C-H bond activation and C-C bond formation in the reactions of the methyl complex [Ir2(CH3)(CO)2(Ph2PCH 2PPh2)2][CF3SO3] with alkynes

Article abstract of DOI:10.1021/om990291o

The methyl complex [Ir₂(CH₃)(CO)(μ-CO)(dppm)₂][CF ₃SO₃] (1) reacts readily with a variety of alkyne molecules. With alkynes containing electron-withdrawing substituents (RC≡CR′; R = R′ = CO₂

Full text of DOI:10.1021/om990291o

4134
Organometallics 1999, 18, 4134-4146
C-H Bon d Activa tion a n d C-C Bon d F or m a tion in th e
Rea ction s of th e Meth yl Com p lex
[Ir 2(CH3)(CO)2(P h 2P CH2P P h 2)2][CF 3SO3] w ith Alk yn es
J eff R. Torkelson, Robert McDonald,† and Martin Cowie*
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
Received April 22, 1999
The methyl complex [Ir2(CH3)(CO)(µ-CO)(dppm)2][CF3SO3] (1) reacts readily with a variety
of alkyne molecules. With alkynes containing electron-withdrawing substituents (RCtCR′;
R ) R′ ) CO2Me, CF3; R ) CO2Me, R′ ) H), the alkyne-bridged products, [Ir2(CH3)(CO)2-
(µ-alkyne)(dppm)2][CF3SO3], result. With other 1-alkynes (HCtCR, R ) Me, Ph) reaction
at -80 °C results in oxidative addition to give acetylide hydrides [Ir2H(CH3)(CO)2(µ-C2R)-
(dppm)2][CF3SO3], which upon warming undergo transfer of the hydride ligand to the
â-carbon of the acetylide to give the vinylidene-bridged products. At ambient temperature
methane elimination occurs, yielding the acetylide-bridged “A-frames”, [Ir2(CO)2(µ-C2R)-
(dppm)2][CF3SO3]. Reaction of 1 with 1 equiv of acetylene proceeds through analogous
acetylide and vinylidene intermediates; however under carbon monoxide exchange of a
vinylidene hydrogen and the methyl ligand occurs to give a methylvinylidene-bridged hydride
[Ir2(H)(CO)3(µ-CCHMe)(dppm)2][CF3SO3]. Reaction of 1 with an excess of acetylene results
in the incorporation of two acetylene molecules, giving [Ir2(CH3)(C2H)(CO)2(µ-H)(µ-
CCH2)(dppm)2][CF3SO3], containing terminal methyl and acetylide ligands and bridging
hydride and vinylidene groups. Reaction of 1 with a number of internal, nonactivated alkynes
results first in the formation of the alkyne-bridged products, which slowly rearrange to the
unusual species [Ir2H(CO)2(µ-CHCRC(H)R)(dppm)2][CF3SO3], in which cleavage of two C-H
bonds of the methyl group has occurred accompanied by condensation of the resulting
methyne group at one end of alkyne linkage and transfer of a hydrogen to the other end.
The resulting hydrocarbyl moiety can be viewed as a vinylcarbene. The X-ray structures of
three representative products are reported, including one of these vinylcarbenes (R ) C2H5).
In tr od u ction
Although this latter reaction does not lead directly to
C-C bond formation, subsequent coupling of the result-
ing vinyl and methylene groups would yield an allyl
ligand, a transformation known to occur in binuclear
complexes4 and proposed to be of significance in Fis-
cher-Tropsch (FT) chemistry.5
In the absence of C-H bond cleavage of the methyl
group, other routes to C-C bond formation involving
the reaction of 1 and alkynes are also available. Al-
though less favorable than insertions involving metal
hydrides,6 insertions of alkynes into metal-alkyl bonds
have been observed.7 Particularly relevant to this study,
We have recently demonstrated that the methyl
complex [Ir2(CH3)(CO)(µ-CO)(dppm)2][CF3SO3] (1) (dppm
) Ph2PCH2PPh2) undergoes facile and, in some cases,
reversible C-H bond cleavage of the methyl group upon
addition of a number of substrates (L ) CO, SO2, PR3,
and CNR), yielding the methylene-bridged hydride
products [Ir2H(L)(CO)2(µ-CH2)(dppm)2][CF3SO3].1 As an
extension of this study we have sought to utilize this
conversion in the formation of C-C bonds through
reactions of 1 with unsaturated organic substrates such
as alkynes. If the above transformation of a methyl
ligand into methylene and hydride groups also occurs
upon coordination of alkynes, two subsequent pathways
become available for C-C bond formation. Migration of
the coordinated alkyne to the bridging methylene group
would yield a vinylcarbene, as has previously been
observed,2 and migratory insertion of the alkyne and
hydrido groups could occur to give a vinyl moiety, a
common transformation involving these fragments.3
(2) (a) Knox, S. A. R. J . Organomet. Chem. 1990, 400, 255. (b) Dyke,
A. F.; Knox, S. A. R.; Naish, P. J .; Taylor, G. E. J . Chem. Soc., Chem.
Commun. 1980, 803. (c) Adams, P. Q.; Davies, D. L.; Dyke, A. F.; Knox,
S. A. R.; Mead, K. A.; Woodward, P. J . Chem. Soc., Chem. Commun.
1983, 222.
(3) (a) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Chapter 2. (b)
Sutherland, B. R.; Cowie, M. Organometallics 1985, 4, 1801. (c)
Vaartstra, B. A.; Cowie, M. Organometallics 1990, 9, 1594. (d) Wang,
L.-S.; Cowie, M. Can. J . Chem. 1995, 73, 1058. (e) Sterenberg, B. T.;
McDonald, R.; Cowie, M. Organometallics 1997, 16, 2297.
* To whom correspondence should be addressed. Fax: (780)492-
8231. E-mail: martin.cowie@ualberta.ca.
(4) Martinez, J .; Gill, J . B.; Adams, H.; Bailey, N. A.; Saez, I. M.;
Sunley, G. J .; Maitlis, P. M. J . Organomet. Chem. 1990, 394, 583.
(5) (a) Turner, M. L.; Byers, P. K.; Lang, H. C.; Maitlis, P. M. J .
Am. Chem. Soc. 1993, 115, 4417. (b) Turner, M. L.; Lang, H. C.;
Stenton, A.; Byers, P. K.; Maitlis, P. M. Chem. Eur. J . 1995, 1, 549.
(6) Foo, T.; Bergman, R. G. Organometallics 1992, 11, 1811.
† Faculty Service Officer, Structure Determination Laboratory.
(1) Torkelson, J . R.; Antwi-Nsiah, F. H.; McDonald, R.; Cowie, M.;
Pruis, J . G.; J alkanen, K. J .; DeKock, R. L. J . Am. Chem. Soc. 1999,
121, 3666.
10.1021/om990291o CCC: $15.00 © 1999 American Chemical Society
Publication on Web 09/03/1999

C-H Bond Activation and C-C Bond Formation
Organometallics, Vol. 18, No. 20, 1999 4135
solution for 30 s, producing a color change to yellow followed
by stirring of the solution under a static atmosphere of the
gas for 5 min. The bright yellow solution was worked up in
the closely related species [Ir2H(CO)3(µ-CH2)(dppm)2]-
[CF3SO3] and [RhIr(CH3)(CO)3(dppm)2][CF3SO3] were
shown to yield the substituted-vinyl products [MIr-
(C(R)dC(Me)R)(CO)3(dppm)2][CF3SO3] (M ) Rh, Ir; R
) CO2Me), through migratory insertion involving di-
methyl acetylenedicarboxylate and the methyl ligand.7g
Furthermore, in reactions involving 1-alkynes, the
formation of acetylide8 and vinylidene9 groups must also
be considered, since C-C bond formation involving
migratory insertion of these fragments has also been
observed.10,11
the same manner as described for compound 2, yielding a
2
yellow powder in 78% yield. 13C{1H} NMR: δ 183.7 (t, J PC
)
2
2
6.3 Hz, CO), 177.7 (t, J PC ) 7.6 Hz, CO), 176.4 (t, J PC ) 24
Hz, CO). Anal. Calcd for Ir2SP4F3O10C61H53: C, 47.46; H, 3.47.
Found: C, 46.99; H, 3.22.
(c) [Ir 2(CH3)(CO)2(P Me3)(µ-DMAD)(dppm )2][CF3SO3] (4).
Compound 2 (50 mg, 0.033 mmol) was dissolved in 5 mL of
CH2Cl2, and trimethylphosphine (3.7 µL, 0.033 mmol) was
added, giving a bright yellow solution. The solution was stirred
for 1 h and then worked up as described for compound 2,
yielding a bright yellow powder in 91% yield. Anal. Calcd for
Ir2ClSP5F3O9C63.5H63: C, 46.67; H, 3.89. Found: C, 46.70; H,
3.63. The compound was crystallized as the hemisolvate 4.
In this article we report the results of the reactions
of 1 with a variety of alkyne molecules, leading in a
number of cases to C-C bond formation.
(d ) [Ir 2(CH3)(CO)2(µ-HF B)(d p p m )2][CF 3SO3] (5). Com-
pound 1 (34 mg, 0.025 mmol) was dissolved in 5 mL of
CH2Cl2, and HFB was passed through the solution for 30 s,
resulting in an immediate color change from red to orange.
The solution was stirred under a static atmosphere of the gas
for 10 min and then worked up as described for compound 2,
yielding a light orange powder in 95% yield. Anal. Calcd for
Ir2SP4F9O5C58H47: C, 45.37; H, 3.09. Found: C, 45.55; H, 3.06.
Exp er im en ta l Section
Gen er a l Com m en ts. Acetylene was obtained from Mathe-
son, 13C-labeled acetylene was purchased from Cambridge
Isotopes, and 13CO (99%) was supplied by Isotec Inc. Propyne
and hexafluoro-2-butyne (HFB) were purchased from Farchan
Laboratories Ltd.; all other alkynes and trimethylphosphine
were purchased from Aldrich. Two-dimensional NMR experi-
ments were performed on a Varian Unity 500 MHz spectrom-
eter. All 13C{1H} NMR spectra were obtained using 13CO-, 13C-
acetylene-, or 13CH3-enriched samples (the latter obtained from
13C-methyl triflate) unless otherwise stated. The compound
[Ir2(CH3)(CO)(µ-CO)(dppm)2][CF3SO3] (1) was prepared by the
published procedure.1 The 31P{1H} and 1H NMR and IR
spectroscopic data for all compounds are given in Table 1,
while selected 13C{1H} and 19F NMR data are given, where
appropriate, with the details on the preparation of the
compounds.
5
19F NMR: δ -44.4 (qu, J F-F ) 14 Hz, 3F), -50.9 (qu, 3F).
Abbreviations as given in Table 1.
(e) [Ir 2(CH3)(CO)2(µ-HCtCC(O)OMe)(d p p m )2][CF 3SO3]
(6). Compound 2 (34 mg, 0.025 mmol) was dissolved in 5 mL
of CH2Cl2 and cooled to -78 °C. Methyl propiolate (2.2 µL,
0.026 mmol) was added, producing a yellow solution that
was stirred at -78 °C for 1 h. The solution was then warmed
to room temperature and worked up as described for compound
2, yielding a yellow powder in 89% yield. Anal. Calcd for
Ir2SP4F3O7C58H51: C, 47.80; H, 3.53. Found: C, 47.57; H, 3.35.
P r ep a r a t ion of Com p ou n d s. (a ) [Ir 2(CH 3)(CO)2(µ-
DMAD)(d p p m )2][CF 3SO3] (2). The compound [Ir2(CH3)(CO)-
(µ-CO)(dppm)2][CF3SO3] (1) (40 mg, 0.029 mmol) was dissolved
in 5 mL of CH2Cl2, and dimethyl acetylenedicarboxylate
(DMAD) (3.65 µL, 0.029 mmol) was added by syringe. The
solution was stirred for 1 h, by which time the color had
changed from red to dark red. The solvent was evaporated to
ca. 2 mL, and the product was precipitated and washed with
Et2O (2 × 10 mL) and dried under vacuum, yielding a brown
powder in 79% yield. Recrystallization was from CH2Cl2/Et2O.
(f) [Ir 2(CO)2(µ-CtCMe)(d p p m )2][CF 3SO3] (9). Compound
1 (30 mg 0.022 mmol) was dissolved in 5 mL of CH2Cl2 and
cooled to -78 °C. Propyne (1 mL) was added via a gastight
syringe, causing a color change from red to yellow, followed
by stirring -78 °C for 1 h. Upon slowly warming, the solution
darkened to a light brown at ca. -20 °C. After stirring at room
temperature for 1 h the solvent was evaporated to ca. 2 mL,
and a light brown powder was precipitated and washed with
Et2O (2 × 10 mL), followed by drying under vacuum. Inter-
mediates in the reaction, observed at low temperature ([Ir2-
(H)(CH3)(CO)2(µ-CtCMe)(dppm)2][CF3SO3] (7) and [Ir2(CH3)-
(CO)2(µ-CdC(H)Me)(dppm)2][CF3SO3] (8)), were characterized
by NMR spectroscopy, as described later.
2
2
13C{1H} NMR: δ 193.6 (t, J PC ) 9.6 Hz, CO), 182.4 (t, J PC
)
8.3 Hz, CO). Anal. Calcd for Ir2SP4F3O9C60H53: C, 47.55; H,
3.53. Found: C, 47.16; H, 3.26.
(b) [Ir 2(CH3)(CO)3(µ-DMAD)(d p p m )2][CF 3SO3] (3). Com-
pound 2 (50 mg, 0.033 mmol) was dissolved in 5 mL of
CH2Cl2. Carbon monoxide gas was passed over the dark red
(g) [Ir 2(CO)2(µ-CtCP h )(d p p m )2][CF 3SO3] (11). The pro-
cedure used was the same as that used for the preparation of
compound 9 except that 1 equiv of phenyl acetylene was used.
Yield: 83%. Anal. Calcd for Ir2SP4F3O5C61H49: C, 50.20; H,
3.39. Found: C, 50.10; H, 3.28. Low-temperature intermediates
in the reaction, [Ir2(H)(CH3)(CO)2(µ-CtCPh)(dppm)2] [CF3SO3]
(10) and [Ir2(CH3)(CO)2(µ-CdC(H)Ph)(dppm)2][CF3SO3] (11),
were characterized by NMR spectroscopy, as described later.
(7) (a) Horton, A. D.; Orpen, A. G. Organometallics 1992, 11, 8. (b)
Davidson, J . L.; Green, M.; Stone, F. G. A.; Welch, A. J . J . Chem. Soc.,
Dalton Trans. 1976, 2044. (c) J ordan, R. G.; LaPointe, R. E.; Bradley,
P. K.; Baenziger, N. Organometallics 1989, 8, 2892. (d) Booth, B. L.;
Hargreaves, R. G. J . Chem. Soc. A 1970, 308. (e) Selnau, H. E.; Merda,
J . S. Organometallics 1993, 12, 3800. (f) Bergman, R. G. Pure Appl.
Chem. 1981, 53, 161. (g) Antwi-Nsiah, F. H.; Oke, O.; Cowie, M.
Organometallics 1996, 15, 506.
(8) (a) Werner, H.; Hohn, A.; Schulz, M. J . Chem. Soc., Dalton Trans.
1991, 777. (b) Bianchini, C.; Peruzzini, M.; Vacca, A.; Zanobini, F.
Organometallics 1991, 10, 3697. (c) Holton, J .; Lappert, M. F.; Pearce,
R.; Yarrow, P. I. W. Chem. Rev. 1983, 83, 135, and references therein.
(9) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197, and references therein.
(b) Werner, H. Angew. Chem., Int. Ed. Engl. 1990, 29, 1077, and
references therein.
(10) (a) Wakatsuki, Y.; Yamazaki, H.; Kemegawa, N.; Satoh, T.;
Satoh, J . Y. J . Am. Chem. Soc. 1991, 113, 9604. (b) George, D. S. A.
Ph.D. Thesis, University of Alberta, 1999, Chapter 3. (c) George, D. S.
A.; Hilts, R. W.; McDonald, R.; Cowie, M. Submitted to Organometal-
lics. (d) J anssen, M. D.; Smeets, W. J . J .; Spek, A. L.; Grove, D. M.;
Lang, H.; van Koten, G. J . Organomet. Chem. 1995, 505, 123.
(11) (a) Werner, H.; Scha¨fer, M., Wolf, J .; Peters, K.; von Schnering,
H. G. Angew. Chem., Int. Ed. Eng. 1995, 34, 192. (b) Wang, L.-S.;
Cowie, M. Organometallics 1995, 14, 2374.
(h ) Low -Tem p er a tu r e Rea ction of Com p ou n d 1 w ith
1 equ iv of Acetylen e. The procedure used is as described
below for the characterization of low-temperature intermedi-
ates. The compound [Ir2(H)(CH3)(CtCH)(CO)2(dppm)2][CF3-
SO3] (13) was formed at -78 °C by addition of ca. 1 equiv of
acetylene by gastight syringe to compound 1 and persisted in
1
solution until ca. 0 °C. 13C{1H} NMR for 13: δ 124.4 (dt, J CC
2
1
) 78.7 Hz, J PC ) 12.6 Hz, CtCH), 76.2 (d, J CC ) 78.7 Hz,
CtCH), 179.8 (b, CO), 178.3 (b, CO). Upon warming 13 to ca.
0 °C [Ir2(CH3)(µ-CdCH2)(CO)2(dppm)2][CF3SO3] (14) began to
appear and persisted in solution until room temperature along
with other minor uncharacterized products. 13C{1H} NMR for
1
2
14: δ 218.2 (dq, J CC ) 63.0 Hz, J PC ) 8.3 Hz, µ-CdCH2),
1
119.7 (d, J CC ) 63.0 Hz, µ-CdCH2). After stirring at room
temperature for 1 day, CO gas was added to the mixture of

4136 Organometallics, Vol. 18, No. 20, 1999
Ta ble 1. Sp ectr oscop ic Da ta for th e Com p ou n d sa
Torkelson et al.
NMRf,g
compound
IR, cm-1 b,c
δ 1Hh,i
δ
31P{1H}j
[Ir2(CH3)(CO)2(µ-DMAD)(dppm)2]-
[CF3SO3] (2)
2009 s,
4.28 (m, 2H), 3.37 (m, 2H), 2.91
7.7 (m),
3
1980 m,
1702 m, b,d
1682 m, bd
2041 s,
(s, 3H), 2.27 (s, 3H), 0.65 (t, 3H, J PH ) 5.6 Hz)
-9.3 (m)
[Ir2(CH3)(CO)3(µ-DMAD)(dppm)2]-
[CF3SO3] (3)
4.87 (m, 2H), 4.28 (m, 2H), 3.55
(s, 3H), 2.22 (s, 3H), -0.39 (t, 3H, J PH ) 5.7 Hz)
-11.2 (m),
-28.9 (m)
3
1995 vs,
1967 s,
1709 s,d
1682 md
1986 vs,
1967 vs,
1695 vsd
2018 vs,
1992 vs,
1547 we
2002 vs,
1982 sh,
1678 sd
[Ir2(CH3)(CO)2(PMe3)(µ-DMAD)-
(dppm)2][CF3SO3] (4)
5.03 (bm, 2H), 4.55 (bm, 2H), 3.56
-22.6 (b, 2P),
-24.3 (b, 2P),
-89.3 (b, 1P)
5.9 (m),
(bs,3H), 1.87 (bs, 3H), 0.71 (bs, 3H), 0.40
2
(d, J PH ) 9 Hz, 9H)
[Ir2(CH3)(CO)2(µ-HFB)(dppm)2]-
[CF3SO3] (5)
4.12 (m, 2H), 3.64 (m, 2H), 0.98
3
(tm, 3H, J PH ) 5.5 Hz)
-15.5 (m)
3
[Ir2(CH3)(CO)2(µ-HCtCC(O)OMe)-
(dppm)2][CF3SO3] (6)
9.9 (tt, J PH ) 4.7 Hz, 4J PH
)
12.3 (m),
-11.7 (m)
2.5 Hz, 1H), 3.89 (m, 2H), 3.19 (m, 2H),
3
2.31 (s, 3H), 0.45 (t, 3H, J PH ) 6.7 Hz)
[Ir2(H)(CH3)(CO)2(µ-CtCMe)(dppm)2]-
[CF3SO3] (7)k
3.62 (m, 2H), 3.01 (m, 2H), 0.62
2.1 (m),-10.4 (m)
3
(s, 3H), 0.19 (t, 3H, J PH ) 5.5 Hz), -9.52
(t, 1H, 2J PH ) 33.6 Hz)
3
[Ir2(CH3)(CO)2(µ-CtC(H)Me)(dppm)2]-
[CF3SO3] (8)l
5.79 (qu, 1H, J HH ) 3.0 Hz), 4.51
24.8 (m),
-6.7 (m)
(m, 2H), 2.95 (m, 2H), 1.73 (t, 3H, 3J PH
7.5 Hz), 0.95 (bd, 3H, 3J HH ) 3.0 Hz)
4.28 (m, 2H), 3.99 (m, 2H), 1.02
)
[Ir2(CO)2(µ-CtCMe)(dppm)2][CF3SO3] (9)
1971 s,
1945 vs
8.3 (s)
4
(q, J PH ) 1.5 Hz, 3H)
[Ir2(H)(CH3)(CO)2(µ-CtCPh)(dppm)2]-
[CF3SO3] (10)k
3.73 (m, 2H), 2.94 (m, 2H), 0.26
-0.9 (m),
-12.4 (m)
23.0 (m),
-10.6 (m)
7.9 (s)
(bt, 3H, J PH ) 5.0 Hz), -9.17 (t, 1H, 2J PH ) 17.4 Hz)
3
[Ir2(CH3)(CO)2(µ-HCtCPh)(dppm)2]-
3.61 (m, 2H), 2.96 (m, 2H), 1.74
[CF3SO3] (11)l
(t, 3H, J PH ) 7.0 Hz)
3
[Ir2(CO)2(µ-CtCPh)(dppm)2]-
[CF3SO3] (12)
1970 sh,
1953 vs, b
4.21 (m, 2H), 3.92 (m, 2H)
1
[Ir2(H)(CH3)(CO)2(µ-CtCH)(dppm)2]-
4.39 (m, 2H), 4.15 (s, 1H, J CH
)
-16.1 (s)
[CF3SO3] (13)k
229 Hz),h 3.40 (m, 2H), 0.68 (t, 3H, J PH
)
3
2
6.0 Hz), -10.06 (t, 1H, J PH ) 13.2 Hz)
1
1
[Ir2(CH3)(CO)2(µ-CdCH2)(dppm)2]-
[CF3SO3] (14)m
6.26(s, J CH ) 160 Hz, 1H),h 6.24 (s, J CH
)
13.3 (m),
3.7 (m)
160 Hz, 1H),h4.42 (m, 2H), 2.99 (m, 2H),
3
-0.20 (t, 3H, J PH ) 5.3 Hz)
1
[Ir2(H)(CO)3(µ-CdCHMe)(dppm)2]-
[CF3SO3] (15)
2045 s,
1992 vs,
1963 sh
2064 s,
2000 vs,
1574 mn
6.50 (b, J CH ) 155 Hz, 1H),h 4.08 (m, 2H),
-7.8 (m),
-14.3 (m)
3.59 (m, 2H), 0.84 (b, J CH ) 126 Hz, 3H),h
1
2
-10.62 (t, 1H, J PH ) 13.1 Hz)
1
[Ir2(CH3)(CtCH)(CO)2(µ-H)(µ-CdCH2)-
(dppm)2][CF3SO3] (16)
6.23 (s, J CH ) 156 Hz, 1H),h 6.21
-7.99 (m),
-24.58 (m)
(s, J CH ) 156 Hz, 1H), h4.12 (m, 2H),
1
3
3.10 (m, 2H), 1.87 (t, J PH ) 1.9 Hz,
1J CH ) 228 Hz, 1H),h -0.35 (t, 3H, J PH
)
3
6.6 Hz), -14.01 (tt, 2J PH ) 10 Hz, 5 Hz, 1H)
[Ir2(CH3)(CO)2(µ-CH3CtCCH3)(dppm)2]-
[CF3SO3] (17)
1982 vs, b,
1959 vs, b
1969 s,b
3.91 (m, 2H), 3.24 (m, 2H), 1.33 (b, 3H),
10.4 (m),
-9.4 (m)
-5.8 (m),
-6.0 (m),
-34.3 (m),
-37.8 (m)
-5.4 (m),
-7.7 (m),
-35.1 (m),
-38.4 (m)
3
0.76 (b, 3H), 0.47 (t, 3H, J PH ) 6.0 Hz)
[Ir2(H)(CO)2(µ-η1:η3-HCC(Me)dCHMe)-
(dppm)2][CF3SO3] (18)
8.79 (m, 1H, J CH ) 155.4 Hz),h 7.12
1
(m, 1H), 5.83 (m, 1H), 4.60 (m, 1H),
3.78 (m, 1H), 3.29 (m, 1H), 2.72 (d, 3H,
4J HH ) 3.9 Hz), 1.42 (bm, 3H), -11.25 (m, 1H)
8.83 (m, 1H), 5.83 (m, 1H), 4.52 (m, 1H),
[Ir2(H)(CO)2(µ-η1:η3-HCC(Et)dCHEt)-
(dppm)2][CF3SO3] (19)
1980 s, sh,
1964 vs
3.68 (bm, 1H), 3.23 (m, 1H), 2.97 (dqu, 1H,
3J HH ) 14.0, 7.8 Hz), 2.56 (dqu, 1H, J HH
)
3
3
14.8, 7.8 Hz), 1.88 (dqu, 1H, J HH ) 11.8, 7.8
3
Hz), 1.43 (t, 3H, J HH ) 7.8 Hz), 1.32 (b, 1H), 0.89
3
(t, 3H, J HH ) 7.5 Hz), -11.2 (m, 1H)
[Ir2(H)(CO)2(µ-η1:η3-HCC(Me)dCHEt)-
(dppm)2][CF3SO3] (20a , 20b)p
1971 s, b
8.80 (m, 2H), 5.85 (m, 2H), 4.57 (m, 2H),
3.73 (m, 2H), 3.28 (m, 2H), 2.98 (m, 1H),
2.73 (d, 3H, J ) 3.6 Hz), 2.52 (m, 1H),
1.82 (m, 1H), 1.43 (t, 3H, J ) 6.3 Hz),
1.40 (t, 3H, J ) 7.5 Hz), 1.32 (m, 1H), 0.96
(t, 3H, J ) 7.5 Hz), -11.2 (m, 2H)
-5.7 (m),
-6.8 (m),
-34.7 (m),
-38.4 (m)
[Ir2(H)(CO)2(µ-η1:η3-HCC(Me)dCHPh)-
(dppm)2][CF3SO3] (21a )
1972 vs, b
8.91 (m, 1H), 5.95 (m, 1H), 4.60 (m, 1H),
-5.7 (m, 2P),
-32.7 (m),
-38.0 (m)
0.1 (m),
-8.4 (m),
-33.7 (m),
-43.2 (m)
-5.0 (m),
-7.4 (m),
-34.8 (m),
-38.1 (m)
3.45 (m, 1H), 2.92 (s, 3H), -11.10 (b)q
[Ir2(H)(CO)2(µ-η1:η3-HCC(Ph)dCHMe)-
(dppm)2][CF3SO3] (21b)
9.22 (m, 1H), 5.70 (m, 1H), 4.80 (m, 1H),
3.20 (m, 1H), 2.92 (s, 3H), -11.10 (b)q
[Ir2(H)(CO)2(µ-η1:η3-HCC(nPr)dCHnPr)-
(dppm)2][CF3SO3] (22)
1968 s, b
8.78 (dm, 1H, J PH ) 10.8 Hz), 7.40
3
(m, 1H), 5.85 (m, 1H), 4.58 (m, 1H),
3
3.25 (m, 1H), 2.15 (t, 3H, J HH ) 7.8 Hz),
0.70 (t, 3H, 3J HH ) 6.0 Hz), -11.19 (m, 1H)q
a
b
The 13C{1H} and 19F NMR spectral data for some compounds are given in the Experimental Section. IR abbreviations (ν(CO) unless
otherwise stated): vs ) very strong, s ) strong, m ) medium, w ) weak, sh ) shoulder, b ) broad. c Nujol mull or CH2Cl2 cast unless
otherwise stated. ν(CdO ester). e ν(CtC). f NMR abbreviations: s ) singlet, d ) doublet, t ) triplet, m ) multiplet, q ) quintet, qu )
d
g
quartet, dm ) doublet of multiplets, dqu ) doublet of quartets, b ) broad, bd ) broad doublet. NMR data at 25 °C in CD2Cl2 unless
otherwise stated. 1J CH coupling values for 13C-labeled compounds. Chemical shifts for the phenyl hydrogens are not given in the 1H
h
i
NMR data. 31P{1H} chemical shifts are referenced vs external 85% H3PO4. NMR data at -80 °C. NMR data at -20 °C. NMR data
j
k
l
m
at 0 °C. ν(CdC). Signals for both isomers (1:1 abundance) listed together; some signals coincident, some distinct. q Some signals obscured
n
p
by impurities.

C-H Bond Activation and C-C Bond Formation
Organometallics, Vol. 18, No. 20, 1999 4137
compound 14 and uncharacterized products, and the solution
was stirred for 2 h, after which, NMR spectra on the complex
reaction mixture showed production of [Ir2(H)(µ-CdC(H)CH3)-
(CO)3(dppm)2][CF3SO3] (15) in ca. 35% yield. 13C{1H} NMR for
temperature, with the sample in place, and allowing the
sample to stand at that temperature for 20 min before
recording the spectra.
X-r a y Da ta Collection . For compounds 4 and 16, crystals
suitable for X-ray diffraction were grown via slow diffusion of
diethyl ether into a concentrated CH2Cl2 solution of the
compound. For compound 19, crystals were grown by diffusing
Et2O into a concentrated 1:1 CH2Cl2/toluene solution of the
compound. Crystals of each compound were mounted and
flame-sealed in glass capillaries under solvent vapor to
minimize decomposition or deterioration resulting from solvent
loss. Data collection details are given in Table 2 together with
crystal parameters. For each compound, three reflections were
chosen as intensity standards and were remeasured every 120
min of X-ray exposure time; in no case was decay evident.
Absorption corrections to 19 were applied by the method of
Walker and Stuart,12 while for 4 and 16 the crystal faces were
indexed and measured, with absorption corrections being
carried out using Gaussian integration.
Str u ctu r e Solu tion a n d Refin em en t. For each structure,
the positions of the iridium and phosphorus atoms were found
using the direct-methods program SHELXS-86;13 the remain-
ing atoms were found using a succession of least-squares and
difference Fourier maps. Refinement of each structure pro-
ceeded using the program SHELXL-93.14 Hydrogen atom
positions (except for hydride ligands as noted below) were
calculated by assuming idealized sp2 or sp3 geometries about
their attached carbon atoms (as appropriate) and were given
thermal parameters 120% of the equivalent isotropic displace-
ment parameters of their attached carbons. For compound 19
the hydride ligand (H(2)) was located and refined with a fixed
Ir(2)-H(2) distance of 1.70 Å and position to minimize non-
bonded contacts. Further details of structure refinement (other
than described below) and final residual indices may be found
in Table 2.
Location of all atoms in [Ir2(CH3)(CO)2(PMe3)(µ-DMAD)-
(dppm)2][CF3SO3] (4)‚3/4CH2Cl2‚H2O proceeded smoothly; how-
ever, the triflate ion and the water molecule did not behave
well, so bond distances were constrained.15 All atoms were
refined isotropically except the iridium and phosphorus atoms,
which were refined anisotropically.
For the compound [Ir2(CH3)(CtCH)(CO)2(µ-CdCH2)(µ-H)-
(dppm)2][CF3SO3] (16)‚CH2Cl2 all nonhydrogen atoms were
located. The hydride ligand (H(1)) was not located from a
difference Fourier map so on the basis of spectroscopic data
was placed in an idealized position bridging the two metals.
The triflate anion and the dichloromethane solvent molecule
were not well behaved so were constrained to idealized
geometries by fixing the bond distances. The same distance
restraints were applied to the triflate ion as for compound 4,15
and the following restraints were applied to enforce an
idealized geometry upon the dichloromethane solvent mol-
1
2
15: δ 192.0 (dq, J CC ) 65.9 Hz, J PC ) 8.0 Hz, µ-CdCHCH3),
1
1
137.1 (dd, J CC ) 65.9, 42.0 Hz, µ-CdCHCH3), 24.6 (d, J CC
42.0 Hz, µ-CdCHCH3).
)
(i)
[Ir 2(CH 3)(CtCH )(CO)2(µ-H )(µ-CdCH 2)(d p p m )2]-
[CF 3SO3] (16). Compound 1 (30 mg, 0.022 mmol) was dis-
solved in 5 mL of CH2Cl2. Acetylene was passed through the
solution for 10 min, causing a color change from red to orange
and then to yellow. The solution was stirred under a static
atmosphere of the gas for 1 h and then worked up as described
for compound 2, giving a yellow powder in 83% yield. Anal.
Calcd for Ir2Cl0.566SP4F3O5C58.283H51.566
: C, 48.29; H, 3.59.
Found: C, 48.18; H, 3.34. The amount of CH2Cl2 present (0.283
mol/mol complex) in the elemental analysis was confirmed by
1H NMR spectroscopy in CDCl3. 13C{1H} NMR: δ 193.6 (dm,
2
1J CC ) 64.9 Hz, CdCH2), 173.8 (t, J PC ) 10.2 Hz, CO), 166.3
(t, 2J PC ) 8.4 Hz, CO), 120.2 (d, 1J CC ) 64.9 Hz, CdCH2), 103.7
1
1
2
(d, J CC ) 119.1 Hz, CtCH), 61.6 (ddt, J CC ) 119.1 Hz, J PC
2
) 15 Hz, J CC ) 15 Hz, CtCH), -5.2 (bs, CH3).
(j) [Ir 2(CH3)(CO)2(µ-CH3CtCCH3)(dppm )2][CF3SO3] (17).
Compound 1 (40 mg, 0.029 mmol) was dissolved in 5 mL of
CH2Cl2. Excess 2-butyne (3.5 µL, 0.045 mmol) was added,
causing an immediate color change from red to dark red.
The solution was stirred for 1 h and then worked up in
a manner similar to that described for compound 2, giving
a reddish brown powder in 86% yield. Anal. Calcd for Ir2-
SP4F3O5C58H53: C, 48.80; H, 3.75. Found: C, 49.02; H, 3.74.
(k ) [Ir 2(H)(CO)2(µ-η1:η3-HCC(CH3)dCHCH3)(d p p m )2]-
[CF 3SO3] (18). Compound 17 was prepared in situ as above
and stirred for a period of 24 h, during which time the color
changed from dark red to yellow. The solvent was evaporated
to ca. 2 mL, and a yellow powder was precipitated and washed
with Et2O (2 × 10 mL) and then dried under vacuum, yield
84%. Anal. Calcd for Ir2SP4F3O5C59H58
: C, 48.80; H, 3.75.
Found: C, 48.30; H, 3.58. 13C{1H} NMR (natural abundance):
2
δ 170.9 (m, CO), 168.2 (m, CO), 138.4 (dm, J PC ) 63.0 Hz,
µ-η1:η3-HCC(CH3)dCHCH3), 110.2 (s, µ-η1:η3-HCC(CH3)d
CHCH3), 64.1 (t, 1J PC ) 28.2 Hz, Ph2PCH2PPh2), 56.2 (m, µ-η1:
η3-HCC(CH3)dCHCH3), 42.3 (t, 1J PC ) 28.2 Hz, Ph2PCH2PPh2),
23.4 (s, µ-η1:η3-HCC(CH3)dCHCH3), 18.1 (s, µ-η1:η3-HCC-
(CH3)dCHCH3).
(l)-(o) [Ir 2(H)(CO)2(µ-η1:η3-HCC(R)dCHR′)(d p p m )2]-
[CF 3SO3] (R ) R′ ) Et (19); R ) Me, R′ ) Et (20); R ) Me,
R′ ) P h (21); R ) R′ ) n P r (22)). Compounds 19-22 were
prepared by adding 1.1 equiv of the appropriate alkyne (3-
hexyne (yielding product 19), 2-pentyne (20), 1-phenyl-2-
propyne (21), 4-octyne (22)) to a CH2Cl2 solution of compound
1, stirring for 24 h, and then working up the same as was done
with compound 18 except that pentane was used for precipita-
tion and washing. In each case the color of the solution
changed from red to dark red upon addition of the alkyne and
then over 24 h changed to yellow. For 19, yield, 83%. Anal.
Calcd for Ir2SP4F3O5C59H57: C, 49.51; H, 3.96. Found: C, 49.66;
(12) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158-166.
(13) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(14) Sheldrick, G. M. SHELXL-93. Program for crystal structure
determination; University of Go¨ttingen: Germany, 1993. Refinement
H, 3.55. For 20, yield, 71%. Anal. Calcd for Ir2SP4F3O5C58H55
:
2
2
on Fo for all reflections having Fo g -3σ(Fo2). Weighted R-factors
C, 49.16; H, 3.85. Found: C, 48.89; H, 3.38. Satisfactory
elemental analyses were not obtained for compounds 21 (yield,
75%) and 22 (yield, 82%) since they could not be separated
from minor impurities, and characterization is based on
similarities in the 31P{1H} and 1H NMR spectra compared to
compounds 18 and 20. (see Table 1).
Gen er a l P r oced u r e for Ch a r a cter iza tion of Low -Tem -
p er a tu r e In ter m ed ia tes. Compound 1 (ca. 20 mg, 0.015
mmol) was dissolved in 0.6 mL of CD2Cl2 in an NMR tube,
capped with a rubber septum, and cooled to -78 °C. Ap-
proximately 1 equiv of the appropriate alkyne was added to
the NMR tube via gastight syringe, and NMR spectra of the
reaction mixture were obtained at temperatures starting from
-80 °C to +25 °C by warming the probe to the desired
2
(wR2) and all goodness of fit parameters (S) are based on Fo
;
conventional R-factors (R1) are based on Fo, with Fo set to zero for
2
negative Fo2. The observed criteria of Fo > 2σ(Fo2) is used only for
calculating R1 and is not relevant to the choice of reflections for
refinement. R-factors based on Fo2 are statistically about twice as large
as those based on Fo, and R-factors based on all data will be even larger.
(15) The following distance restraints were applied to enforce an
idealized geometry upon the triflate ion (d(S-C(98)) ) 1.80(1) Å; d(S-
O(91)) ) d(S-O(92)) ) d(S-O(93)) ) 1.45(1) Å; d(F(91)-C(98)) )
d(F(92)-C(98)) ) d(F(93)-C(98)) ) 1.35(1) Å; d(F(91)‚‚‚F(92)) )
d(F(91)‚‚‚F(93)) ) d(F(92)‚‚‚F(93)) ) 2.20(1) Å; d(O(91)‚‚‚O(92)) )
d(O(91)‚‚‚O(93)) ) d(O(92)‚‚‚O(93)) ) 2.37(1) Å; d(F(91)‚‚‚O(92)) )
d(F(91)‚‚‚O(93)) ) d(F(92)‚‚‚O(91)) ) d(F(92)‚‚‚O(93)) ) d(F(93)‚‚‚O(91))
) d(F(93)‚‚‚O(92)) ) 3.04(1) Å) and to the hydrogen atoms of the water
molecule (d(O(99)-H(99C)) ) d(O(99)-H(99D)) ) 1.00(1) Å; d(H(99C)‚
‚‚H(99D)) ) 1.00(1) Å; d(O(91)‚‚‚H(99C)) ) d(O(3)‚‚‚H(99D)) ) 1.86(2)
Å).

4138 Organometallics, Vol. 18, No. 20, 1999
Ta ble 2. Cr ysta llogr a p h ic Da ta for Com p ou n d s 4, 16, a n d 19
Torkelson et al.
[Ir2(CH3)(CO)2(PMe3)-
[Ir2(CH3)(CtCH)(CO)2
(µ-CdCH2)(µ-H)(dppm)2]-
[CF3SO3] (16)‚CH2Cl2
[Ir2H(CO)2(µ-η3:η1-HCCEtCHEt)-
(dppm)2][CF3SO3]
(µ-DMAD)(dppm)2][CF3SO3]
(4)‚3/4CH2Cl2‚H2O
(19)‚2PhMe
A. Crystal Data
formula
fw
C
63.75H65.5Cl1.5F3Ir2O10P5S
C59H53Cl2F3Ir2O5P4S
1510.25
C74H73F3Ir2O5P4S
1639.66
1673.15
crystal dimens (mm)
color
0.40 × 0.15 × 0.05
0.42 × 0.24 × 0.08
0.43 × 0.19 × 0.08
dark red
yellow
yellow
crystal system
space group
unit cell params
a (Å)
b (Å)
c (Å)
monoclinic
P21/c (No. 14)
monoclinic
P21/c (No. 14)
triclinic
P1h (No. 2)
12.9605(15)a
39.912(6)
13.224(2)
90.0
109.610(10)
90.0
6444.0(15)
4
1.725
12.5041(9)b
21.7598(15)
21.5316(15)
90.0
99.522(5)
90.0
5777.7(7)
4
1.736
12.599(2)c
14.284(3)
18.871(4)
88.50(2)
84.946(15)
89.16(2)
3381.4(12)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Fcalcd (g cm-3
)
1.610
4.116
µ (mm-1
)
4.410
11.50
B. Data Collection and Refinement Conditions
diffractometer
radiation (λ [Å])
Enraf-Nonius CAD4d
Siemens P4A/RAe
graphite-monochromated
Cu KR (1.54178)
-60
Enraf-Nonius CAD4d
graphite-monochromated
Mo KR (0.71073)
-50
θ-2θ
50.0
graphite-monochromated
Mo KR (0.71073)
temp (°C)
scan type
-50
ω
50.0
θ-2θ
113.50
data collection
2θ limit (deg)
total no. of data collected
7137 (-15 e h e 14,
0 e ke 34, 0 e l e 15)
6801
8144 (0 e h e 13,
0 e k e 23, -23 e l e 23)
7730
12231 (-14 e h e 14,
-16 e k e 16, 0 e l e 22)
11827
no. of indep reflns
no. of -observations (NO)
range of abs corr factors
no. of data/restraints/
params
3394 (Fo2 g 2σ(Fo2))
0.7996-0.3593
6784 [Fo2 g -3σ(Fo2)]/
24/446
5472 (Fo2 g 2σ(Fo2))
0.4240-0.1714
7716 [Fo2 g -3σ(Fo2)]/
24/663
8426 (Fo2 g 2σ(Fo2))
1.223-0.892
11827 [Fo2 g -3σ(Fo2)]/
4/808
largest diff peak and
1.268 and -1.277
2.179 and -1.202
1.290 and -1.362
hole (e Å-3
)
final R indicesf
R1
0.0627
0.1579
0.0640
0.1755
0.0364
0.0958
[Fo2 g2σ(Fo2)]
wR2
[Fo2 g -3σ(Fo2)]
GOF (S)g
2
2
2
1.002 [Fo g -3σ(Fo2)]
1.041 [Fo g -3σ(Fo2)]
1.050 [Fo g -3σ(Fo2)]
a
b
Obtained from least-squares refinement of 24 reflections with 19.9° < 2θ < 23.6°. Obtained from least-squares refinement of 46
reflections with 57.0° e 2θ e 58.9°. c Obtained from least-squares refinement of 24 reflections with 20.9° < 2θ < 23.9°. Programs for
d
diffractometer operation, data collection, and processing were those supplied by Enraf-Nonius. e Programs for diffractometer operation,
data collection, and data processing were those of the XSCANS system supplied by Siemens. f R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑w(Fo
-
2
Fc2)2/∑w(Fo4)]1/2
.
S ) [∑w(Fo - Fc2)2/(n - p)]1/2 (n ) number of data; p ) number of parameters varied; w ) [σ2(Fo2) + (a0P)2 + a1P]-1
,
g
2
where P ) [max(Fo2, 0) + 2Fc2]/3). For compound 4 a0 ) 0.0507, a1 ) 34.2392; for compound 16 a0 ) 0.0725, a1 ) 101.6339; for compound
19 a0 ) 0.0481, a1 ) 0.0.
ecule: d(C(99)-Cl(1)) ) d(C(99)-Cl(2)) ) 1.80(1) Å; d(Cl(1)-
Cl(2)) ) 2.90(1) Å. Owing to the structural similarities between
the acetylide and carbonyl groups, the atoms C(5) and O(1)
were interchanged. However, least-squares refinement re-
sulted in an abnormally large thermal parameter for O(1) and
an unusually small thermal parameter for C(5), confirming
the original assignment.
For the compound [Ir2H(CO)2(µ-η1:η3-HCC(Et)C(H)Et)-
(dppm)2][CF3SO3] (19)‚2C6H5CH3 all nonhydrogen atoms were
located; even the hydride ligand (H(2)) was located on a
difference Fourier map and refined with a fixed Ir(2)-H(2)
distance of 1.70 Å while minimizing nonbonded contacts with
the carbonyl carbon (C(2)), the vinyl carbene hydrogen (H(7)),
and the dppm phenyl hydrogen (H(46)). The restraints are as
follows: H2‚‚‚H7, H2‚‚‚H46 (both not less than 2.0 Å) and H2‚
‚‚C2 (not less than 2.2 Å).
[Ir2(CH3)(CO)2(µ-DMAD)(dppm)2][CF3SO3] (2), as out-
lined in Scheme 1, in which the alkyne lies parallel to
the metals as is often observed.16 The 1H NMR reso-
nance for the Ir-bound methyl group appears as a triplet
at δ 0.65 and the coupling (3J PH ) 5.6 Hz) to two
adjacent phosphorus nuclei demonstrates that this
group has remained bound to one metal. Addition of CO
to 2 in attempts to yield the previously characterized
product of migratory insertion of the alkyne and methyl
(16) (a) Sutherland, B. R.; Cowie, M. Organometallics 1984, 3, 1869.
(b) Cowie, M.; Southern, T. G. J . Organomet. Chem. 1980, 193, C46.
(c) Cowie, M.; Southern, T. G. Inorg. Chem. 1982, 21, 246. (d) Cowie,
M.; McKeer, I. R. Inorg. Chim. Acta 1982, 65, L107. (e) Cowie, M.;
Dickson, R. S.; Hames, B. W. Organometallics 1984, 3, 1879. (f) Mague,
J . T.; DeVries, S. H. Inorg. Chem. 1982, 21, 1632. (g) Mague, J . T.
Inorg. Chem. 1983, 22, 1158. (h) Vaartstra, B. A.; Xiao, J .; J enkins, J .
A.; Verhagen, R.; Cowie, M. Organometallics 1991, 10, 2708. (i) Antwi-
Nsiah, F. H.; Torkelson, J . R.; Cowie, M. Inorg. Chim. Acta 1997, 259,
213. (j) George, D. S. A.; McDonald, R.; Cowie, M. Can. J . Chem. 1996,
74, 2289. (k) Mague, J . T. Organometallics 1986, 5, 918. (l) Mague, J .
T.; Klein, C. L.; Majeste, R. J .; Stevens, E. D. Organometallics 1984,
3, 1860.
Resu lts a n d Ch a r a cter iza tion of Com p ou n d s
Compound 1 reacts with dimethyl acetylenedicar-
boxylate (DMAD) to produce the alkyne-bridged product

C-H Bond Activation and C-C Bond Formation
Organometallics, Vol. 18, No. 20, 1999 4139
Sch em e 1
Figu r e 1. Perspective view of the [Ir2(CH3)(CO)2(µ-DMAD)-
(dppm)2]+ cation of compound 4. Thermal ellipsoids are
shown at the 20% probability level except for hydrogens,
which are shown artificially small. Phenyl hydrogens are
omitted.
groups7g yields only the carbonyl adduct, [Ir2(CH3)-
(CO)3(µ-DMAD)(dppm)2][CF3SO3] (3). Similarly, phos-
phine addition also does not induce migration but yields
the phosphine adduct [Ir2(CH3)(CO)2(PMe3)(µ-DMAD)-
Ta ble 3. Selected In ter a tom ic Dista n ces a n d
An gles for Com p ou n d 4
1
(dppm)2][CF3SO3] (4). Although the H NMR spectrum
of 3 at ambient temperature shows a triplet for the
methyl resonance, displaying coupling to the two 31P
nuclei on one metal, as expected for a terminally bound
methyl ligand, the resonances of 4 are broad and
unresolved. At -60 °C the 1H NMR signals for 4
sharpen and the methyl resonance appears as a doublet,
displaying 9.0 Hz coupling to the coordinated PMe3, as
established by selective 31P-decoupling experiments.
Coupling to the dppm 31P nuclei is not resolved. The
coupling between the methyl and PMe3 groups is
consistent with the geometry established in the X-ray
study, in which these groups are opposite the Ir-Ir bond
(vide infra). Strong coupling through a metal-metal
bond has been observed previously.16h,i,k A spin-satura-
tion transfer experiment at ambient temperature es-
tablishes that the broad signals result from exchange
of free and coordinated PMe3. Irradiation at the 31P
frequency for free PMe3 (carried out in the presence of
a 3-fold excess of the ligand) results in a drop in
intensity of the coordinated PMe3 to one-quarter of its
original value. The X-ray structure of 4 was carried out
in order to determine whether the alkyne and methyl
groups were mutually cis and therefore capable of
migratory insertion without significant rearrangement,
or whether their positions were unfavorable for migra-
tion. A representation of the molecule is shown in Figure
1, with selected distances and angles given in Table 3.
The structure confirms the alkyne-bridged formulation
with the methyl ligand bound terminally to Ir(2) cis to
one end of the alkyne. The overall geometry is best
described as octahedral at each metal having the
carbonyls essentially opposite the bridging alkyne group,
with the PMe3 and methyl ligands trans to each other
across the metal-metal bond, almost bisecting the
angles between the respective µ-DMAD and terminal
carbonyl groups. The metal-metal separation of 3.022-
(2) Å is long for an iridium-iridium single bond, but
electron counting suggests its presence, giving each
(a) Distances (Å)
atom1
atom2
distance
atom1
atom2
distance
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(2)
Ir(2)
Ir(1)
Ir(1)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
P(1)
P(3)
P(5)
P(2)
P(4)
C(1)
C(5)
C(2)
C(3)
C(4)
3.022(2)
2.348(9)
2.342(9)
2.453(11)
2.336(9)
2.357(10)
1.91(4)
2.14(3)
1.87(4)
2.16(3)
2.11(3)
O(1)
O(2)
O(3)
O(4)
O(4)
O(5)
O(6)
O(6)
C(4)
C(4)
C(5)
C(1)
C(2)
C(6)
C(6)
C(7)
C(8)
C(8)
C(9)
C(5)
C(6)
C(8)
1.10(4)
1.14(4)
1.21(4)
1.32(4)
1.46(4)
1.22(4)
1.32(4)
1.46(5)
1.33(4)
1.49(5)
1.49(5)
(b) Angles (deg)
angle atom1 atom2 atom3
P(5) 156.6(3)
atom1 atom2 atom3
angle
Ir(2)
Ir(2)
Ir(2)
P(1)
P(1)
P(3)
P(5)
P(5)
C(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
C(4)
O(3)
O(3)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(2)
Ir(2)
Ir(2)
C(5)
C(5)
C(6)
C(6)
P(2)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
O(4)
O(6)
C(1)
C(2)
C(4)
C(4)
C(4)
C(5)
C(6)
C(8)
C(8)
C(8)
P(4) 160.5(4)
C(3) 89.0(15)
C(1) 115.5(12) C(2)
C(5) 64.1(10) C(2)
P(3) 161.2(4)
P(5) 97.2(3)
P(5) 100.3(4)
C(4) 168.4(17)
C(4) 102.5(14)
C(7) 118.1(31)
C(9) 115.9(33)
O(1) 177.0(39)
O(2) 176.1(34)
C(5) 109.1(27)
C(6) 130.8(30)
C(6) 120.0(36)
C(4) 117.6(28)
C(4) 113.9(35)
O(6) 125.1(39)
C(5) 123.0(35)
C(5) 111.9(33)
C(3)
C(6)
C(8)
C(1)
C(5)
87.8(12) Ir(1)
92.6(10) Ir(2)
C(5) 179.3(15) Ir(2)
C(2) 99.5(12) Ir(2)
C(3) 171.5(9) C(5)
C(4) 69.0(11) Ir(1)
C(8) 121.6(27) O(4)
C(8) 120.0(35) O(5)
O(4) 122.5(39) O(5)
C(4) 123.5(42) O(6)
metal an 18-electron configuration. Compound 4 re-
sembles related complexes having unusually long M-M
single bonds, most probably resulting from the almost
eclipsed octahedral coordinations at both metals, which
result in strong ligand-ligand repulsions and a con-
comitant lengthening of the M-M bond.3b,17 Both ends
of the diphosphine ligands are bent significantly from
a trans alignment owing to repulsions involving the
(17) Mague, J . T. Inorg. Chem. 1983, 22, 1158.

4140 Organometallics, Vol. 18, No. 20, 1999
Torkelson et al.
Sch em e 2
ligands are terminally bound to the same metal. On the
basis that methane elimination is not observed from 7,
even upon warming (vide infra), the compound is
assumed to have the structure shown in which the
hydride and methyl ligands are separated by a carbonyl.
Upon warming to -20 °C, compound 7 begins to
1
rearrange to 8, in which the hydride signal in the H
NMR spectrum has disappeared. On the basis of this
observation two structures seem possible for compound
8, having either a bridging alkyne or a bridging vi-
nylidene functionality. The vinylidene formulation,
[Ir2(CH3)(CO)2(µ-CdC(H)Me)(dppm)2][CF3SO3], is pro-
posed based on the 3 Hz coupling observed between the
vinylidene hydrogen (δ 5.79) and methyl (δ 0.95) sub-
stituents, which compares favorably with that observed
(5 Hz) between the vinylidene hydrogen and benzyl
hydrogens in [RhIr(CH3)(CO)2(µ-CdC(H)CH2Ph)(dppm)2-
[CF3SO3].19 Furthermore, vinylidene products are un-
ambiguously identified in the analogous reaction of 1
with acetylene (vide infra). The Ir-bound terminal
methyl group appears as a triplet at δ 1.73 displaying
coupling to the two adjacent 31P nuclei. Warming
compound 8 results in reductive elimination of meth-
ane with formation of the bridging acetylide species,
[Ir2(CO)2(µ-CtCMe)(dppm)2][CF3SO3] (9). The µ-η1:η2-
bridging mode proposed for the acetylide group in
compound 9 is common,20 and this compound is analo-
gous to the related acetylide-bridged A-frames [Rh2-
(CO)2(µ-C2R)(dppm)2]+ 20e,21 and [RhIr(CO)2(µ-C2Ph)-
(dppm)2]+,22 previously studied. The 31P{1H} NMR
spectrum for 9, at ambient temperature, shows a singlet
at δ 8.3, indicative of a symmetrical species. However
this can also be explained by a fluxional windshield-
wiper motion of the acetylide ligand in which it transfers
back and forth between the two metals. This type of
fluxionality is common in homobimetallic complexes
with bridging acetylide ligands,21,23 for which the low-
temperature limiting spectra were also not obtained,
PMe3 group and the large alkyne substituents, (P(1)-
Ir(1)-P(3) ) 161.2(4)° and P(2)-Ir(2)-P(4) ) 160.5(4)°).
The bonding of the alkyne, which can be considered as
a cis-dimetalated olefin, is supported by the C(4)-C(5)
distance of 1.33(4) Å, which is consistent with a carbon-
carbon double bond, and by the angles at these carbons,
which suggest sp2 hybridization. The Ir(2)-C(4) and Ir-
(1)-C(5) distances (2.11(3) and 2.14(3) Å) are not
significantly different from the Ir(2)-C(3) distance of
2.16(3) Å, even though the former pair involves sp2
carbons, while the latter involves an sp3 carbon. The
Ir-P distances for the dppm ligands are all quite
consistent (2.348(9), 2.342(9), 2.336(9), 2.357(10) Å);
however, the Ir(1)-P(5) distance (2.453(11) Å) involving
the PMe3 group is ca. 0.1 Å longer, possibly owing to
the trans influence of the metal-metal bond.18
The reaction of compound 1 with other activated
alkynes such as hexafluorobutyne (HFB) and methyl-
propiolate gives the products [Ir2(CH3)(CO)2(µ-HFB)-
(dppm)2][CF3SO3] (5) and [Ir2(CH3)(CO)2(µ-HCtCC(O)-
OMe)(dppm)2][CF3SO3] (6), respectively, which, on the
basis of the similarity of their spectral parameters with
those of 2, are assigned similar structures (see Scheme
1
even at -80 °C. The H NMR spectrum of 9 shows the
acetylide methyl protons at δ 1.02 as a quintet (4J H-P
) 1.5 Hz) coupling equally to all four phosphorus nuclei.
If the acetylide were bridging the two metals in a
symmetric fashion, binding only via the R-carbon, we
would not expect the methyl protons to show 5-bond
coupling to the phosphorus nuclei.
1
1). For compound 6, the H NMR spectrum with selec-
tive phosphorus decoupling shows that the terminal
acetylenic carbon having the small hydrogen substituent
is bound to the more crowded iridium center, bearing
the methyl ligand, as expected on the basis of steric
arguments.
Compound 1 reacts with phenyl acetylene in much
the same way, first yielding an acetylide hydride species
[Ir2(H)(CH3)(CO)2(µ-CtCPh)(dppm)2][CF3SO3] (10) at
low temperature, which upon warming transforms into
a vinylidene-bridged intermediate [Ir2(CH3)(CO)2(µ-
CtCHPh)(dppm)2][CF3SO3] (11), which at ambient
Compound 1 also reacts with nonactivated 1-alkynes.
However, alkyne adducts similar to those described
above are not observed; instead, the products result from
oxidative addition of the acetylenic C-H bond. At -78
°C compound 1 reacts with propyne yielding the acetyl-
ide hydride methyl compound [Ir2(H)(CH3)(CO)2(µ-
(19) (a) Oke, O.; McDonald, R.; Cowie, M. Manuscript in preparation.
(b) Oke, O. Ph.D. Thesis, University of Alberta, 1999, Chapter 4.
(20) (a) Salah, O. M. A.; Bruce, M. I. J . Chem. Soc., Dalton Trans.
1975, 2311. (b) Churchill, M. R.; Bezman, S. A. Inorg. Chem. 1974,
13, 1418. (c) Smith, W. F.; Yule, J .; Taylor, N. J .; Paik, H. N.; Carty,
A. J . Inorg. Chem. 1977, 16, 1593. (d) For a review of cluster bound
acetylides see: Carty, A. J . Pure Appl. Chem. 1982, 54, 113. (e) Cowie,
M.; Loeb, S. J . Organometallics 1985, 4, 852. (f) Yam, V. W.; Chan, L.;
Lai, T. Organometallics 1993, 12, 2197.
(21) (a) Grundy, K. R.; Deraniyagala, S. P. Organometallics 1985,
4, 424. (b) Deraniyagala, S. P. Ph.D. Thesis, Dalhousie University,
1984.
(22) George, D. S. A.; McDonald, R.; Cowie, M. Organometallics
1998, 17, 2553.
1
CtCMe)(dppm)2][CF3SO3] (7) (see Scheme 2). The H
NMR at -80 °C shows the acetylide methyl protons as
a singlet at δ 0.62, the Ir-bound methyl resonance as a
triplet at δ 0.19, and the terminal hydride signal as a
1
triplet at δ -9.52. H NMR experiments with selective
31P decoupling indicate that the methyl and hydride
(18) (a) Sutherland, B.; Cowie, M. Organometallics 1984, 3, 1869.
(b) Cowie, M.; Dwight, S. K. Inorg. Chem. 1980, 19, 209. (c) Cowie,
M.; Gibson, J . A. E. Organometallics 1984, 3, 984.
(23) Esteruelas, M. A.; Lahuerta, O.; Modrego, J .; Nurnberg, O.; Oro,
L. A.; Rodriguez, L.; Sola, E.; Werner, H. Organometallics 1993, 12,
266.

C-H Bond Activation and C-C Bond Formation
Organometallics, Vol. 18, No. 20, 1999 4141
Sch em e 3
of phosphorus nuclei, the lack of phosphorus coupling
to the â-carbon, and the relatively large carbon-carbon
coupling suggest a weaker η2-interaction with the
second metal than often observed. The presence of the
weak η2-interaction is proposed on the basis of differ-
ences in the chemical shifts when compared to terminal
acetylides (see compound 16 below). Upon warming to
0 °C the vinylidene compound [Ir2(CH3)(CO)2(µ-Cd
CH2)(dppm)2][CF3SO3] (14) begins to appear in solution.
The 1H NMR spectrum of compound 14 shows the
vinylidene protons at δ 6.26 and 6.24 as broad signals
with the Ir-bound methyl protons appearing at δ -0.20
as a triplet. When 14 is prepared using 13C-enriched
acetylene, the vinylidene protons show coupling of 160
Hz to the â-carbon, consistent with one-bond C-H
coupling of an sp2-hybridized carbon.25 The 13C{1H}
NMR spectrum shows the vinylidene R-carbon as a
1
doublet of quintets at δ 218.2 with J CC ) 63.0 Hz and
the â-carbon as a doublet at δ 119.7. In this case the
R-carbon shows approximately equal coupling to all
phosphorus nuclei. Compound 14 decomposes after a
period of 3 days in solution. However, under CO, 14
yields the methylvinylidene compound [Ir2(H)(CO)3(µ-
CdCHMe)(dppm)2][CF3SO3] (15) in about 35% yield, as
determined by NMR spectroscopy. The many other
products remain uncharacterized. Compound 15 is an
unusual example of carbon-carbon bond formation in
which the methyl group and one of the vinylidene
hydrogens in the precursor have exchanged positions.
If 15 is prepared from 13CH3-labeled compound 1 and
13C-enriched acetylene, and purified by recrystallization,
temperature eliminates methane, yielding [Ir2(CO)2(µ-
CtCPh)(dppm)2][CF3SO3] (12). The 31P{1H} NMR spec-
tra for the three compounds 10, 11, and 12 are very
similar to the analogous products of the propyne reac-
tion (7, 8, 9) and by analogy are assumed to have the
same structures.
1
its H NMR spectrum shows the vinylidene proton as a
broad signal at δ 6.50 with the typical one-bond C-H
coupling of 155 Hz,25 the methyl protons as a broad
signal at δ 0.84 showing one-bond C-H coupling of 126
Hz, consistent for a sp3-hybridized carbon,25 and the
terminal hydride as a triplet at δ -10.62. In the 13C-
{1H} NMR spectrum the R-carbon of the vinylidene
appears as a doublet of quintets at δ 192.0, showing
coupling to the â-carbon (65.9 Hz) and the four phos-
phorus nuclei, the â-carbon appears as a doublet of
doublets at δ 137.1, and the methyl substituent of the
vinylidene appears as a doublet at δ 24.6, showing
coupling of 42.0 Hz to the â-carbon.
The reaction of compound 1 with 1 equiv of acetylene
at -80 °C initially proceeds much like the reactions with
propyne and phenylacetylene, producing an acetylide
hydride species, [Ir2(H)(CH3)(CO)2(µ-CtCH)(dppm)2]-
[CF3SO3] (13), as outlined in Scheme 3. Although the
31P{1H} NMR spectrum shows a singlet at -80 °C, there
is actually a coincidental overlap of two signals that
upon warming begin to separate, demonstrating the
expected AA′BB′ pattern. The 1H NMR spectrum at this
temperature shows the bridging acetylide proton as a
singlet at δ 4.15 and the terminal methyl and hydride
signals as triplets at δ 0.68 and -10.06, respectively.
Selective 31P decoupling experiments could not be done
on this compound because of the close proximity of the
phosphorus resonances, but the proposed trans ar-
rangement of the hydride and methyl ligands is based
on similarities between the spectral data of compounds
7 and 10 as well as the previously characterized
tricarbonyl species [Ir2(H)(CH3)(CO)3(µ-CtCH)(dppm)2]-
[CF3SO3].7g The 13C{1H} NMR spectrum of 13, which
was prepared using 13C-enriched acetylene, shows the
acetylide R-carbon as a doublet of triplets at δ 124.4
(1J CC ) 78.7 Hz) with the â-carbon appearing as a
doublet at δ 76.2. These chemical shifts and coupling
constant appear typical of bridging acetylide groups.7g,24
However the triplet coupling of the R-carbon to one set
If compound 1 is reacted with a large excess of
acetylene at room temperature, 2 equiv of acetylene
are incorporated, producing the compound [Ir2(CH3)-
(CtCH)(CO)2(µ-H)(µ-CdCH2)(dppm)2][CF3SO3] (16), as
shown in Scheme 3. The bridging vinylidene protons
1
appear as singlets in the H NMR at δ 6.23 and 6.21,
1
showing the typical J CH values for a vinylidene when
prepared using 13C-enriched acetylene. The terminal
acetylide proton resonance appears at δ 1.87 as a triplet
with 1.9 Hz coupling to one set of phosphorus nuclei
and 228 Hz coupling to the â-carbon for the 13C-enriched
sample. The Ir-bound methyl resonance appears as a
triplet at δ -0.35 in the 1H NMR spectrum, and the
bridging hydride appears at δ -14.01 as an apparent
septet, which upon selective phosphorus decoupling is
better described as a triplet of triplets showing 5 and
10 Hz coupling to the two different sets of phosphorus
1
1
(24) Average values for J C-C (Hz) for different hybridizations:
(25) Average values for J C-H (Hz) for different hybridizations:
acetylene (sp ) 172), ethylene (sp2 ) 68), ethane (sp3 ) 35). From:
Friebolin, H. Basic One- and Two-Dimensional NMR Spectroscopy;
VCH Publishers: New York and Weinheim, Germany, 1991; p 99.
acetylene (sp ) 249), ethylene (sp2 ) 156), ethane (sp3 ) 125). From:
Friebolin, H. Basic One- and Two-Dimensional NMR Spectroscopy;
VCH Publishers: New York and Weinheim, Germany, 1991; p 95.

4142 Organometallics, Vol. 18, No. 20, 1999
Torkelson et al.
Ta ble 4. Selected In ter a tom ic Dista n ces a n d
An gles for Com p ou n d 16.
(a) Distances (Å)
atom1
atom2
distance
atom1
atom2
distance
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir2
Ir2
Ir2
P1
P3
C2
C3
C6
P2
P4
2.9460(9)
2.354(4)
2.345(4)
1.90(2)
2.13(2)
2.07(2)
Ir2
Ir2
Ir2
O1
O2
C4
C6
C1
C4
C6
C1
C2
C5
C7
1.94(2)
2.01(2)
2.09(1)
1.15(2)
1.14(2)
1.13(2)
1.31(2)
2.340(4)
2.337(4)
(b) Angles (deg)
atom1 atom2 atom3
angle
atom1 atom2 atom3
angle
Ir2
Ir2
Ir2
P1
C2
C2
C3
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir2
Ir2
Ir2
C2
C3
C6
P3
C3
C6
C6
C1
C4
C6
137.0(5)
132.2(5)
45.4(4)
176.2(1)
90.8(7)
177.5(7)
86.8(6)
134.1(5)
132.2(5)
44.6(4)
P2
Ir2
Ir2
Ir2
Ir2
C1
C2
C4
C6
C6
C6
P4
C4
C6
C6
O1
O2
C5
Ir2
C7
C7
176.7(1)
93.7(7)
178.7(6)
87.6(6)
170.7(15)
167.8(17)
174.1(18)
90.0(6)
135.0(13)
135.0(13)
C1
C1
C4
Ir2
Ir1
Ir2
Ir1
Ir1
Ir2
F igu r e 2. Perspective view of the [Ir2(CH3)(CtCH)(CO)2-
(µ-H)(µ-CtCH)(dppm)2]+ cation of compound 16. Thermal
ellipsoids as for Figure 1.
Sch em e 4
nuclei. The infrared spectrum displays a stretch at 1574
cm-1 for the bridging vinylidene and stretches at 2064
and 2000 cm-1 that are assigned to the terminal
acetylide and carbonyl groups, respectively. A labeling
experiment using a 13CO-enriched sample of compound
16 confirmed the assignment for the acetylide and
carbonyl bands, showing a lowering of the carbonyl
stretch to 1956 cm-1 with no change in the acetylide
band. In the 13C{1H} NMR spectrum the R-carbon of
the bridging vinylidene appears as a broad doublet at δ
193.6 and the â-carbon as a doublet at δ 120.2 (1J CC
)
64.9 Hz). The acetylide R-carbon appears at δ 61.6 as a
doublet of doublets of triplets coupling to the â-carbon
(1J CC ) 119.1 Hz), the vinylidene R-carbon, and the
dppm phosphines, with the â-acetylide carbon appearing
at δ 103.7 as a doublet.24 The iridium-bound methyl
carbon appears at δ -5.2 as a broad, unresolved singlet.
The structure proposed is supported by the X-ray
structure determination, a representation of which is
shown in Figure 2. A compilation of important bond
lengths and angles is given in Table 4. Although the
metal-metal bond length of 2.9460(9) Å is longer than
typically observed for an Ir-Ir single bond, this length-
ening is in line with the presence of a bridging hydride
ligand,26 which was not located but was fixed in the
(2) Å corresponds to a normal double bond in an olefinic
unit.28 The acetylide ligand is σ-bound to Ir(2) with a
metal-carbon bond length of 2.01(2) Å, similar to the
distance seen for the terminal acetylide in [RhIr(Ct
CPh)(CO)2(µ-H)(µ-CtCPh)(dppm)2][CF3SO3],7g and the
short C(4)-C(5) distance (1.13(2) Å) is consistent with
the triple-bond order.28
Reaction of the internal alkyne, 2-butyne, with 1
initially occurs much as described for HFB and DMAD,
initially giving a product [Ir2(CH3)(CO)2(µ-CH3Ct
CCH3)(dppm)2][CF3SO3] (17) (see Scheme 4), in which
the alkyne group bridges the two metals. The assign-
ment of this structure is based upon similarities with
the 31P{1H} and 1H NMR data for compound 2. How-
ever, upon stirring for 24 h at ambient temperature,
compound 17 disappears, being replaced by the unusual
vinylcarbene compound [Ir2(H)(CO)2(µ-η1:η3-HCC(Me)d
1
position shown, based upon H NMR data. Both carbo-
nyl ligands are terminally bound, one to each metal in
the sites opposite the bridging vinylidene group, with
the methyl and acetylide ligands on the opposite face,
trans to the bridging hydride. The vinylidene group
symmetrically bridges the two metals with Ir-C(6)
distances of 2.07(2) and 2.09(1) Å and an Ir(1)-C(6)-Ir-
(2) angle of 90.0(6)°, in good agreement with the
parameters observed in a number of vinylidene-bridged
complexes,11b,27 and the C(6)-C(7) bond distance of 1.31-
(26) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; p 83.
(27) (a) Xiao, J .; Cowie, M. Organometallics 1993, 12, 463. (b) Wang,
L.-S.; Cowie, M. Organometallics 1995, 14, 3040.
(28) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.

C-H Bond Activation and C-C Bond Formation
Organometallics, Vol. 18, No. 20, 1999 4143
CHMe)(dppm)2][CF3SO3] (18). The 31P{1H} NMR spec-
trum shows a complex pattern with four individual
resonances at δ -5.8, -6.0, -34.3, and -37.8, indicating
an ABCD spin system, and the 1H NMR spectrum shows
the bridgehead or carbene proton as a multiplet at δ
8.79,29 the methyl groups on the vinyl substituent
appearing as a doublet and a broad multiplet at δ 2.72
and 1.42, respectively, and the hydride resonance as a
1
complex multiplet at δ -11.25. Two-dimensional H-
13C correlation NMR data help in establishing the dppm
methylene proton resonances at δ 7.12, 5.83, 4.60, and
3.78, with the vinylic hydrogen resonance appearing at
δ 3.29. Both carbonyls are terminally bound, appearing
in the 13C{1H} NMR spectrum as multiplets at δ 170.9
and 168.2. The carbene carbon appears as a doublet of
multiplets at δ 138.4, displaying 63.0 Hz coupling to one
phosphine (presumably in a trans or almost-trans
location) and unresolved coupling to the other phospho-
rus nuclei, with the vinyl resonances appearing as a
singlet at δ 110.2 for the R-carbon and as a multiplet
at δ 56.2 for the â-carbon. The R and â methyl-sub-
stituents on the vinyl moiety appear as singlets at δ 23.4
and 18.1, respectively. If 13CH3-labeled 1 is used in the
preparation of 18, the 13C{1H} NMR spectrum shows
that the methyl carbon has been incorporated only into
the carbene or bridgehead position, and in this case the
attached proton is shown to have coupling to this carbon
of 155.4 Hz. The fragments of the original Ir-bound
methyl group are shown in boxes in Scheme 4.
F igu r e 3. Perspective view of the [Ir2H(CO)2(µ-η1:η3-
HCCEtC(H)Et)(dppm)2]+ cation of compound 19. Thermal
parameters as for Figure 1.
Ta ble 5. Selected In ter a tom ic Dista n ces a n d
An gles for Com p ou n d 19
(a) Distances (Å)
atom1
atom2
distance
atom1
atom2
distance
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir2
Ir2
Ir2
Ir2
P1
P3
C1
C3
C6
C7
P2
P4
C2
2.7623(7)
2.329(2)
2.361(2)
1.864(7)
2.207(6)
2.233(6)
2.220(7)
2.322(2)
2.372(2)
1.869(7)
Ir2
O1
O2
C3
C4
C5
C6
C7
C8
C3
C1
C2
C6
C5
C6
C7
C8
C9
2.064(7)
1.164(8)
1.141(8)
1.440(10)
1.505(10)
1.520(9)
1.431(9)
1.497(10)
1.503(11)
Compound 1 reacts similarly with other internal
alkynes, producing the vinylcarbene compounds [Ir2(H)-
(CO)2(µ-η1:η3-HCC(R)dCHR′)(dppm)2][CF3SO3] (R ) R′
) Et (19); R, R′ ) Me, Et (20); R, R′ ) Me, Ph (21); R )
R′ ) nPr (22)) (outlined in Scheme 4), and their
characterization is based on similarities with the spec-
tral data of compound 18. All show similar ABCD
patterns in the 31P{1H} NMR spectra and have a
characteristic downfield shift in the 1H NMR spectra
between δ 8.79 to 9.22 for the proton on the bridgehead
carbon. Positive assignment of some 1H NMR reso-
nances proved to be very difficult due to the number,
overlap, and complexity of the signals, and so is incom-
plete. In most cases the low-field resonance for one of
the dppm methylene hydrogens is buried under the
phenyl resonances and is not identified; it was identified
in compounds 18 and 22 by 2-D NMR experiments. In
19 all methylene hydrogens are inequivalent (they are
diastereotopic), and those on the ethyl groups couple
(b) Angles (deg)
angle atom1 atom2 atom3
atom1 atom2 atom3
angle
Ir2
Ir2
Ir2
Ir2
P1
C1
C1
C1
C3
C3
C6
Ir1
Ir1
P2
C2
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir1
Ir2
Ir2
Ir2
Ir2
C1
C1
C3
C6
C7
P3
C3
C6
C7
C6
C7
C7
C2
C3
P4
C3
O1
168.8(2) Ir2
47.5(2) Ir1
76.9(2) Ir1
83.1(2) Ir2
96.79(6) C4
122.3(3) Ir1
91.9(3) Ir1
88.3(3) Ir1
37.9(2) C3
67.1(2) C3
37.5(2) C5
159.6(2) Ir1
52.0(2) Ir1
98.39(6) C6
109.3(3) C7
175.8(6)
C2
C3
C3
C3
C5
C6
C6
C6
C6
C6
C6
C7
C7
C7
C8
O2
Ir2
C6
C6
C6
C3
C5
C7
C5
C7
C7
C6
C8
C8
C9
175.5(7)
80.5(2)
72.1(4)
126.0(5)
111.6(6)
70.1(4)
127.5(5)
70.7(4)
119.8(6)
116.9(6)
123.3(6)
71.8(4)
123.9(5)
124.2(6)
112.6(7)
1
equivalently in the H NMR spectrum to their adjacent
methyl hydrogens, giving apparent triplets for the
latter. Compounds 20 and 21, prepared using unsym-
metrical alkynes, each yielded two isomers, differing by
the relative positions of the two substituents. The
isomers of compound 20 were produced in a 1:1 ratio,
while those of 21 appeared in a 4:1 ratio, as determined
by NMR experiments.
The proposed structures for these products are sup-
ported by the X-ray structure determination of 19, a
representation of which is shown in Figure 3. A com-
pilation of important bond lengths and angles is given
in Table 5. The diphosphine groups are in a cis orienta-
tion, with angles of 96.79 (6)° and 98.39 (6)° for P(1)-
Ir(1)-P(3) and P(2)-Ir(2)-P(4), respectively, and the Ir-
Ir distance of 2.7623 (7) Å is typical of a metal-metal
bond.30 The carbonyls are terminally bound to each
metal, and the vinylcarbene moiety asymmetrically
(29) For typical comparisons see: (a) Sumner, C. E., J r.; Collier, J .
A.; Pettit, R. Organometallics 1982, 1, 1350. Examples for 13C{1H}
NMR: (b) Chetcuti, M. J .; McDonald, S. R.; Rath, N. P. Organometallics
1989, 8, 2077. (c) Howard, J . A. K.; Knox, S. A. R.; Terrill, N. J .; Yates,
M. I. J . Chem. Soc., Chem. Commun. 1989, 640. (d) Eisenstadt, A.;
Efraty, A. Organometallics 1982, 1, 1100.
(30) (a) Kubiak, C. P.; Woodcock, C.; Eisenberg, R. Inorg. Chem.
1980, 19, 2733. (b) Sutherland, B. R.; Cowie, M. Organometallics 1984,
3, 1869. (c) Sutherland, B. R.; Cowie, M. Inorg. Chem. 1984, 23, 2324.
(d) Sutherland, B. R.; Cowie, M. Organometallics 1985, 4, 1801. (e)
Xiao, J .; Cowie, M. Organometallics 1993, 12, 463.

4144 Organometallics, Vol. 18, No. 20, 1999
Torkelson et al.
bridges the metals, being η1-bound to Ir(2) (Ir(2)-C(3)
) 2.064(7) Å) and η3-bound to Ir(1) (Ir(1)-C distances:
2.207(6), 2.233(6), 2.220(7) Å). The C(3)-C(6) and C(6)-
C(7) bonds of the resulting fragment (1.440(10), 1.431-
(9) Å) are typical of an η3-bound allyl group.31 In this
geometry the vinylcarbene unit can equally well be
considered as a metallaallyl moiety, and both formula-
tions have previously been considered.32 Both formula-
tions are diagrammed below.
The reactions of terminal alkynes such as propyne,
phenylacetylene, and acetylene with 1 to give acetylide-
containing intermediates which subsequently undergo
hydrogen migration to give the vinylidene-bridged spe-
cies, [Ir2(CH3)(CO)2(µ-CC(R)H)(dppm)2][CF3SO3] (R )
CH3, Ph, H), are also not unexpected outcomes. How-
ever, the subsequent elimination of methane from the
above methyl- and phenylvinylidene, methyl intermedi-
ates was unexpected to us. Apparently the acetylide-
to-vinylidene transformation is reversible, and at the
higher temperatures the intermediate containing the
hydrido and methyl groups eliminates methane.
For the vinylidene-bridged species, [Ir2(CH3)(CO)2(µ-
CCH2)(dppm)2][CF3SO3] (14), the transformation into
the methylvinylidene hydride product [Ir2(H)(CO)3(µ-
CC(H)CH3)(dppm)2][CF3SO3] (15) upon reaction with
CO was even more surprising, with the obvious question
arising as to how exchange between a vinylidene
hydrogen and the methyl ligand occurred. On the basis
of analogies with the previous reactions of propyne and
phenylacetylene, we propose a reversible vinylidene to
acetylide hydride transformation, converting 14 back to
13, or to an isomer thereof. At higher temperatures we
assume that this is followed by methyl, rather than
hydride, migration to the acetylide ligand to give the
product 15. It appears that the hydride migration yields
the kinetically favored product (14), whereas methyl
migration to give 15 is the thermodynamically favored
transformation. In any case, although this reaction did
not proceed as anticipated, it did give rise to C-C bond
formation, as originally targeted. Although hydride
migration to the â-carbon of an acetylide to give a
vinylidene is common,9,22,34 we are aware of only two
examples involving migration of a σ-bound hydrocarbyl
fragment to the â-carbon of an acetylide; the first
involves migration of an aryl group,10d and the second
involves allyl migration,10b,c giving a bridging vinylidene
in each case. We are unaware of any previous examples
of methyl migration to the â-carbon of acetylides.
The product of addition of two acetylene molecules to
1, [Ir2(CH3)(CCH)(CO)2(µ-H)(µ-CCH2)(dppm)2][CF3SO3]
(16), in which a bridging vinylidene is flanked by a
methyl ligand on one side and an acetylide on the other,
suggests the possibility of C-C bond formation involving
the vinylidene ligand and either of the adjacent hydro-
carbyl anions. However, no C-C bond formation was
observed; presumably the coordinative saturation at
both metals and the strong Ir-C bonds inhibit any
subsequent reactivity. Species such as 16, having ad-
jacent vinylidene and alkynyl groups, are of interest
owing to the involvement of vinylidene/alkynyl com-
plexes or iron, ruthenium, and osmium in the coupling
of 1-alkynes.35
Discu ssion
We had anticipated that alkyne coordination to [Ir2-
(CH3)(CO)(µ-CO)(dppm)2][CF3SO3] (1) might result in
C-H bond cleavage of the methyl group, as observed
in reactions of 1 with a number of other substrates, and
that this might be followed at some stage by C-C bond
formation between the two hydrocarbyl fragments on
the metals. Instead, a range of reactivities is observed,
depending upon the class of alkyne investigated, al-
though internal, nonactivated alkynes do appear to
react as anticipated, as will be discussed later. Reactions
with the activated alkynes, DMAD, HFB, and methyl-
propiolate, were the most disappointing, yielding the
simple alkyne adducts [Ir2(CH3)(CO)2(µ-η1:η1-alkyne)-
(dppm)2][CF3SO3], in which the methyl group has
remained intact and the alkynes occupy a bridging
position parallel to the metals, much as observed in the
majority of dppm- and alkyne-bridged complexes.16
Although the methyl ligand was shown to lie cis to the
bridging DMAD group, reaction with CO and PMe3 has
not resulted in migratory insertion of the methyl and
DMAD ligands, yielding instead only the ligand adducts.
These observations are somewhat surprising in view of
the observed insertion of DMAD into an Ir-CH3 bond
in the tricarbonyl analogue to give [Ir2(C(R)dC(Me)R)-
(CO)3(dppm)2][CF3SO3] (R ) CO2Me). The idea that
migratory insertion for the CO and PMe3 adducts (3 and
4) did not occur owing to unfavorable arrangements of
the alkyne and methyl groups was eliminated by the
structural determination of 4, which showed a mutually
cis arrangement. These results suggest that reaction of
the tricarbonyl precursor with DMAD results in migra-
tory insertion before the DMAD ligand enters the
bridging site. The inertness of activated alkynes when
bridging two metals as cis-dimetalated olefins has
previously been noted,16i,j,33 suggesting that in this case
migration may involve an η2-bound alkyne intermediate
at a single metal.
Without doubt, the most unusual transformation in
the reactions described herein is that involving 1 with
the internal alkynes RCtCR′, in which the alkyne
substituents are various combinations of alkyl and
phenyl groups (see Scheme 4). The vinylcarbene prod-
(31) (a) Wakefield, J . B.; Stryker, J . M. Organometallics 1990, 9,
2428 (Supporting Information). (b) Collman, J . P.; Hegedus, L. S.;
Norton, J . R.; Finke, R. G. Principles and Applications of Organ-
otransition Metal Chemistry; University Science Books: Mill Valley,
CA, 1987; p 176. (c) Comprehensive Organometallic Chemistry; Wilkin-
son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: New York, 1982;
Vol. 6, Sections 37.6, 38.7, and 39.9. (d) Tulip, T. H.; Ibers, J . A. J .
Am. Chem. Soc. 1978, 100, 3252.
(32) See for example “allylidene (vinylcarbene)”: (a) Dyke, A. F.;
Knox, S. A. R.; Naish, P. J .; Taylor, G. E. J . Chem. Soc., Chem.
Commun. 1980, 803. (b) Eisenstadt, A.; Efraty, A. Organometallics
1982, 1, 1100. “Metallaallyl”: (c) Chetcuti, M. J .; McDonald, S. R.; Rath,
N. P. Organometallics 1989, 8, 2077. (d) Muller, J .; Passon, B.;
Pickardt, J . J . Organomet. Chem. 1982, 236, C11.
(33) (a) Cowie, M.; Vasapollo, G.; Sutherland, B. R.; Ennett, J . P.
Inorg. Chem. 1986, 25, 2648. (b) McKeer, I. R.; Sherlock, S. J .; Cowie,
M. J . Organomet. Chem. 1988, 352, 205.
(34) (a) Xiao, J .; Cowie, M. Organometallics 1993, 12, 463. (b) Wang,
L.-S.; Cowie, M. Organometallics 1995, 14, 2374. (c) Wang, L.-S.; Cowie,
M. Organometallics 1995, 14, 3040.
(35) Bianchini, C.; Innocenti, P.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. Organometallics 1996, 15, 272, and references therein.

C-H Bond Activation and C-C Bond Formation
Organometallics, Vol. 18, No. 20, 1999 4145
Sch em e 5
ucts obtained, [Ir2H(CO)2(µ-η1:η3-CHCRCHR′)(dppm)2]-
[CF3SO3] (18-22), have resulted from formal cleavage
of two C-H bonds of the methyl ligand, accompanied
by addition of the methyne fragment to one of the alkyne
carbons and hydrogen transfer to the other. A prelimi-
nary report of this work has appeared.36 Vinylcarbenes
are typically formed by the addition of alkynes to
methylene-bridged complexes,32,37 suggesting the in-
volvement of a methylene-bridged moiety in these
reactions of 1. As suggested earlier, compound 1 is
known to react with substrates to generate the meth-
ylene-bridged hydrides [Ir2H(CO)2L(µ-CH2)(dppm)2][CF3-
SO3]. If this occurs with alkynes, two routes to the
vinylcarbene products can be proposed, as presented in
Scheme 5, in which the ancillary ligands are not shown.
If the alkyne coordinates adjacent to the methylene
group as in species A, insertion into the adjacent Ir-
CH2 bond would yield the vinylcarbene B. A metal-
mediated, 1,3-shift of one of the methylenic hydrogens
in B would yield the isomeric vinylcarbene C, as
observed in products 18-22. An alternate proposal,
which we find particularly intriguing, is that depicted
by transformations D-C in Scheme 5. If the alkyne
coordinates adjacent to the hydride ligand as in D,
migratory insertion to give the vinyl-containing species
E should occur, which can then give the allyl product
F . Transformations of vinyl and methylene groups to
give allyl groups have been documented4 and are
proposed to be pivotal in Fischer-Tropsch chemistry.5
The conversion of F to C would occur by C-H activation
at the less crowded end of the allyl group by the adjacent
metal. Although we have no evidence supporting either
proposed route at this time, we are investi-
gating both possibilities via reactions of related meth-
ylene-bridged species, not containing hydride ligands,
with internal alkynes and with vinyl sources such as
vinyl Grignards.
The two isomers obtained when unsymmetrical alkynes
are used result from one end or the other binding to
the methyne carbon and are readily rationalized in the
“vinyl route” (steps D-C) by the steric considerations
that would favor the bulkier substituent at the â-posi-
tion of the vinyl moiety.
The kinetic products in these reactions of 1 with
internal alkynes are again the simple alkyne-bridged
species. We assume that these products are reversibly
formed and that alkyne loss is followed by coordination
as shown in either A or D of Scheme 5 to give the ther-
modynamic products. The failure of the activated alkyne
adducts (2-6) to react in a manner analogous to the
nonactivated alkyne adducts (e.g., 17), even though they
are structurally analogous, adds further support to the
idea that once in the µ-η1:η1-binding mode the activated
alkynes in this system are rather unreactive, binding
essentially irreversibly to the metals. Certainly metal-
carbon σ-bonds are known to be strong when the
R-carbon has electron-withdrawing substituents.38
Con clu sion s
Although alkynes react with the binuclear methyl
complex [Ir2(CH3)(CO)(µ-CO)(dppm)2][CF3SO3] (1) in a
variety of ways, the most interesting transformations
result from the reactions of 1 with internal, nonacti-
vated alkynes, in which a series of vinylcarbenes are
obtained. These transformations result from the activa-
tion of the methyl C-H bonds in 1 upon addition of
substrate molecules and demonstrate the utility of this
process in the formation of C-C bonds, by reaction of
unsaturated hydrocarbons (in this case alkynes) with
either the methylene or hydrido ligands generated in
the C-H bond-cleavage step. Studies are currently
under way to determine the extent of this reactivity with
a number of other unsaturated substrates and to
elaborate the mechanism(s) of these transformations.
(36) Torkelson, J . R.; McDonald, R.; Cowie, M. J . Am. Chem. Soc.
1998, 120, 4047.
(37) (a) Dickson, R. S.; Greaves, B. C. Organometallics 1993, 12,
3249. (b) Carroll, W. E.; Green, M.; Orpen, A. G.; Schaverien, C. J .;
Williams, I. D. Welch, A. J . J . Chem. Soc., Dalton Trans. 1986, 1021.
(c) Gracey, B. P.; Knox, S. A. R.; Macpherson, K. A.; Orpen, A. G.;
Stobart, S. J . Chem. Soc., Dalton Trans. 1985, 1935. (d) Davies, D. L.;
Knox, S. A. R.; Mead, K. A.; Morris, M. J .; Woodward, P. J . Chem.
Soc., Dalton Trans. 1984, 2293. (e) Colborn, R. E.; Dyke, A. F.; Knox,
S. A. R.; Macpherson, K. A.; Orpen, A. G. J . Organomet. Chem. 1982,
239, C15. (f) Sumner, C. E., J r.; Collier, J . A.; Pettit, R. Organometallics
1982, 1, 1350. (g) Dyke, A. F.; Guerchais, J . E.; Knox, S. A. R.; Roue,
J , Short, R. L.; Taylor, G. E.; Woodward, P. J . Chem. Soc., Chem.
Commun. 1981, 537. (h) Levisalles, J .; Rose-Munch, F.; Rudler, H.;
Daran, J .-C.; Dromzee, Y.; J eannin, Y. J . Chem. Soc., Chem. Commun.
1981, 152. (i) J effrey, J . C.; Moore, I.; Razay, H.; Stone, F. G. A. J .
Chem. Soc., Chem. Commun. 1981, 1255. (j) Barker, G. K.; Carroll,
W. E.; Green, M.; Welch, A. J . J . Chem. Soc., Chem. Commun. 1980,
1071. (k) Dyke, A. F.; Knox, S. A. R.; Naish, P. J . J . Organomet. Chem.
1980, 199, C47. (l) Howard, J . A. K.; Knox, S. A. R.; Terrill, N. J .; Yates,
M. I. J . Chem. Soc., Chem. Commun. 1989, 640.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council of Canada (NSERC)
(38) (a) Reger, D. L.; McElligot, P. J . J . Organomet. Chem. 1981,
216, C12. (b) Elschenbroich, C.; Salzer, A. Organometallics: A Concise
Introduction; VCH Publishers: New York, 1989; Chapter 13. (c)
Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University
Science Books: Mill Valley, CA, 1987; p 99.

4146 Organometallics, Vol. 18, No. 20, 1999
Torkelson et al.
tances and angles, anisotropic thermal parameters, and hy-
drogen parameters for compounds 4, 16, and 19. This ma-
terial is available free of charge via the Internet at http://
pubs.acs.org.
and the University of Alberta for financial support of
the research and for scholarships (to J .R.T.), and
NSERC for funding of the P4/RA diffractometer.
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
OM990291O
experimental details, atomic coordinates, interatomic dis-