Versatility of Cyclooctadiene Ligands in Iridium Chemistry and Catalysis

Article abstract of DOI:10.1021/om034218g

In the presence of reactants such as acetonitrile, trimethylphosphine, and diphenylacetylene, the 1,5-cyclooctadiene iridium(I) complex [Ir(1,2,5,6-η-C₈H₁₂)(NCCH₃)(PMe ₃)]BF₄ (1) has been found to transform into compounds containing cyclooctadiene or cyclooctadienyl ligands in η ³,η²-; κ,η³-; κ ²,η²-; and η³-coordination modes. All these reactions are initiated by an intramolecular C-H activation of the COD ligand and followed by either inter- or intramolecular insertion, or reductive elimination and further C-H activation elementary steps. Compound 1 has also been observed to undergo facile intermolecular oxidative additions of dihydrogen, hydrosilanes, and phenylacetylene to afford iridium(III) hydride complexes. Evidence for the insertion of COD into the Ir-H bonds of these new complexes has been obtained from the isolation of a monohydride complex containing a κ,η²-cyclooctenyl ligand, from the isomerization of a silyl derivative into analogues containing 1,4- and 1,3-cycloctadiene ligands, and from the occurrence of H/D scrambling among Ir-H and COD C-H sites in the product of DC≡CPh oxidative addition. Si-Si coupling reactions to give disilanes and C-C coupling reactions to give an iridacyclopentadiene complex and 1,2,4-triphenylbenzene have also been observed in silane and phenylacetylene excess, respectively. Competition of all these intra- and intermolecular reactions under the conditions of phenylacetylene hydrosilylation has been found to result in catalytic reactions, the selectivity of which depends on the presence of introduced acetonitrile and its concentration.

Full text of DOI:10.1021/om034218g

5406
Organometallics 2003, 22, 5406-5417
Ver sa tility of Cycloocta d ien e Liga n d s in Ir id iu m
Ch em istr y a n d Ca ta lysis
Marta Mart´ın, Eduardo Sola,* Olga Torres, Pablo Plou, and Luis A. Oro*
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received October 7, 2003
In the presence of reactants such as acetonitrile, trimethylphosphine, and diphenylacety-
lene, the 1,5-cyclooctadiene iridium(I) complex [Ir(1,2,5,6-η-C8H12)(NCCH3)(PMe3)]BF4 (1)
has been found to transform into compounds containing cyclooctadiene or cyclooctadienyl
ligands in η3,η2-; κ,η3-; κ2,η2-; and η3-coordination modes. All these reactions are initiated by
an intramolecular C-H activation of the COD ligand and followed by either inter- or
intramolecular insertion, or reductive elimination and further C-H activation elementary
steps. Compound 1 has also been observed to undergo facile intermolecular oxidative
additions of dihydrogen, hydrosilanes, and phenylacetylene to afford iridium(III) hydride
complexes. Evidence for the insertion of COD into the Ir-H bonds of these new complexes
has been obtained from the isolation of a monohydride complex containing a κ,η2-cyclooctenyl
ligand, from the isomerization of a silyl derivative into analogues containing 1,4- and 1,3-
cycloctadiene ligands, and from the occurrence of H/D scrambling among Ir-H and COD
C-H sites in the product of DCtCPh oxidative addition. Si-Si coupling reactions to give
disilanes and C-C coupling reactions to give an iridacyclopentadiene complex and 1,2,4-
triphenylbenzene have also been observed in silane and phenylacetylene excess, respectively.
Competition of all these intra- and intermolecular reactions under the conditions of
phenylacetylene hydrosilylation has been found to result in catalytic reactions, the selectivity
of which depends on the presence of introduced acetonitrile and its concentration.
In tr od u ction
diene ligands in the metal coordination sphere is far
from irrelevant in catalytic reactions that use COD
compounds as precursors. This is illustrated by showing
the potential of this ligand as a reversible source of
hydrides and coordination vacancies and its ability to
accommodate the electronic and steric demands of metal
fragments. Together, these capabilities confer to the
nearly ubiquitous and often ignored cyclooctadiene
highly interesting properties as an ancillary ligand, the
consideration of which could be essential in understand-
ing the reactivity and selectivity of systems generated
from COD precursors.
1,5-Cyclooctadiene (COD) rhodium and iridium com-
plexes are readily accessible compounds and common
starting materials in the chemistry of these metals.1 As
a result of their accessibility, complexes such as [M-
(µ-X)(COD)]2 (M ) Rh, Ir; X ) Cl, OMe) are often the
chosen catalyst precursors for a variety of homogeneous
catalytic reactions.2 In many of these applications, it is
assumed that cyclooctadiene is readily released from the
metal coordination sphere by the action of added ligands
or substrates; hence its presence in the reaction is often
considered irrelevant. Nevertheless, while this assump-
tion has been sufficiently verified in catalytic transfor-
mations such as hydrogenations, hydroformylations, or
carbonylations,3 it does not seem fully justified in other
processes involving milder reaction conditions and less
coordinating substrates. In this context, the selected
reactivity of the cationic iridium(I) complex [Ir(COD)-
(NCCH3)(PMe3)]BF4 described in this study intends to
substantiate that the presence or absence of cycloocta-
Resu lts a n d Discu ssion
In tr a m olecu la r C-H Activa tion a n d In ser tion .
In CDCl3 solution and in the presence of the 1,5-
cyclooctadiene complex [Ir(1,2,5,6-η-C8H12)(NCCH3)-
(PMe3)]BF4 (1), a kinetically stable olefin such as cis-
stilbene was found to slowly isomerize into its thermo-
dynamically stable trans isomer. No changes in complex
1 nor new iridium species were detected by NMR during
the isomerization process, but when assuming the
commonly accepted mechanism for olefin isomerization,
the experiment suggests the formation of a reactive
hydride intermediate (eq 1) from complex 1. In an
attempt to obtain further evidence for this postulated
hydride compound, we replaced the alkene reactant by
an alkyne, since the difficult hydrogen â-elimination
from an alkenyl species was expected to stop at this
intermediate the likely sequence of reversible reactions
* Corresponding author. E-mail: oro@unizar.es.
(1) (a) Sharp, P. R. In Comprehensive Organometallic Chemistry,
2nd ed.; Atwood, J . D., Abel, E. W., Stone, F. G. A., Wilkinson, G.,
Eds.; Pergamon: Oxford, 1995; Vol. 8, pp 115-302. (b) Atwood, J . D.
In Comprehensive Organometallic Chemistry, 2nd ed.; Atwood, J . D.,
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford,
1995; Vol. 8, pp 303-407.
(2) Applied Homogeneous Catalysis with Organometallic Com-
pounds; Cornils, B., Herrmann, W. A., Eds.; VCH: Weinheim, 1996.
(3) (a) Chaloner, P. A.; Esteruelas, M. A.; J oo´, F.; Oro, L. A.
Homogeneous Hydrogenation; Kluwer: Dordrecht, 1993. (b) Rhodium
Catalyzed Hydroformylation; van Leeuwen, P. W. M. N., Claver, C.,
Eds.; Kluwer: Dordrecht, 2000.
10.1021/om034218g CCC: $25.00 © 2003 American Chemical Society
Publication on Web 11/15/2003

Versatility of Cyclooctadiene Ligands
Organometallics, Vol. 22, No. 26, 2003 5407
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 2
Ir-P
2.3179(12)
2.070(3)
2.101(5)
2.162(5)
2.344(5)
2.353(5)
Ir-C(6)
2.378(5)
2.072(4)
1.440(6)
1.369(7)
1.329(7)
1.345(6)
Ir-N
Ir-C(9)
Ir-C(1)
Ir-C(2)
Ir-C(3)
Ir-C(5)
C(1)-C(2)
C(2)-C(3)
C(5)-C(6)
C(9)-C(10)
Ma-Ir-P
100.3
90.3
84.6
91.8
72.5
171.6
92.08(10)
100.77(14)
137.30(14)
166.84(13)
88.09(12)
166.82(16)
128.96(16)
N-Ir-C(3)
98.87(16)
89.82(14)
39.45(17)
68.01(19)
93.49(17)
35.07(18)
81.70(18)
99.16(17)
172.8(3)
M-Ir-N
N-Ir-C(9)
M-Ir-C(1)
M-Ir-C(2)
M-Ir-C(3)
M-Ir-C(9)
P-Ir-N
P-Ir-C(1)
P-Ir-C(2)
P-Ir-C(3)
P-Ir-C(9)
N-Ir-C(1)
N-Ir-C(2)
C(1)-Ir-C(2)
C(1)-Ir-C(3)
C(1)-Ir-C(9)
C(2)-Ir-C(3)
C(2)-Ir-C(9)
C(3)-Ir-C(9)
Ir-N-C(23)
Ir-C(9)-C(10)
C(10)-C(9)-C(17)
C(9)-C(10)-C(11)
124.0(3)
120.5(4)
130.9(4)
a
M is the midpoint of the C(5)-C(6) double bond.
hydride intermediate, the lifetime of which seems to be
long enough to allow for intermolecular insertions with
alkenes or alkynes. In the absence of such substrates,
an intramolecular insertion with the remaining CdC
double bond of the η3,η2-cyclooctadienyl ligand was
observed instead, yielding the Ir(III) complex [Ir(1-κ-
4,5,6-η-C8H12)(NCCH3)2(PMe3)]BF4 (3) (eq 2). Using 1,2-
dichloroethane as solvent, this transformation was
found to require the addition of 1 equiv of acetonitrile,
since in its absence the solutions of 1 were perfectly
stable. It is likely that this additional acetonitrile is
required to stabilize the final insertion product as a
coordinatively saturated compound, thus allowing for
favorable thermodynamics.
F igu r e 1. Molecular structure of the cation of complex 2.
Thermal ellipsoids are drawn at the 50% probability level.
involved in the isomerization process. Indeed, the treat-
ment of 1 with 1 equiv of diphenylacetylene, in CH2Cl2
at room temperature, led to the formation of the alkenyl
complex [Ir(1,2,3,5,6-η-C8H11)(Z-C(Ph)dCHPh)(NCCH3)-
(PMe3)]BF4 (2), the X-ray structure of which is shown
in Figure 1. Relevant bond distances and angles of the
structure are collected in Table 1. A precedent for a
closely related reaction has been reported,4 and several
compounds containing similar η3,η2-cyclooctadienyl
ligands have been described for iridium5 and other
metals.6
The analytic data of 3 agree with the proposed
stoichiometry, and its NMR spectra are consistent with
the presence of a κ,η3-cyclooctadiene ligand,7 indicating
an asymmetric structure. The proposed relative position
of the phosphine in this structure, trans to allyl, can be
inferred from the J CP coupling constant of 30.0 Hz in
the 13C{1H} NMR signal attributable to one of the allylic
carbons at δ 81.16. Our attempts to corroborate the
proposed structure of 3 by X-ray diffraction were unsuc-
cessful due to the poor quality of its crystals. Neverthe-
The ease with which complex 2 is formed and its
structure together with the occurrence of the aforemen-
tioned alkene isomerization strongly suggest that the
1,5-cyclooctadiene ligand of 1 undergoes facile and
reversible allylic C-H activation to give a labile Ir(III)
(6) (a) Hodson, B. E.; Ellis, D.; McGrath, T. D.; Monaghan, J . J .;
Rosair, G. M.; Welch, A. J . Angew. Chem., Int. Ed. 2001, 46, 715-717.
(b) McComas, C. C.; Ziller, J . W.; Van Vranken, D. L. Organometallics
2000, 19, 2853-2857. (c) Burrows, A. D.; Green, M.; J effery, J . C.;
Lynam, J . M.; Mahon, M. F. Angew. Chem., Int. Ed. 1999, 38, 3043-
3045. (d) Steed, J . W.; Tocher, D. A.; Rogers, R. D. J . Chem. Soc., Chem.
Commun. 1996, 1589-1590. (e) Bennet, M. A.; Willis, A. C.; Goh, L.
Y.; Chen, W. Polyhedron 1996, 15, 3559-3567. (f) Wiles, J . A.; Lee, C.
E.; McDonald, R.; Bergens, S. H. Organometallics 1996, 15, 3782-
3784. (g) Beddoes, R. L.; Spencer, D. M.; Whiteley, M. W. J . Chem.
Soc., Dalton Trans. 1995, 2915-2917. (h) J effery, J . C.; Stone, F. G.
A.; Topaloglu, I. Polyhedron 1993, 12, 319-325. (i) Ashworth, T. V.;
Chalmers, A. A.; Liles, D. C.; Meitjies, E.; Singleton, E. Organometallics
1987, 6, 1543-1552. (j) Ashworth, T. V.; Nolte, M. J .; Reimann, R. H.;
Singleton, E. J . Chem. Soc., Chem. Commun. 1977, 937-939.
(4) (a) Russell, D. R.; Tucker, P. A. J . Organomet. Chem. 1977, 125,
303-312. (b) Clarke, D. A.; Kemmitt, R. D. W.; Russell, D. R.; Tucker,
P. A. J . Organomet. Chem. 1975, 93, C37-C39.
(5) (a) Dorta, R.; Togni, A. Organometallics 1998, 17, 5441-5443.
(b) Bianchini, C.; Farnetti, E.; Graziani, M.; Nardin, G.; Vacca, A.;
Zanobini, F. J . Am. Chem. Soc. 1990, 112, 9190-9197. (c) Ferna´ndez,
M. J .; Esteruelas, M. A.; Oro, L. A.; Apreda, M. C.; Foces-Foces, C.;
Cano, F. H. Organometallics 1987, 6, 1751-1756. (d) Bushnell, G. W.;
Fjeldsted, D. O. K.; Stobart, S. R.; Zaworotko, M. J . J . Chem. Soc.,
Chem. Commun. 1983, 580-581.

5408 Organometallics, Vol. 22, No. 26, 2003
Mart´ın et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 4b
Ir-P(1)
Ir-P(2)
Ir-N
Ir-C(1)
Ir-C(4)
2.3085(9)
2.3085(9)
2.115(3)
2.079(3)
2.238(3)
Ir-C(5)
2.186(3)
2.239(4)
1.419(5)
1.414(5)
Ir-C(6)
C(4)-C(5)
C(5)-C(6)
P(1)-Ir-P(2)
P(1)-Ir-N
98.92(3)
90.34(8)
P(2)-Ir-C(6)
N-Ir-C(1)
163.02(10)
178.82(13)
96.89(12)
81.77(12)
82.23(14)
97.06(14)
82.12(14)
67.90(14)
176.5(3)
P(1)-Ir-C(1)
P(1)-Ir-C(4)
P(1)-Ir-C(5)
P(1)-Ir-C(6)
P(2)-Ir-N
90.31(10)
163.27(10)
130.14(10)
96.33(10)
90.52(8)
N-Ir-C(4)
N-Ir-C(5)
C(1)-Ir-C(4)
C(1)-Ir-C(5)
C(1)-Ir-C(6)
C(4)-Ir-C(6)
Ir-N-C(9)
P(2)-Ir-C(1)
P(2)-Ir-C(5)
90.36(10)
130.09(10)
fragment, permitting the isolation of complexes in both
Ir(I) and Ir(III) formal oxidation states.
F igu r e 2. Molecular structure of the cation of complex 4b.
Thermal ellipsoids are drawn at the 50% probability level.
less, crystals allowing for an X-ray diffraction experi-
ment could be obtained for derivatives of 3 when
prepared by ligand substitution. Figure 2 shows the
molecular structure of the cation of complex [Ir(1-κ-
4,5,6-η-C8H12)(NCCH3)(PMe3)2]BF4 (4), which was pre-
pared by treatment of 3 with 1 equiv of PMe3. The
structure corresponds to the thermodynamically stable
isomer of this compound (4b in eq 3), which resulted
from the slow isomerization of the substitution kinetic
product 4a . The characterization data of this latter
kinetic isomer indicate a nonsymmetric structure with
a phosphine ligand in the position trans to the σ-bonded
carbon of the cyclic ligand. The sequence of reactions
leading to 4b, depicted in eq 3, is consistent with the
large trans effect and influence that this σ-bonded
carbon is expected to exert.8 This large trans influence
also results in a long Ir-N bond distance of 2.115(3) Å
for the acetonitrile ligand of compound 4b (Table 2).
Consistently with this long bond distance, the re-
maining acetonitrile ligand of 4b could be readily
substituted by another equivalent of PMe3, yielding the
complex [Ir(1-κ-4,5,6-η-C8H12)(PMe3)3]BF4 (5). Interest-
ingly, this compound is an Ir(III) isomer of the already
reported Ir(I) derivative [Ir(COD)(PMe3)3]BF4 (6), which
contains a 1,2,5,6-η-C8H12 ligand (eq 4).9 This indicates
that both coordination modes of the cyclooctadiene
ligand are compatible with the [Ir(PMe3)3]+ metal
The thermal behavior in solution of complexes 5 and
6 was investigated in order to determine whether these
two isomers can convert into each other and thus
evaluate their relative thermodynamic stability. The
solutions of 5 in 1,2-dichloroethane were found to be
stable, even after heating them at 333 K for 6 h. On
the contrary and under the same conditions, compound
6 afforded a mixture containing two new products in
approximately 1:1 molar ratio, along with significant
amounts of the starting compound. Although these two
new products could not be separated from the reaction
mixture and independently characterized, the combina-
tion of 1H-COSY, 13C-DEPT, 1H,13C-HSQC, and 1H-
NOESY NMR experiments on the mixture (see Sup-
porting Information) permitted their identification as
two new isomers of 5 and 6, [Ir(1,4-κ-2,3-η-C8H12)-
(PMe3)3]BF4 (7) and [IrH(1,2,3-η-C8H11)(PMe3)3]BF4 (8)
(eq 4).
The 31P{1H} NMR spectrum of compound 7 in CD2-
Cl2 displays two broad signals of relative intensity 2 to
1. As in the starting complex 6, the broadening can be
attributed to the presence of a small unresolved J PP
mutual coupling constant. This spectrum indicates a
structure with two equivalent phosphines, although it
is compatible with both fac and mer arrangements of
the PMe3 ligands. The two 1H NMR signals of 7 at
lowest field, being two multiplets at δ 4.91 and 3.15,
(7) For precedents of this coordination mode of COD and function-
alized COD ligands see: (a) Flood, T. C.; Iimura, M.; Perotti, J . M.;
Rheingold, A. L.; Concolino, T. E. Chem. Commun. 2000, 1681-1682.
(b) Burrows, A. D.; Green, M.; J effrey, J . C.; Lynam, J . M.; Mahon, M.
F. Angew. Chem., Int. Ed. 1999, 38, 3043-3045. (c) de Bruin, B.;
Brands, J . A.; Donners, J . J . J . M.; Donners, M. P. J .; de Gelder, R.;
Smits, J . M. M.; Gal, A. W.; Spek, A. L. Chem. Eur. J . 1999, 5, 2921-
2936. (d) Day, V. W.; Eberspacher, T. A.; Klemperer, W. G.; Zhong, B.
J . Am. Chem. Soc. 1994, 116, 3119-3120. (e) Esteruelas, M. A.; Oliva´n,
M.; Oro, L. A.; Schulz, M.; Sola, E.; Werner, H. Organometallics 1992,
11, 3659-3664. (f) Day, V. W.; Klemperer, W. G.; Lockledge, S. P.;
Main, D. J . J . Am. Chem. Soc. 1990, 112, 2031-2033. (g) Bo¨nnemann,
H.; Goddard, R.; Grub, J .; Mynott, R.; Raabe, E.; Wendel, S. Organo-
metallics 1989, 8, 1941-1958. (h) Cotton, F. A.; LaPrade, M. D. J .
Organomet. Chem. 1972, 39, 345-354.
1
correlate in the H,13C-HSQC spectrum with two 13C-
{1H} signals corresponding to CH carbons, a doublet of
triplets at δ 89.12 with J CP coupling constants of 5.6
and 2.1 Hz, and the multiplet at δ 43.19 shown in Figure
(8) Coe, B. J .; Glenwright, S. J . Coord. Chem. Rev. 2000, 203, 5-80.
(9) Frazier, J . F.; Merola, J . S. Polyhedron 1992, 11, 2917-2927.

Versatility of Cyclooctadiene Ligands
Organometallics, Vol. 22, No. 26, 2003 5409
The 31P{1H} NMR spectrum of compound 8 consists
of three signals, a doublet of doublets at δ -55.51 with
J PP coupling constants of 20.5 and 20.8 Hz, and two
broad doublets at δ -50.04 and -52.85. The high-field
region of the 1H NMR spectrum shows a doublet of
triplets at δ -14.11 with J HP coupling constants of 148.2
and 21.9 Hz respectively, confirming the fac arrange-
ment of the three PMe3 ligands in this hydride complex.
The low-field region of the proton spectrum shows five
multiplets which correlate in the 1H,13C-HSQC spec-
trum with five 13C{1H} signals corresponding to CH
carbons. The 1H-COSY and NOESY NMR spectra
indicate that these five proton multiplets correspond to
hydrogens occupying consecutive positions in the cyclic
ligand. Together, this spectroscopic information points
to the structure depicted in eq 4 as the most likely for
complex 8.
The above experiments involving the isomeric com-
pounds 5-8 suggest that, although the iridium(I)
complex 6 initiates its thermal transformation into the
thermodynamic stable isomer 5, the process cannot be
completed in the presence of three PMe3 ligands, which
in turn drive the reaction to the alternative Ir(III)
compounds 7 and 8. A plausible explanation for this
behavior results from taking into account the larger
coordination capability of PMe3 when compared to that
of acetonitrile. This may favor the release of the CdC
double bond from the iridium center of the postulated
hydride intermediate of eq 1, thus precluding the
subsequent intramolecular insertion. Under these cir-
cumstances, the only possible elementary steps on the
cyclooctadiene moiety would be C-H reductive elimina-
tions and activations, which still allow for the migration
of the double bond, thus eventually leading to com-
pounds 7 and 8. This transformation indicates that the
sequence of intramolecular reactions leading to cyclooc-
tadiene ligand isomerization can be altered by inter-
molecular competing processes such as the coordination
of strong ligands. A related conclusion is inferred from
the formation of the alkenyl complex 2, in which the
COD isomerization sequence is intercepted by an in-
termolecular insertion reaction. Interestingly, compound
2 could also be prepared by reaction of the iridium(III)
complex 3 with diphenylacetylene (eq 5), suggesting that
all steps involved in the 1,2,5,6-η- to 1-κ-4,5,6-η-isomer-
ization of the cyclooctadiene ligand are reversible under
relatively mild reaction conditions. Further examples
for the reversibility of these elementary steps are given
in the following section.
F igu r e 3. 13C{1H} NMR signals corresponding to two
equivalent CH carbons of the cyclooctadiene (left) and two
equivalent PMe3 (right) ligands of complex 7; experimental
(below) and simulated (above).
3, respectively. This latter 13C{1H} NMR multiplet is
similar to that at δ 18.62, also shown in Figure 3, which
is attributable to the methyl groups of the two equiva-
lent phosphine ligands. Both multiplets could be suc-
cessfully simulated as corresponding to atoms coupled
to three 31P nuclei, two of which were nonequivalent just
as the result of different 12C/13C isotopic shifts. Both
simulated spectra agreed in a coupling constant of 17.8
Hz between these latter “equivalent” phosphorus atoms,
which indicates the fac arrangement of the three phos-
phine ligands of 7.
The 1H-COSY and NOESY NMR spectra of 7 also
suggest that the former 1,5-cyclooctadiene ligand has
been transformed into its 1,3-isomer, since the 1H NMR
signal at lower field does not show either scalar coupling
or NOE effect with any of the signals attributable to
CH2 groups. Moreover, the aforementioned 13C{1H}
NMR data suggest that the ligand adopts the 1,4-κ-2,3-
η-coordination mode rather than the 1,2,3,4-η-alterna-
tive. This is inferred from the large 2J CP(trans) coupling
constant obtained in the simulation of Figure 3 (43.4
Hz), much larger than those observed in the other CH
13C{1H} NMR signal of the complex (5.6 and 2.1 Hz).
Moreover, the magnitude of the 13C isotopic shift
induced by this CH group in the trans phosphorus nuclei
(2∆δ ) (0.009) is comparable to that caused by the
direct isotopic substitution at the phosphorus atom
(1∆δ ) (0.013).10
In ter m olecu la r Oxid a tive Ad d ition s a n d In ser -
tion . Cationic cyclooctadiene complexes of iridium
similar to 1 are known to be excellent catalyst precur-
sors in homogeneous hydrogenation reactions.11 Under
hydrogenation conditions these compounds have been
(10) Hansen, P. E. Prog. NMR Spectrosc. 1988, 20, 207-255.

5410 Organometallics, Vol. 22, No. 26, 2003
Mart´ın et al.
reported to undergo partial or total hydrogenation of the
cyclooctadiene ligand to yield the catalytic active spe-
cies.12 Consistent with this proposal and previous stud-
ies in related compounds,13 we observed that the
treatment of 1 with dihydrogen in CH2Cl2 at 253 K
afforded, in good yield, the dihydride complex [IrH2-
(1,2,5,6-η-C8H12)(NCCH3)(PMe3)]BF4 (9) (eq 6).
five corresponding to CH2 carbons and three due to CH
ones. The latter are doublets at δ 87.40, 84.32, and 4.81,
with J CP coupling constants of 14.7, 10.1, and 3.7 Hz,
respectively. These chemical shifts and couplings con-
stants are consistent with the presence of a CdC double
bond coordinated trans to the phosphine and a σ-bonded
CH cis to this ligand. The 13C{1H} NMR spectrum also
shows two singlets at δ 118.36 and 121.48 corresponding
to acetonitrile quaternary carbons. Under off-resonance
conditions, the signal at δ 121.48 splits into a doublet
due to a J CH coupling constant of 9.0 Hz with the trans-
located hydride ligand, in agreement with the structural
proposal for 10 depicted in eq 6.
Compound 1 was also found to undergo facile oxida-
tive addition of hydrosilanes such as HSiEt3 and HSi-
(OMe)3 to give the corresponding hydride-silyl iridium-
(III) derivatives [IrH(SiR3)(1,2,5,6-η-C8H12)(NCCH3)-
(PMe3)]BF4 (11, 12) (eq 7). Both complexes could be
conveniently obtained by reaction of 1 with 1 equiv of
the silane in CH2Cl2 at 233 K, followed by precipitation
with diethyl ether.
The two hydride-silyl compounds 11 and 12 were
found to significantly differ in stability. Whereas the
solutions of the latter remained unchanged after several
hours at room temperature, the triethylsilyl compound
11 was observed to readily disproportionate into the
starting compound 1, the dihydride 9, and disilane. This
reaction indicates the oxidative addition of HSiEt3 to
be reversible and also shows that compound 11 is
capable of reacting with a second equivalent of silane
to give an irreversible Si-Si coupling reaction. In fact,
both 11 and 12 were found to react with a second
equivalent of silane to give 9 and the corresponding
disilane (eq 7). In CH2Cl2 at 233 K, both reactions were
completed after several minutes.
1
The H NMR spectrum of 9 in CD2Cl2 at 243 K shows
two hydride resonances at δ -17.01 and -12.70, with
J HP coupling constants of 18.0 and 21.0 Hz, respectively,
without appreciable J HH mutual coupling. This is con-
sistent with a fac arrangement of the two hydrides and
the phosphine. The structural assignment of this com-
pound can be completed after observing that the 13C-
{1H} NMR resonance due to the acetonitrile quaternary
carbon, a singlet at δ 123.63, splits into a doublet under
off-resonance conditions due to a coupling of 9.0 Hz with
the trans-located hydride ligand.
The addition of 1 equiv of acetonitrile to a solution of
9 in CD2Cl2 readily led to the formation of a monohy-
dride compound. This new compound could be prepared
as a pale yellow solid by precipitation in diethyl ether
at room temperature, although the solid was found to
transform into an oil upon drying. The NMR spectra at
233 K of the CDCl3 solutions obtained from this oil
allowed the characterization of the new compound as
complex [IrH(1-κ-4,5-η-C8H13)(NCCH3)2(PMe3)]BF4 (10)
(eq 6). Compound 10 was also found to be the reaction
product after treatment of the Ir(III) complex 3 with
dihydrogen at room temperature. The formation of a
common reaction product from complexes containing
isomeric C8H12 ligands again suggests the facility and
reversibility of the elementary steps involved in the
exchange of hydrogens between the cyclic ligand and
the iridium center.
The 1-κ-4,5-η-C8H13 ligand of 10 gives rise to eight
separate signals in the 13C{1H} DEPT NMR spectrum,
The Si-Si coupling reaction was also observed when
the Ir(III) precursor 3 was used instead of 1. In this case,
due to the presence of an additional acetonitrile ligand
in the starting complex, the final reaction products were
disilane and the monohydride complex 10 (eq 8). The
reaction in CH2Cl2 at 233 K seemed to be nearly
instantaneous, and no reaction intermediates could be
detected even when silane was scarce and at lower
temperatures. This suggests that a different and faster
reaction sequence, without participation of Ir(1,2,5,6-
(11) (a) Crabtree, R. H. In Homogeneous Catalysis with Metal
Phosphine Complexes; Pignolet, L. H., Ed.; Plenum Press: New York,
1983; pp 285-316. (b) Oro, L. A.; Cabeza, J . A.; Cativiela, C.; D´ıaz de
Villegas, M. D.; Mele´ndez, E. J . Chem. Soc., Chem. Commun. 1983,
1383-1384. (c) Cabeza, J . A.; Cativiela, C.; D´ıaz de Villegas, M. D.;
Oro, L. A. J . Chem. Soc., Perkin Trans. 1 1988, 1881-1884. (d) Oro,
L. A.; Sola, E.; Navarro, J . In Perspectives in Organometallic Chemistry;
Screttas, C. G., Steele, B. R., Eds.; RSC: Cambridge, 2003; pp 297-
305.
(12) Crabtree, R. H. Acc. Chem. Res. 1979, 12, 331-338.
(13) Kimmich, B. F. M.; Somsook, E.; Landis, C. R. J . Am. Chem.
Soc. 1998, 120, 10115-10125.

Versatility of Cyclooctadiene Ligands
Organometallics, Vol. 22, No. 26, 2003 5411
η-C8H12) intermediates, may operate when the Si-Si
coupling process starts from complex 3.
previous mechanistic proposals for similar isomeriza-
tions of COD ligands,15 insertion processes similar to
that in eq 6 followed by â-elimination steps would
constitute the likely mechanism for this transformation.
Phenylacetylene has also been found to undergo
oxidative addition to complex 1, yielding the complex
[IrH(CtCPh)(1,2,5,6-η-C8H12)(NCCH3)(PMe3)]BF4 (16).
The characterization data of this compound indicate a
structure analogue to those of the previously described
kinetic oxidative addition products 9 and 11-13 (eq 10).
The use of DCtCPh as reactant provided evidence for
the occurrence of an insertion step after oxidative
addition, in the form of H/D exchange among Ir-H and
COD C-H sites. The kinetic isotopomer of this reaction,
which contains a deuteride ligand, shows characteristic
downfield isotopic shifts16 affecting, inter alia, the 31P-
{1H} NMR signal (∆δ ) 0.12 ppm) and the 13C{1H}
NMR resonance due to the alkynyl R carbon (∆δ ) 0.17
ppm). In CD2Cl2 at 233 K, this isotopomer slowly
transformed into others containing a hydride ligand.
The 13C{1H} NMR of the isotopomeric mixture gener-
ated from this H/D scrambling did not reveal a preferred
position for deuterium incorporation into the COD
ligand. Instead, only very small signals next to the
resonances of COD carbons could be detected.
The NMR characterization data of the hydride-silyl
compounds 11 and 12 indicate similar structures. Out
of the five possible isomers of a concerted silane oxida-
tive addition to 1, only that displaying a trans arrange-
ment of hydride and acetonitrile was formed. The
identity of this isomer was confirmed, in both com-
pounds, by the splitting into a doublet of the 13C NMR
signal corresponding to the acetonitrile quaternary
carbon under off-resonance conditions. Note that all
bulky ligands in this isomer share the same equatorial
plane, a feature that allowed for an interesting observa-
tion as the steric demands of the ligands were increased.
Thus, the oxidative addition of the bulky HSiPh3 was
observed to give a kinetic product, isostructural to 11
and 12, which could be conveniently isolated as the
tetraphenylborate salt [IrH(SiPh3)(1,2,5,6-η-C8H12)-
(NCCH3)(PMe3)]BPh4 (13) (eq 9). Although no dispro-
portionation of this compound was observed by NMR
in CD2Cl2 at room temperature, it sequentially evolved
to two new compounds. The final product of the trans-
formation was isolated and characterized as the complex
[IrH(SiPh3)(1,2,3,4-η-C8H12)(NCCH3)(PMe3)]BPh4 (15),
which retains the trans arrangement of hydride and
acetonitrile but contains a 1,3-cyclooctadiene ligand.
The behavior of 16 was found to be related to that of
the triethylsilyl analogue 11, since at room temperature
it was observed to disproportionate into the stating
complex 1 and the iridacyclopentadiene complex [Ir(1,4-
κ-CHdC(Ph)CHdCPh)(1,2,5,6-η-C8H12)(NCCH3)(PMe3)]-
BF4 (17). The latter complex could be obtained as a
single isomer by treatment of 1 with 2 equiv of the
alkyne at 273 K. The structure of this compound is
shown in Figure 4, and its bond distances and angles
are collected in Table 3. Despite the fact that metalla-
cyclopentadiene complexes are frequently observed as
intermediates in alkyne cyclotrimerization reactions,17
The isomerization of the COD ligand is again deduced
from the information in the 1H-COSY and NOESY
spectra. Due to its transient nature, the intermediate
compound of this transformation could not be isolated
and fully characterized. Nevertheless, its NMR data are
compatible with the formulation [IrH(SiPh3)(1,2,4,5-η-
C8H12)(NCCH3)(PMe3)]BPh4 (14), which corresponds to
an expected intermediate along the 13 to 15 isomeriza-
tion containing a 1,4-cycloctadiene ligand. Taking into
account the smaller size of the 1,3-cycloctadiene ligand
compared with that of the 1,5-isomer, the observed
isomerization can be rationalized as the cyclooctadiene
response to the steric demands introduced into the
complex by the bulky triphenylsilyl ligand.14 In line with
(14) Similar steric arguments have been previously used to rational-
ize related COD isomerizations, see: Ashworth, T. V.; Chalmers, A.
A.; Meitjies, E.; Oosthuizen, H. E.; Singleton, E. Organometallics 1984,
3, 1485-1491.
(15) See for example refs 7e and 14, and: Bennet, M. A.; McMahon,
I. J .; Pelling, S.; Brookhart, M.; Lincoln, D. M. Organometallics 1992,
11, 127-138.
(16) (a) Torres, F.; Sola, E.; Mart´ın, M.; Lo´pez, J . A.; Lahoz, F. J .;
Oro, L. A. J . Am. Chem. Soc. 1999, 121, 10632-10633. (b) J ime´nez,
M. V.; Sola, E.; Mart´ınez, A.; Lahoz, F. J .; Oro, L. A. Organometallics
1999, 18, 1125-1136.

5412 Organometallics, Vol. 22, No. 26, 2003
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles (d eg) for Com p lex 17
Mart´ın et al.
a a
b
a
b
Ir-P
2.305(3)
2.100(8)
2.053(9)
2.061(9)
2.260(11)
2.296(10)
2.332(9)
2.336(8)
2.317(2)
2.093(9)
N-C(25)
1.111(12)
1.339(12)
1.442(12)
1.337(12)
1.368(12)
1.370(13)
1.133(12)
1.371(15)
1.449(13)
1.371(15)
1.359(16)
1.341(15)
Ir-N
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(17)-C(18)
C(21)-C(22)
Ir-C(1)
Ir-C(4)
Ir-C(17)
Ir-C(18)
Ir-C(21)
Ir-C(22)
2.025(12)
2.061(11)
2.293(10)
2.283(10)
2.319(10)
2.316(11)
M(1)-Ir-M(2)b
M(1)-Ir-P
M(1)-Ir-N
M(1)-Ir-C(1)
M(1)-Ir-C(4)
M(2)-Ir-P
M(2)-Ir-N
M(2)-Ir-C(1)
M(2)-Ir-C(4)
P-Ir-N
81.8
176.5
94.2
94.2
90.6
95.7
95.6
96.9
170.7
88.4(3)
83.4(3)
91.7(3)
165.7(3)
90.4(3)
78.2(4)
82.2
176.5
94.9
95.4
90.1
95.1
96.6
171.0
81.0
87.6(2)
82.6(3)
92.4(3)
165.4(4)
90.2(4)
79.4(4)
Ir-N-C(25)
172.7(11)
116.5(7)
114.1(7)
126.2(6)
113.6(8)
124.7(8)
117.4(8)
121.7(8)
118.9(8)
174.8(8)
116.5(7)
113.9(7)
125.8(8)
113.8(10)
123.8(9)
116.3(11)
122.4(10)
119.5(10)
Ir-C(1)-C(2)
Ir-C(4)-C(3)
Ir-C(4)-C(11)
C(1)-C(2)-C(3)
C(1)-C(2)-C(5)
C(2)-C(3)-C(4)
C(3)-C(2)-C(5)
C(3)-C(4)-C(11)
P-Ir-C(1)
P-Ir-C(4)
N-Ir-C(1)
N-Ir-C(4)
C(1)-Ir-C(4)
a
b
The asymmetric unit is formed by two independent but chemically equivalent molecules. M(1) and M(2) are the midpoints of the
C(17)-C(18) and C(21)-C(22) double bonds.
require the use of ca. 6 equiv of the alkyne and, in route
to 17, the alkyne excess was converted into 1,2,4-
triphenylbenzene. Only traces of the other possible
cyclotrimerization product, the 1,3,5-triphenylbenzene,
were detected in the GC-MS and NMR analysis of the
reaction products. Again, this reaction suggests that the
achievement of a common reaction product from 1 and
3 may involve rather different reaction pathways.
In flu en ce of COD Ver sa tility in Ca ta lysis. The
previous paragraphs have described several intra- and
intermolecular transformations of complex 1 that take
place under relatively mild conditions. All these reac-
tions, and possibly others, are expected to directly
compete with each other in a catalytic process such as
phenylacetylene hydrosilylation.18 Considering the va-
riety of possible reactions, their comparable kinetics,
and the dependence of the observed equilibria on the
nature of reactants and the presence of added ligands,
it could be expected that such a catalytic process would
be rather unselective and strongly dependent on the
actual substrates and reaction conditions. Our explora-
tion of 1 as hydrosilylation catalyst has indeed con-
firmed these expectations, since in general, these cata-
lytic reactions have been found to yield alkenylsilanes
(gem, trans, and cis), the products of alkyne dehydro-
genative silylation and those of silane dehydrodimer-
ization. Moreover, the selectivity of the processes cata-
lyzed by 1 was found to depend on the concentration of
added ligands such as acetonitrile, as illustrated by the
selected reactions between triethylsilane and phenyl-
acetylene in Table 4.
F igu r e 4. Molecular structure of the cation of complex 17.
Thermal ellipsoids are drawn at the 50% probability level.
compound 17 has been found to be inert in phenylacety-
lene excess. However, a product of phenylacetylene
cyclotrimerization was observed when the synthesis of
17 was attempted from complex 3 (eq 10). This reaction
was less selective than that starting from 1, affording
several byproducts detectable by 31P NMR. The forma-
tion of 17 as the major reaction product was found to
Under the conditions of Table 4, complex 1 was found
to be a fast hydrosilylation catalysts, affording cis-
alkenylsilane as the major product.19 The addition of
acetonitrile to the catalytic reaction was found to lower
(17) See for example: (a) Takeuchi, R. Synlett. 2002, 12, 1954-1965.
(b) Calhorda, M. J .; Hirchner, K.; Veiros, L. F. In Perspectives in
Organometallic Chemistry; Screttas, C. G., Steele, B. R., Eds., RSC:
Cambridge, 2003; pp 111-119. (c) O’Connor, J . M.; Closson, A.; Hiibner,
K.; Mervin, R.; Gantzel, P. Organometallics 2001, 20, 3710-3717. (d)
Baxter, R. J .; Knox, G. R.; Pauson, P. L.; Spicer, M. D. Organometallics
1999, 18, 197-205. (e) Diercks, R.; Eaton, B. E.; Gu¨rtzen, S.; J alisatgi,
S.; Matzger, A. J .; Radde, R. H.; Volhardt, K. P. C. J . Am. Chem. Soc.
1998, 120, 8247-8248.
(18) Several iridium complexes related to 1 have been previously
described as efficient alkyne hydrosilylation catalysts. See: Ojima, I.;
Zhaoyang, L.; Zhu, J . In The Chemistry of Organic Silicon Compounds;
Rappoport, Z., Apeloig, Y., Eds.; J ohn Wiley and Sons: New York, 1998;
Vol. 2, pp 1687-1792.

Versatility of Cyclooctadiene Ligands
Organometallics, Vol. 22, No. 26, 2003 5413
Ta ble 4. Rea ction s betw een HSiEt3 a n d P h CtCH Ca ta lyzed by th e Ca tion ic Ir id iu m Com p ou n d s
[Ir (COD)(NCCH3)(P Me3)]BF 4 (1), [Ir (TF B)(NCCH3)(P iP r 3)]BF 4 (18), a n d [Ir H2(NCCH3)3(P iP r 3)]BF 4 (19)a
product distribution (%)
alkenylsilanes
complex
[NCCH3] (M)
time (h)
yieldb (%)
gem
trans
cis
styrene
PhCtCSiEt3
Si2Et6
1
1
1
18
18
19
19
1
2
2
1
3
0.2
1.3
100
90
47
100
74
100
61
2
3
6
5
6
9
7
9
21
27
24
23
26
25
74
50
35
47
45
35
37
7
13
16
12
13
15
18
8
10
8
12
13
15
13
0
3
8
0
0
0
0
0.25
2.5
2.5
2.5
a
b
Conditions: [com p lex] ) 2.5 × 10-3 M, [PhCtCH] ) [HSiEt3] ) 0.25 M, solvent ) 1,2-dichloroethane, T ) 333 K. Based on silane
consumption.
the yield of this product, while increasing the conversion
ylphosphine, hydrosilanes, and alkynes have led, under
mild conditions, to compounds containing cyclooctadi-
ene, cyclooctadienyl, or cyclooctenyl ligands in eight
different coordination modes. This versatility of the
COD ligand in the presence of an iridium center is due
to the facile and reversible exchange of hydrogens
between Ir-H and COD ligand sites. Such an exchange
can involve elementary steps of C-H oxidative addition,
C-H reductive elimination, insertion, and hydrogen
â-elimination and is driven by the electronic and steric
demands of the metal fragment. Given that such
elementary steps generate reactive hydride ligands and/
or coordination vacancies, the equilibria among the
various kinetically accessible species can be shifted or
intercepted at a given species, by the action of intro-
duced ligands or reactants. This fact seems to be
responsible, at least in part, for the variety of reactions
and products observed under the conditions of catalytic
hydrosilylation of phenylacetylene. Even though the
understanding of this unselective catalytic system will
require a more profound mechanistic investigation, the
observed selectivity dependence due to acetonitrile
concentration suggests that COD versatility may well
be turned into an advantageous property as a means of
achieving versatile and selective catalysts, provided that
the various transformations affecting the COD ligand
and those involved in the catalytic reactions could be
correctly synchronized.
to trans-alkenylsilane20 and promoting the formation of
disilane.21 Since this effect on the selectivity was found
to increase at higher acetonitrile concentrations, it
might be attributed to an increasing participation in the
catalysis of species such as 3 and 10, which are those
favored in acetonitrile excess. It is interesting to note
that the product of triethylsilane dehydrodimerization
could only be obtained from catalytic reactions in the
presence of added acetonitrile. This observation cor-
relates with that previously mentioned suggesting the
faster formation of this Si-Si coupling product from the
bis-acetonitrile Ir(III) derivative 3. Moreover, the use
of related catalyst precursors containing diolefin ligands
which cannot participate in the versatile chemistry of
COD has led to reactions in which selectivity remained
unaffected by the addition of acetonitrile. This is the
case, for example, of complex [Ir(TFB)(NCCH3)(PiPr3)]-
BF4 (18), which contains the diolefin tetrafluoroben-
zobarrelene (5,6,7,8-tetrafluoro-1,4-dihydro-1,4-etheno-
naphthalene) as ligand.22 The selectivity of this catalytic
transformation also remained insensitive to acetonitrile
concentration when using the catalyst precursor [IrH2-
(NCCH3)3(PiPr3)]BF4 (19), which can be obtained from
18 or the PiPr3 analogue of 1 after removal of the
diolefin ligand by hydrogenation.23
Con clu sion s
The reactions of complex [Ir(COD)(NCCH3)(PMe3)]-
BF4 (1) toward reactants such as acetonitrile, trimeth-
Exp er im en ta l Section
Equ ip m en t. Infrared spectra were recorded in KBr using
a Nicolet 550 spectrometer. C, H, N, and S analyses were
carried out in a Perkin-Elmer 2400 CHNS/O analyzer. NMR
spectra were recorded on Bruker Avance 300 MHz spectrom-
eter. 1H (300.13 MHz) and 13C (75.47 MHz) NMR chemical
shifts were measured relative to partially deuterated solvent
peaks but are reported in ppm relative to tetramethylsilane.
31P (121.48 MHz) and 19F (282 MHz) NMR chemical shifts were
measured relative to H3PO4 (85%) and CFCl3, respectively.
Coupling constants, J , are given in hertz. Generally, spectral
assignments were achieved by 1H COSY, NOESY, and 13C
DEPT experiments. MS data were recorded on a VG Autospec
double-focusing mass spectrometer operating in the positive
mode; ions were produced with the Cs+ gun at ca. 30 kV, and
3-nitrobenzyl alcohol (NBA) was used as the matrix. Conduc-
tivities were measured in ca. 5 × 10-4 M solutions using a
Philips PW 9501/01 conductimeter.
(19) The formation of this type of product, formally involving a trans
addition of the silane across the CtC bond, seems to be relatively
favored in the presence of late transition metal catalysts (ref 18),
although its mechanism remains controversial. See: (a) Crabtree, R.
H. New J . Chem. 2003, 27, 771-772. (b) Trost, B. M.; Ball, T. Z. J .
Am. Chem. Soc. 2003, 125, 30. (c) Mart´ın, M.; Sola, E.; Lahoz, F. J .;
Oro, L. A. Organometallics 2002, 21, 4027-4029.
(20) The cis/trans isomerization of the alkenylsilanes has been found
to require very prolonged reaction times under the conditions of this
catalysis, and therefore it is nonrelevant for the selectivity.
(21) Silane dehydrodimerization, which constitutes the main reac-
tion catalyzed by 1 in the presence of phenylacetylene and other silanes
such as HSi(OMe)3 or HSi(OEt)3, requires the presence of alkyne as
hydrogen acceptor. It is worth noting that all previously reported silane
dehydrocoupling reactions catalyzed by early or late transition metal
complexes are acceptorless. See for example: (a) Harrod, J . F. Coord.
Chem. Rev. 2000, 206-207, 493-531. (b) Gauvin, F.; Harrod, J . F.;
Woo, H. G. Adv. Organomet. Chem. 1998, 42, 363-405. (c) Rosenberg,
L.; Davies, C. W.; Yao, J . J . Am. Chem. Soc. 2001, 123, 5120-5121.
(d) Rosenberg, L.; Fryzuk, M. D.; Rettig, S. J . Organometallics 1999,
18, 958-969. (e) Fontaine, F.-G.; Kadkhodazadeh, T.; Zargarian, D.
Chem. Commun. 1998, 1253-1254.
Syn th esis. All reactions were carried out with exclusion of
air by using standard Schlenk techniques. Solvents were dried
by known procedures and distilled under argon prior to use.24
The complexes [Ir(µ-OMe)(COD)]2,25 [Ir(µ-OMe)(TFB)]2,26 and
[IrH2(NCCH3)3(PiPr3)]BF4 (19)23 and the phosphonium salt
(22) Esteruelas, M. A.; Oro, L. A. Coord. Chem. Rev. 1999, 193-
195, 557-618.
(23) Sola, E.; Navarro, J .; Lo´pez, J . A.; Lahoz, F. J .; Oro, L. A.;
Werner, H. Organometallics 1999, 18, 3534-3546.

5414 Organometallics, Vol. 22, No. 26, 2003
Mart´ın et al.
[HPiPr3]BF4 were prepared by known procedures. [HPMe3]-
δ 2.65, 3.64 (both s, NCCH3), 15.62 (d J CP ) 34.9, PCH3), 22.61
(d, J CP ) 3.7, CH2), 22.74 (d, J CP ) 4.4, CH), 27.21 (s, CH2),
45.28 (d, J CP ) 2.3, CH2), 50.62 (d, J CP ) 9.7, CH2), 54.41 (d,
J CP ) 1.4, CH), 81.16 (d, J CP ) 30.0, CH), 96.35 (d, J CP ) 0.8,
CH), 119.00, 122.11 (both s, NCCH3).
23
BF4 was prepared in quantitative yield by slow addition of a
solution of HBF4 (54% in diethyl ether) to a diethyl ether
solution of PMe3. The white solid obtained was filtered, washed
with ether, and dried in vacuo. 1H NMR (CD2Cl2, 293 K): δ
1.95 (dd, J HP ) 15.6, J HH ) 5.4, 9H, PCH3), 6.44 (dm, J HP
)
P r ep a r a tion of [Ir (1-K-4,5,6-η-C8H12)(NCCH3)(P Me3)2]-
BF 4 (4a ). A solution of 3 (100 mg, 0.18 mmol) in CH2Cl2 (2
mL) at 258 K was treated with PMe3 (20 mL, 0.18 mmol), and
the mixture was stirred for 5 min. Diethyl ether was slowly
added to produce a pale yellow solid. The solid was separated
by decantation, washed with diethyl ether, and dried in
vacuo: yield 89 mg (83%). Anal. Calcd for C16H33NP2IrBF4:
C, 33.11; H, 5.73; N, 2.41. Found: C, 32.94; H, 5.61; N, 2.48.
ΛM (acetone) ) 96 Ω-1 cm2 mol-1 (1:1). MS (FAB+, m/z (%)):
510.2, J HH ) 5.4, 1H, PH). 31P{1H} NMR (CD2Cl2, 293 K): δ
-4.32 (s). All other reagents were obtained from commercial
sources and were used as received. All the compounds whose
preparations are described below are air-sensitive in solution.
P r ep a r a tion of [Ir (1,2,5,6-η-C8H12)(NCCH3)(P Me3)]BF 4
(1). A solution of [Ir(µ-OMe)(1,2,5,6-η-C8H12)]2 (150 mg, 0.22
mmol) in acetone/acetonitrile (10/1, 8 mL) was treated with
[HPMe3]BF4 (68 mg, 0.44 mmol) and stirred for 10 min at room
temperature. The resulting solution was concentrated to ca.
0.5 mL, and diethyl ether was slowly added to give an orange
solid. The solid was separated by decantation, washed with
diethyl ether, and dried in vacuo: yield 137 mg (62%). Anal.
Calcd for C13H24BF4IrNP: C, 30.96; H, 4.80; N, 2.78. Found:
1
494 (10) [M+]. H NMR (CDCl3, 293 K): δ 1.31 (d, J HP ) 7.5,
9H, PCH3), 1.62 (m, 2H, CH2), 1.68 (m, 1H, CH), 1.75 (d,
J HP ) 9.6, 9H, PCH3), 1.97, 2.04, 2.31 (all m, 2H each, CH2),
2.67 (s, 3H, NCCH3), 3.74, 4.22, 5.00 (all m, 1H each, CH).
31P{1H} NMR (CDCl3, 293 K): δ -51.60, -40.91 (both d,
J PP ) 19.9). 13C{1H} NMR (CDCl3, 293 K): δ 4.11 (s, NCCH3),
13.62 (d, J CP ) 26.7, PCH3), 18.24 (dd, J CP ) 35.3, 3.4, PCH3),
24.14 (dd, J CP ) 5.8, 3.5, CH2), 30.32 (d, J CP ) 8.5, CH2), 36.44
(dd, J CP ) 74.1, 5.1, CH), 43.27 (s, CH2), 52.06 (d, J CP ) 10.7,
CH2), 55.42 (s, CH), 78.18 (d, J CP ) 30.2, CH), 90.21 (s, CH),
121.85 (s, NCCH3).
1
C, 31.06; H, 5.10; N, 3.01. IR (cm-1): 2251 ν(CtN). H NMR
(CDCl3, 293 K): δ 1.47 (d, J HP ) 9.9, 9H, PCH3), 1.93 (m, 4H,
CH2), 2.22 (m, 4H, CH2), 2.68 (s, 3H, NCCH3), 4.0-5.0 (m, 4H,
CH). 31P{1H} NMR (CDCl3, 293 K): δ -18.06 (s).
P r ep a r a tion of [Ir (1,2,3,5,6-η-C8H11)(Z-C(P h )dCHP h )-
(NCCH3)(P Me3)]BF 4 (2). A solution of 1 (100 mg, 0.20 mmol)
in CH2Cl2 (8 mL) was treated with diphenylacetylene (35.6
mg, 0.20 mmol), and the mixture was stirred for 40 min at
room temperature. The resulting solution was concentrated
to ca. 0.5 mL, and diethyl ether was slowly added to give a
pale yellow solid. The solid was separated by decantation,
washed with diethyl ether, and dried in vacuo: yield 113 mg
(83%). Anal. Calcd for C27H34NPIrBF4: C, 47.51; H, 5.02; N,
2.05. Found: C, 47.32; H, 5.00; N, 1.99. ΛM (acetone) ) 88 Ω-1
cm2 mol-1 (1:1). IR (cm-1): 1636, 1595, 1562 ν(CdC). 1H NMR
(CD2Cl2, 293 K): δ 1.89 (m, 1H, CH2), 1.96 (d, J HP ) 10.5, 9H,
PCH3), 2.01 (s, NCCH3), 2.25 (m, 1H, CH2), 2.48, 3.64 (both
m, 2H each, CH2), 3.77, 3.93, 4.54, 4.74, 5.05 (all m, 1H each,
CH), 6.04 (s, 1H, IrC(Ph)dCHPh), 6.71, 6.84 (both m, 2H each,
CH), 6.97 (m, 1H, CH), 7.03 (m, 2H, CH), 7.17 (m, 1H, CH),
7.26 (m, 2H, CH). 31P{1H} NMR (CD2Cl2, 293 K): δ -35.87
(s). 13C{1H} NMR (CD2Cl2, 293 K): δ 2.67 (s, NCCH3), 16.85
(d, J CP ) 39.1, PCH3), 20.82 (d, J CP ) 4.2, CH2), 27.81 (d,
P r ep a r a tion of [Ir (1-K-4,5,6-η-C8H12)(NCCH3)(P Me3)2]-
BF 4 (4b). A solution of 3 (100 mg, 0.18 mmol) in CH2Cl2 (8
mL) was treated with PMe3 (19 mL, 0.18 mmol), and the
mixture was stirred for 24 h at room temperature. The
resulting solution was filtered through Celite and concentrated
to ca. 0.5 mL. Addition of diethyl ether produced a pale yellow
solid, which was separated by decantation, washed with
diethyl ether, and dried in vacuo: yield 80 mg (73%). Anal.
Calcd for C16H33NP2IrBF4: C, 33.11; H, 5.73; N, 2.41. Found:
C, 32.91; H, 5.65; N, 2.17. ΛM (acetone) ) 95 Ω-1 cm2 mol-1
(1:1). 1H NMR (CD2Cl2, 293 K): δ 1.45, 1.48 (both m, 2H each,
CH2), 1.65 (m, 1H, CH), 1.75 (d, J HP ) 9.3, 18H, PCH3), 1.81,
1.90 (both m, 2H each, CH2), 2.37 (s, 3H, NCCH3), 4.42 (m,
1H, CH), 5.00 (m, 2H, CH). 31P{1H} NMR (CD2Cl2, 293 K): δ
-46.35 (s). 13C{1H} NMR (CD2Cl2, 293 K): δ 2.80 (s, NCCH3),
18.04 (dd, J CP ) 34.5, 1.6, PCH3), 20.16 (t, J CP ) 4.2, CH),
23.72, 51.26 (both m, CH2), 75.43 (dd, J CP ) 30.9, 1.5, CH),
102.43 (t, J CP ) 1.8, CH), 118.64 (s, NCCH3).
J CP ) 1.6, CH2), 31.30 (s, CH2), 47.61 (s, CH), 51.63 (d, J CP
)
16.9, CH), 68.97 (d, J CP ) 5.8, CH), 102.55 (d, J CP ) 0.8, CH),
103.32, 125.46, 125.55, 126.49, 127.61, 128.18 (all s, CH) 126.0
(s, NCCH3), 131.20 (d, J CP ) 10.0, IrC(Ph)dCHPh), 132.50 (d,
J CP ) 7.3, IrC(Ph)dCHPh), 139.32, 148.13 (both s, C).
P r ep a r a tion of [Ir (1-K-4,5,6-η-C8H12)(P Me3)3]BF 4 (5). A
solution of 3 (100 mg, 0.18 mmol) in CH2Cl2 (8 mL) was treated
with PMe3 (38 mL, 0.36 mmol) and the mixture was stirred
for 24 h at room temperature. The resulting solution was
filtered through Celite and concentrated to ca. 0.5 mL. Addi-
tion of diethyl ether produced a white solid, which was
separated by decantation, washed with diethyl ether, and dried
in vacuo: yield 84 mg (76%). Anal. Calcd for C17H39P3IrBF4:
C, 33.18; H, 6.38. Found: C, 33.03; H, 6.45. ΛM (acetone) ) 89
P r ep a r a tion of [Ir (1-K-4,5,6-η-C8H12)(NCCH3)2(P Me3)]-
BF 4 (3). A solution of 1 (200 mg, 0.40 mmol) in 1,2-dichloro-
ethane (8 mL) was treated with 1 mL of acetonitrile, and the
mixture was stirred for 12 h at 333 K. The resulting solution
was concentrated to ca. 0.5 mL, and diethyl ether was slowly
added to give a pale yellow solid. The solid was separated by
decantation, washed with diethyl ether, and dried in vacuo:
yield 169 mg (78%). Anal. Calcd for C15H27N2PIrBF4: C, 33.03;
1
Ω-1 cm2 mol-1 (1:1). MS (FAB+, m/z (%)): 529 (100) [M+]. H
NMR (CDCl3, 293 K): δ 1.16 (d, J HP ) 12.3, 9H, PCH3), 1.39
(m, 2H, CH2), 1.68 (d, J HP ) 9.3, 18H, PCH3), 1.78, 1.87 (both
m, 2H each, CH2), 1.95 (m, 1H, CH), 2.01 (m, 2H, CH2), 4.15
(m, 1H, CH), 4.48 (m, 2H, CH). 31P{1H} NMR (CDCl3, 293 K):
δ -59.52 (t, J PP ) 20.3), -53.23 (d, J PP ) 20.3). 13C{1H} RMN
(CDCl3, 293 K): δ 16.21 (dt, J CP ) 27.8, 1.0, PCH3), 20.93 (ddd,
J CP ) 35.4, 3.2, 2.0, PCH3), 26.13 (ddd, J CP ) 6.6, 3.3, 0.8, CH2),
33.05 (dt, J CP ) 67.7, 5.0, CH), 51.51 (dd, J CP ) 9.9, 4.7, CH2),
74.48 (dd, J CP ) 30.2, 1.3, CH), 96.07 (t, J CP ) 1.7, CH).
1
H, 4.99; N, 5.14. Found: C, 32.54; H, 4.79; N, 4.95. H NMR
(CDCl3, 293 K): δ 1.00, 1.08, 1.24, 1.33, 1.66, (all m, 1H each,
CH2), 1.68 (d, J HP ) 10.0, 9H, PCH3), 1.70, 1.76, 1.78 (all m,
1H each, CH2), 1.93 (m, 1H, CH), 2.26 (s, 3H, NCCH3), 2.60
(d, J HP ) 1.4, 3H, NCCH3), 4.05 (m, 1H, CH), 4.32 (td, J HH
)
8.1, J HP ) 1.5, 1H, CH), 5.39 (m, 1H, CH). 31P{1H} NMR
(CDCl3, 293 K): δ -34.65 (s). 13C{1H} NMR (CDCl3, 293 K):
(24) (a) Shriver, D. F. The Manipulation of Air-sensitive Compounds;
McGraw-Hill: New York, 1969. (b) Armarego, W. L. F.; Perrin, D. D.
Purification of Laboratory Chemicals, 4th ed.; Butterworth-Heinmann;
Oxford, 1996.
(25) Uso´n, R.; Oro, L. A.; Cabeza, J . Inorg. Synth. 1985, 23, 126-
130.
(26) Uso´n, R.; Oro, L. A.; Carmona, D.; Esteruelas, M. A.; Foces-
Foces, C.; Cano, F. H.; Garc´ıa-Blanco, S.; Va´zquez de Miguel, A. J .
Organomet. Chem. 1984, 273, 111-128.
[Ir (1,4-K-,2,3-η-C8H12)(P Me3)3]BF 4 (7) a n d [Ir H(1,2,3-η-
C8H11)(P Me3)3]BF 4 (8). A solution of 6 (100 mg, 0.16 mmol)
in 1,2-dichloroethane (8 mL) was stirred for 3 h at 333 K. The
resulting solution was evaporated to dryness, and the residue
was dissolved in CD2Cl2. The spectroscopic analysis of the
resulting solution revealed the presence of compounds 6, 7,
and 8 in molar ratio 2:1:1. Partial data for 7: 1H NMR (CD2-

Versatility of Cyclooctadiene Ligands
Organometallics, Vol. 22, No. 26, 2003 5415
Cl2, 293 K): δ 1.52 (d, J HP ) 8.2, 18H, PCH3), 1.82 (d, J HP
)
CH3), 9.39 (s, SiCH2CH3), 17.40 (d, J CP ) 40.2, PCH3), 29.41,
28.59, 36.72 (all s, CH2), 87.56 (d, J CP ) 11.9, CH), 89.60 (s,
CH), 101.65 (d, J CP ) 9.6, CH), 102.93 (s, CH), 125.03 (s,
NCCH3).
9.2, 9H, PCH3), 3.15, 4.91 (both m, 2H each, CH). 31P{1H} NMR
(CD2Cl2, 293 K): δ -56.48, -46.60 (both br). 13C{1H} NMR
(CD2Cl2, 293 K): δ 18.62 (m, PCH3), 20.91 (dt, J CP ) 34.6, 2.7,
PCH3), 43.19 (m, CH), 89.12 (dt, J CP ) 5.6, 2.1, CH). Partial
P r epar ation of [Ir H{Si(OMe)3}(1,2,5,6-η-C8H12)(NCCH3)-
(P Me3)]BF 4 (12). The compound was prepared as a pale
yellow solid following the procedure described for 11, by using
1 (125 mg, 0.25 mmol) and HSi(OMe)3 (63 µL, 0.50 mmol):
yield 76 mg (61%). Anal. Calcd for C16H34BF4IrNO3PSi: C,
30.67; H, 5.47; N, 2.24. Found: C, 30.57; H, 5.46; N, 2.14. IR
data for 8: 1H NMR (CD2Cl2, 293 K): δ -14.11 (dt, J HP
148.2, 21.9, 1H, Ir-H), 1.38 (dd, J HP ) 7.7, 0.9, 9H, PCH3),
1.85 (d, J HP ) 9.7, 18H, PCH3), 3.63, 4.15, 4.30, 5.04, 6.31 (all
m, 1H each, CH). 31P{1H} NMR (CD2Cl2, 293 K): δ -55.51
)
(dd, J PP ) 20.5, 20.8), -52.85 (d, J PP ) 20.5), -51.04 (d, J PP
)
20.8). 13C{1H} NMR (CD2Cl2, 293 K): δ 15.39 (dt, J CP ) 28.8,
1.7, PCH3), 23.45 (ddd, J CP ) 36.9, 3.9, 1.7, PCH3), 23.54 (ddd,
J CP ) 37.1, 3.8, 1.7, PCH3), 52.92 (d, J CP ) 24.7, CH), 55.13
1
(cm-1): 2202 ν(Ir-H). H NMR (CD2Cl2, 293 K): δ -17.36 (d,
J HP ) 15.9, 1H, Ir-H), 1.68 (d, J HP ) 11.1, 9H, PCH3), 2.61
(d, J CP ) 1.2, 3H, NCCH3), 2.30-2.90 (m, 8H, CH2), 3.50 (s,
9H, SiOCH3), 4.76, 5.11, 5.35, 5.45 (all m, 1H each, CH). 31P-
{1H} NMR (CD2Cl2, 293 K): δ -33.88 (s). 13C{1H} NMR (CD2-
Cl2, 293 K): δ 3.75 (s, NCCH3), 17.15 (d, J CP ) 40.0, PMe3),
27.28 (d, J CP ) 3.0, CH2), 30.11 (s, CH2), 30.38 (d, J CP ) 2.5,
CH2), 33.94 (s, CH2), 50.45 (s, SiOCH3), 90.36 (d, J CP ) 11.0,
CH), 91.92 (d, J CP ) 9.0, CH), 103.21, 103.65 (both s, CH),
124.51 (s, NCCH3).
(d, J CP ) 26.9, CH), 93.02 (d, J CP ) 0.9, CH), 122.92 (d, J CP
4.8, CH), 135.84 (dd, J CP ) 4.4, 0.8, CH).
)
P r ep a r a tion of [Ir H2(1,2,5,6-η-C8H12)(NCCH3)(P Me3)]-
BF 4 (9). A solution of 1 (125 mg, 0.20 mmol) in acetone (4 mL)
was stirred under dihydrogen atmosphere (P ) 1 atm) for 1 h
at 253 K. The resulting pale yellow solution was concentrated
to ca. 0.5 mL, and diethyl ether was slowly added to give a
white solid. The solid was separated by decantation, washed
with ether, and dried in vacuo: yield 59 mg (70%). Anal. Calcd
for C13H26BF4IrNP: C, 30.84; H, 5.18; N, 2.77. Found: C, 31.14;
H, 4.98; N, 2.33. IR (cm-1): 2330 ν(CtN), 2209 ν(Ir-H). 1H
NMR (CD2Cl2, 243 K): δ -17.01 (d, J HP ) 18.0, 1H, Ir-H),
-12.70 (d, J HP ) 21.0, 1H, Ir-H), 1.62 (d, J HP ) 11.0, 9H,
PCH3), 1.98-2.58 (m, 8H, CH2), 2.64 (s, 3H, NCCH3), 4.57 (m,
2H, CH), 4.78 (m, 1H, CH), 5.33 (m, 1H, CH). 31P{1H} NMR
(CD2Cl2, 243 K): δ -34.21 (s). 13C{1H} NMR (CD2Cl2, 243 K):
δ 2.77 (s, NCCH3), 18.22 (d, J CP ) 40.7, PCH3), 27.75 (s, CH2),
29.27 (d, J CP ) 1.2, CH2), 29.47 (d, J CP ) 2.3, CH2), 34.81 (s,
P r ep a r a tion of [Ir H(SiP h 3)(1,2,5,6-η-C8H12)(NCCH3)-
(P Me3)]BP h 4 (13). The procedure described for 11, using
compound 1 (125 mg, 0.25 mmol) and HSiPh3 (64.5 mg, 0.25
mmol) as starting materials, afforded a yellow oil. This oil was
dissolved in methanol at 233 K and treated with an excess of
NaBPh4 to afford a yellow solid. The solid was separated by
decantation, washed with methanol, and dried in vacuo: yield
127 mg (51%). Anal. Calcd for C55H60BIrNPSi: C, 66.25; H,
6.06; N, 1.40. Found: C, 66.67; H, 6.32; N, 1.89. IR (cm-1):
1
2264 ν(Ir-H). H NMR (CD2Cl2, 243 K): δ -16.53 (d, J HP
)
18.0, 1H, Ir-H), 0.93 (d, J HP ) 10.4, 9H, PCH3), 1.60 (m, 2H,
CH2), 1.80 (s, 3H, NCCH3), 2.02, 2.14, 2.39, 2.49, 2.78, 3.13
(all m, 1H each, CH2), 3.58 (m, 1H, CH), 4.75 (m, 2H, CH),
5.16 (m, 1H, CH). 31P{1H} NMR (CD2Cl2, 243 K): δ -39.93
(s). 13C{1H} NMR (CD2Cl2, 243 K): δ 2.86 (s, NCCH3), 16.00
(d, J CP ) 41.0, PCH3), 25.85, 25.97, 30.34, 38.20 (all s, CH2),
91.55 (d, J CP ) 8.0, CH), 92.48 (d, J CP ) 11.8, CH), 98.70,
103.02 (both s, CH), 124.55 (s, NCCH3). The NMR signals
corresponding to phenyl groups have been omitted.
CH2), 88.65 (s, CH), 89.24 (d, J CP ) 7.6, CH), 89.68 (d, J CP
5.4, CH), 89.94 (s, CH), 123.63 (s, NCCH3).
)
P r ep a r a tion of [Ir H(1-K-4,5-η-C8H13)(NCCH3)2(P Me3)]-
BF 4 (10). A solution of 1 (125 mg, 0.20 mmol) in acetonitrile
(4 mL) was stirred under dihydrogen atmosphere (P ) 1 atm)
for 15 min at room temperature. The solution was concentrated
to ca. 0.5 mL, and diethyl ether was added to give a yellow
solid. When the solid was separated by decantation, washed
with diethyl ether, and taken to dryness, it transformed into
a yellow oil. This oil could be dissolved and precipitated as a
yellow solid, although again it became an oil after isolation.
The NMR analysis of this oil in CDCl3 at 233 K showed the
[Ir H(SiP h 3)(1,2,4,5-η-C8H12)(NCCH3)(P Me3)]BP h 4 (14).
A NMR tube containing a solution of 13 in CD2Cl2 (0.5 mL)
was placed at 273 K for 4 h. After this period of time the NMR
spectra of the resulting solution revealed the presence of a
mixture containing compound 13 (ca. 50% of the reaction
mixture) and two new species 14 and 15 in approximately 1:1
molar ratio. The evolution of this solution at 293 K for 1 h
quantitatively produced complex 15. Partial data for 14: 1H
NMR (CD2Cl2, 233 K): δ -16.51 (d, J HP ) 18.0, 1H, Ir-H),
1.53 (d, J HP ) 10.9, 9H, PCH3), 2.11 (s, 3H, NCCH3), 3.60, 4.36
(both m, 1H each, CH), 4.90 (m, 2H, CH). 31P{1H} NMR (CD2-
Cl2, 233 K): δ -35.46 (s). 13C{1H} NMR (CD2Cl2, 233 K): δ
3.28 (s, NCCH3), 16.79 (d, J CP ) 40.9, PCH3), 26.79, 27.06,
29.56, 36.86 (all s, CH2), 90.03 (d, J CP ) 9.4, CH), 91.61 (d,
J CP ) 11.4, CH), 99.45, 103.59 (both s, CH), 123.41 (s, NCCH3).
1
presence of 10 as the only reaction product. H NMR (CDCl3,
233 K): δ -20.35 (dd, J HP ) 22.2, J HH ) 3.9, 1H, Ir-H), 1.11
(m, 2H, CH2), 1.55 (m, 1H, CH), 1.67 (d, J HP ) 8.7, 9H, PCH3),
1.70, 1.80, 2.05 (all m, 2H each, CH2), 2.24, 2.43 (both s, 3H
each, NCCH3), 2.45, 3.21 (both m, 1H each, CH2), 4.75, 4.78
(both m, 1H each, CH). 31P{1H} NMR (CDCl3, 233 K): δ -29.79
(s). 13C{1H} NMR (CDCl3, 233 K): δ 2.77, 3.14 (both s, NCCH3),
4.81 (d, J CP ) 3.7, Ir-CH), 15.25 (d, J CP ) 38.7, PCH3), 24.75,
30.59, 39.05 (all s, CH2), 24.88 (d, J CP ) 2.3, CH2), 41.23 (d,
J CP ) 5.3, CH2), 84.32 (d, J CP ) 10.1, CH), 87.40 (d, J CP ) 14.7,
CH), 118.36, 121.48 (both s, NCCH3).
P r ep a r a tion of [Ir H(SiEt3)(1,2,5,6,-η-C8H12)(NCCH3)-
(P Me3)]BF 4 (11). A solution of 1 (125 mg, 0.20 mmol) in CH2-
Cl2 (2 mL) at 233 K was treated with HSiEt3 (31 µL, 0.20
mmol) and stirred for 10 min. The resulting yellow solution
was concentrated to ca. 0.5 mL, and diethyl ether was added
to give a pale yellow solid. The solid was separated by
decantation, washed with diethyl ether, and dried in vacuo:
yield 83 mg (67%). Anal. Calcd for C19H40BF4IrNPSi: C, 36.77;
H, 6.50; N, 2.26. Found: C, 37.27; H, 6.91; N, 2.41. IR (cm-1):
P r ep a r a tion of [Ir H(SiP h 3)(1,2,3,4-η-C8H12)(NCCH3)-
(P Me3)]BP h 4 (15). A solution of 13 (100 mg, 0.10 mmol) in
CH2Cl2 (2 mL) was allowed to react at room temperature for
1 h. The resulting solution was concentrated to ca. 0.5 mL,
and diethyl ether was added to give a pale yellow solid. The
solid was separated by decantation, washed with diethyl ether,
and dried in vacuo: yield 83 mg (83%). Anal. Calcd for C55H60
-
BIrNPSi: C, 66.25; H, 6.06; N, 1.40. Found: C, 66.05; H, 5.74;
N, 1.20. 1H NMR (CD2Cl2, 233 K): δ -16.46 (d, J HP ) 12.9,
1H, Ir-H), 1.31 (d, J HP ) 10.8, 9H, PCH3), 1.83 (s, 3H, NCCH3),
2.25-2.65 (m, 8H, CH2), 4.40 (m, 2H, CH), 4.81, 4.98 (both m,
1H each, CH). 31P{1H} NMR (CD2Cl2, 233 K): δ -32.88 (s).
13C{1H} NMR (CD2Cl2, 233 K): δ 2.56 (s, NCCH3), 14.41 (d,
J CP ) 40.6, PCH3), 27.76, 29.60, 30.89, 33.05 (all s, CH2), 91.23,
2206 ν(Ir-H). 1H NMR (CDCl3, 233 K): δ -17.19 (d, J HP
)
18.0, 1H, Ir-H), 0.51, 0.68 (both m, 3H each, SiCH2CH3), 0.87
(m, 9H, SiCH2CH3), 1.65 (d, J HP ) 10.3, 9H, PCH3), 2.00 (m,
1H, CH2), 2.24-2.60 (m, 4H, CH2), 2.63 (s, 3H, NCCH3), 2.67
(m, 2H, CH2), 3.08 (m, 1H, CH2), 4.39, 5.11, 5.19, 5.29 (all m,
1H each, CH). 31P{1H} NMR (CDCl3, 233 K): δ -35.4 (s). 13C-
{1H} NMR (CD2Cl2, 233 K): δ 4.77 (s, NCCH3), 7.65 (m, SiCH2-
92.65 (both s, CH), 93.91 (d, J CP ) 13.9, CH), 98.15 (d, J CP
)

5416 Organometallics, Vol. 22, No. 26, 2003
Mart´ın et al.
11.5, CH), 122.90 (s, NCCH3). The NMR signals corresponding
to phenyl groups have been omitted.
(cross-linked methyl silicone gum, 25 m × 0.32 mm × 0.17
µm) at an initial temperature of 353 K for 4.5 min followed by
a rate ramp of 22 K/min to a final temperature of 493 K.
Calibration of the detector response to the substrates and
products was made by comparing the GC integrals with those
obtained in the same samples by 13C{1H} NMR, setting the
relaxation delay between pulses to 20 s. Products were
P r ep a r a tion of [Ir H(CtCP h )(1,2,5,6-η-C8H12)(NCCH3)-
(P Me3)]BF 4 (16). A solution of 1 (125 mg, 0.20 mmol) in CH2-
Cl2 (2 mL) at 253 K was treated with phenylacetylene (22 µL,
0.20 mmol) and allowed to react for 30 min. The resulting
solution was concentrated to ca. 0.5 mL, and diethyl ether was
added to give a pale yellow solid. The solid was separated by
decantation, washed with diethyl ether, and dried in vacuo:
yield 87 mg (72%). Anal. Calcd for C21H30BF4IrNP: C, 41.60;
H, 4.99; N, 2.31. Found: C, 42.01; H, 5.25; N, 2.25. IR (cm-1):
1
identified by H NMR and GC-MS analysis on the mixtures
of reaction products.
Str u ctu r a l An a lysis of Com p lexes 2, 4b, a n d 17. X-ray
data were collected at 100.0(2) K on a Bruker SMART APEX
CCD diffractometer with graphite-monochromated Mo KR
radiation (λ ) 0.71073 Å) using ω scans (0.3°). Data were
collected over the complete sphere by a combination of four
sets and corrected for absorption using a multiscan method
applied with the SADABS program.27 The structures were
solved by the Patterson method. Refinement, by full-matrix
least squares on F2 using SHELXL97,28 was similar for all
complexes, including isotropic and subsequently anisotropic
displacement parameters for all non-hydrogen nondisordered
atoms. Particular details concerning the presence of solvent,
static disorder, and hydrogen refinement are listed below. All
the highest electronic residuals were observed in close proxim-
ity of the Ir centers and make no chemical sense.
2212 ν(Ir-H), 2124 ν(CtC). 1H NMR (CD2Cl2, 233 K):
δ
-16.90 (d, J HP ) 13.2, 1H, Ir-H), 1.75 (d, J HP ) 11.7, 9H,
PCH3), 2.20-2.60 (m, 8H, CH2), 2.64 (s, 3H, NCCH3), 4.76,
4.83, 4.98, 5.55 (all m, 1H each, CH), 7.10-7.40 (m, 5H, CH).
31P{1H} NMR (CD2Cl2, 233 K): δ -30.12 (s). 13C{1H} NMR
(CD2Cl2, 233 K): δ 4.71 (s, NCCH3), 15.42 (d, J CP ) 41.9,
PCH3), 28.03, 31.74, 32.01, 33.50 (all s, CH2), 79.91 (d, J CP
13.6, Ir-CtCPh), 89.22 (s, CH), 98.03 100.93 (both d, J CP
)
)
11.3, CH), 102.21 (s, Ir-CtCPh), 122.91 (s, NCCH3), 126.89
(s, CH), 127.21 (s, C), 128.69, 131.90 (both s, CH).
P r ep a r a t ion of [Ir (1,4-K-CH dC(P h )CH dCP h )(1,2,5,6-
η-C8H12)(NCCH3)(P Me3)]BF 4 (17). A solution 16 (120 mg,
0.20 mmol) in CH2Cl2 (2 mL) was treated with phenylacetylene
(22 µL, 0.20 mmol), and the mixture was stirred for 4 h at
273 K. The resulting solution was concentrated to ca. 1 mL,
and diethyl ether was slowly added to produce a white
microcrystalline solid. The solid was separated by decantation,
washed with diethyl ether, and dried in vacuo. Yield: 85 mg
(60%). Anal. Calcd for C29H36BF4IrNP‚0.5 C3H6O: C, 49.67;
Cr ysta l Da ta for 2. C27H34BF4IrNP, M ) 682.53; colorless
plate, 0.22 × 0.10 × 0.02 mm3; monoclinic, P21/n; a ) 16.711-
(3) Å, b ) 13.970(3) Å, c ) 11.966(2) Å, â ) 110.471(8)°; Z )
4; V ) 2617.1(8) Å3; Dc ) 1.732 g cm-3; µ ) 5.208 mm-1
,
minimum and maximum transmission factors 0.474 and 0.652;
2θmax ) 56.9°; 30 313 reflections collected, 6197 unique
[R(int) ) 0.0503]; number of data/restraints/parameters 6197/
0/344; final GoF 0.944, R1 ) 0.0309 [4717 reflns I > 2σ(I)],
1
H, 5.33; N, 1.90. Found: C, 50.16; H, 5.51; N, 2.18. H NMR
(CDCl3, 293 K): δ 1.47 (d, J HP ) 10.8, 9H, PCH3), 2.22 (d,
J HP ) 0.9, 3H, NCCH3), 2.3-2.8 (m, 8H, CH2), 4.63, 4.73, 5.19,
5.47 (all m, 1H each, CH), 6.77 (dd, J HH ) 3.0, J HP ) 0.9, 1H,
CHdC(Ph)CHdCPh), 6.94 (m, 2H, CH), 7.18 (m, 2H, CH), 7.28
(m, 4H, CH), 7.42 (m, 2H, CH), 7.49 (dd, J HP ) 6.0, J HH ) 3.0,
1H, CHdC(Ph)CHdCPh). 31P{1H} NMR (CDCl3, 293 K): δ
-32.05 (s). 13C{1H} NMR (CDCl3, 293 K): δ 3.77 (s, NCCH3),
wR2 ) 0.0622 for all data; largest difference peak 2.097 e Å-3
.
Hydrogen atoms were included in calculated positions and
refined riding on carbon atoms with the thermal parameter
related to bonded atoms, or in observed positions and refined
freely.
12.65 (d, J CP ) 42.3, PCH3), 27.54 (s, CH2), 28.01 (d, J CP
)
Cr ysta l Da ta for 4b. C16H33BF4IrNP2, M ) 580.38; color-
less irregular block, 0.20 × 0.10 × 0.08 mm3; monoclinic,
P21/c; a ) 9.9665(8) Å, b ) 12.3631(10) Å, c ) 16.6245(14) Å,
3.0, CH2), 30.65 (d, J CP ) 4.1, CH2), 31.91 (s, CH2), 100.53 (s,
CH), 101.22 (d, J CP ) 11.0, CH), 101.75 (s, CH), 111.58 (d,
J CP ) 11.5, CH), 123.75 (s, NCCH3), 125.21, 126.01, 126.53,
126.84, 128.00 (all s, CH), 128.01 (d, J CP ) 15.0, CHdC(Ph)-
CHdCPh), 128.70 (s, CH), 139.25 (s, CHdC(Ph)CHdCPh),
139.64, 148.32 (both s, C), 155.68 (d, J CP ) 3.5, CHdC(Ph)-
CHdCPh), 158.57 (d, J CP ) 11.1, CHdC(Ph)CHdCPh).
P r ep a r a tion of [Ir (TF B)(NCCH3)(P iP r 3)]BF 4 (18). The
compound was prepared following the procedure described for
1 by using [Ir(µ-OMe)(TFB)]2 (150.0 mg, 0.17 mmol) and
[HPiPr3]BF4 (82.8 mg, 0.33 mmol): yield 188 mg (80%). Anal.
Calcd for C23H30BF8IrNP: C, 39.10; H, 4.28; N, 1.98. Found:
C, 38.72; H, 4.08; N, 1.89. 1H NMR (acetone-d6, 293 K): δ 1.28
(dd, J HP ) 14.1, J HH ) 7.2, 9H, PCHCH3), 2.30 (m, 3H,
PCHCH3), 2.68 (s, 3H, NCCH3), 3.45 (br, 2H, CH), 4.45 (br,
2H, CH), 5.81 (m, 2H, CH). 31P{1H} NMR (acetone-d6, 293 K):
δ 32.62 (s). 19F NMR (acetone-d6, 293 K): δ -162.53 (m, 2F,
TFB), -152.83, -152.78 (both s, 11BF4 and 10BF4), -149.29 (m,
2F, TFB).
â ) 90.775(1)°; Z ) 4; V ) 2048.2(3) Å3; Dc ) 1.882 g cm-3
;
µ ) 6.710 mm-1, minimum and maximum transmission factors
0.388 and 0.545; 2θmax ) 57.8°; 24 476 reflections collected,
4937 unique [R(int) ) 0.0382]; number of data/restraints/
parameters 4937/0/245; final GoF 0.900, R1 ) 0.0251 [4168
reflns I > 2σ(I)], wR2 ) 0.0492 for all data; largest difference
peak 2.820 e Å-3. Hydrogen atoms were included in calculated
positions and refined riding on carbon atoms, or in observed
positions and refined freely with the thermal parameter
related to bonded atoms.
Cr ysta l Da ta for 17. C29H36BF4IrNP‚0.5 C3H6O, M )
737.61; colorless irregular block, 0.14 × 0.12 × 0.10 mm3;
monoclinic, C2/c; a ) 33.404(3) Å, b ) 11.7355(11) Å, c )
32.244(3) Å, â ) 90.264(2)°; Z ) 16; V ) 12640(2) Å3; Dc )
1.550 g cm-3; µ ) 4.321 mm-1, minimum and maximum
transmission factors 0.307 and 0.684; 2θmax ) 55°; 69 711
reflections collected, 14 435 unique [R(int) ) 0.1322]; number
of data/restraints/parameters 69 711/226/779; final GoF 1.023,
R1 ) 0.0674 [8953 reflns I > 2σ(I)], wR2 ) 0.1484 for all data;
largest difference peak 2.355 e Å-3. A BF4 anion was found to
be disordered by rotation around a B-F bond. This anion and
the two solvent molecules were refined with retraints in the
geometry and in the thermal parameters. Hydrogen atoms
were included in calculated positions and refined riding on the
Ca ta lytic Exp er im en ts. The reactions were carried out
under argon in 1,2-dichloroethane with magnetic stirring. The
equipment consisted of a 50 mL two-necked flask fitted with
a condenser and a septum to allow sampling without opening
the system. In a typical procedure, 4 mL of reactants solution
(PhCtCH and silane) in 1,2-dichloroethane was injected into
a solution of the catalyst precursor in 4 mL of the same solvent.
The flask was then immersed in a thermostated bath. Positive
pressure of argon (ca. 1.1 atm) was maintained in the reaction
mixture during the runs to exclude the penetration of oxygen
during sampling. The progress of the reactions was followed
by GC on a Hewlett-Packard HP-5890-Series II gas chromato-
graph with a FID detector and using a HP-Ultra 1 column
(27) Blessing, R. H. Acta Crystallogr. 1995, A51, 33-38. SADABS:
Area-detector absorption correction; Bruker-AXS: Madison, WI, 1996.
(28) SHELXTL Package v. 6.10; Bruker-AXS: Madison, WI, 2000.
Sheldrick, G. M. SHELXS-86 and SHELXL-97; University of Go¨ttin-
gen: Go¨ttingen, Germany, 1997.

Versatility of Cyclooctadiene Ligands
Organometallics, Vol. 22, No. 26, 2003 5417
corresponding carbon atoms, or in observed positions and
refined freely.
Su p p or t in g In for m a t ion Ava ila b le: 1H-COSY, 1H-
1
NOESY, and H,13C-HSQC NMR spectra of a mixture of 6, 7,
and 8, and details of the X-ray crystallographic study of 2, 4b,
and 17 (PDF). A crystallographic information file (CIF) on the
structural analysis of complexes 2, 4b, and 17. This material
is available free of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. Financial support for this re-
search was provided by Plan Nacional de Investigacio´n,
MCYT (Project No. BQU2000-1170). We wish to thank
Dr. Enrique On˜ate for his important contribution to this
work.
OM034218G