289.9 ppm with
a C-P coupling constant of 9.0 Hz, whereas the OsCH
and dCH2 resonances are observed at 140.0 and 123.3
ppm, respectively, the first of them as a triplet with a
C-P coupling constant of 8.0 Hz and the second one as
a singlet. The 31P{1H} NMR spectrum shows a singlet
at 22.9 ppm, in agreement with the mutually trans
disposition of the phosphine ligands.
2. F or m a tion a n d Ch a r a cter iza tion of th e Bu ta -
d ien yl Com p lex Os{C(CHdCH2)dCH2}{K1-OC(O)-
CH3}(CO)2(P iP r 3)2. Following the pioneering leads of
the Rosenblum16 and Wojcicki17 groups, over the last
years, several groups have been investigating the
organic applications of cycloaddition reactions between
transition-metal complexes containing σ bonds to un-
saturated ligands and electrophiles.18 Along this line,
we were interested in preparing the title compound, so
that its cycloaddition chemistry could be investigated
(vide infra).
The synthetic strategy to prepare this butadienyl
complex is shown in Scheme 2. Treatment of dichloro-
methane solutions of 2 with a stoichiometric amount of
KOH in methanol produces the deprotonation of the
carbyne ligand and formation of the neutral vinyl-
(16) Rosenblun, M. J . Organomet. Chem. 1986, 300, 191.
(17) Wojcicki, A.; Schuchart, C. E. Coord. Chem. Rev. 1990, 105,
35.
1
In the H NMR spectrum of 4 the CH3 resonance of
the carbene appears at 2.62 ppm, whereas the vinylic
resonances are observed as two doublets and a doublet
of doublets at 5.91, 6.40, and 8.34 ppm, respectively,
with H-H coupling constants of 10.8 and 17.2 Hz. In
the 13C{1H} NMR spectrum the OsdC carbon atom
gives rise to a triplet at 288.2 ppm with a C-P coupling
constant of 4.0 Hz, while the carbon atoms of the vinyl
group display singlets at 149.0 and 114.9 ppm. The 31P-
{1H} NMR spectrum shows a singlet at 28.6 ppm.
(18) See for example: (a) Kuo, G.-H.; Helquist, P.; Kerber, R. C.
Organometallics 1984, 3, 806. (b) Wright, M. E.; Hoover, J . F.; Nelson,
G. O.; Scott, C. P.; Glass, R. S. J . Org. Chem. 1984, 49, 3059. (c) Glass,
R. S.; McConnell, W. W.; Andruski, S. W. J . Org. Chem. 1986, 51, 5123.
(d) Yang, G.-M.; Lee, G.-H.; Peng, S.-M.; Liu, R.-S. Organometallics
1991, 10, 2531. (e) Smalley, T. L., J r.; Wright, M. W.; Garmon, S. A.;
Welker, M. E.; Rheingold, A. L. Organometallics 1993, 12, 998. (f)
Wright, M. W.; Smalley, T. L., J r.; Welker, M. E.; Rheingold, A. L. J .
Am. Chem. Soc. 1994, 116, 6777. (g) Stokes, H. L.; Welker, M. E.
Organometallics 1996, 15, 2624. (h) Chapman, J . J .; Welker, M. E.
Organometallics 1997, 16, 747. (i) Adams, T. A.; Welker, M. E.; Day,
C. S. J . Org. Chem. 1998, 63, 3683. (j) Richardson, B. M.; Day, C. S.;
Welker, M. E. J . Organomet. Chem. 1999, 577, 120. (k) Lohr, G. J .;
Welker, M. E. Inorg. Chim. Acta 1999, 296, 13. (l) Chapman, J . J .;
Day, C. S.; Welker, M. E. Organometallics 2000, 19, 1615.
(15) Schrock, R. R.; Luo, S.; Lee, J . C., J r.; Zanetti, N. C.; Davis, W.
M. J . Am. Chem. Soc. 1996, 118, 3883 and references therein.

[OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4
Organometallics, Vol. 19, No. 24, 2000 5101
vinylidene derivative Os(CHdCH2)(κ2-O2CCH3)(dCd
CH2)(PiPr3)2 (6), which under a carbon monoxide atmo-
sphere affords the desired butadienyl compound Os{C-
(CHdCH2)dCH2}{κ1-OC(O)CH3}(CO)2(PiPr3)2 (7).
The deprotonation reaction of 2 is reversible. Thus,
the addition of a stoichiometric amount of HBF4‚OEt2
to diethyl ether solutions of 6 regenerates 2. The Câ
atoms of both alkenyl19 and vinylidene20 ligands have
shown to be nucleophilic centers; therefore, the above-
mentioned reaction indicates that under, strictly, the
same metal-ligand system the Câ of a vinylidene ligand
is a stronger nucleophilic center than the Câ atom of an
alkenyl group.
The presence of the vinylidene and alkenyl ligands
1
in 6 is strongly supported by the H and 13C{1H} NMR
1
spectra of this compound in benzene-d6. In the H NMR
spectrum the dCH2 protons of the vinylidene display a
triplet at 0.64 ppm with an H-P coupling constant of 3
Hz, while the vinylic protons give rise to two doublets
of doublets of triplets at 6.04 and 4.76 ppm and a
doublet of doublets at 8.68 ppm, with H-H coupling
constants of 16.5 and 10.5 Hz, respectively, and H-P
coupling constants of about 3 Hz. In the 13C{1H} NMR
spectrum, the resonances corresponding to the carbon
atoms of the vinylidene appear as triplets at 287.2 (Osd
C) and 87.7 (dCH2) ppm with C-P coupling constants
of 11.2 and 3.5 Hz, respectively, whereas the resonances
due to the carbon atoms of the vinyl ligand are observed
at 149.6 (dCH) and 115.7 (dCH2) ppm. The first of them
appears as a triplet with a C-P coupling constant of
8.1 Hz and the second one as a singlet. The 31P{1H}
NMR spectrum shows a singlet at 1.1 ppm.
The presence of the butadienyl ligand in 7 has been
confirmed by an X-ray investigation on a monocrystal
of this complex. A view of the molecular geometry is
shown in Figure 1. Selected bond distances and angles
are listed in Table 1.
The coordination geometry around the osmium atom
can be rationalized as a distorted octahedron with the
two phosphorus atoms of the phosphine ligands occupy-
ing opposite positions (P(1)-Os-P(2) ) 177.85(5)°). The
perpendicular plane is formed by the mutually cis-
disposed carbonyl ligands (C(9)-Os-C(10) ) 93.3(2)°),
the acetate group and the butadienyl ligand also being
cis-disposed (O(1)-Os-C(1) ) 85.55(8)°).
F igu r e 1. Molecular diagram of the complex Os{C(CHd
CH2)dCH2}(κ1-OC(O)CH3)(CO)2(PiPr3)2 (7). Thermal el-
lipsoids are shown at 50% probability.
Ta ble 1. Selected Bon d (Å) a n d An gles (d eg) for
th e Com p lex
Os{C(CHdCH2)dCH2}(K1-OC(O)CH3)(CO)2(P iP r 3)2
(7)
Os-P(1)
Os-P(2)
Os-O(1)
Os-C(1)
Os-C(9)
Os-C(10)
O(1)-C(7)
2.4592(14)
2.4609(15)
2.102(4)
2.195(5)
1.838(6)
1.945(6)
1.285(7)
O(2)-C(7)
O(3)-C(9)
O(4)-C(10)
C(1)-C(2)
C(1)-C(3)
C(3)-C(4)
C(7)-C(8)
1.211(7)
1.156(7)
1.333(7)
1.317(8)
1.483(8)
1.313(9)
1.519(9)
P(1)-Os-P(2)
P(1)-Os-O(1)
P(1)-Os-C(1)
P(1)-Os-C(9)
P(1)-Os-C(10)
P(2)-Os-O(1)
P(2)-Os-C(1)
P(2)-Os-C(9)
P(2)-Os-C(10)
O(1)-Os-C(1)
O(1)-Os-C(9)
O(1)-Os-C(10)
C(1)-Os-C(9)
177.85(5)
89.10(11)
91.38(15)
88.07(18)
92.84(18)
88.75(12)
88.54(15)
94.08(18)
87.15(18)
85.55(8)
174.1(2)
92.0(2)
C(1)-Os-C(10)
C(9)-Os-C(10)
Os-O(1)-C(7)
O(1)-C(7)-O(2)
O(1)-C(7)-C(8)
O(2)-C(7)-C(8)
Os-C(1)-C(2)
Os-C(1)-C(3)
C(2)-C(1)-C(3)
C(1)-C(3)-C(4)
Os-C(9)-O(3)
Os-C(10)-O(4)
175.1(2)
93.3(2)
126.7(4)
127.5(6)
113.0(5)
119.6(6)
123.6(5)
121.1(4)
115.3(5)
126.7(7)
177.0(5)
172.2(6)
89.4(2)
The C(2)-C(1)-C(3)-C(4) torsion angle in the buta-
dienyl ligand is 50.7(8)°. This value is quite similar to
those found in related compounds18f and agrees with
Wiberg’s calculations on rotational barriers in butadiene
and heterobutadienes, which predict minimum-energy
conformations with typical torsion angles of 25-55°.21
The bond length Os-C(1) (2.195(5) Å) is as expected for
an Os-C(sp2) single bond. It is even longer than those
found in the alkenyl-osmium(II) complexes Os{(E)-
(OCH3)dO}(η6-C6H6)(PiPr3)]+ (2.02(1) Å),22 Os{CHd
CHC(OCH3)dO}(C2CO2CH3)(CO)(PiPr3)2 (2.103(4) Å),23
and [Os{C[C(O)OCH3]dCH2}(CdCdCPh2)(CO)(PiPr3)2]+
(2.146(6) Å).5b The C(1)-C(2) bond lies in the plane
containing the carbonyl groups, the osmium atom, and
the coordinated oxygen atom of the acetate ligand. Its
distance, 1.317(8) Å, is statistically identical with the
C(3)-C(4) (1.313(9) Å) bond length and agrees with the
average carbon-carbon distance for a C(sp2)-C(sp2)
double bond (1.32(1) Å).24 The C(1)-C(3) (1.483(8) Å)
bond length also compares well with the distance
expected for a C(sp2)-C(sp2) single bond (about 1.48 Å).
CHdCHPh}Cl(CO)(PiPr3)2 (1.99(1) Å),4a [Os{CHdC(I)C-
(19) See for example: (a) Esteruelas, M. A.; Lahoz, F. J .; Lo´pez, A.
M.; On˜ate, E.; Oro, L. A. Organometallics 1994, 13, 1669. (b) Albe´niz,
M. J .; Esteruelas, M. A.; Lledo´s, A.; Maseras, F.; On˜ate, E.; Oro, L. A.;
Sola, E.; Zeier, B. J . Chem. Soc., Dalton Trans. 1997, 181.
(20) See for example: (a) Bourgault, M.; Castillo, A.; Esteruelas,
M. A.; On˜ate, E.; Ruiz, N. Organometallics 1997, 16, 636. (b) Esteru-
elas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J . I. Organometallics 1997,
16, 4657.
(22) Werner, H.; Weinand, R.; Otto, H. J . Organomet. Chem. 1986,
307, 49.
(23) Espuelas, J .; Esteruelas, M. A.; Lahoz, F. J .; Oro, L. A.; Valero,
C. Organometallics 1993, 12, 663.
(21) Wiberg, K. B.; Rablen, P. R.; Marquez, M. J . Am. Chem. Soc.
1992, 114, 8654.
(24) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989, S1.

5102 Organometallics, Vol. 19, No. 24, 2000
Esteruelas et al.
1
1
F igu r e 2. (a) H and (b) H{31P} NMR spectra (benzene-d6) of the isomeric mixture of Os{C(CHdCH2)dCH2}(κ1-OC(O)-
CH3)(CO)2(PiPr3)2 (7) in the vinylic proton region.
In accordance with the sp2 hybridization at C(1), the
angles around this atom are in the range 115.2(5)-
123.6(5)°.
3. Diels-Ald er Rea ction s on th e Bu ta d ien yl
Com plex Os{C(CHdCH2)dCH2}{K1-OC(O)CH3}(CO)2-
(P iP r 3)2. At 45 °C, a benzene solution of 7 reacts with
dimethyl acetylenedicarboxylate to give the cyclohexenyl
In solution, complex 7 exists as a mixture of the
isomers 7a and 7b shown in Scheme 2. We assume that
the major isomer is 7b (60%), which is the one found in
the solid state. The existence of these isomers can be
explained by hindered rotation around the Os-C(1)
axis. Because the Os-C(1) bond length does not suggest
any degree of double-bond character, the reason for the
existence of 7a and 7b appears to be steric in origin,
probably due to the high steric demand of the isopropyl
groups of the phosphine ligands.
derivative Os{CdCHCH2C(CO2Me)dC(CO2Me)CH2{κ1-
OC(O)CH3}(CO)2(PiPr3)2 (8), as a result of a Diels-Alder
reaction between the butadienyl ligand of 7 and the
activated alkyne. The cycloaddition was carried out
using 2 equiv of alkyne, and after 33 h, the product was
1
obtained in quantitative yield, according to the H and
31P{1H} NMR spectra of the reaction mixture.
In solution complex 8 also exists as a mixture of the
isomers 8a and 8b shown in Scheme 3. During the
reaction the molar ratio between them (4:6) is constant
and is the same as that between the starting isomers.
This suggests that both 7a and 7b are active dienes and
that the rates of formation of 8a and 8b are similar.
1
Figure 2 shows the H NMR spectrum of the isomeric
mixture in the vinylic region. Each isomer gives rise to
five resonances. Those corresponding to the Os(CdCH2)
unit (H2 and H2′) are observed between 5.5 and 7.0 ppm
and show spin coupling with the phosphorus atoms
bonded to the metallic center (about 3 Hz). The reso-
nances corresponding to the H2 protons, those disposed
trans to the CHdCH2 unit, appear as a doublet of
doublets by spin coupling with H3 (about 1 Hz) and H2′
(about 4 Hz), whereas H2′ is observed as a doublet by
spin coupling with H2. The geminal H4 and H4′ protons
of the CHdCH2 unit appear as two doublets of doublets
between 4.7 and 5.4 ppm, as a result of the geminal spin
coupling (about 3 Hz) and the cis H3-H4 (about 10 Hz)
or trans H3-H4′ (about 17 Hz) spin couplings. The
resonances due to the dCH protons (H3) are observed
between 7.0 and 7.7 ppm, as the expected doublet of
doublet of doublets.
In the 13C{1H} NMR spectrum of the isomers 7a and
7b, the resonances of the Os-C carbon atoms are
observed as triplets at 157.1 (7a ) and 153.6 (7b) ppm
with C-P coupling constants of about 11 Hz, whereas
the resonances due to the CHd, OsCdCH2 and CHd
CH2 carbon atoms are observed as singlets at 150.4,
123.4, and 106.3 (7a ) ppm and at 154.9, 120.2, and 107.4
(7b) ppm, respectively.
1
In the H NMR spectrum of the isomeric mixture of
8a and 8b, the most noticeable resonances are those
corresponding to the dCH protons of the cyclohexadi-
enyl ligands, which appear as broad signals at about
6.5 ppm. In the 13C{1H} NMR spectrum, the OsC and
CHd resonances of the cyclohexadienyl groups are
observed as triplets at 140.3 and 130.0 (8a ) ppm and at
132.8 and 124.6 (8b) ppm, with C-P coupling constants
of about 12 and 3 Hz, respectively, whereas the C(CO2-
Me) and CH2 carbon atoms display singlets between 140
and 129 ppm and between 44 and 29 ppm, respectively.
The 31P{1H} NMR spectrum contains two singlets at 4.7
(8a ) and 3.1 (8b) ppm, indicating that the phosphine
ligands are equivalent. This suggests that the carbon-
carbon double bonds of the cyclohexadienyl ligand of 8
lie in the plane containing the osmium atom, the car-
bonyl groups, and the oxygen atom of the acetate ligand.
The isomeric mixture of 8a and 8b in chloroform-d
reacts with 1 equiv of HBF4‚OEt2 to give the acetate-
dicarbonyl complex 5 and dimethyl 1,4-cyclohexadiene-
1,2-dicarboxylate in quantitative yield, according to eq
1.
The 31P{1H} NMR spectrum of the isomeric mixture
shows two singlets at 6.2 (7a ) and 4.1 (7b) ppm,
indicating that although the rotation of the butadienyl
ligand around the Os-C bond is hindered, the rotation
of the CHdCH2 moiety around the OsCdCH2 bond of
the dienyl is free.

[OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4
Organometallics, Vol. 19, No. 24, 2000 5103
Sch em e 3
Sch em e 4
Dimethyl 1,4-cyclohexadiene-1,2-dicarboxylate has
been previously synthesized by three methods: (i)
dimethyl 3-vinyl-1,2-dichlorocyclobutane-1,2-dicarboxy-
late undergoes a ring expansion, with concomitant loss
of the chlorines to give the cyclohexadiene in 52% yield,
upon treatment with Ni(CO)4 in refluxing benzene-
dimethylformamide,25 (ii) butadiene sulfone and di-
methyl acetylenedicarboxylate have been allowed to
reflux in xylene for 150 min, and (iii) butadiene and
dimethyl acetylenedicarboxylate have been mixed in
dioxane in a sealed tube and allowed to stand at room
temperature for 5 days.26 For methods ii and iii, the
yields of the reaction were not given.
The reactions shown in Scheme 4, which summarize
some of the processes described in this paper, constitute
a novel method to prepare dimethyl 1,4-cyclohexadiene-
1,2-dicarboxylate. The method starts from 2 equiv of
acetylene and 1 equiv of dimethyl acetylenedicarboxy-
late and uses the Os(CH3CO2)(PiPr3)2 unit as a tem-
plate.
In solution, as is the case for 7 and 8, complex 9 also
exists as a mixture of the isomers 9a and 9b shown in
Scheme 3. During the reaction, the rate of disappear-
ance of 7b is higher than that of 7a . As a consequence,
the molar ratio between 9a and 9b (25:75) is lower than
that between 7a and 7b, when the reaction is finished.
Attempts to separate the bicycle from the metallic
fragment by reaction of the isomeric mixture with H2
or I2 were unsuccessful.
1
In the H NMR spectrum of the isomeric mixture of
9a and 9b, the most noticeable feature is the presence
of two broad resonances at 6.60 (9a ) and 6.27 (9b) ppm,
due to the vinylic CHd hydrogen atom of the bicyclic
ligands. In the 13C{1H} NMR spectrum the OsC and
CHd resonances of the bicycles are observed as triplets
at 138.5 and 126.0 (9a ) ppm and at 148.2 and 132.6 (9b)
ppm with C-P coupling constants of about 11 and 4 Hz,
respectively, while the CH and CH2 resonances appear
as singlets at about 40 ppm and between 38 and 26 ppm,
respectively. The 31P{1H} NMR spectrum shows an AB
spin system for each isomer, indicating that the phos-
phine ligands are not equivalent, in agreement with the
structure proposed for these isomers in Scheme 3.
Complex 7 also reacts with maleic anhydride. In this
case the cycloaddition reaction leads to Os{CdCHCH2-
CH[C(O)OC(O)]CHCH2}{κ1-OC(O)CH3}(CO)2(PiPr3)2 (9)
Con clu d in g Rem a r k s
in quantitative yield after 1 week. The reaction was
carried out in benzene as solvent, at room temperature,
using 2 equiv of maleic anhydride. Under reflux, the
reagents give rise to an ill-defined straw-colored solid.
This study has revealed that the dihydride-osmium-
(IV) complex [OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4 is a
useful precursor for stoichiometric and catalytic carbon-
carbon coupling reactions, including the formation of
novel organometallic derivatives such as carbene, buta-
dienyl, cyclohexadienyl, and dioxohexahydroisobenzo-
(25) (a) Scharf, H. D.; Korte, F. Chem. Ber. 1966, 99, 1299. (b) Scharf,
H. D.; Korte, F. Chem. Ber. 1966, 99, 3925.
(26) DiFrancesco, D.; Pinhas, A. R. J . Org. Chem. 1986, 51, 2098.

5104 Organometallics, Vol. 19, No. 24, 2000
Esteruelas et al.
observed. The polyacetylene was then removed by filtration
to obtain a yellow solution. This yellow solution was concen-
trated to ca. 0.5 mL and diethyl ether added to afford a pale
yellow solid, which was washed with diethyl ether and dried
in vacuo. Yield: 90.5 mg (75%). Anal. Calcd for C24H51BF4O2-
OsP2: C, 40.57; H, 7.23. Found: C, 40.75; H, 7.20. IR (KBr,
cm-1): ν(CdC) 1625, νasym(OCO) 1572, νsym(OCO) 1470, ν(BF4)
1000-1100. 1H NMR (300 MHz, CDCl3, 25 °C): δ 7.55 (dd,
J H-H ) 16.2, J H-H ) 10.5, 1 H, CHdCH2), 5.87 (d, J H-H ) 10.5,
1 H, CHdCH2), 4.69 (d, J H-H ) 16.2, 1 H, CHdCH2), 2.80-
2.60 (m, 6 H, PCH(CH3)2), 1.84 (t, J P-H ) 0.9, 3 H, tCCH3),
1.66 (s, 3 H, OCOCH3), 1.38 (dvt, N ) 14.4, J H-H ) 7.2, 18 H,
PCH(CH3)2), 1.35 (dvt, N ) 15.0, J H-H ) 7.2, 18 H, PCH(CH3)2).
31P{1H} NMR (121.42 MHz, CDCl3, 25 °C): δ 22.9 (s). 13C{1H}
NMR (75.47 MHz, CD2Cl2, -30 °C, plus APT): δ 289.9 (t, J P-C
) 9.0, OstCCH3), 186.5 (s, OCOCH3), 140.0 (t, J P-C ) 8.0,
Os-CHdCH2), 123.3 (s, Os-CHdCH2), 41.4 (s, OstCCH3),
25.5 (s, OCOCH3), 24.7 (vt, N ) 26.6, PCH(CH3)2), 19.2 and
19.1 (both s, PCH(CH3)2). MS (FAB+): m/z 625 (100) (M+), 465
(25) (M+ - PiPr3).
furanyl compounds, the polymerization of acetylene, and
the synthesis of dimethyl 1,4-cyclohexadiene-1,2-dicar-
boxylate.
In contrast to the previously observed reactions
between alkynes and osmium compounds containing
two hydrogen atoms bonded to the metallic center, two
molecules of alkyne are activated when the dihydride-
osmium(IV) complex [OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]-
BF4 is exposed under 1 atm of acetylene. The resulting
product, [Os(CHdCH2)(κ2-O2CCH3)(tCCH3)(PiPr3)2]BF4,
is the key to the carbon-carbon bond-forming processes.
The carbyne ligand of this vinyl-carbyne complex has
a tendency to undergo a migratory insertion into the
Os-vinyl bond to give a carbene species, which can be
detected under carbon monoxide atmosphere and is
responsible for the acetylene polymerization.
In basic medium, the carbyne ligand of the vinyl-
carbyne complex undergoes deprotonation to give the
vinyl-vinylidene derivative Os(CHdCH2)(κ2-O2CCH3)-
(dCdCH2)(PiPr3)2. Under a carbon monoxide atmo-
sphere, this complex also evolves by migration insertion,
in this case of the vinylidene into the osmium-vinyl
bond, to afford the butadienyl compound Os{C(CHd
CH2)dCH2}(κ1-OC(O)CH3)(CO)2(PiPr3)2. The butadienyl
ligand of this complex acts as a diene in Diels-Alder
reactions with activated dienophiles such as dimethyl
acetylenedicarboxylate and maleic anhydride. The pro-
Rea ction of [Os(CHdCH2)(K2-O2CCH3)(tCCH3)(P iP r 3)2]-
2
BF4 with Car bon Mon oxide. For m ation of [Os(K -O2CCH3)-
{dC(CHdCH2)CH3}(CO)(P iP r 3)2]BF 4 (4) a n d [Os(K -O2-
2
CCH3)(CO)2(P iP r 3)2]BF 4 (5). A solution of 2 (120 mg, 0.17
mmol) in dichloromethane (10 mL) was stirred overnight under
a carbon monoxide atmosphere. The resulting solution was
concentrated to ca. 0.5 mL and diethyl ether added to afford a
pale yellow solid. Yield: 97.2 mg. 1H and 31P{1H} NMR
spectroscopy show a 70:30 mixture of compounds 4 and 5. All
attempts to separate the two products either by column
chromatography or by fractional crystallization failed. The
spectroscopic data of 5 agree with those reported previously.11
Spectroscopic data for 4 are as follows. IR (KBr, cm-1): ν-
(CO) 1946 (s), ν(OCO) 1626 (m), 1389 (m), ν(BF4) 1100-1000
(s). 1H NMR (300 MHz, CDCl3, 25 °C): δ 8.34 (dd, J H-H ) 10.8,
J H-H ) 17.2, 1 H, -CHd), 6.40 (d, J H-H ) 17.2, 1 H, dCH2),
5.91 (d, J H-H ) 10.8, 1 H, dCH2), 2.62 (s, 3 H, OsdC(CH3)),
2.47 (m, 6 H, PCH(CH3)2), 2.04 (t, J P-H ) 1.2, 3 H, OCOCH3),
1.33 (dvt, N ) 15, J H-H ) 7.5, 18 H, PCH(CH3)2), 1.27 (dvt, N
) 14.1, J H-H ) 6.9, 18 H, PCH(CH3)2). 31P{1H} NMR (121.42
MHz, CDCl3, 25 °C): δ 28.6 (s). 13C{1H} NMR (75.47 MHz,
CDCl3, 25 °C): δ 288.2 (t, J P-C ) 4.0, OsdC), 187.5 (s,
OCOCH3), 180.3 (t, J P-C ) 8.6, Os-CO), 149.0 (s, -CHd),
114.9 (s, dCH2), 45.1 (s, -CH3), 26.9 (vt, N ) 25.6, PCH(CH3)2),
24.9 (s, OCOCH3), 19.6 and 19.4 (both s, PCH(CH3)2). MS
(FAB+): m/z 653 (M+).
tonation of the cyclohexadienyl derivative Os{Cd
CHCH2C(CO2Me)dC(CO2Me)CH2{κ1-OC(O)CH3}(CO)2-
(PiPr3)2, resulting from the reaction of the butadienyl
complex with dimethyl acetylenedicarboxylate, yields
dimethyl 1,4-cyclohexadiene-1,2-dicarboxylate.
The previously mentioned sequence of reactions con-
stitutes a novel method to prepare dimethyl 1,4-cyclo-
hexadiene-1,2-dicarboxylate, starting from acetylene
and dimethyl acetylenedicarboxylate and using the Os-
(CH3CO2)(PiPr3)2 unit as a template.
Exp er im en ta l Section
All reactions were carried out with rigorous exclusion of air
using standard Schlenk techniques. Solvents were dried by
known procedures and distilled under argon prior to use.
[OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4 (1) and [OsH(κ2-O2CCH3)-
(tCCH3)(PiPr3)2]BF4 (3) were prepared as previously re-
ported.12 MeO2CCtCCO2Me (Fluka) was distilled prior to use,
while maleic anhydride (Fluka) was used as received. Infrared
spectra were recorded either on a Nicolet 550 or on a Perkin-
Elmer 883 spectrometer as solids (KBr pellet or Nujol mull)
or in solution (CH2Cl2). 1H, 13C{1H}, and 31P NMR spectra were
recorded either on a Varian Gemini 2000 or a Bruker AXR
300 instrument. Chemical shifts are referenced to residual
solvent peaks (1H, 13C{1H}) or external H3PO4 (31P). Coupling
P r ep a r a t ion of Os(CH dCH 2)(K2-O2CCH 3)(dCdCH 2)-
(P iP r 3)2 (6). A solution of 2 (100 mg, 0.14 mmol) in CH2Cl2
(10 mL) was treated with a stoichiometric amount of KOH in
methanol (0.75 mL, 0.14 mmol, 0.187 N). After it was stirred
for 20 min at room temperature, the solution was evaporated
to dryness. Toluene (10 mL) was added, and the resulting
suspension was filtered through Celite. The filtrate was dried
in vacuo, and an oil was obtained. All attempts to get a solid
1
from this oil failed. H NMR (300 MHz, C6D6, 25 °C): δ 8.68
(dd, J H-H ) 16.5, J H-H ) 10.5, 1 H, Os-CHdCH2), 6.04 (ddt,
J H-H ) 10.5, J P-H ) 2.4, J H-H ) 2.1, 1 H, Os-CHdCH2), 4.76
(ddt, J H-H ) 16.5, J P-H ) 2.7, J H-H ) 2.1, 1 H, Os-CHdCH2),
2.91 (m, 6 H, PCH(CH3)2), 1.65 (s, 3 H, OCOCH3), 1.34 (dvt,
N ) 12.9, J H-H ) 7.2, 18 H, PCH(CH3)2), 1.27 (dvt, N ) 12.6,
J H-H ) 6.9, 18 H, PCH(CH3)2), 0.64 (t, J P-H ) 3, 1 H, OsdCd
CH2). 31P{1H} NMR (121.42 MHz, C6D6, 25 °C): δ 1.1 (s). 13C-
{1H} NMR (75.47 MHz, C6D6, 20 °C): δ 287.2 (t, J P-C ) 11.2,
OsdCdCH2), 181.6 (s, OCOCH3), 149.6 (t, J P-C ) 8.1, Os-
CHdCH2), 115.7 (s, Os-CHdCH2), 87.7 (t, J P-C ) 3.5, Osd
CdCH2), 25.5 (s, OCOCH3), 23.2 (vt, N ) 22.8, PCH(CH3)2),
19.8 and 19.6 (both s, PCH(CH3)2).
1
constants, J and N (N ) J P-H + J P′-H for H; N ) J P-C + J P′-C
for 13C{1H}) are given in hertz. C, H, and N analyses were
measured on a Perkin-Elmer 2400 CHNS/O analyzer. Mass
spectra analyses were performed with a VG Auto Spec instru-
ment.
P r ep a r a t ion of [Os(CH dCH 2)(K2-O2CCH 3)(tCCH 3)-
(P iP r 3)2]BF 4 (2). This compound was prepared by starting
from 1 or from 3, using the same procedure. Only the synthesis
from 1 is described. A solution of 1 (116 mg, 0.17 mmol) in
dichloromethane (10 mL) was cooled to 0 °C. The argon
atmosphere was replaced by an acetylene atmosphere, and the
reaction mixture was stirred for 6 h at 0 °C, during which time
the formation of a dark blue precipitate (polyacetylene) was
P r ep a r a tion of Os{C(CHdCH2)dCH2}(K1-OC(O)CH3)-
(CO)2(P iP r 3)2 (7). A solution of 6 (200 mg, 0.16 mmol) in
toluene (10 mL) was stirred overnight under a carbon mon-
oxide atmosphere. The resulting solution was concentrated to

[OsH2(κ2-O2CCH3)(H2O)(PiPr3)2]BF4
Organometallics, Vol. 19, No. 24, 2000 5105
dryness, and pentane was added to afford a pale yellow solid,
which was washed several times with pentane and dried in
vacuo. Yield: 124 mg (57%). Anal. Calcd for C26H50O4OsP2:
C, 46.00; H, 7.42. Found: C, 45.63; H, 7.15. IR (Nujol, cm-1):
NMR data of the major isomer (60%) are as follows. 1H NMR
(300 MHz, C6D6, 25 °C): δ 6.70 (br, 1 H, dCH), 3.88 (t, J H-H
) 7.8, 2 H, -CH2-), 3.56 (s, 3 H, CO2Me), 3.35 (s, 3 H, CO2-
Me), 3.27 (m, 2 H, -CH2-), 2.44 (m, 6 H, PCH(CH3)2), 2.18 (s,
3 H, OCOCH3), 1.15 (m, 36 H, PCH(CH3)2). 31P{1H} NMR
(121.42 MHz, C6D6, 25 °C): δ 3.1 (s). 13C{1H} NMR (75.47
MHz, C6D6, 20 °C, plus DEPT): δ 185.1 (t, J P-C ) 7.6, Os-
CO), 184.4 (t, J P-C ) 8.3, Os-CO), 176.3 (s, OCOCH3), 170.2
(s, CO2CH3), 167.8 (s, CO2CH3), 139.6 (s, C-CO2CH3), 132.8
1
ν(CO) 2002, 1919 νasym(OCO) 1630. The H and 31P{1H} NMR
spectra show the presence of two isomers (ratio 40:60).
NMR data of the minor isomer (40%) are as follows. 1H NMR
(300 MHz, C6D6, 25 °C, plus COSY): δ 7.67 (ddd, J H-H ) 17.1,
J H-H ) 10.5, J H-H ) 0.9, 1 H, Os-C(CHdCH2)dCH2), 6.91
(ddt, J H-H ) 4.0, J H-H ) 0.9, J P-H ) 2.7, 1 H, Os-C(CHd
CH2)dCH2), 5.77 (dt, J H-H ) 4.0, J P-H ) 2.4, 1 H, Os-C(CHd
CH2)dCH2), 5.42 (dd, J H-H ) 17.2, J H-H ) 3, 1 H, Os-C(CHd
CH2)dCH2), 4.95 (dd, J H-H ) 10.5, J H-H ) 3, 1 H, Os-C(CHd
CH2)dCH2), 2.52 (m, 6 H, PCH(CH3)2), 2.20 (s, 3 H, OCOCH3),
1.15 (dvt, J H-H ) 7.2, N ) 13.5, 36 H, PCH(CH3)2). 31P{1H}
NMR (121.42 MHz, C6D6, 25 °C): δ 6.2 (s). 13C{1H} NMR (75.47
MHz, C6D6, 20 °C, plus DEPT): δ 185.9 (t, J P-C ) 7.3, Os-
CO), 185.0 (t, J P-C ) 6.9, Os-CO), 176.6 (s, OCOCH3), 157.1
(t, J P-C ) 11.5, Os-C), 150.4 (s, Os-C(CHdCH2)dCH2), 123.4
(br s, Os-C(CHdCH2)dCH2), 106.3 (s, Os-C(CHdCH2)dCH2),
25.9 (vt, N ) 24.9, PCH(CH3)2), 24.4 (s, OCOCH3), 19.8 (s,
PCH(CH3)2).
NMR data of the major isomer (60%) are as follows. 1H NMR
(300 MHz, C6D6, 25 °C, plus COSY): δ 7.23 (ddd, J H-H ) 16.6,
J H-H ) 10.2, J H-H ) 1, 1 H, Os-C(CHdCH2)dCH2), 6.52 (ddt,
J H-H ) 4.7, J H-H ) 1, J P-H ) 2.7, 1 H, Os-C(CHdCH2)dCH2),
6.11 (dt, J H-H ) 4.7, J P-H ) 2.4, 1 H, Os-C(CHdCH2)dCH2),
5.26 (dd, J H-H ) 16.6, J H-H ) 2.7, 1 H, Os-C(CHdCH2)dCH2),
4.78 (dd, J H-H ) 10.2, J H-H ) 2.7, 1 H, Os-C(CHdCH2)dCH2),
2.52 (m, 6 H, PCH(CH3)2), 2.23 (s, 3 H, OCOCH3), 1.21 (dvt,
(t, J P-C ) 11.9, Os-C), 129.7 (s, C-CO2CH3), 124.6 (t, J P-C
)
3, dCH), 51.6 (s, CO2CH3), 51.2 (s, CO2CH3), 43.7 (s, -CH2-),
29.3 (s, -CH2-), 26.2 (vt, N ) 24.9, PCH(CH3)2), 24.3 (s,
OCOCH3), 19.5 (s, PCH(CH3)2), 19.3 (s, PCH(CH3)2).
Rea ction of 7 w ith Ma leic An h yd r id e: P r ep a r a tion of
Os{CdCHCH2CH[C(O)OC(O)]CHCH2}{K1-OC(O)CH3}(CO)2-
(P iP r 3)2 (9). A solution of 7 (200 mg, 0.29 mmol) in benzene
(15 mL) was treated with maleic anhydride (58 mg, 0.59
mmol). The resulting solution was stirred at room temperature
for 1 week. After this time the solution was filtered through
Celite and evaporated to ca. 0.5 mL. Addition of pentane (0.5
mL) gave an oily residue. After the mixture was stirred for 5
min, the pentane was removed with a cannula and more
pentane was added. After this mixture was stirred for 3 h, a
beige solid was obtained, which was washed with pentane and
dried in vacuo. Yield: 105 mg (46%). The reaction was found
to be quantitative (1H and 31P{1H} NMR spectroscopy); the low
isolated yield is due to the high solubility in pentane. Anal.
Calcd for C30H52O7OsP2: C, 46.38; H, 6.75. Found: C, 45.99;
H, 6.54. IR (Nujol, cm-1): ν(CO) 2001 (s), 1922 (m), 1955 (s),
1920 (m); ν(CdO) 1852 (m), 1776 (s); ν(C-O-C) 914 (s). The
1H and 31P{1H} NMR spectra show the presence of two isomers
(ratio 75:25).
J H-H ) 7.2, N ) 12.9, 18 H, PCH(CH3)2), 1.19 (dvt, J H-H
)
7.2, N ) 12.9, 18 H, PCH(CH3)2). 31P{1H} NMR (121.42 MHz,
C6D6, 25 °C): δ 4.1 (s). 13C{1H} NMR (75.47 MHz, C6D6, 20
°C, plus DEPT): δ 185.1 (t, J P-C ) 7.3, Os-CO), 184.6 (t, J P-C
) 8.3, Os-CO), 176.4 (s, OCOCH3), 154.9 (s, Os-C(CHdCH2)d
CH2), 153.6 (t, J P-C ) 11.4, Os-C), 120.2 (br s, Os-C(CHd
CH2)dCH2), 107.4 (s, Os-C(CHdCH2)dCH2), 26.2 (vt, N )
24.7, PCH(CH3)2), 24.4 (s, OCOCH3), 19.8 (s, PCH(CH3)2), 19.5
(s, PCH(CH3)2).
NMR data of the major isomer (75%) are as follows. 1H NMR
(300 MHz, C6D6, 25 °C): δ 6.27 (br, 1 H, dCH), 3.53 (dd, J H-H
) 7.8, J H-H ) 16, 1 H, -CH2-), 2.52 (m, 1 H, -CH), 2.39 (m,
1 H, -CH), 2.26 (m, 9 H, PCH(CH3)2, -CH2-), 2.16 (s, 3 H,
OCOCH3), 1.14-0.98 (m, 36 H, PCH(CH3)2). Most of the
aliphatic protons of the bicycle are overlapping with the
PCH(CH3)2 multiplet. 31P{1H} NMR (121.42 MHz, C6D6, 25
°C): two lines (AB pattern) at 6.76 and 6.74 ppm. 13C{1H}
NMR (75.47 MHz, C6D6, 20 °C, plus DEPT): δ 185.3 (t, J P-C
) 7.5, Os-CO), 184.8 (t, J P-C ) 8.7, Os-CO), 176.4 (s,
Rea ction of 7 w ith MeO2CCtCCO2Me: P r ep a r a tion of
Os{CdCH CH 2C(CO2Me)dC(CO2Me)CH 2{K1-OC(O)CH 3}-
(CO)2(P iP r 3)2 (8). To a solution of 7 (196 mg, 0.29 mmol) in
benzene (15 mL) was added MeO2CCtCCO2Me (71 µL, 0.58
mmol) with a syringe. The resulting solution was heated at
45 °C for 33 h. After this time the solution was filtered through
Celite and was then dried to ca. 0.5 mL. Addition of pentane
(5 mL) gave an oily residue. After the mixture was stirred for
5 min, the pentane was removed with a cannula, and more
pentane was added. After this mixture was stirred for 3 h, a
beige solid was obtained, which was washed with pentane and
dried in vacuo. Yield: 84 mg (35.6%). The reaction was found
to be quantitative (1H and 31P{1H} NMR spectroscopy); the low
isolated yield is due to the high solubility in pentane. Anal.
Calcd for C32H56O8OsP2: C, 46.18; H, 7.50. Found: C, 46.62;
H, 6.88. IR (Nujol, cm-1): ν(CO) 2001, 1922; ν(CdO) 1733,
1722; νasym(OCO) 1630. The 1H and 31P{1H} NMR spectra show
the presence of two isomers (ratio 40:60).
OCOCH3), 174.9 (s, CdO), 174.7 (s, CdO), 148.2 (t, J P-C
)
11.7, Os-C), 132.6 (t, J P-C ) 4, dCH), 40.7 (s, CH), 40.2 (s,
CH), 30.2 (s, -CH2-), 27.8 (s, -CH2-), 26.2 (vt, N ) 24.5,
PCH(CH3)2), 24.4 (s, OCOCH3), 19.4 (s, PCH(CH3)2), 19.3 (s,
PCH(CH3)2).
NMR data of the minor isomer (25%) are as follows. 1H NMR
(300 MHz, C6D6, 25 °C): δ 6.60 (br, 1 H, dCH), 2.89 (m, 1 H),
2.52 (m, 1 H), 2.26 (m, 10 H, PCH(CH3)2 plus 4 H of the
bicycle), 2.11 (s, 3 H, OCOCH3), 1.14-0.98 (m, 36 H, PCH-
(CH3)2). Most of the aliphatic protons of the bicycle are
overlapping with the PCH(CH3)2 multiplet. 31P{1H} NMR
(121.42 MHz, C6D6, 25 °C): two lines (AB pattern) at 3.73 and
3.71 ppm. 13C{1H} NMR (75.47 MHz, C6D6, 20 °C, plus
DEPT): δ 184.6 (t, J P-C ) 7.5, Os-CO), 184.3 (t, J P-C ) 8.4,
Os-CO), 176.3 (s, OCOCH3), 174.6 (s, CdO), 174.5 (s, CdO),
138.5 (t, J P-C ) 11, Os-C), 126.0 (t, J P-C ) 4, dCH), 40.9 (s,
CH), 39.1 (s, CH), 37.4 (s, -CH2-), 26.7 (vt, N ) 24, PCH-
(CH3)2), 26.5 (s, -CH2-), 24.4 (s, OCOCH3), 19.7 (s, PCH-
(CH3)2), 19.6 (s, PCH(CH3)2).
NMR data of the minor isomer (40%) are as follows. 1H NMR
(300 MHz, C6D6, 25 °C): δ 6.43 (br, 1 H, dCH), 3.78 (t, J H-H
) 7.8, 2 H, -CH2-), 3.54 (s, 3 H, CO2Me), 3.41 (s, 3 H, CO2-
Me), 3.20 (m, 2 H, -CH2-), 2.44 (m, 6 H, PCH(CH3)2), 2.20 (s,
3 H, OCOCH3), 1.15 (m, 36 H, PCH(CH3)2). 31P{1H} NMR
(121.42 MHz, C6D6, 25 °C): δ 4.7 (s). 13C{1H} NMR (75.47
MHz, C6D6, 20 °C, plus DEPT): δ 185.6 (t, J P-C ) 7.1, Os-
CO), 184.8 (t, J P-C ) 7.8, Os-CO), 176.2 (s, OCOCH3), 170.1
(s, CO2CH3), 167.8 (s, CO2CH3), 140.3 (t, J P-C ) 11.5, Os-C),
Rea ction of 8 w ith HBF 4‚OEt2: F or m a tion of [Os(K2-
O2CCH3)(CO)2(P iP r 3)2]BF 4 (5) a n d Dim eth yl 1,4-Cyclo-
h exa d ien e-1,2-d ica r boxyla te. A solution (0.5 mL) of 8 (18.5
mg, 0.02 mmol) in CDCl3 was placed in a 5 mm NMR tube,
and a stoichiometric amount (3 µL, 0.02 mmol) of HBF4‚OEt2
1
139.8 (s, C-CO2CH3), 130.2 (s, C-CO2CH3), 130.0 (t, J P-C
)
was added from a syringe. The H and 31P{1H} NMR spectra
3, dCH), 51.4 (s, CO2CH3), 51.3 (s, CO2CH3), 36.3 (s, -CH2-),
32.5 (s, -CH2-), 26.4 (vt, N ) 24.7, PCH(CH3)2), 24.2 (s,
OCOCH3), 19.7 (s, PCH(CH3)2), 19.5 (s, PCH(CH3)2).
recorded after 3 min show quantitative formation of 511 and
1
dimethyl 1,4-cyclohexadiene-1,2-dicarboxylate. H NMR (300
MHz, CDCl3, 25 °C): δ 5.69 (s, 2 H, dCH), 3.76 (s, 6 H, CO2-

5106 Organometallics, Vol. 19, No. 24, 2000
Esteruelas et al.
with those reported previously.26 MS (EI): m/z 163 (C10H12O4
- OMe - 2 H), 149 (C10H12O4 - OMe - Me - H), 134
(C10H12O4 - 2OMe), 106 (C10H12O4 - OMe - CO2Me).
Cr ysta l Da ta for 7. Crystals suitable for the X-ray diffrac-
tion study were obtained by cooling an acetone solution of 7
at -30 °C. A summary of crystal data and refinement
parameters is reported in Table 2. The colorless crystal was
mounted onto a glass fiber and transferred to an Bruker-
Siemens STOE AED-2 (T ) 298.0(2) K) automatic diffracto-
meter (Mo KR radiation, graphite monochromator, λ ) 0.71073
Å). Accurate unit cell parameters were determined by least-
squares fitting from the settings of 60 high-angle reflections.
Data were collected by the ω/2θ scan method. Lorentz and
polarization corrections were applied. Decay was monitored
by measuring three standards throughout data collection.
Corrections for decay and absorption (semiempirical ψ-scan
method) were also applied.
Ta ble 2. Cr ysta l Da ta a n d Da ta Collection a n d
Refin em en t for
Os{C(CHdCH2)dCH2}(K1-OC(O)CH3)(CO)2(P iP r 3)2
(7)
Crystal Data
formula
C26H50O4OsP2
mol wt
678.8
color and habit
symmetry, space group
colorless, prismatic block
monoclinic, P21/c
17.198(3)
10.774(2)
17.028(3)
107.93(2)
3001.9, 4
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
4
D
calcd, g cm-3
1.502
Data Collection and Refinement
diffractometer
λ(Mo KR), Å
monochromator
µ, mm-1
Bruker-Siemens STOE-AED2
0.71073
graphite oriented
4.38
The structure was solved by Patterson methods and refined
by full-matrix least-squares methods on F2.27 Non-hydrogen
atoms were anisotropically refined, and the hydrogen atoms
were observed or included at idealized positions.
scan type
ω/2θ
2θ range, deg
temp, K
3 e 2θ e 50
298.0(2)
no. of data collected
6610 (h, -2 to +20; k, -12 to 0;
Ack n ow led gm en t. We acknowledge financial sup-
port from the DGES of Spain (Project PB98-1591). C.G.-
Y. thanks CSIC-Repsol YPF for a postdoctoral grant.
l, -20 to +20)
no. of unique data
no. of params refined
R1a (F2> 2σ(F2))
wR2b (all data)
Sc (all data)
5260 (merging R factor 0.046)
311
0.0339
0.09
0.971
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and equivalent isotropic displacement coefficients,
anisotropic thermal parameters, experimental details of the
X-ray studies, and bond distances and angles for 7. This
material is available free of charge via the Internet at
http://pubs.acs.org.
R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR2(F2) ) {∑[w(Fo - Fc2)2]/
a
b
2
∑[w(Fo2)2]}1/2
.
c GOF ) S ) {∑[w(Fo - Fc2)2]/(n - p)}1/2, where n
2
is the number of reflections and p is the number of refined
parameters.
OM000475Z
CH3), 2.97 (s, 4 H, -CH2-), 2.64 (m, 6 H, PCH(CH3)2), 1.38
(dvt, J H-H ) 6.9, N ) 14.1, 36 H, PCH(CH3)2). 31P{1H} NMR
(121.42 MHz, CDCl3, 25 °C): δ 30.0 (s). The peaks correspond-
ing to dimethyl 1,4-cyclohexadiene-1,2-dicarboxylate agree well
(27) Sheldrick, G. SHELX97: Programs for Crystal Structure Solu-
tion and Refinement; Institut fu¨r Anorganische Chemie der Universita¨t
Go¨ttingen, Go¨ttingen, Germany, 1997.