Hydrogen migration and HCl elimination promoted by metal-centered nucleophilic attack on osmium hydrido-carbynes

Article abstract of DOI:10.1021/om980597f

The carbynes [OsHCl₂(CCH₂R)L₂] (R = Ph, CH₃; L = PⁱPr₃) react with CO to give, after 1,2-hydride migration from osmium to C_α of the carbyne ligand, the osmium carbene complexes [

Full text of DOI:10.1021/om980597f

5260
Organometallics 1998, 17, 5260-5266
Hyd r ogen Migr a tion a n d HCl Elim in a tion P r om oted by
Meta l-Cen ter ed Nu cleop h ilic Atta ck on Osm iu m
Hyd r id o-Ca r byn es
Greg J . Spivak and Kenneth G. Caulton*
Department of Chemistry, Indiana University, Bloomington, Indiana 47405-4001
Received J uly 14, 1998
The carbynes [OsHCl2(CCH2R)L2] (R ) Ph, CH3; L ) PiPr3) react with CO to give, after
1,2-hydride migration from osmium to CR of the carbyne ligand, the osmium carbene
complexes [OsCl2(CO)(dCHCH2R)L2]. For R ) Ph, reactions with excess CO lead to HCl
elimination to form [OsCl(CO)2((E)-CHdCHPh)L2], which reacts with liberated HCl at CR
to yield [OsCl2(CO)2L2] and CH2dCHPh. Abstraction of chloride from either the carbynes
or carbenes with NaBAr′4 (Ar′ ) 3,5-C6H3(CF3)2) yields the corresponding coordinatively
unsaturated carbyne and carbene complexes [OsHCl(CCH2R)L2][BAr′4] and [OsCl(CO)(d
CHCH2R)L2][BAr′4], respectively. The carbynes [OsHCl(CCH2Ph)L2]+ react with reagent
L′ (L′ ) CO, HCCR′) to initially give the carbenes [OsCl(L′)(dCHCH2Ph)L2]+ after 1,2-hydride
migration to CR of the carbyne ligand. These carbenes react further, eliminating HCl and
undergoing selective protonation to yield either [OsCl(CO)3L2]+ and CH2dCHPh (with L′ )
CO) or the σ-vinyl carbyne complexes [OsCl(CCH2R′)((E)-CHdCHPh)L2]+ (with L′ ) HCCR′).
In tr od u ction
tion occurs directly at CR of the carbyne ligand or if the
metal is first protonated, followed by rapid hydrogen
migration to CR. Moreover, in at least one case,3f,k,n
hydrogen migration between the metal and CR was
found to occur quite easily at room temperature.
In a recent preliminary communication4 regarding the
synthesis of the osmium carbynes [OsHCl2(CCH2R)L2],
1 (L ) PiPr3; R ) Ph, 1a ; R ) CH3, 1b), from the
versatile reagent [OsH2Cl2L2] and terminal olefins
CH2dCHR, we briefly reported that reactions of 1 with
CO at room temperature induce a 1,2-hydride migration
from osmium to CR of the carbyne ligand to yield the
corresponding carbenes [OsCl2(CO)(dCHCH2R)L2], 2 (R
) Ph, 2a ; R ) CH3, 2b), as illustrated in eq 1. This
novel intramolecular rearrangement offers another ap-
proach toward generating osmium alkylidene com-
plexes.2g-i We have since expanded upon this unique
and interesting chemistry and now report the full details
below.
The availability of late transition metal alkylidene
complexes which function as olefin metathesis catalysts
has allowed their exceptional use in organic synthesis.1
Although the convenient synthetic utility of such com-
plexes in practical applications continues to expand
today, the focus of several recent reports2 has been the
development of new methods of synthesizing late tran-
sition metal alkylidene complexes, which have the
potential to serve as olefin metathesis catalysts.
One approach toward generating metal-carbene com-
plexes LnM(dCRR′) involves electrophilic addition of
(R′)+ to nucleophilic carbyne ligands of metal-carbyne
complexes LnM(CR). In fact, a large number of alkyl-
idene complexes have been conveniently prepared by
protonating alkylidyne complexes.3 In many instances,
however, it is not clearly understood whether protona-
* Corresponding author. E-mail: caulton@indiana.edu.
(1) (a) Metathesis Polymerization of Olefins and Polymerization of
Alkynes; Imamoglu, Y., Ed.; Kluwer Academic: Boston, 1998; Part I,
pp 1-356. (b) Grubbs, R. H.; Miller, S. J .; Fu, G. C. Acc. Chem. Res.
1995, 28, 446. (c) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed.
Engl. 1997, 36, 2036. (d) Moore, J . S. In Comprehensive Organometallic
Chemistry II; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Pergamon Press, Ltd.: New York, 1996; Vol. 12, pp 1209-1229. (e)
Toreki, R.; Schrock, R. R. J . Am. Chem. Soc. 1990, 112, 2448. (f) Pariya,
C.; J ayaprakash, K. N.; Sarkar, A. Coord. Chem. Rev. 1998, 168, 1.
(2) (a) Grunwald, C.; Gevert, O.; Wolf, J .; Gonzalez-Herrero, P.;
Werner, H. Organometallics 1996, 15, 1960. (b) Belderrain, T. R.;
Grubbs, R. H. Organometallics 1997, 16, 4001. (c) Wilhelm, T. E.;
Belderrain, T. R.; Brown, S. N.; Grubbs, R. H. Organometallics 1997,
16, 3867. (d) Olivan, M.; Caulton, K. G. J . Chem. Soc., Chem. Commun.
1997, 1733. (e) Wolf, J .; Stuer, W.; Grunwald, C.; Werner, H.; Schwab,
P.; Schulz, M. Angew. Chem., Int. Ed. 1998, 37, 1124. (f) Coalter, J .
N.; Spivak, G. J .; Gerard, H.; Clot, E.; Davidson, E. R.; Eisenstein, O.;
Caulton, K. G. J . Am. Chem. Soc., submitted. (g) Werner, H.; Stuer,
W.; Laubender, M.; Lehmann, C.; Herbst-Irmer, R. Organometallics
1997, 16, 2236. (h) Bohle, D. S.; Clark, G. R.; Rickard, C. E. F.; Roper,
W. R.; Wright, L. J . J . Organomet. Chem. 1988, 358, 411. (i) Hill, A.
F.; Roper, W. R.; Waters, J . M.; Wright, A. H. J . Am. Chem. Soc. 1983,
105, 5939.
(3) For example, see: (a) Brew, S. A.; Stone, F. G. A. Adv.
Organomet. Chem. 1993, 35, 135, and references therein. (b) Giannini,
L.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem.
Soc. 1998, 120, 823. (c) Garrett, K. E.; Sheridan, J . B.; Pourreau, D.
B.; Feng, W. C.; Geoffroy, G. L.; Staley, D. L.; Rheingold, A. L. J . Am.
Chem. Soc. 1989, 111, 8383, and references therein. (d) Clark, G. R.;
Marsden, K.; Roper, W. R.; Wright, L. J . J . Am. Chem. Soc. 1980, 102,
6570. (e) Vogler, A., Kisslinger, J .; Roper, W. R. Z. Naturforsch. 1983,
38b, 1506. (f) Holmes, S. J .; Schrock, R. R. J . Am. Chem. Soc. 1981,
103, 4599. (g) Doyle, R. A.; Angelici, R. J . Organometallics 1989, 8,
2207. (h) Blosch, L. L.; Abboud, K.; Boncella, J . M. J . Am. Chem. Soc.
1991, 113, 7066. (i) Etienne, M.; White, P. S.; Templeton, J . L. J . Am.
Chem. Soc. 1991, 113, 2324. (j) Bastos, C. M.; Daubenspeck, N.; Mayr,
A. Angew. Chem., Int. Ed. Engl. 1993, 32, 743. (k) Wengrovius, J . H.;
Schrock, R. R.; Churchill, M. R.; Wasserman, H. J . J . Am. Chem. Soc.
1982, 104, 1739. (l) Mayr, A.; Asaro, M. F.; Kjelsberg, M. A.; Lee, K.
S.; Van Engen, D. Organometallics 1987, 6, 432. (m) Freudenberger,
J . H.; Schrock, R. R. Organometallics 1985, 4, 1937. (n) Holmes, S. J .;
Clark, D. N.; Turner, H. W.; Schrock, R. R. J . Am. Chem. Soc. 1982,
104, 6322.
(4) Spivak, G. J .; Coalter, J . N.; Olivan, M.; Eisenstein, O.; Caulton,
K. G. Organometallics 1998, 17, 999.
10.1021/om980597f CCC: $15.00 © 1998 American Chemical Society
Publication on Web 10/28/1998

Nucleophilic Attack on Os Hydrido-Carbynes
Organometallics, Vol. 17, No. 24, 1998 5261
and the contents of the flask were evacuated. Excess CO (1
atm) was admitted into the flask, and upon thawing, the
solution was allowed to stir for 48 h. After this time, the
remaining excess CO was flushed from the flask with argon,
and the yellow solution was once again frozen in liquid
nitrogen. After evacuating the flask, excess HCl gas (1 atm)
was admitted into the flask. The solution was thawed and
allowed to stir for 1.5 h. The volatiles were removed under
reduced pressure to yield a yellow powder. Yield: 63%. IR
(CD2Cl2, cm-1): 2019 (s), 1946 (s). 1H NMR (300 MHz, CD2Cl2,
20 °C): 1.40 (dvt, N ) 14.4 Hz, 18H, PCHCH3), 2.95 (m, 6H,
PCHCH3). 13C{1H} NMR (75.3 MHz, CD2Cl2, 20 °C): 20.08
(s, PCHCH3), 24.54 (vt, N ) 12.3 Hz, PCHCH3), 176.95 (t,
2J (PC) ) 7.3 Hz, Os-CO). 31P{1H} NMR (121.4 MHz, CD2Cl2,
20 °C): 8.03 (s, PiPr3).
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were conducted
under an inert atmosphere of prepurified argon using standard
Schlenk techniques or in a Vacuum Atmospheres Corp. drybox.
All bulk solvents (pentane and CH2Cl2) used in large-scale
preparations were distilled from appropriate drying agents and
stored in bulbs with Teflon taps. All NMR solvents were dried
with appropriate drying agents, vacuum distilled, and stored
under argon prior to use. NMR spectra (1H, 13C, and 31P) were
obtained on a Varian XL 300 MHz spectrometer, with chemical
shifts (in ppm) referenced to residual solvent peaks (1H and
13C) or external H3PO4 (31P). Elemental analyses were per-
formed on a Perkin-Elmer 2400 CHNS/O elemental analyzer
in the Department of Chemistry, Indiana University. The
complexes [OsHCl2(CCH2R)(PiPr3)2] (R ) Ph, 1a ; R ) CH3, 1b)4
Rea ction of 1a w ith Excess 13CO: F or m a tion of [OsCl-
(
13CO)2((E)-CHdCHP h )(P iP r 3)2], 3′, a n d [OsCl2(13CO)2-
(P iP r 3)2], 4′. In an NMR tube fitted with a Teflon tap, complex
1a (0.010 g, 0.016 mmol) was dissolved in CD2Cl2 (0.5 mL).
The solution was frozen in liquid nitrogen, and the headspace
was evacuated. A slight excess of 13CO (ca. 3-4 equiv) was
admitted into the NMR tube, and upon thawing, the solution
was allowed to mix (tumbling). The NMR (1H, 13C{1H}, and
31P{1H}) spectra of the solution were recorded over a 48 h
period and revealed the formation of 3′ and 4′. Complex 3′
5
and NaBAr′4 were prepared according to the method cited
1
was identified by comparison to the literature data.7 The H
previously.
NMR data for 4′ were the same as for 4 cited above; 13C{1H}
and 31P{1H} data for 4′ follow. 13C{1H} NMR (75.3 MHz,
CD2Cl2, 20 °C): 20.08 (s, PCHCH3), 24.54 (vt, N ) 12.3 Hz,
PCHCH3), 176.95 (t, 2J (PC) ) 7.3 Hz, Os-CO). 31P{1H} NMR
Rea ction of 1a w ith CO: F or m a tion of [OsCl2(CO)(d
CHCH2P h )(P iP r 3)2], 2a , a n d [OsCl(CO)2((E)-CHdCHP h )-
(P iP r 3)2], 3. In an NMR tube fitted with a Teflon tap, complex
1a (0.010 g, 0.016 mmol) was dissolved in CD2Cl2 (ca. 0.5 mL)
to give a yellow solution. The solution was frozen in liquid
nitrogen, and the headspace was evacuated; CO (ca. 1 equiv)
was then readmitted into the tube. The solution was thawed
and allowed to mix (tumbling) for 2 h to give a pale yellow
solution. After such time, all of 1a had been consumed, and
2a and 3 were produced in an approximately 1:1 ratio. The
spectroscopic (NMR) data for 2a and 3 were analogous to those
cited previously.6,7
2
(121.4 MHz, CD2Cl2, 20 °C): 8.02 (t, J (PC) ) 7.3 Hz, PiPr3).
Syn th esis of [OsHCl(CCH2P h )(P iP r 3)2][BAr ′4], 5a. Com-
plex 1a (0.050 g, 0.082 mmol) in CH2Cl2 (10 mL) was treated
with 1 equiv (0.082 mmol) of NaBAr′4 (0.072 g). The mixture
was stirred for 90 min, and the dark yellow solution was
filtered through Celite. The dark yellow filtrate was concen-
trated to dryness under reduced pressure to yield pure 5a .
Yield: 83%. 1H NMR (300 MHz, CD2Cl2, 20 °C): -9.84 (t,
2J (PH) ) 14.1 Hz, 1H, Os-H), 1.25 (dvt, N ) 15.9 Hz, 18H,
PCHCH3), 1.28 (dvt, N ) 15.3 Hz, 18H, PCHCH3), 2.71 (m,
6H, PCHCH3), 3.13 (s, 2H, OsCCH2Ph), 7.17-7.42 (m, 5H,
OsCCH2Ph), 7.57, 7.74 (BAr′4). 13C{1H} NMR (75.3 MHz,
CD2Cl2, 20 °C): 19.82 (s, PCHCH3), 20.39 (s, PCHCH3), 26.52
(vt, N ) 13.7 Hz, PCHCH3), 57.69 (s, OsCCH2Ph), 129.79,
130.35, 130.77 (all s, Ph), 282.58 (t, 2J (PC) ) 6.1 Hz, OsCCH2-
Ph). 31P{1H} NMR (121.4 MHz, CD2Cl2, 20 °C): 62.17 (s,
PiPr3).
Syn th esis of [OsCl2(CO)(dCHCH2CH3)(P iP r 3)2], 2b. A
solution of complex 1b (0.060 g, 0.096 mmol) in CH2Cl2 (10
mL) was frozen in liquid nitrogen, and the headspace was
evacuated. Excess CO (1 atm) was admitted into the flask,
and after thawing, the solution was allowed to stir for 3 h.
Filtering the solution through Celite yielded a bright yellow
solution. The filtrate was concentrated to ca. 1 mL under
reduced pressure and then treated with excess (20 mL)
pentane. The murky solution was left in an ice bath for 30
min, and finally the solvent was removed under reduced
pressure to yield a slightly pale yellow solid. Yield: 78%. Anal.
Calcd for C22H48Cl2OOsP2: C, 40.55; H, 7.42. Found: C, 40.35;
H, 7.28. 1H NMR (300 MHz, CD2Cl2, 20 °C): 1.26 (dvt, N )
14.4 Hz, 18H, PCHCH3), 1.34 (dvt, N ) 13.8 Hz, 18H,
PCHCH3), 2.26 (q, 3J (HH) ) 6.6 Hz, 2H, OsdCHCH2CH3), 2.76
(m, 6H, PCHCH3), 18.62 (t, 3J (HH) ) 6.6 Hz, 1H, OsdCHCH2-
CH3); the methyl resonance of the ethyl group was obscured
Syn th esis of [OsHCl(CCH2CH3)(P iP r 3)2][BAr ′4], 5b. Com-
plex 5b was prepared as a yellow solid in a manner analogous
to that described for 5a , except the two reagents were allowed
to mix for 2.5 h before filtering. Yield: 74%. 1H NMR (300
2
MHz, CD2Cl2, 20 °C): -9.79 (t, J (PH) ) 14.1 Hz, 1H, Os-H),
1.28 (dvt, N ) 15.3 Hz, 18H, PCHCH3), 1.30 (dvt, N ) 16.5
Hz, 18H, PCHCH3), 1.86 (q, 3J (HH) ) 7.5 Hz, 2H, OsCCH2-
CH3), 2.80 (m, 6H, PCHCH3), 7.54-7.71 (BAr′4). 13C{1H} NMR
(75.3 MHz, CD2Cl2, 20 °C): 1.05 (s, OsCCH2CH3), 19.83 (s,
PCHCH3), 20.65 (s, PCHCH3), 26.38 (vt, N ) 14.1 Hz,
by the Pr proton signals. 13C{1H} NMR (75.3 MHz, CD2Cl2,
i
20 °C): 14.97 (s, OsdCHCH2CH3), 19.43 (s, PCHCH3), 20.04
(s, PCHCH3), 25.34 (vt, N ) 12.5 Hz, PCHCH3), 55.12 (s,
OsdCHCH2CH3), 180.32 (t, 2J (PC) ) 8.3 Hz, Os-CO), 306.41
(br, OsdCHCH2CH3). 31P{1H} NMR (121.4 MHz, CD2Cl2, 20
°C): 12.10 (s, PiPr3).
2
PCHCH3), 45.82 (s, OsCCH2CH3), 288.64 (t, J (PC) ) 6.9 Hz,
OsCCH2CH3). 31P{1H} NMR (121.4 MHz, CD2Cl2, 20 °C):
62.86 (s, PiPr3).
F or m a tion of [OsCl(CO)(dCHCH2P h )(P iP r 3)2][BAr ′4],
6a . A crude sample containing an approximately 1:1 mixture
of 2a and 3 (ca. 0.060 g) in CD2Cl2 (0.5 mL) was treated with
excess NaBAr′4 (ca. 0.09 g, 0.10 mmol) in an NMR tube. After
mixing (tumbling) for 1 h, the heterogeneous mixture appeared
dark green-yellow. NMR spectroscopy revealed that all of 2a
had been consumed, and the solution now contained an
approximately 1:1 mixture of 6a and 3. Spectroscopic (NMR)
data for 6a follow. 1H NMR (300 MHz, CD2Cl2, 20 °C): 1.28
(dvt, N ) 15.6 Hz, 18H, PCHCH3), 1.29 (dvt, N ) 15.3 Hz,
Syn th esis of [OsCl2(CO)2(P iP r 3)2], 4. Complex 1a (0.017
g, 0.028 mmol) in CH2Cl2 (2 mL) was frozen in liquid nitrogen,
(5) Brookhart, M.; Grant, R. G.; Volpe, A. F., J r. Organometallics
1992, 11, 3920.
(6) Esteruelas, M. A.; Lahoz, F. J .; Onate, E.; Oro, L. A.; Valero, C.;
Zeier, B. J . Am. Chem. Soc. 1995, 117, 7935. Baker, L.; Clark, G. R.;
Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J . J .
Organomet. Chem. 1998, 551, 247.
(7) Werner, H.; Esteruelas, M. A.; Otto, H. Organometallics 1986,
5, 2295.
3
18H, PCHCH3), 2.92 (m, 6H, PCHCH3), 3.44 (d, J (HH) ) 6.0

5262 Organometallics, Vol. 17, No. 24, 1998
Spivak and Caulton
3
Hz, OsdCHCH2Ph), 7.72, 7.56 (BAr′4), 17.15 (t, J (HH) ) 6.0
Hz, OsdCHCH2Ph). 13C{1H} NMR (75.3 MHz, CD2Cl2, 20
°C): 19.31 (s, PCHCH3), 20.05 (s, PCHCH3), 26.12 (vt, N )
13.7 Hz, PCHCH3), 67.62 (s, OsdCHCH2Ph), 128.57, 128.94,
Syn th esis of [OsCl(η2-HCCSiMe3)(dCHCH2P h )(P iP r 3)2]-
[BAr ′4], 8a . Complex 5a (0.010 g, 0.0070 mmol) was dissolved
in CD2Cl2 (0.5 mL) in an NMR tube fitted with a Teflon tap.
To this solution, 1 equiv (0.0070 mmol, 1 µL) of HCCSiMe3
was added. The solution was allowed to mix (tumbling) for
24 h, after which it turned pale gray. The reaction was
quantitative, as determined by NMR (1H and 31P{1H}) spec-
troscopy. 1H NMR (300 MHz, CD2Cl2, 20 °C): 0.35 (s, 9H,
Si(CH3)3), 1.27 (dvt, N ) 15.9 Hz, 18H, PCHCH3), 1.29 (dvt,
N ) 15.3 Hz, 18H, PCHCH3), 1.99 (br m, 2H, OsdCHCH2Ph),
3.16 (m, 6H, PCHCH3), 7.13-7.40 (m, 5H, Ph), 7.56, 7.72
(BAr′4), 15.91 (br, 1H, OsdCHCH2Ph); the acetylenic hydrogen
was partially obscured by the methine hydrogen multiplet.
13C{1H} NMR (75.3 MHz, CD2Cl2, 20 °C): 2.07 (s, Si(CH3)3),
19.31 (s, PCHCH3), 20.00 (s, PCHCH3), 24.71 (vt, N ) 12.8
Hz, PCHCH3), 68.33 (br, Os(η2-HCCSiMe3)), 91.81 (br, Os(η2-
HCCSiMe3)), 128.53, 129.20, 130.31 (all s, Ph), 285.06 (t,
2J (PC) ) 8.4 Hz, OsdCHCH2Ph); the CH2Ph carbon was
obscured by the solvent peak. 31P{1H} NMR (121.4 MHz,
CD2Cl2, 20 °C): 45.01 (s, PiPr3).
2
129.94 (all s, Ph), 179.95 (t, J (PC) ) 8.7 Hz, Os-CO), 278.82
(t, 2J (PC) ) 7.2 Hz, OsdCHCH2Ph). 31P{1H} NMR (121.4
MHz, CD2Cl2, 20 °C: 54.10 (s, PiPr3).
Syn th esis of [OsCl(CO)(dCHCH2CH3)(P iP r 3)2][BAr ′4],
6b. Complex 2b (0.049 g, 0.075 mmol) and 1 equiv of NaBAr′4
(0.066 g, 0.075 mmol) were treated with CH2Cl2 (10 mL), and
the heterogeneous mixture was stirred for 3 h. The solution
was filtered through Celite, and the dark yellow filtrate was
concentrated to ca. 1 mL under reduced pressure. Excess
pentane (25 mL) was added, and the flask was placed in an
ice bath for 30 min. The solvent was then decanted, and the
microcrystalline solid that remained was dried under reduced
pressure. Yield: 68%. Anal. Calcd for C55H64BClF24OOsP2:
C, 43.83; H, 4.10. Found: C, 43.42; H, 4.10. 1H NMR (300
MHz, CD2Cl2, 20 °C): 1.28 (dvt, N ) 15.0 Hz, 18H, PCHCH3),
3
1.30 (dvt, N ) 14.7 Hz, 18H, PCHCH3), 2.18 (q, J (HH) ) 5.7
Hz, 2H, OsdCHCH2CH3), 2.98 (m, 6H, PCHCH3), 7.72, 7.56
(BAr′4), 16.87 (t, 3J (HH) ) 5.7 Hz, 1H, OsdCHCH2CH3).
13C{1H} NMR (75.4 MHz, CD2Cl2, 20 °C): 12.45 (s, Osd
CHCH2CH3), 19.01 (s, PCHCH3), 19.90 (s, PCHCH3), 25.80 (vt,
N ) 13.4 Hz, PCHCH3), 56.22 (s, OsdCHCH2CH3), 178.30 (t,
2J (PC) ) 7.0 Hz, Os-CO), 284.85 (br, OsdCHCH2CH3).
31P{1H} NMR (121.4 MHz, CD2Cl2, 20 °C): 53.92 (s, PiPr3).
Syn th esis of [OsCl(CO)3(P iP r 3)2][BAr ′4], 7. Complex 5a
(0.020 g, 0.013 mmol) in CH2Cl2 (2 mL) was frozen in liquid
nitrogen. The flask was evacuated on a gas line manifold, and
excess CO (1 atm) was then added. The mixture was warmed
to room temperature and allowed to stir for 3 h. The volatiles
were then removed under reduced pressure to yield a pale
white solid. Yield: 82%. IR (CD2Cl2, cm-1): 2131 (w), 2056
(s), 2017 (s). 1H NMR (300 MHz, CD2Cl2, 20 °C): 1.43 (dvt, N
) 14.7 Hz, 18 H, PCHCH3), 2.84 (m, 6H, PCHCH3), 7.56, 7.72
(BAr′4). 13C{1H} NMR (75.3 MHz, CD2Cl2, 20 °C): 19.81 (s,
PCHCH3), 26.53 (vt, N ) 13.7 Hz, PCHCH3), 169.20 (tt, 2J (PC)
Syn th esis of [OsCl(η2-HCCtBu )(dCHCH2P h )(P iP r 3)2]-
[BAr ′4], 8b. In an NMR tube fitted with a Teflon tap, 5a
(0.010 g, 0.0066 mmol) in CD2Cl2 (0.5 mL) was treated with 1
equiv (0.0066 mmol) of HCCtBu (1 µL). After mixing (tum-
bling) for 3 h, the solution became pale yellow, almost colorless,
and all of the carbyne reagent had been consumed, as
determined by NMR (1H and 31P{1H}) spectroscopy. 1H NMR
(300 MHz, CD2Cl2, 20 °C): 1.26 (dvt, N ) 14.7 Hz, 18H,
PCHCH3), 1.28 (dvt, N ) 14.7 Hz, 18 H, PCHCH3), 1.36 (s,
9H, C(CH3)3), 1.56 (br, 2H, OsdCHCH2Ph), 3.17 (m, 6H,
PCHCH3), 3.26 (br, 1H, HCCtBu), 7.11-7.37 (m, 5H, Ph), 7.56,
7.72 (BAr′4), 15.02 (br, 1H, OsdCHCH2Ph). 31P{1H} (121.4
MHz, CD2Cl2, 20 °C): 41.90 (s, PiPr3).
Syn th esis of [OsCl(CCH2tBu )((E)-CHdCHP h )(P iP r 3)2]-
[BAr ′4], 9a . An NMR tube was charged with 5a (0.010 g,
0.0066 mmol) and CD2Cl2 (0.5 mL). One equivalent of HCCtBu
(0.0066 mmol, 1 µL) was added, and the solution was allowed
to mix (tumbling) for 16 h, at which point it became dark red-
purple. NMR spectroscopy revealed complete conversion to
9a . 1H NMR (300 MHz, CD2Cl2, 20 °C): 1.20 (s, 9H, C(CH3)3),
1.30 (dvt, N ) 15.0 Hz, 18H, PCHCH3), 1.42 (dvt, N ) 15.3
Hz, 18H, PCHCH3), 2.35 (s, 2H, OsCCH2tBu), 5.90 (d, 3J (HH)
) 12.9 Hz, 1H, OsCHdCHPh), 7.08-7.38 (m, 5H, Ph), 7.47
2
2
) 5.9 Hz, J (CC) ) 4.1 Hz, Os-CO), 176.98 (dt, J (PC) ) 8.3
Hz, 2J (CC) ) 3.6 Hz, Os-CO). 31P{1H} NMR (121.4 MHz,
CD2Cl2, 20 °C): 17.4 (s, PiPr3).
Syn th esis of [OsCl(13CO)3(P iP r 3)2][BAr ′4], 7′. In an NMR
tube fitted with a Teflon tap, complex 5a (0.0050 g, 0.0035
mmol) was dissolved in CD2Cl2 (0.5 mL). The solution was
frozen in liquid nitrogen, and the tube was evacuated. Excess
13CO (1 atm) was admitted into the tube, and after thawing,
the solution was allowed to mix (tumbling) for 30 min to yield
a colorless solution. Most of the excess 13CO was removed by
briefly exposing the solution to a vacuum and then replacing
3
(d, J (HH) ) 12.9 Hz, 1H, OsCHdCHPh), 7.56, 7.72 (BAr′4).
13C{1H} NMR (75.3 MHz, CD2Cl2, 20 °C): 19.98 (s, PCHCH3),
20.29 (s, OsCCH2C(CH3)3), 20.53 (s, PCHCH3), 26.48 (vt, N )
13.0 Hz, PCHCH3), 31.23 (s, OsCCH2CMe3), 33.68 (s, OsCCH2-
tBu), 125.68, 127.54, 129.29 (all s, OsCHdCHPh), 136.04 (t,
2J (PC) ) 7.6 Hz, OsCHdCHPh), 140.91 (s, OsCHdCHPh),
285.10 (t, 2J (PC) ) 6.2 Hz, OsCCH2tBu). 31P{1H} NMR (121.4
MHz, CD2Cl2, 20 °C): 39.54 (s, PiPr3).
1
with argon. The reaction was shown to be quantitative by H
1
and 31P{1H} NMR spectroscopy. The H NMR data were the
same as those cited for 7, above; 13C{1H} and 31P{1H} NMR
data follow.13C{1H} NMR (75.3 MHz, CD2Cl2, 20 °C): 19.81
(s, PCH(CH3)2), 26.53 (vt, N ) 13.7 Hz, PCCH3), 169.20 (tt,
2J (PC) ) 5.5 Hz, 2J (CC) ) 4.1 Hz, Os-CO), 176.98 (dt, 2J (PC)
) 8.3 Hz, 2J (CC) ) 3.6 Hz, Os-CO). 31P{1H} NMR (121.4
Syn th esis of [OsCl(CCH2CH3)((E)-CHdCHP h )(P iP r 3)2]-
[BAr ′4], 9b. Complex 5a (0.100 g, 0.0664 mmol) in CH2Cl2 (3
mL) was frozen in liquid nitrogen, and the headspace was
removed under reduced pressure. Excess propyne (1 atm) was
admitted into the flask, and the mixture was allowed to warm
to room temperature. After stirring for 20 min, the solution
became deep, dark red. The volatiles were removed under
reduced pressure, yielding a dark red solid. Yield: 78%. Anal.
Calcd for C61H66BClF24OsP2: C, 47.15; H, 4.29. Found: C,
46.55; H, 4.32. 1H NMR (300 MHz, CD2Cl2, 20 °C): 1.36 (dvt,
N ) 13.5 Hz, 18 H, PCHCH3), 1.39 (dvt, N ) 14.7 Hz, 18 H,
PCHCH3), 1.52 (t, 3J (HH) ) 7.8 Hz, 3H, OsCCH2CH3), 2.45
(q, 3J (HH) ) 7.8 Hz, 2H, OsCCH2CH3), 3.02 (m, 6H, PCHCH3),
2
2
MHz, CD2Cl2, 20 °C): 17.45 (dt, J (PC1) ) 5.5 Hz, J (PC2) )
8.3 Hz, PiPr3).
F or m a tion of 6a a n d 7 fr om 5a a n d CO. A CD2Cl2 (0.5
mL) solution of 5a (0.0050 g, 0.0033 mmol) in an NMR tube
fitted with a Teflon tap was frozen in liquid nitrogen. The
tube was evacuated, and ca. 1 equiv (0.0033 mmol) of CO was
added. The mixture was allowed to warm to room temperature
and mix (tumbling) for 30 min, after which a pale yellow
solution was obtained. NMR spectroscopy (1H and 31P{1H})
revealed the presence of both 7 and 6a in an approximately
6:1 ratio. The sample was frozen in liquid nitrogen once again
and evacuated. Excess (1 atm) of CO was added, and after
warming to room temperature and allowing to mix (tumbling)
for 30 min, a colorless solution was obtained, which was shown
3
5.97 (d, J (HH) ) 12.6 Hz, 1H, OsCHdCHPh), 7.08-7.37 (m,
3
5H, Ph), 7.50 (d, J (HH) ) 12.6 Hz, 1H, OsCHdCHPh), 7.56,
7.72 (BAr′4). 13C{1H} NMR (75.3 MHz, CD2Cl2, 20 °C): 8.67
(s, OsCCH2CH3), 19.67 (s, PCHCH3), 20.37 (s, PCHCH3), 25.88
(vt, N ) 13.0 Hz, PCHCH3), 46.98 (s, OsCCH2CH3), 126.00,
1
2
to contain pure 7 by H and 31P{1H} NMR spectroscopy.
127.79, 129.65 (all s, Ph), 137.79 (t, J (PC) ) 7.6 Hz, OsCHd

Nucleophilic Attack on Os Hydrido-Carbynes
Organometallics, Vol. 17, No. 24, 1998 5263
2
CHPh), 142.06 (s, OsCHdCHPh), 287.04 (t, J (PC) ) 6.1 Hz,
Sch em e 1
OsCCH2CH3). 31P{1H} (121.4 MHz, CD2Cl2, 20 °C): 44.26 (s,
PiPr3).
Rea ction of [OsH2Cl2(P iP r 3)2] w ith CD2dCD(C6D5). The
procedure followed was the same as that described4 for the
synthesis of 1a except the reaction was performed in C6D6,
rather than C6H6. Although the reaction was clean (as
determined by 31P{1H} NMR spectroscopy), the 1H NMR
spectrum of the product showed (broadened) hydride, benzyl
i
methylene, and Pr methyl signals, which presumably came
i
about as a result of H,D exchange with the Pr hydrogens
catalyzed by the metal.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of th e Ca r ben es
[OsCl2(CO)(dCHCH2R)(P iP r 3)2], 2. When solutions
of 1 are reacted with CO at room temperature, subtle
color changes from yellow to pale yellow are observed
and the carbenes 2 are produced (eq 1). Thus, when a
CD2Cl2 solution of 1a is exposed to approximately 1
equiv of CO, a color change from yellow to lighter yellow
is observed after several hours and the known6 carbene
complex 2a is formed, along with one other additional
product (3, see below). In contrast to that observed for
2a , a solution of complex 1b reacts with excess CO over
several hours to yield only the carbene complex 2b as a
pale yellow solid. Note that in each case hydride
migration leads to a formal reduction of the osmium
carbyne bond (and, therefore, the osmium formal oxida-
tion state) and that the CO is cis to the resulting carbene
ligand (eq 1), consistent with that observed in a recent
X-ray structure determination of 2a .6 A similar CO-
induced hydride migration was also observed in the
IrCo3 hydrido-carbyne cluster complex [Cp*Ir(CpCo)2-
(µ2-H)(µ3-CH)(µ3-CO)], which yielded the carbene com-
plex [Cp*Ir(CpCo)2(µ2-CH2)(µ2-CO)2] upon treatment
with CO.8
The carbene and CO ligands and the trans arrange-
ment of the phosphine ligands in 2 are easily identified
in their NMR spectra. For example, the 1H NMR
spectra contain low-field triplets around δ(1H) ) 18.7
ppm [3J (HH) ) 6.6 Hz] and two sets of doublets of
virtual triplets, consistent with mutually trans phos-
phines and cis chloride ligands. The CO ligands appear
as triplets around δ(13C) ) 180 ppm in the 13C{1H} NMR
spectra due to coupling to two magnetically equivalent
phosphines [2J (PC) ca. 8 Hz], while those signals at-
tributed to the carbene carbons are observed centered
at about δ(13C) ) 300 ppm. The substituents on the
carbene carbon lie at or near the OsCl2 plane, as
revealed by the 31P{1H} NMR spectra of 2, which show
singlets around δ(31P) ) 12.0 ppm.
which is easily identified by comparison of its spectro-
scopic data with those previously reported.7 Within an
additional 6 h of mixing, 2a ′ is completely converted to
3′, and a third product assigned as [OsCl2(13CO)2L2],
4′, begins to appear, along with small amounts of
styrene. Spectroscopically, the phosphines in 4′ appear
as a triplet [2J (PC) ) 8.3 Hz] centered at δ(31P) ) 8.0
ppm in the 31P{1H} NMR spectrum, and their trans
1
disposition is clear from the H NMR spectrum, which
i
shows a doublet of virtual triplets for the Pr methyl
groups. Furthermore, the 13CO ligands in 4′ are ob-
served as a triplet at δ(13C) ) 176.95 ppm [2J (PC) )
8.3 Hz], and their cis arrangement is clear from the IR
spectrum of unlabeled [OsCl2(CO)2L2], 4, in CD2Cl2,
which shows two strong absorptions with frequencies
[ν(CO) ) 2019, 1946 cm-1] consistent with those ob-
served for other related complexes.9 As the reaction
progresses, the concentrations of 4′ and styrene in-
crease, while that of 3′ decreases; the complete trans-
formation of 3′ into 4′ and styrene is slow, and only
about 50% conversion is observed after 48 h.
The transformations leading to the reductive cleavage
of the carbyne ligand from 1a are interesting and
warrant further comment. After the addition of one CO
ligand to 1a to produce 2a , the production of 3 formally
requires further addition of one CO ligand to 2a and
the elimination of 1 equiv of HCl. The subsequent
elimination of styrene to produce 4 is readily explained
(at least formally) by selective electrophilic attack of H+
(produced in situ) on the vinyl ligand of 3, followed by
coordination of Cl- to the osmium center. In fact, 3 is
observed to be stable in solution in the absence of excess
CO and HCl for at least 48 h. This selectivity toward
protonation at CR of the vinyl ligand is unusual since a
number of recent reports6,10 have established that Câ is
generally the preferred site of electrophilic attack in
osmium vinyl complexes, to yield the corresponding
carbene. Furthermore, selective electrophilic attack at
CR of a vinyl ligand (to eliminate olefin) has only been
Alternately, if in the synthesis of 2a , complex 1a is
treated with more than one equivalent of CO, and the
progress of the reaction is monitored (via NMR spec-
troscopy) over time, a number of subsequent reactions
are observed beyond the formation of 2a (Scheme 1), in
particular the reductive cleavage of the carbyne ligand
from 1a . Thus, treatment of 1a with a slight excess of
13CO in CD2Cl2 yields after 2 h an approximately 1:1
mixture of 13CO-labeled 2a , 2a ′, and a second product,
the σ-vinyl complex [OsCl(13CO)2((E)-CHdCHPh)(L2], 3′,
(9) (a) Chatt, J .; Melville, D. P.; Richards, R. L. J . Chem. Soc. (A)
1971, 1169. (b) Levison, J . J .; Robinson, S. D. J . Chem. Soc. (A) 1970,
639. (c) Collman, J . P. J . Am. Chem. Soc. 1966, 88, 3504. (d) Hieber,
W.; Frey, V.; J ohn, P. Chem. Ber. 1967, 100, 1961.
(10) (a) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics
1995, 14, 3596. (b) Albeniz, M. J .; Esteruelas, M. A.; Lledos, A.;
Maseras, F.; Onate, E.; Oro, L. A.; Sola, E.; Zeier, B. J . Chem. Soc.,
Dalton Trans. 1997, 181.
(8) Forsterling, F. H.; Barnes, C. E. Organometallics 1994, 13, 3770.

5264 Organometallics, Vol. 17, No. 24, 1998
Spivak and Caulton
reported in a few cases.10b,11 Apparently, then, the
selectivity toward protonation is quite sensitive to the
ligands, and hence the electronic environment, about
the osmium. The slow production of 4 from 3 is
presumably a function of the low concentration of HCl
generated in the reaction. Indeed, treating a CD2Cl2
solution of 3 with excess (10 equiv) gaseous HCl cleanly
yields 4 within minutes, together with approximately
1 equiv of styrene, as determined by NMR spectroscopy.
The mechanism of eq 1 is of interest due to the 18-
electron character of the osmium reagent. We wished
to consider that eq 1 begins with chloride loss and
therefore sought to effect such removal with electro-
philes, in the absence of added CO.
position trans to an empty coordination site. They are,
however, similar to those observed for the hydrido-
vinylidene complexes [OsHCl(dCdCHR)L2], in which
the H, Cl, and vinylidene ligands adopt a “Y” stereo-
chemistry about the metal.14 It is therefore anticipated
that the stereochemistry about the osmium in 5 is also
similar.
Under similar conditions, the golden yellow, coordi-
natively unsaturated carbene complexes [OsCl(CO)(d
CHCH2R)L2][BAr′4], 6 (R ) Ph, 6a ; R ) CH3, 6b), are
Ha lid e Abstr a ction fr om th e Ca r byn es [OsHCl2-
(CCH2R)(P iP r 3)2], 1, a n d th e Ca r ben es [OsCl2(CO)-
(dCHCH2R)(P iP r 3)2], 2. Under the proper conditions,
a chloride ligand may be abstracted from either complex
1 or 2. Thus, treatment of the hydrido-carbyne com-
plex 1 with a stoichiometric amount of NaBAr′4 (Ar′4 )
3,5-C6H3(CF3)2) in CH2Cl2 yields, after several hours,
the dark yellow, coordinatively unsaturated hydrido-
carbyne complexes [OsHCl(CCH2R)L2][BAr′4], 5 (R )
Ph, 5a ; R ) CH3, 5b). The length of time required to
isolated from heterogeneous mixtures of the carbene
complexes 2 and NaBAr′4 (1:1) in CH2Cl2 after several
hours. In view of the apparent stability of the cationic,
coordinatively unsaturated carbyne complexes 5, it is
interesting that even though a vacant coordination site
is generated on the metal in the synthesis of 6, the
carbene hydrogen does not migrate back to osmium to
regenerate a coordinatively saturated (cationic) carbyne
complex. One would expect the driving forces of the
reaction to be the generation of coordinative saturation
about the metal center and the (formal) oxidation of
osmium from +4 to +6. We recently determined that
the energy of the optimized structure of the transition
state for 1,2-hydride migration in [OsHCl2(CCH3)(PH3)2]
to yield [OsCl2(dCHCH3)(PH3)2] was quite high (ca. 27
kcal/mol),4 rendering the unimolecular rearrangement
energetically not feasible. It is possible that a high
transition-state energy also exists between 5 and the
corresponding cationic carbynes [OsHCl(CO)(CCH2R)-
L2]+. We find that, in reactions of 5a with CO, the first
observed product is the carbene 6a (see below); clearly,
then, adding CO to the metal greatly facilitates (i.e., the
thermodynamics and kinetics of) migration of the hy-
dride to CR in the production of both 2 and 6a .
attain completion in these reactions is presumably a
function of the low solubility of NaBAr′4 in CH2Cl2. In
a previous study,12 it was proposed that the cation of
5a was formed in equilibrium by the dissociation of a
water molecule from [OsHCl(H2O)(CCH2R)L2]+, al-
though it was not described in full detail. Complex 5
is soluble in CH2Cl2 and toluene and shows no dramatic
differences in the spectroscopic (NMR) signals when
compared in each solvent. The most diagnostic features
of the 13C{1H} NMR spectra of 5 are the signals
attributed to the carbyne carbons, which appear as
triplets centered at about δ(13C) ) 285 ppm [2J (PC) )
6.5 Hz] and are shifted slightly downfield relative to the
parent carbynes 1.4 The trans disposition of the phos-
Removing the chloride ligand from 2 produces a slight
upfield shift in certain 1H and 13C{1H} NMR signals
observed for 6. Thus, the triplet carbene hydrogen
signal now appears at about δ(1H) ) 17.0 ppm [3J (HH)
ca. 6 Hz] in the 1H NMR spectra, while the 13C{1H}
NMR spectra show carbene and CO signals centered at
about δ(13C) ) 280 ppm [2J (PC) ca. 7 Hz] and δ(13C) )
178 ppm [2J (PC) ) 7 Hz], respectively. Doublets of
1
phines in 5 is evident from the H NMR spectra, which
show doublets of virtual triplets (i.e., diastereotopic
inequivalence) for the iPr methyl signals. The chemical
shifts [δ(1H) ca. -9.8 ppm] of the triplets [2J (PH) ) 14
Hz] attributed to the hydride ligands in 5 are shifted
only slightly upfield relative to the octahedral complexes
1 [δ(1H) ca. -7.0 ppm] and are dramatically different
from those reported13 for the square pyramidal com-
plexes [OsHCl(CO)L2] (L ) tertiary phosphine), in which
the hydride [δ(1H) ca. -32 ppm] occupies the apical
i
virtual triplets observed for the Pr methyl signals in
the 1H NMR spectra are consistent with transoid
phosphines about the osmium. In the 31P{1H} NMR
spectra, singlets are observed around δ(31P) ) 54 ppm,
implying that the carbene substituents preferentially
occupy the plane that bisects the plane containing the
osmium and phosphorus atoms. It is, of course, impos-
sible to know from the NMR data the angles between
the π-acceptor (i.e., CO and CCH2R) and π-donor (i.e.,
Cl) ligands about the metal in 6. In view of our interest
in establishing the stereochemistry of 6, we sought an
(11) Bohanna, C.; Esteruelas, M. A.; Lahoz, F. J .; Onate, E.; Oro,
L. A. Organometallics 1995, 14, 4685.
(12) Bourgault, M.; Castillo, A.; Esteruelas, M. A.; Onate, E.; Ruiz,
N. Organometallics 1997, 16, 636.
(13) (a) Esteruelas, M. A.; Werner, H. J . Organomet. Chem. 1986,
303, 221. (b) Werner, H.; Esteruelas, M. A.; Meyer, U.; Wrackmeyer,
B. Chem. Ber. 1987, 120, 11. (c) Moers, F. G.; Langhout, J . P. Recl.
Trav. Chim. Pays-Bas. 1972, 91, 591 (d) Moers, F. G.; Ten Hoedt, R.
W. M. J . Inorg. Nucl. Chem. 1974, 36, 279.
(14) Oliva´n, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organo-
metallics 1998, 17, 3091.

Nucleophilic Attack on Os Hydrido-Carbynes
Organometallics, Vol. 17, No. 24, 1998 5265
Sch em e 2
Sch em e 3
these reactions, and no intermediates containing vinyl
ligands (e.g., 10, see Scheme 2) could be detected during
reactions at 20 °C, although the ruthenium analogue
of 10, [Ru(CO)3((E)-CHdCHPh)(PiPr3)2]+, has been re-
ported recently.11 Moreover, our attempts to scavenge
any eliminated HCl during the reaction using triethyl-
amine, 2,6-lutidine, DBU, lithium 2,2,6,6-tetramethyl-
piperide, and even PiPr3 were thwarted by the rapid
(seconds) formation of the vinylidene complex [OsHCl-
(dCdCHPh)L2]12 from 5a ; in contrast, poly(4-vinyl-
pyridine) had no effect on the outcome of the reaction
with CO. Evidently the methylene hydrogens of the
benzyl group of 5a are acidic and easily deprotonated
by even weak bases. Indeed, this is certainly not
surprising in view of the fact that 5a is cationic. Thus,
as in Scheme 1, loss, then readdition, of HCl is a central
theme.
X-ray structure determination of 6b. However, despite
numerous attempts at growing X-ray quality single
crystals, we were unsuccessful.
Rea ctivity of [OsHCl(CCH2P h )(P iP r 3)2][BAr ′4],
5a , tow a r d Nu cleop h iles L′. A facile migration of
hydride to CR was also observed in reactions of CH2Cl2
solutions of 5a with various nucleophiles L′ (L′ ) CO,
HCCR′) to yield (initially) the corresponding carbene
adduct [OsCl(L′)(dCHCH2Ph)L2]+. However, the course
of the reaction beyond the formation of the carbene
depends on the nature of L′.
(a ) L′ ) CO. Treatment of a solution of 5a with
approximately 1 equiv of 13CO produces a color change
from dark yellow to pale yellow after 30 min and yields
the corresponding 13CO-labeled analogue of the carbene
complex 6a and a second product, the carbonyl complex
[OsCl(13CO)3L2]+, 7′, in approximately a 1:6 ratio, along
with small amounts of styrene. If this same solution is
further treated with excess 13CO (i.e., greater than 1
equiv), or if a solution of 5a is treated with excess (1
atm) CO, within 30 min the solution becomes nearly
colorless and only the tricarbonyl complex is observed,
along with 1 equiv of styrene (Scheme 2). Complexes
(b) L′ ) HCCR′. When these reactions were ex-
tended to terminal acetylenes, a somewhat different
reactivity pattern emerged. Thus, in reactions of 5a
with various terminal acetylenes HCCR′ (R′ ) SiMe3,
tBu, Me), in each case, initial η2-coordination of the
acetylene was accompanied by a 1,2-migration of the
hydride to CR to give the corresponding alkyne-carbene
adduct [OsCl(η2-HCCR′)(dCHCH2Ph)L2]+, 8 (Scheme 3).
For example, treatment of 5a with 1 equiv of HCCSiMe3
in CD2Cl2 at room temperature gave, after 24 h, a pale
gray solution of the alkyne-carbene complex [OsCl(η2-
of the type [OsX(CO)3(PR3)2]+ (X ) halide; PR3
)
tertiary phosphine) have been prepared previously by
other methods.9c,d Complex 7′ shows a doublet of
triplets centered at δ(31P) ) 17.4 ppm [2J (PC1) ) 5.5
2
Hz and J (PC2) ) 8.3 Hz, where C1 corresponds to the
1
HCCSiMe3)(dCHCH2Ph)L2]+, 8a . The H NMR spec-
CO ligand trans to chloride and C2 corresponds to those
CO ligands trans to one another] in its 31P{1H} NMR
spectrum and two multiplets in its 13C{1H} NMR
spectrum for the two sets of CO ligands, a triplet of
triplets at δ(13C) ) 169.2 ppm [2J (PC1) ) 5.5 Hz, 2J (CC)
) 3.6 Hz] for the CO ligand trans to chloride, and a
doublet of triplets at δ(13C) ) 177.0 ppm [2J (PC2) ) 8.3
trum of 8a revealed diastereotopic inequivalent iPr
methyls (and trans phosphines) and showed the pres-
ence of a carbene hydrogen as a broad signal with no
resolved coupling at δ(1H) ) 15.9 ppm. This carbene
was also evident in the 13C{1H} NMR spectrum as a
triplet at δ(13C) ) 285.1 ppm [2J (PC) ) 8.4 Hz],
corresponding to the carbene carbon; the acetylenic
carbons were observed as weak, slightly broadened
signals at δ(13C) ) 91.8 (HCCSiMe3) and δ(13C) ) 68.3
(HCCSiMe3) ppm, in the region expected for η2-HCCR
ligands acting as two-electron-donor ligands.15 Attempts
to promote any further reaction by heating a solution
2
Hz, J (CC) ) 3.6 Hz] for the two trans CO ligands (see
Scheme 2). Further support for the identity of 7′ is
found in the IR spectrum of unlabeled [OsCl(CO)3-
(L2][BAr′4], 7, in CD2Cl2, which reveals three absorp-
tions [ν(CO) ) 2131, 2056, 2017 cm-1] with frequencies
similar to those observed for analogous complexes.9c,d
Unfortunately, complex 7 is formed quite rapidly in
(15) Templeton, J . L. Adv. Organomet. Chem. 1989, 29, 1.

5266 Organometallics, Vol. 17, No. 24, 1998
Spivak and Caulton
of 8a at 70 °C for several hours only produced 5a ,
HCCSiMe3, and a small amount of unidentified decom-
position products.
of 8b and 8c to carbon of the η2-alkyne. Since HCl
elimination is a fundamental step in Schemes 1 and 2,
we proceeded with a similar hypothesis. After 5a adds
HCCR′ to yield 8, we believe the acetylene ligand
isomerizes to a vinylidene ligand, accompanied by rapid
loss of HCl to give the σ-vinyl-vinylidene intermediate
complex [OsCl(dCdCHR′)((E)-CHdCHPh)L2]+, 11. The
intermediate 11 then undergoes selective protonation
at Câ of the vinylidene ligand and adds Cl- to give the
σ-vinyl-carbyne complex 9. It is interesting and im-
portant that this mechanism suggests Câ of the vinyl-
idene ligand is the preferred site of electrophilic attack
over attack at CR of the vinyl ligand, which is the
pattern in Schemes 1 and 2. However, protonating
vinylidene ligands to give carbynes is well docu-
mented.16 We attempted to establish the fate of the
various hydrogens in 8b and 8c by preparing [OsDCl-
(CCD2Ph)L2]+, but were frustrated by hydrogen-
When terminal acetylenes with other R′ groups were
employed, complex 8 formed more rapidly; however,
further reactions were observed (Scheme 3). Thus,
reaction of 5a with 1 equiv of HCCtBu yields a pale
yellow, almost colorless solution of [OsCl(η2-HCCtBu)-
(dCHCH2Ph)L2]+, 8b, within 3 h. The NMR (1H and
31P{1H}) spectroscopic data for 8b showed it to be
structurally similar to 8a : (i) a clear indication of trans-
disposed phosphines, and (ii) a (broad) carbene hydrogen
signal at δ(1H) ) 15.0 ppm. However, allowing the
reaction to continue for a further 16 h results in the
formation of the reddish-purple σ-vinyl-carbyne com-
plex [OsCl(CCH2tBu)((E)-CHdCHPh)L2]+, 9a . Thus, in
this reaction, the original carbyne skeleton has now
become a vinyl group! Similarly, when the less bulky
acetylene HCCCH3 is used, the reaction proceeds much
more rapidly. In fact, when solutions of 5a are exposed
to an excess of HCCCH3, a rapid (less than 1 min) color
change from yellow to pale gray is observed, and after
20 min, the deep, dark red complex [OsCl(CCH2CH3)-
((E)-CHdCHPh)L2]+, 9b, is formed. Once again, the
carbyne is not passive, but has become a vinyl ligand
(and not merely a carbene). It is believed that the pale
gray intermediate that precedes the formation of 9b is
the (expected) propyne-carbene adduct, [OsCl(η2-
HCCCH3)(dCHCH2Ph)L2]+, 8c (doublets of virtual trip-
lets are observed for the iPr methyl groups, and a broad
carbene hydrogen signal is observed at δ(1H) ) 15.6
i
deuterium exchange with the Pr groups of the phos-
phine ligands during the attempted synthesis of OsDCl2-
(CCD2Ph)L2.17
Con clu d in g Rem a r k s
We have demonstrated in this report an alternate
approach to generating osmium alkylidene complexes
via nucleophilic attack on osmium hydrido-carbyne
precursor complexes, in particular, [OsHCl2(CCH2R)-
L2] and [OsHCl(CCH2R)L2]+. For the former class of
complexes, in particular for R ) Ph, further reactions
were observed beyond the formation of the alkylidene
complex in the presence of an excess of the nucleophile
(i.e., CO), which lead to complete cleavage of the carbyne
ligand from the metal. In reactions of the coordinatively
unsaturated complex [OsHCl(CCH2R)L2]+ (R ) Ph) with
L′, alkylidene formation was also observed initially;
however the ultimate fate of the reaction was deter-
mined by the nature of L′. Thus, for L′ ) CO, cleavage
of the carbyne ligand from the metal was observed,
while for L′ ) HCCR′, the alkylidene complexes [OsCl-
(η2-HCCR′)(dCHCH2Ph)L2]+ isomerized to the corre-
sponding σ-vinyl-carbyne complexes [OsCl(CCH2R′)-
((E)-CHdCHPh)L2]+.
1
ppm, in the H NMR spectrum, while a sharp singlet
at δ(31P) ) 43.3 ppm appears in the 31P{1H} NMR
spectrum); however, its rapid reaction to yield 9b
precluded its full characterization. The vinyl ligands
1
are easily identified in the H NMR spectra of 9a and
9b, which show doublets around δ(1H) ) 5.9 ppm and
δ(1H) ) 7.5 ppm, corresponding to HR and Hâ, respec-
tively, with 3J (HH) ) 12.5 Hz, indicative of a trans
coupling. In both cases, the carbyne carbon is observed
around δ(13C) ) 286 ppm as a triplet [2J (PC) ca. 6.1 Hz].
It is important to note not only the differences in the
rates of formation of complex 8 (R′ ) Me > tBu > SiMe3)
but also that for R′ ) SiMe3 complex 8a does not react
further to yield [OsCl(CCH2SiMe3)((E)-CHdCHPh)L2]+.
Considering the relative bulkiness of the R′ groups
examined and the bulkiness of the PiPr3 ligands on the
osmium, it’s reasonable to assume that steric demands
play a role in determining both the differences in
reaction rate and outcome. Note the thermodynamic
implication of this result: the η2-alkyne-carbene isomer
is less stable than the vinyl-carbyne form.
Ack n ow led gm en t. We thank the U.S. National
Science Foundation for financial support.
OM980597F
(16) For examples of metal-carbyne complexes prepared by pro-
tonation of metal-vinylidene precursors, see: (a) Carvalho, M. F. N.
N.; Almeida, S. S. P. R.; Pombeiro, A. J . L.; Henderson, R. A.
Organometallics 1997, 16, 5441. (b) Nickias, P. N.; Selegue, J . P.;
Young, B. A. Organometallics 1988, 7, 2248. (c) Hohn, A.; Werner, H.
Angew. Chem., Int. Ed. Engl. 1986, 25, 737. (d) Beevor, R. G.; Green,
M.; Orpen, A. G.; Williams, I. D. J . Chem. Soc., Dalton Trans. 1987,
1319.
The isomerizations observed in these reactions involve
one hydrogen moving from (either carbon of) the carbene
(17) Moers, F. G.; Muskens, P. J . W. M. Transition Met. Chem. 1982,
7, 261.