An examination of C-H bond activation by cationic TpMe2Ir(III) complexes

Article abstract of DOI:10.1021/om010697c

Synthesis and characterization of a set of iridium(III) compounds utilizing the sterically encumbering hydridotris(3,5-dimethylpyrazolyl)borate ligand (Tp^Me2) has been performed, and a comparison with the corresponding Cp* complexes is presented. Tp^Me2(PMe₃)Ir(Me)OTf (7, OTf = O₃SCF₃) was synthesized and found to be unreactive toward a variety of C-H bonds, in contrast to the behavior of Cp*(PMe₃)Ir(Me)OTf (1). We have rationalized this lack of reactivity in terms of an electronic effect rather than a steric effect imposed by the Tp^Me2 ligand. Metathesis of the triflate ligand with the BAr_f (BAr_f = B[3,5-C₆H₃ (CF₃)₂]₄) anion under a N₂ atmosphere produces the dinitrogen complex [Tp^Me2(PMe₃)Ir(N₂)(Me)][BAr_f] (3-N₂). Compound 3-N₂ is indeed reactive toward dative ligands, H₂, and hydrocarbons, activating the C-H bonds of benzene and aldehydes but not those of saturated hydrocarbons. A rationale for the difference in behavior between the Cp* and Tp^Me2 systems with respect to C-H activation is presented.

Full text of DOI:10.1021/om010697c

Organometallics 2001, 20, 4819-4832
4819
An Exa m in a tion of C-H Bon d Activa tion by Ca tion ic
Tp Me Ir (III) Com p lexes
2
David M. Tellers and Robert G. Bergman*
Department of Chemistry and Center for New Directions in Organic Synthesis, University of
California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California 94720
Received August 1, 2001
Synthesis and characterization of a set of iridium(III) compounds utilizing the sterically
encumbering hydridotris(3,5-dimethylpyrazolyl)borate ligand (TpMe ) has been performed,
2
and a comparison with the corresponding Cp* complexes is presented. TpMe (PMe3)Ir(Me)-
2
OTf (7, OTf ) O3SCF3) was synthesized and found to be unreactive toward a variety of C-H
bonds, in contrast to the behavior of Cp*(PMe3)Ir(Me)OTf (1). We have rationalized this
lack of reactivity in terms of an electronic effect rather than a steric effect imposed by the
TpMe ligand. Metathesis of the triflate ligand with the BArf (BArf ) B[3,5-C6H3(CF3)2]4)
2
anion under a N2 atmosphere produces the dinitrogen complex [TpMe (PMe3)Ir(N2)(Me)][BArf]
2
(3-N2). Compound 3-N2 is indeed reactive toward dative ligands, H2, and hydrocarbons,
activating the C-H bonds of benzene and aldehydes but not those of saturated hydrocarbons.
A rationale for the difference in behavior between the Cp* and TpMe systems with respect
2
to C-H activation is presented.
Sch em e 1
In tr od u ction
The controlled, efficient functionalization of saturated
hydrocarbons remains an elusive goal.1-5 We and others
have focused on developing homogeneous transition
metal complexes capable of catalytically dehydrogenat-
ing alkanes (eq 1).6-10
R-CH2CH3 [M]8 R-CHdCH2 + H2
(1)
A general mechanism for the metal-catalyzed dehydro-
genation of an alkane involves oxidative addition of the
alkane to an unsaturated metal hydride species, reduc-
tive elimination of H2, â-hydride elimination, and dis-
sociation of the olefin to regenerate the metal hydride.11
In addition to being able to activate the strong alkane
C-H bond, the metal complex must neither bind the
olefin product irreversibly11 nor react with itself.
We previously reported the synthesis and study of two
Ir(III) compounds, Cp*(PMe3)Ir(Me)OTf (1) (Cp* ) C5-
Me5, OTf ) OSO2CF3) and [Cp*(PMe3)Ir(Me)(ClCH2Cl)]-
[BArf] (2-CH2Cl2) (BArf ) B[3,5-C6H3(CF3)2]4), that are
capable of selectively cleaving carbon-hydrogen bonds
in a wide variety of hydrocarbons under mild conditions
(three examples are illustrated in Scheme 1).12-17 The
reaction of 1 or 2-CH2Cl2 with ethane, shown in Scheme
1, to produce the ethylene hydride complex [Cp*-
(PMe3)IrH(CH2CH2)][X] (X ) OTf, BArf) demonstrated
that “Cp*(PMe3)IrMe+” could potentially serve as a
precursor to a dehydrogenation catalyst. Unfortunately,
attempts to induce olefin dissociation from [Cp*-
(PMe3)IrH(CH2CH2)][X] were unsuccessful. Addition-
ally, the potential dehydrogenation catalyst, [Cp*-
(PMe3)IrH(CH2Cl2)][X], irreversibly dimerizes at tempera-
tures greater than -20 °C.18
In an effort to address these shortcomings, we focused
on increasing the size of the ancillary ligand at the
metal center in hopes that this would lower the barrier
of olefin dissociation from iridium and prevent the
decomposition of an iridium hydride intermediate. One
such ligand that would allow us to test this hypothesis
(1) Stahl, S. S.; Labinger, J . A.; Bercaw, J . E. Angew. Chem., Int.
Ed. 1998, 37, 2181-2192.
(2) Sen, A. Acc. Chem. Res. 1998, 31, 550-557.
(3) Shilov, A. E.; Shul’pin, G. B. Chem. Rev. 1997, 97, 2879-2932.
(4) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H.
Acc. Chem. Res. 1995, 28, 154-162.
(12) Burger, P.; Bergman, R. G. J . Am. Chem. Soc. 1993, 115,
10462-10463.
(13) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970-1973.
(14) Arndtsen, B. A.; Bergman, R. G. J . Organomet. Chem. 1995,
504, 143-146.
(5) McCosh, D. Pop. Sci. 1999, 254, 56-59.
(6) For examples, see refs 7-10.
(7) Kanzelberger, M.; Singh, B.; Czerw, M.; Krogh-J espersen, K.;
Goldman, A. S. J . Am. Chem. Soc. 2000, 122, 11017-11018.
(8) Fuchen, L.; Pak, E. B.; Singh, B.; J ensen, C. M.; Goldman, A. S.
J . Am. Chem. Soc. 1999, 121, 4086-4087.
(15) Luecke, H. F.; Arndtsen, B. A.; Burger, P.; Bergman, R. G. J .
Am. Chem. Soc. 1996, 118, 2517-2518.
(16) Alaimo, P. J .; Arndtsen, B. A.; Bergman, R. G. Organometallics
2000, 19, 2130-2143.
(9) Gupta, M.; Hagen, C.; Kaska, W. C.; Cramer, R. E.; J ensen, C.
M. J . Am. Chem. Soc. 1997, 119, 840-841.
(10) Aoki, T.; Crabtree, R. H. Organometallics 1993, 12, 294-298.
(11) Niu, S.; Hall, M. B. J . Am. Chem. Soc. 1999, 121, 3992-3999.
(17) Tellers, D. M.; Yung, C. M.; Arndtsen, B. A.; Bergman, R. G.
Submitted for publication.
(18) Golden, J . T.; Andersen, R. A.; Bergman, R. G. J . Am. Chem.
Soc. 2001, 123, 5837-5838.
10.1021/om010697c CCC: $20.00 © 2001 American Chemical Society
Publication on Web 10/10/2001

4820 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
Sch em e 2
is the hydridotris(3,5-dimethylpyrazolyl)borate (TpMe
)
2
ligand. The TpMe ligand is isoelectronic to Cp* but
occupies substantially increased space in the coordina-
tion sphere of metals.19,20 We therefore decided to
2
develop the methodology needed to synthesize the TpMe
2
analogues of 1 and 2 and investigate their C-H activat-
ing properties, hoping that the use of the bulky TpMe
2
ligand would promote rapid formation of the corre-
sponding 16-electron Ir cations.21
This paper details the preparation of a series of TpMe
-
2
Ir(III) compounds, including TpMe (PMe3)Ir(Me)OTf (7).
22
2
This compound does not react with C-H bonds, and an
examination of the differences between the TpMe and
2
Cp* ligands revealed that this lack of reactivity is the
result of an electronic effect imposed by the TpMe ligand.
2
Salt metathesis with 7 facilitated the synthesis of [TpMe
-
2
(PMe3)Ir(Me)N2][BArf] (3-N2), the first structurally
characterized monomeric iridium dinitrogen complex.
The reactions of 3-N2 with dative ligands, C-H bonds,
and H2 are detailed herein.
F igu r e 1. ORTEP diagram of TpMe (PMe3)IrMeOTf (7).
Resu lts
2
Thermal ellipsoids are shown at the 50% probability level.
Hydrogen atoms are omitted for clarity.
Syn th esis of th e Tp Me Ir (III) Com p lexes. Routes
2
analogous to those used in the synthesis of compounds
112 and 213 were not successful with the TpMe ligand.
2
Ta ble 1. Selected In tr a m olecu la r Dista n ces a n d
An gles for Tp Me (P Me3)Ir MeOTf (7)
2
As a result, we developed a new route into the TpMe
(PMe3)IrMe(X) systems (Scheme 2). Treatment of TpMe
-
-
2
2
Distance (Å)
(PMe3)IrH2 (4)23 with 2 equiv of NBS in CCl4 resulted
Ir-O(1)
Ir-C(1)
Ir-P(1)
2.128(5)
2.098(7)
2.289(2)
Ir-N(2)
Ir-N(4)
Ir -N(6)
2.028(6)
2.134(6)
2.230(6)
in the clean formation of TpMe (PMe3)IrBr2 (5) (53%
2
yield). This compound can be selectively monoalkylated
with methyllithium to generate TpMe (PMe3)Ir(Me)Br (6)
2
Angles (deg)
O(1)-Ir(1)-C(1)
C(1)-Ir(1)-P(1)
P(1)-Ir(1)-O(1)
91.2(2)
92.6(2)
97.5(1)
N(2)-Ir(1)-N(4)
N(4)-Ir(1)-N(6)
N(6)-Ir(1)-N(2)
84.7(2)
84.0(2)
94.3(2)
(62% yield), which underwent facile anion metathesis
upon treatment with AgOTf to provide TpMe (PMe3)Ir-
2
(Me)OTf (7) (47% yield). The structure of 7 was deter-
mined by X-ray crystallography (Figure 1). Interest-
ingly, the Ir-O bond length of 2.128(5) Å in 7 is much
shorter than the analogous bond length in Cp*(PMe3)-
Ir(Me)OTf (1) (2.216(10) Å).12 The data collection and
refinement parameters are listed in Table 5, and a list
of selected bond distances and angles is located in Table
1.
This short Ir-O bond length presaged our finding
that triflate 7 is unreactive toward a variety of hydro-
carbons, including benzene and methane. This stands
in contrast to the behavior of the Cp* analogue 1, which
rapidly cleaves the C-H bonds of all these substrates.12
Complex 7 is also inert toward Lewis bases. Displace-
ment of the triflate ligand by CO, PMe3, or CH3CN, all
of which are rapid for 1, is not observed, even at elevated
(19) Kitajima, N.; Tolman, B. W. Prog. Inorg. Chem. 1995, 43, 419-
531.
(20) Trofimenko, S. Scorpionates: The Coordination Chemistry of
Polypyrazolylborate Ligands; Imperial College: London, 1999.
(21) For a review of C-H activation by neutral TpRh and TpIr
complexes, see: Slugovc, C.; Padilla-Mart´ınez, I.; Sirol, S.; Carmona,
E. Coord. Chem. Rev. 2001, 213, 129-157.
(22) Some of these results have been communicated: Tellers, D. M.;
Bergman, R. G. J . Am. Chem. Soc. 2000, 122, 954-955.
(23) Oldham, W. J .; Heinekey, D. M. Organometallics 1997, 16, 467-
474.

Cationic TpMe Ir(III) Complexes
Organometallics, Vol. 20, No. 23, 2001 4821
2
Sch em e 3
temperatures (>75 °C) and pressures (>5 atm) in
dichloromethane solution.
In analogy with the enhanced reactivity of 2-CH2Cl2
relative to 1,13 we expected that replacing the triflate
anion in 7 with the noncoordinating BArf anion would
produce a more reactive species. Accordingly, treatment
of a dichloromethane solution of triflate 7 with NaBArf
under an argon atmosphere resulted in the quantitative
formation of [TpMe (PMe3)Ir(Me)CH2Cl2][BArf] (3-CH2Cl2)
2
(Scheme 3). Compound 3-CH2Cl2 is thermally sensitive,
and as a result, attempts to isolate it have been
unsuccessful. Confirmation of this assignment was
obtained by low-temperature 13C NMR spectroscopy,
where at -80 °C in CH2Cl2 a triplet at 62.4 ppm (1J C-H
) 186 Hz) is observed assigned to the carbon atom on
the dichloromethane molecule bound to the cationic
iridium center.24-26 Exchange with the bulk solvent
becomes fast on the NMR time scale at approximately
-20 °C. For [Cp*(PMe3)Ir(CH2Cl2)Me][BArf], attempts
to observe the bound dichloromethane were unsuccess-
ful even at -80 °C, presumably because exchange is
rapid even at this low temperature.
F igu r e 2. ORTEP diagram of the major component of the
cationic portion of [TpMe (PMe3)IrMeN2][BArf] (3-N2). Ther-
2
mal ellipsoids are shown at the 50% probability level.
Hydrogen atoms have been omitted for clarity.
ligand positions in 3-N2 prevented the determination
of exact bond lengths or angles.
Sp ectr oscop ic Obser va tion of [Cp *(P Me3)Ir Me-
(N2)][BAr f]. The affinity for dinitrogen over dichlo-
+
romethane exhibited by [TpMe (PMe3)IrMe] was sur-
2
prising considering the pentamethylcyclopentadienyl
analogue, [Cp*(PMe3)IrMe]+, preferably binds dichlo-
romethane under identical conditions. This observation
provided motivation to explore whether [Cp*(PMe3)-
IrMe(N2)][BArf] (2-N2) could be generated by subjecting
2-CH2Cl2 to high dinitrogen pressures. Placing a high-
pressure NMR tube containing a CD2Cl2 solution of
The thermal sensitivity of 3-CH2Cl2 prompted us to
explore whether other dative ligands could stabilize the
+
cationic [TpMe (PMe3)IrMe] fragment without drasti-
2
cally attenuating its reactivity. Dinitrogen effectively
serves this purpose. When 3-CH2Cl2 is placed under N2
(1 atm), displacement of CH2Cl2 occurs in less than 5
min to generate the isolable, thermally stable dinitrogen
complex 3-N2 (Scheme 3). Alternatively, 3-N2 can be
isolated in 74% yield by treating a dichloromethane
solution of triflate 7 with NaBArf under 1 atm of N2
(Scheme 3). Compound 3-N2 exhibits a strong infrared
absorption at 2225 cm-1 (CH2Cl2) assigned to the NtN
stretch. Substitution of 14N2 by 15N2 produces the
expected isotopic shift in the infrared spectrum to 2151
cm-1. This infrared behavior compares well with that
1
2-CH2Cl2 under 8 atm of dinitrogen results in H and
31P{1H} NMR spectroscopic resonances that are slightly
shifted with respect to those of the starting dichlo-
romethane complex.30 We attribute this shift to the
establishment of a rapid equilibrium between 2-CH2Cl2
and 2-N2 (eq 2) (vide infra). After venting the NMR tube,
the 1H and 31P{1H} NMR spectra indicate complete
reversion to 2-CH2Cl2.
of TpMe Ir(Ph)2N2 (2190 cm-1, Nujol) reported by Car-
2
mona and co-workers.27 Complex 3-N2 was further
characterized by single-crystal X-ray diffraction (Figure
2). Despite the fact that iridium was one of the first
metals found to coordinate N2,28 to our knowledge 3-N2
is the first structurally characterized monomeric iridium
dinitrogen complex to be reported. Two dimeric iridium
dinitrogen complexes have been verified crystallograph-
ically.27,29 Unfortunately, disorder in the Me and N2
Conclusive spectroscopic evidence for the formation
of a dinitrogen complex was obtained by high-pressure
infrared spectroscopy. Exposure of 2-CH2Cl2 to 10-40
atm of N2 resulted in observation of an IR absorbance
at 2207 cm-1, assigned to the NtN stretching mode of
2-N2 (Figure 3).30 This peak is red-shifted with respect
(24) Free CH2Cl2: δ 54 ppm (1J C-H ) 180 Hz).
(25) Vincent-Huhmann, J .; Scott, B. L.; Kubas, G. J . J . Am. Chem.
Soc. 1998, 120, 6808-6809.
(26) Peng, T.; Winter, C. H.; Gladysz, J . A. Inorg. Chem. 1994, 33,
2534-2542.
(27) Gutie´rrez-Puebla, E.; Monge, A.; Nicasio, M. C.; Pe´rez, P. J .;
Poveda, M. L.; Carmona, E. Chem. Eur. J . 1998, 4, 2225-2236.

4822 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
source of “CH2Cl+” (i.e., not the iridium-CH3). In a
control experiment, dissolution of PMe3 in CH2Cl2
results in the formation of [Me3PCH2Cl][Cl], but the
reaction is very slow (25 °C, t1/2 ) 10 days).31 This
+
demonstrates that [TpMe (PMe3)IrMe] dramatically
2
accelerates the rate of nucleophilic attack on dichlo-
romethane.
C-H Bon d Activa tion by 3-N2. In contrast to
triflate 7, compound 3-N2 reacts with the C-H bonds
of benzene and aldehydes. Reaction of 3-N2 with 1 equiv
of benzene in CH2Cl2 under a dinitrogen atmosphere
produces CH4 and [TpMe (PMe3)IrPh(N2)][BArf] (9) (76%,
2
t1/2 ) 3 h) (eq 5).
F igu r e 3. Infrared spectra of [Cp*(PMe3)IrMe][BArf] in
CH2Cl2 at various N2 pressures.
to the dinitrogen absorbance in 3-N2 (2225 cm-1). N2
coordination to 2 is completely reversible; the absor-
bance disappeared when N2 pressure is removed and
returns when nitrogen pressure is reintroduced. 31P{1H}
NMR spectroscopic analysis of an aliquot of this mixture
after venting the cell indicated that 2-CH2Cl2 had not
decomposed.
Complex 9 exhibits a strong infrared stretch at 2236
cm-1, which we attribute to iridium-bound N2. In the
1H NMR spectrum (CD2Cl2) of 9, five phenyl C-H bond
resonances are observed. This is likely the result of
hindered rotation about the Ir-Ph bond, as seen in
other TpIr systems.27,32
Rea ction of 3-N2 w ith Da tive Liga n d s. The dini-
trogen ligand in 3 is a better leaving group than the
triflate anion and as a result is readily displaced by
dative ligands in dichloromethane solution. Treating
A single-crystal X-ray diffraction study of 9 was
performed due to the disorder in the structure of 3-N2.
An ORTEP diagram of this molecule is shown in Figure
4. Selected bonding parameters are displayed in Table
2, and the data collection parameters for 9 are presented
in Table 5. As would be predicted by the inequivalent
aromatic resonances in the 1H NMR spectrum, the
phenyl moiety in 9 lies in the wedge created by the
3-N2 with CO, CH3CN, or AsPh3 yields [TpMe (PMe3)-
2
IrMe(L)][BArf] (L ) CO (77%), CH3CN (83%), AsPh3
(99%); t1/2 < 5 min) (eq 3).
pyrazole groups of the TpMe ligand. This orientation
2
likely minimizes interactions with the pyrazole moieties
and prevents Ir-phenyl rotation. The NtN bond length
in the dinitrogen ligand of 9 (1.095(6) Å) is slightly
shorter than that observed in the two dimeric iridium
dinitrogen complexes (1.13(3) Å27 and 1.176(13) Å29).
This bond length is identical to that observed in free
N2 (1.09 Å),33 demonstrating that the extent of back-
bonding into the N2 antibonding orbitals is negligible.
The reaction of 3-N2 with benzene is substantially
slower than that observed with the Cp* analogue 2.34
A similar difference in reaction rates is observed with
aldehydes. Treatment of 3-N2 with acetaldehyde and
p-tolualdehyde results in formation of the “O-bound”
An interesting deviation in the reactivity of 3-N2 is
observed with PMe3. Instead of the expected bisphos-
phine adduct, [TpMe (PMe3)2IrMe][BArf], the reaction of
2
3-N2 with PMe3 in dichloromethane produces TpMe
-
2
(PMe3)IrMe(Cl) (8) and the phosphonium salt [Me3-
PCH2Cl][BArf] (t1/2 ) 5 min, 25 °C) (eq 4).
1
aldehyde complexes [TpMe (PMe3)IrMe(η -OC(H)Me)]-
2
1
[BArf] (10) and [TpMe (PMe3)IrMe(η -OC(H)Tol)][BArf]
2
(11), respectively (Scheme 4). Although the aldehydes
(28) Karsch, H. H. Phosphorus Sulfur 1982, 12, 217-225.
(29) Collman, J . P.; Kubota, M.; Vastine, F. D.; Sun, J . Y.; Kang, J .
W. J . Am. Chem. Soc. 1968, 90, 5430-5437.
(30) Lee, D. W.; Kaska, W. C.; J ensen, C. M. Organometallics 1998,
17, 1-3.
(31) See Experimental Section for details.
(32) Ferrari, A.; Polo, E.; Ru¨egger, H.; Sostero, S.; Venanzi, L. M.
Inorg. Chem. 1996, 35, 1602-1608.
Performing the reaction with PMe3-d9 and 3-N2 in CH2-
Cl2 yields TpMe (PMe3-d0)IrMe(Cl)and [Me3PCH2Cl-d9]-
2
(33) Cohen, J . D.; Mylvaganam, M.; Fryzuk, M. D.; Loehr, T. M. J .
Am. Chem. Soc. 1994, 116, 9529-9534.
[BArf], demonstrating that the phosphonium salt is
generated from added phosphine. In CD2Cl2 solution,
(34) The Cp* analogue reacts with benzene at -30 °C (t1/2 ) 5 min).
Complex 3-CH2Cl2 reacts with C6H6 at 25 °C to produce [TpMe
-
2
only TpMe (PMe3)IrMe(Cl) and [Me3PCD2Cl][BArf] are
2
(PMe3)IrPh(CH2Cl2)][BArf] (t1/2 ) 15 min). Like 3-CH2Cl2, this complex
is thermally sensitive, preventing its isolation.
observed. This is consistent with the solvent being the

Cationic TpMe Ir(III) Complexes
Organometallics, Vol. 20, No. 23, 2001 4823
2
Ta ble 2. Selected In tr a m olecu la r Dista n ces a n d
An gles for [Tp Me (P Me3)Ir P h (N2)][BAr f] (9)
2
Distance (Å)
Ir-N(1)
1.950(5)
2.098(7)
2.289(2)
1.095(6)
Ir-N(4)
Ir-N(6)
Ir -N(8)
2.028(6)
2.115(4)
2.227(4)
Ir-C(16)
Ir-P(1)
N(1)-N(2)
Angles (deg)
N(1)-Ir(1)-C(16)
C(16)-Ir(1)-P(1)
P(1)-Ir(1)-N(1)
89.7(2)
92.8(1)
92.4(1)
N(4)-Ir(1)-N(6)
N(6)-Ir(1)-N(8)
N(8)-Ir(1)-N(4)
84.0(2)
84.9(2)
91.1(2)
Ta ble 3. P a r tia l List of NMR Ch em ica l Sh ifts Used
in Assign in g th e Str u ctu r es of Ald eh yd e
Com p lexes 10 a n d 11
compound
δ OdC(H)Ra
δ OdC(H)Rb
acetaldehyde
9.77
9.23
199.7
223.7
[TpMe PMe3(Me)Ir(OdC(H)Me)]-
2
[BArf] (10)
p-tolualdehyde
9.72
9.18
192.2
207.6
[TpMe PMe3(Me)Ir(OdC(H)Tol)]-
2
[BArf] (11)
a
b
500 MHz, CD2Cl2, 25 °C 125 MHz, CD2Cl2, 25 °C
1
observed in the H NMR spectrum of 12, due again to
hindered rotation of the aryl group. We were unable to
observe coalescence of these resonances by 1H NMR
spectroscopy (115 °C, 1,2-dichloroethane-d4).
F igu r e 4. ORTEP diagram of the cationic portion of [TpMe
-
2
(PMe3)IrPhN2][BArf]. Thermal ellipsoids are shown at the
50% probability level. Hydrogen atoms have been omitted
for clarity.
In contrast to 1 and 2, 3-N2 does not react with the
C-H bonds of saturated alkanes such as methane,
ethane, pentane, and cyclopropane. For example, when
a CD2Cl2 solution of 3-N2 is placed under an atmosphere
of 13CH4, no incorporation of the isotopic label into the
iridium complex is observed after heating at 45 °C for
2 days, at which point 3-N2 decomposes. Furthermore,
addition of an excess of ethane to CD2Cl2 solutions of
are bound directly to iridium, the aldehyde C-H bonds
are completely unreactive at room temperature. The “O-
bound” assignment (vs an “η2 CdO-bound” structure)
is based on NMR and IR spectroscopic data.35-37 As
1
demonstrated by the data in Table 3, the H and 13C-
{1H} NMR chemical shifts of the aldehyde complexes
are similar to those of the free aldehyde.38-42 An
η2-aldehyde complex would exhibit NMR resonances
shifted significantly upfield from the corresponding free
aldehyde.41 Furthermore, no phosphorus coupling to the
aldehydic protons of 10 and 11 is observed, as would be
predicted for an η2-aldehyde ligand.
44
3-N2 does not produce [TpMe (PMe3)IrH(CH2CH2)][BArf].
2
Rea ction of 3-N2 w ith H2. As described in the
Introduction, the design of a system capable of catalyti-
cally dehydrogenating alkanes would potentially involve
a metal hydride intermediate. We therefore examined
the reaction of 3-N2 with H2. Exposing a degassed CD2-
Cl2 solution of 3-N2 to an atmosphere of H2 for 3 h
While complexes 10 and 11 are stable at room
temperature, the aldehydic C-H bond is cleaved at
elevated temperatures (Scheme 4). Thermolysis of 10
at 75 °C in dichloromethane results in liberation of
methane and formation of the methyl carbonyl species
results in the formation of [TpMe (PMe3)IrH(CD2Cl2)]-
2
[BArf]. This compound is characterized by a resonance
2
at -21.60 ppm (d, J P-H ) 20 Hz). Exposing this
solution to N2 results in growth of a new hydride
2
[TpMe (PMe3)IrMe(CO)][BArf] (3-CO) (77%, t1/2 ) 3 h).
2
resonance at -18.80 (d, J P-H ) 19 Hz, 1H, Ir-H) with
Similarily, the tolyl carbonyl species [TpMe (PMe3)Ir-
2
concomitant loss of the resonance at -21.60 ppm. We
attribute this resonance to the hydride ligand of the new
(CO)Tol][BArf] (12) is obtained after heating dichlo-
romethane solutions of 11 at 105 °C (88%, t1/2 ) 4 h).43
Four inequivalent tolyl C-H bond resonances are
complex [TpMe (PMe3)IrH(N2)][BArf] (13). An infrared
2
absorbance at 2231 cm-1 assigned to the N2 stretch and
an absorbance at 2205 cm-1 assigned to the Ir-H
stretch are observed for 13. Substitution of 14N2 for 15N2
produces the expected isotopic shift of the former
absorption in the infrared spectrum to 2157 cm-1 and
(35) For examples of TpMo and TpW aldehyde complexes, see refs
36 and 37.
(36) Schuster, D. M.; White, P. S.; Templeton, J . L. Organometallics
2000, 19, 1540-1548.
(37) Caldarelli, J . L.; Wagner, L. E.; White, P. S.; Templeton, J . L.
J . Am. Chem. Soc. 1994, 116, 2878-2888.
no change in the stretch at 2205 cm-1
.
Preparative amounts of 13 can be obtained by placing
degassed CH2Cl2 solutions of 3-N2 under 1 atm of H2
and stirring for 3 h (Scheme 5). In this case, mixtures
(38) For a discussion of characterization and bonding modes of
transition metal-aldehyde complexes, see refs 39-42.
(39) Gladysz, J . A.; Boone, B. J . Angew. Chem., Int. Ed. Engl. 1997,
36, 550-583.
of [TpMe (PMe3)IrH(CH2Cl2)][BArf] and the known hy-
2
(40) Lenges, C. P.; Brookhart, M.; White, P. S. Angew. Chem., Int.
Ed. 1999, 38, 552-554.
45
drido-dihyrogen complex [TpMe (PMe3)IrH(H2)][BArf]
2
(41) Faller, J . W.; Ma, Y. J . Am. Chem. Soc. 1991, 113, 1579-1586.
(42) Cicero, R. L.; Protasiewicz, J . D. Organometallics 1995, 14,
4792-4798.
(44) Al´ıas, F. M.; Poveda, M. L.; Sellin, M.; Carmona, E. J . Am.
Chem. Soc. 1998, 120, 5816-5817.
(45) Oldham, W. J .; Hinkle, A. S.; Heinekey, D. M. J . Am. Chem.
Soc. 1997, 119, 11028-11036.
(43) For aldehyde activation by a TpMe Ir complex see: Gutierrez-
2
Puebla, E.; Monge, A.; Paneque, M.; Poveda, M. L. Salazar, V.;
Carmona, E. J . Am. Chem. Soc. 1999, 121, 248-249.

4824 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
Sch em e 4
are obtained. Placing this mixture under 40 atm of N2
a variety of hydrocarbons and dative ligands. From this
lack of reactivity we concluded that triflate dissociation
from 7 is substantially slower than it is in the corre-
sponding Cp* complex. We had predicted quite the
opposite: the larger coordination sphere occupied by the
results in clean conversion to [TpMe (PMe3)IrH(N2)]-
2
[BArf] (13) in 64% yield. Analytically pure material was
obtained by crystallization from CH2Cl2/pentane. Un-
fortunately, crystals suitable for X-ray analysis could
not be grown.
TpMe ligand should facilitate loss of the triflate leaving
2
Consistent with the increased steric bulk around the
metal, 13 is remarkably stable compared to the Cp*
analogue.18 Decomposition is not observed. This stability
is accompanied by reduced reactivity with hydrocarbons.
Treating solutions of this compound with hydrocarbons
(R-H) does not result in the liberation of hydrogen and
group.55,56 This lack of reactivity must be the result of
a difference in the electronic character of the TpMe and
2
Cp* ligands. In a search for precedent, a survey of the
Tp and TpMe literature revealed different and some-
2
times conflicting reports on the relative electron-donat-
ing properties of the Cp and Cp* vs Tp and TpMe ligands
2
formation of [TpMe (PMe3)IrR(N2)][BArf], nor does the
2
toward different metals.57 In several cases, the Tp or
TpMe ligand is claimed to be a stronger electron donor
hydrido complex catalyze hydrogen/deuterium exchange,
2
as is observed in the Cp* case.18,46
than Cp or Cp*. This discrepancy encouraged us to focus
more specifically on the electronic differences between
TpMe and Cp* bound to iridium.
2
Discu ssion
Infrared spectroscopy often provides a reliable mea-
sure of electron density at a metal center, especially for
metal carbonyl and N2 complexes.58 A table of infrared
Rea ctivity of Tp Me (P Me3)Ir MeOTf. Our reactivity
2
studies with the Cp* complexes 1 and 2 demonstrated
that the triflate complex 1 and the CD2Cl2/borate salt
2 lead to common or similar cationic Ir intermediates
via dissociation of triflate or dichloromethane.17,47-53 We
therefore hypothesized that replacing the Cp* ligand
data for a series of Tp/TpMe and Cp/Cp* iridium
2
complexes is provided in Table 4.59-66 In all cases, the
CO and N2 stretches of the Cp/Cp* compounds are red-
shifted with respect to the Tp/TpMe complexes. These
2
with the more sterically encumbering TpMe ligand (cone
2
data clearly indicate a less electron rich metal center
angle ) 276° vs 182° for Cp*)19 would promote dissocia-
tion of the leaving group and facilitate formation of the
unsaturated intermediate thought to be responsible for
hydrocarbon C-H bond activation.54
in the TpMe case. Further support for this difference
2
was obtained by examining the proton-transfer equili-
(55) Support for dissociative loss of the triflate ligand can be found
in ref 56.
(56) Tellers, D. M.; Bergman, R. G., Tellers, D. M.; Bergman, R. G.
Can. J . Chem. Accepted for publication.
Triflate 7 was synthesized by a straightforward route
from TpMe (PMe3)IrH2. Surprisingly, 7 did not react with
2
(57) Tellers, D. M.; Skoog, S. J .; Gunnoe, T. B.; Harman, W. D.;
Bergman, R. G. Organometallics 2000, 19, 2428-2432.
(58) Hunter, A. D.; Mozol, V.; Tsai, S. D. Organometallics 1992, 11,
2251-2262.
(46) H/D exchange reactions were attempted with c-C6D12/CH4 and
C6D6. Small amounts of CH3D (<5%) were observed after extended
heating (2 days) of 13 and C6D12/CH4 at 75 °C along with decomposi-
tion.
(47) An extensive amount of work has recently appeared on C-H
activation by cationic late transition metals. See refs 48-53.
(48) Stahl, S. S.; Labinger, J . A.; Bercaw, J . E. J . Am. Chem. Soc.
1996, 118, 5961.
(59) Ball, R. G.; Ghosh, C. K.; Hoyano, J . K.; McMaster, A. D.;
Graham, W. G. J . Chem. Soc., Chem Commun. 1989, 341-342.
(60) Hoyano, J . K.; Graham, W. G. J . Am. Chem. Soc. 1982, 104,
3723-3724.
(61) Fernandez, M. J .; Rodriguez, M. J .; Oro, L. A. J . Organomet.
Chem. 192, 438, 337-342.
(49) J ohansson, L.; Ryan, O. B.; Tilset, M. J . Am. Chem. Soc. 1999,
121, 1974.
(62) Shapley, J . R.; Adair, P.; Lawson, R. J .; Pierpoint, C. G. Inorg.
Chem. 1982, 21, 1701-1709.
(50) J ohansson, L.; Tilset, M.; Labinger, J . A.; Bercaw, J . E. J . Am.
Chem. Soc. 2000, 122, 10846-10855.
(63) Gutie´rrez-Puebla, E.; Monge, A.; Nicasio, M. C.; Perez, P. J .;
Poveda, M. L.; Rey, L.; Ruiz, C.; Carmona, E. Inorg. Chem. 1998, 37,
4538-4546.
(51) J ohansson, L.; Tilset, M. J . Am. Chem. Soc. 2001, 123, 739-
740.
(52) Fang, X.; Scott, B. L.; Watkin, J . G.; Kubas, G. Organometallics
2000, 19, 4193.
(53) Peters, R. G.; White, S.; Roddick, D. M. Organometallics 1998,
17, 4493-4499.
(54) Krogh-J espersen, K.; Czerw, M.; Kanzelberger, M.; Goldman,
A. S. J . Chem. Inf. Comput. Sci. 2001, 41, 56-63.
(64) Bell, T. W.; Haddleton, D. M.; McCamley, A.; Partridge, M. G.;
Perutz, R. N.; Willner, H. J . Am. Chem. Soc. 1990, 112, 9212-9226.
(65) Ciriano, M. A.; Ferna´ndez, M. J .; Modrego, J .; Rodr´ıguez, M.
J .; Oro, L. A. J . Organomet. Chem. 1993, 438, 337-342.
(66) Szajek, L. P.; Lawson, R. J .; Shapley, J . R. Organometallics
1991, 10, 357-361.

Cationic TpMe Ir(III) Complexes
Organometallics, Vol. 20, No. 23, 2001 4825
2
Sch em e 5
Ta ble 4. Su m m a r y of th e In fr a r ed Absor p tion
F r equ en cies for Som e Ir id iu m Cyclop en ta d ien yl
a n d Hyd r id otr is(p yr a zolyl)bor a te Com p lexes
+
-
bration of TpMe (PMe3)Ir(H)2H OTf (14)45 and Cp*-
2
(PMe3)Ir(H)2 (15) (eq 6).67
compound
data (solvent)
ref
TpMe Ir(CO)2
Cp*Ir(CO)2
νCO ) 2039, 1960 cm-1 (hexanes) 59
2
νCO ) 2020, 1953 cm-1 (hexanes) 60
Tp(H)2Ir(CO)
Cp(H)2Ir(CO)
νCO ) 2020 cm-1 (CH2Cl2)
νCO ) 2002 cm-1 (CH2Cl2)
νCO ) 1990 cm-1 (Nujol)
61
62
63
65
66
TpMe Ir(C2H4)CO
2
TpIr(C2H4)CO
CpIr(C2H4)CO
νCO ) 2000 cm-1 (cyclohexane)
νCO ) 1980 cm-1 (cyclohexane)
TpMe (C2H3)Ir(H)CO
νCO ) 2020 cm-1 (petroleum ether) 63
2
Cp(C2H3)Ir(H)CO
νCO ) 2021 cm-1 (CO matrix)
64
a
[TpMe (PMe3)IrMe(CO)][BArf] νCO ) 2060 cm-1 (KBr)
[Cp*(PMe3)IrMe(CO)][BArf] νCO ) 2035 cm-1 (KBr)
2
Treatment of a CD2Cl2 solution of 14 with a CD2Cl2
solution of 15 results in the quantitative formation of
57
a
a
[TpMe (PMe3)IrMe(N2)][BArf] νNN ) 2225 cm-1 (CH2Cl2)
2
[Cp*(PMe3)IrMe(N2)][BArf]
νNN ) 2207 cm-1 (CH2Cl2)
Cp*(PMe3)Ir(H)3+OTf- (16) and TpMe (PMe3)Ir(H)2 (4),
2
1
as determined by H and 31P{1H} NMR spectroscopy.
a
This work.
Thus, the equilibrium lies heavily in favor of the
protonated and therefore more strongly basic Cp*
complex. Finally, the relative Ir-O bond lengths in
triflate 7 and its Cp* analogue 1 are consistent with 7
having the more electrophilic metal center (vide supra).
The above results are all consistent with a stronger
cation(iridium)/anion(triflate) interaction, which has the
effect of slowing the rate of triflate dissociation. The
larger barrier to ionization disfavors formation of the
key intermediate that reacts with C-H bonds or Lewis
bases.
Rea ctivity of [Tp Me (P Me3)Ir Me(N2)][BAr f] to-
w a r d Da tive Liga n d s. In an attempt to generate a
more reactive complex, metathesis of the triflate ligand
with the BArf anion in CH2Cl2 under N2 was performed.
Instead of obtaining the expected dichloromethane
complex, we isolated the dinitrogen complex, 3-N2.
Structural characterization of 3-N2 was also performed
since there are surprisingly few iridium dinitrogen
complexes.27-29,72-81
2
The affinity for N2 over CH2Cl2 exhibited by the
cationic iridium center in 3 is in direct contrast to that
of the Cp* analogue 2, where reversible binding to N2
is observed only at elevated N2 pressures (Figure 3). It
has recently been noted that CH2Cl2 is a better σ donor
and a poorer π acceptor than N2.82 It is therefore
surprising that the more electron rich Cp* compound 2
It should be mentioned that the Cp/Cp* and Tp/TpMe
2
ligands interact with the iridium center in fundamen-
tally different ways. The Tp ligand possesses relatively
hard nitrogen σ donors, while the Cp ligand possesses
relatively soft carbon π donors. Furthermore, the Tp
ligand generally enforces an octahedral geometry about
the metal center.68-71 These differences may contribute
to the observed differences in reactivity (i.e., the rate
of triflate loss) between 1 and 7. Despite this, we feel
that the experimentally confirmed electronic differences
between the two ligands described here provide a
simple, straightforward explanation for our observa-
tions.
(72) Please see refs 27-29 and 73-81 for other iridium dinitrogen
complexes.
(73) Uguagliati, P.; Deganelo, G.; Busetto, L.; Belluco, U. Inorg.
Chem. 1969, 8, 1625-1630.
(74) Chatt, J .; Melville, D. P.; Richards, R. L. J . Chem. Soc. A 1969,
2841-2844.
(75) Fitzgerald, R. J .; Lin, H.-M. Inorg. Chem. 1972, 11, 2270-2272.
(76) Blake, D. M. Chem. Commun. 1974, 815-816.
(77) Olgemoeller, B.; Bauer, H.; Beck, W. J . Organomet. Chem. 1981,
213, C57-C59.
(67) Heinekey, D. M.; Hinkle, A. S.; Close, J . D. J . Am. Chem. Soc.
1996, 118, 5353-5361.
(78) Werner, H.; A., H. Z. Naturforsch. B: Anorg. Chem. 1984, 39b,
1505-1509.
(68) Curtis, M. D.; Shiu, K.-B. Inorg. Chem. 1985, 24, 1213-1218.
(69) Curtis, M. D.; Shiu, K.; Butler, W. M.; Huffman, J . C. J . Am.
Chem. Soc. 1986, 108, 3335-3343.
(79) Bauer, H.; Sheldrick, G. M.; Nagel, U.; Beck, W. Z. Naturforsch.
B: Anorg. Chem. 1985, 40b, 1237-1242.
(80) Bauer, H.; Beck, W. J . Organomet. Chem. 1986, 308, 73-83.
(81) Goldman, A. S.; Halpern, J . J . Organomet. Chem. 1990, 382,
237-253.
(70) Curtis, M. D.; Shiu, K.-B.; Butler, W. M. J . Am. Chem. Soc.
1986, 108, 1550-1561.
(71) Ru¨ba, E.; Simanko, W.; Mereiter, K.; Schmid, R.; Kirchner, K.
Inorg. Chem. 2000, 39, 382-384.
(82) Toupadakis, A.; Kubas, G. J .; King, W. A.; Scott, B. L.;
Huhmann-Vincent, J . Organometallics 1998, 17, 5315-5323.

4826 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
Sch em e 6
prefers to bind the weaker π acceptor, while the more
electron poor compound, 3, preferentially coordinates
the poorer σ donor N2. We suggest that in this case the
required for dissociation of the weakly bound dative
ligand (OTf-, CH2Cl2, N2) from the 18-electron Ir center,
and/or it can raise the energy of the C-H activation
transition state itself. Our most recent low-temperature
NMR investigations of the two systems demonstrate
that they show a strong difference in dative ligand
dissociation rate. As noted in the Results section, we
are unable to freeze out separate resonances for bound
and free dichloromethane in [Cp*(PMe3)Ir(CH2Cl2)]+ at
-80 °C (indicating that dissociation is relatively rapid
even at this temperature), whereas this can be done
steric bulk of the TpMe ligand is importantsthe larger
2
CH2Cl2 molecule has more difficulty fitting into the
coordination sphere of the TpMe Ir fragment than the
2
Cp*Ir fragment, an effect that is much reduced with the
smaller N2 molecule.83 The increased steric demand of
the TpMe ligand compared to the Cp* ligand is also
2
demonstrated by the barrier to rotation of an Ir-bound
phenyl group: the TpMe systems (9 and 12) exhibit
2
with the analogous TpMe complex. In [Tp(PMe3)Ir(CH2-
2
hindered rotation, while the analogous Cp* systems
exhibit free rotation.13,16,84
Cl2)]+, dissociation of CH2Cl2 is slow even at mildly
elevated temperatures. Since this preequilibrium di-
rectly affects the overall rate of the C-H activation
reaction, we conclude that it must be an important
factor in slowing the process.
Replacing the triflate ligand with the noncoordinating
BArf anion demonstrated that triflate loss from 7 was
at least partially responsible for the diminished reactiv-
ity in the TpMe system. Dinitrogen, in contrast to
2
triflate, is a good leaving group; Lewis bases readily
displace N2 (eq 3). Further illustration that N2 readily
dissociates is obtained in the reaction of 3-N2 with PMe3
(eq 4). Instead of the expected phosphine adduct, the
Given the fact that compounds such as aldehydes and
arenes do ultimately react in the TpMe system, it is
2
perplexing that we see no reaction at all with alkanes
even under the most stringent conditions we can reach,
short of irreversible decomposition of the complexes.
Although this observation is purely qualitative, on the
basis of it we continue to believe that there must also
be a contribution of electron donor stabilization to the
C-H oxidative addition transition state. When the
amount of donation is insufficient, as it must be in the
phosphonium salt [Me3PCH2Cl][BArf] and TpMe (PMe3)-
2
IrMe(Cl) are generated. A plausible mechanism to
explain formation of these products is illustrated in
Scheme 6. Complex 3-N2 is in rapid equilibrium with
3-CH2Cl2. Subsequent PMe3 attack on bound CH2Cl2
yields the observed products.85 In this case, the cationic
+
[TpMe (PMe3)IrMe] fragment serves as a Lewis acid,
TpMe and Tp systems, C-H activation shuts down
2
2
activating the dichloromethane toward nucleophilic
attack. Similar Lewis acid-assisted reactions have been
observed with rhenium26,86 and ruthenium.87 While the
preference for PMe3 attack at the Ir-bound dichlo-
romethane carbon over attack at the iridium center is
not completely understood, this reaction provides evi-
dence for the dynamic preequilibrium illustrated in
Scheme 6.
completely. One other factor to consider is the ease or
difficulty of expanding the Ir coordination sphere.
Mechanistic and theoretical work provide strong evi-
dence that C-H activation by cationic iridium(III)
complexes proceeds through 18 e-, iridium(V) interme-
diates.11,16,88,89 Accordingly, it is likely that the inter-
mediate in the TpMe system is an 18 e-, seven-
2
coordinate, Ir(V) species of the type shown in Figure 5A.
There are few seven-coordinate Tp complexes known,
compared to (formally) seven-coordinate Cp com-
Wh y is th e Tp Me System Less Rea ctive Th a n th e
2
Cp * System ? Complex 3-N2 is capable of activating the
C-H bonds of arenes and aldehydes under moderate
conditions, albeit at a slower rate than the correspond-
ing Cp* systems. As we have stated in two previous
papers, we are convinced that Tp ligands are poorer
electron donors than Cp* toward Ir.22,57 However, this
can lower the relative C-H activation reactivity of the
Tp-type systems in two ways: it can increase the energy
plexes.69,71,90,91 If this reflects the difficulty of expanding
92-94
the coordination sphere in Tp and TpMe complexes,
2
(88) Klei, S. R.; Bergman, R. G. J . Am. Chem. Soc. 2000, 122, 1816-
1817.
(89) Strout, D. L.; Zaric, S.; Niu, S.; Hall, M. B. J . Am. Chem. Soc.
1996, 118, 6068-6069.
(90) Skagestad, V.; Tilset, M. J . Am. Chem. Soc. 1993, 115, 5077-
5083.
(91) Tenorio, M. J .; Tenorio, M. A. J .; Puerta, M. C.; Valerga, P.
Inorg. Chim. Acta 1997, 259, 77-84.
(92) The desire to maintain an octahedral geometry has been used
to explain why TpM complexes form nonclassical dihydrogen structures
whereas the corresponding Cp* complexes will go seven-coordinate and
form classical dihydride structures. See the two references immediately
following this one.
(83) Support for this hypothesis obtained by utilizing the Tp ligand
will be published separately.
(84) Woerpel, K. A.; Bergman, R. G. J . Am. Chem. Soc. 1993, 115,
7888-7889.
(85) See ref 27 for a description of the reaction of PMe3 with ethylene
in TpMe (CH2CH2)Ir(CHCH2)H.
2
(86) Igau, A.; Gladysz, J . A. Polyhedron 1991, 10, 1903-1909.
(87) Kulawiec, R. J .; Crabtree, R. H. Organometallics 1988, 7, 1891-
1893.
(93) Gutie´rrez-Puebla, E.; Monge, A.; Paneque, M.; Poveda, M. L.;
Taboada, S.; Trujillo, M.; Carmona, E. J . Am. Chem. Soc. 1999, 121,
346-354.

Cationic TpMe Ir(III) Complexes
Organometallics, Vol. 20, No. 23, 2001 4827
2
external CH3NO2. 19F NMR spectra were recorded at 377 MHz,
and chemical shifts (δ) are reported relative to external CFCl3.
31P{1H} NMR spectra were recorded at 162 MHz, and chemical
shifts (δ) are reported relative to external 85% H3PO4. X-ray
structural analyses were performed at the UC Berkeley
CHEXRAY facility by Dr. Fred Hollander and Dr. Dana
Caulder.
Sealed NMR tubes were prepared by attaching the NMR
tube directly to a Kontes high-vacuum stopcock via a Cajon
Ultra-Torr reducing union and then flame-sealing on a vacuum
line. Reactions with gases and low-boiling liquids involved
condensation of a calculated pressure of gas from a bulb of
known volume into the reaction vessel at -196 °C. Known-
volume bulb vacuum-transfers were accomplished with a
digital MKS Baratron gauge attached to a vacuum line.
F igu r e 5. Proposed Ir(V) intermediates in C-H activation
by 3+.
this effect may also be important in raising the energy
of the C-H oxidative addition transition state. Dech-
elation of one of the pyrazole arms would provide a
means of preventing the necessity of forming a seven-
coordinate intermediate (Figure 5B). Such a complex
would be analogous to those proposed in neutral Rh(I)
C-H activation reactions.95,96 However, if it were to
occur, dechelation would require additional energy input
and would also diminish the already relatively poor
Ma ter ia ls. Unless otherwise noted, reagents were pur-
chased from commercial suppliers and used without further
purification. Potassium bromide (Aldrich), Celite (Aldrich),
silica gel (Merck 60, 230-400), and silylated silica gel (EM
Science, silica gel 60, 63-200 µm) were dried in vacuo at 250
°C for 48 h. Toluene (Fisher) was either distilled from sodium
metal under N2 or passed through a column of activated
alumina (type A2, size 12 × 32, Purifry Co.) under nitrogen
pressure and sparged with N2 prior to use.97 Pentane, hexanes,
and benzene (Fisher) were either distilled from purple sodium/
benzophenone ketyl under N2 or passed through a column of
activated alumina (type A2, size 12 × 32, Purifry Co.) under
nitrogen pressure and sparged with N2 before use.97 Diethyl
ether and tetrahydrofuran (Fisher) were distilled from purple
sodium/benzophenone ketyl under N2 prior to use. Dichlo-
romethane (Fisher) was either distilled from CaH2 (Aldrich)
under N2 or passed through a column of activated alumina
(type A2, size 12 × 32, Purifry Co.) under nitrogen pressure
and sparged with N2 prior to use.97 Deuterated solvents
(Cambridge Isotope Laboratories) were purified by vacuum-
transfer from the appropriate drying agent (Na/Ph2CO or
CaH2) prior to use.
electron-donating ability of the TpMe ligand.
2
Con clu sion
This work has provided an account of the chemistry
of a series of TpMe Ir(III) complexes. A comparison of
2
the relative electron-donating abilities of the Tp and Cp
ligand toward iridium has been made, and it was shown
that electronic effects play an important role in defining
the reactivity of these complexes. In particular, triflate
dissociation from TpMe PMe3Ir(Me)OTf occurs very slowly
2
because the iridium center is more electrophilic than it
is in the Cp* complex. Replacement of triflate with BArf
provides access to a variety of new cationic iridium
Trimethylphosphine (Aldrich) was vacuum-transferred from
sodium metal prior to use. N-Bromosuccinimide was crystal-
lized from water and dried in vacuo for 2 days before use.98
Tolualdehyde and CCl4 were dried over 4 Å molecular sieves
dinitrogen complexes, [TpMe PMe3Ir(R)N2][BArf] (R )
2
Me, Ph, H). In the case of R ) Me (3-N2), C-H
activation of benzene and aldehydes occurs, but satu-
rated hydrocarbons fail to react. It is postulated that
prior to use. Acetaldehyde was stored over 3 Å sieves at 0 °C.
23
TpMe (PMe3)IrH2, [Cp*(PMe3)IrMe(CH2Cl2)][BArf],13 and Na-
2
99
BArf were prepared according to literature procedures.
the inability of the TpMe framework to support a seven-
Tp Me (P Me3)Ir Br 2 (5). In a drybox, precooled CCl4 (20 mL,
2
2
-20 °C) was added to a vial containing TpMe (PMe3)IrH2 (1.40
2
coordinate intermediate, coupled with its poor electron-
donating ability, prevents activation of the saturated
hydrocarbons. In predicting and interpreting chemistry
with the Tp ligand, consideration should be given to the
electron-donating abilities of the ligand, not just to its
steric properties. A catalytically active dehydrogenation
system will require a large, electron-rich, ancillary
ligand set.
g, 0.0024 mol) and N-bromosuccinimide (0.87 g, 0.0048 mol).
The resulting green solution was stirred vigorously at 22 °C
for 3 h, over which time a light green solid precipitated. The
vial was removed from the drybox, and the precipitate was
collected on a Buchner funnel, rinsed with ether (5 × 10 mL),
and dissolved in a minimum of CH2Cl2 (3 mL). The solution
was run through a column of silica gel (10 cm × 3 cm) in order
to remove the residual succinimide. The light yellow eluent
was collected, and the solvent was removed under reduced
pressure to yield a yellow solid. Yield: 930 mg, 53%. This
material was judged sufficiently pure (>95%) by 1H NMR
spectroscopy for subsequent transformations. Analytically pure
material can be obtained by crystallization from CH2Cl2/Et2O.
1H NMR (400 MHz, CDCl3, 25 °C): δ 5.79 (s, 1H, pyrCH), 5.78
(s, 2H, pyrCH), 2.85 (s, 3H, pyrCH3), 2.70 (s, 6H, pyrCH3), 2.42
Exp er im en ta l Section
Gen er a l P r oced u r es. General experimental information
has been reported elsewhere.16 All NMR spectra were obtained
at room temperature (except where noted) using Bruker AM-
400 or DRX-500 MHz spectrometers. 11B NMR spectra were
recorded at 160 MHz, and chemical shifts (δ) are reported
relative to external BF3‚Et2O. 15N NMR spectra were recorded
at 50.7 MHz, and chemical shifts (δ) are reported relative to
2
(s, 6H, pyrCH3), 2.33 (s, 3H, pyrCH3), 1.74 (d, J P-H ) 10 Hz,
9H, PMe3). 13C{1H} NMR (125 MHz, CD2Cl2, 25 °C): δ 12.8
1
(s, pyrCH3), 13.5 (s, pyrCH3), 16.7 (s, pyrCH3), 17.3 (d, J P-C
4
) 41 Hz, PMe3), 18.3 (s, pyrCH3), 109.2 (d, J P-C ) 5 Hz,
(94) Oldham, W. J .; Hinkle, A. S.; Heinekey, D. M. J . Am. Chem.
Soc. 1997, 119, 11028-11036.
pyrCH), 110.5 (s, pyrCH), 144.2 (s, pyrCq), 145.6 (s, pyrCq),
(95) Bromberg, S. E.; Yang, H.; Asplund, M. C.; Lian, T.; McNamara,
B. K.; Kotz, K. T.; Yeston, J . S.; Wilkens, M.; Frei, H.; Bergman, R.
G.; Harris, C. B. Science 1997, 278, 260-263.
(97) Alaimo, P. J .; Peters, D. W.; Arnold, J .; Bergman, R. G. J . Chem.
Educ. 2001, 78, 64.
(98) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.
(96) Wick, D. D.; Reynolds, K. A.; J ones, W. D. J . Am. Chem. Soc.
1999, 121, 3974-3983.

4828 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
Ta ble 5. Cr ysta l Da ta Collection a n d Refin em en t
P a r a m eter s for Com p lexes 3-N2, 7, a n d 9
0.002 mol). The brown slurry was shielded from light and
stirred for 12 h. The solution was filtered through silanized
silica gel, concentrated to ∼1 mL, layered with pentane, and
3-N2
7
9
cooled to -40 °C. Light yellow crystals of TpMe (PMe3)IrMe-
2
empirical formula IrCl3PF24C52.5N8- IrSPF3O3N6C21- IrPF24N8C56
-
1
(OTf) were isolated after 24 h. Yield: 630 mg, 42%. H NMR
B2H55
BH36Cl2
814.52
H
48B2
1533.82
yellow prisms
(400 MHz, CD2Cl2, 25 °C): δ 5.92(s, 1H, pyrCH), 5.78 (s, 2H,
pyrCH), 2.44 (s, 3H, pyrCH3), 2.44 (s, 3H, pyrCH3), 2.42 (s,
fw
1605.20
cryst habit
cryst size, mm
pale yellow plates yellow blades
0.40 × 0.22 ×
0.16 × 0.12 × 0.23 × 0.21 ×
3
3H, pyrCH3), 2.29 (s, 9H, pyrCH3), 2.17 (d, J P-C ) 3 Hz, Ir-
0.10
0.06 0.14
2
Me), 1.49 (d, J P-C ) 10 Hz, PMe3). 13C{1H} NMR (125 MHz,
cryst syst
lattice type
a, Å
monoclinic
C-centered
39.1718(7)
12.9265(2)
26.0390(4)
107.452(1)
12578.0(3)
C2/c (#15)
8
monoclinic
primitive
8.8148(1)
15.8021(1)
20.0649(3)
92.853(1)
2791.42(5)
P21/c (#14)
4
monoclinic
primitive
12.2962(2)
20.4899(1)
27.0853(3)
100.130(1)
6717.7(1)
P21/c (#14)
4
3
CD2Cl2, 25 °C): δ -27.9 (d, 3H, J P-C ) 5 Hz, Ir-Me), 13.0 (s,
pyrCH3), 13.1 (s, pyrCH3), 13.6 (s, pyrCH3), 13.7 (s, pyrCH3),
b, Å
4
1
15.6 (s, J P-C ) 2 Hz, pyrCH3), 16.3 (d, J P-C ) 39 Hz, PMe3),
c, Å
4
â, deg
16.6 (s, pyrCH3), 108.2 (d, J P-C ) 4 Hz, pyrCH), 108.8 (s,
V, Å3
pyrCH), 109.9 (s, pyrCH), 144.4 (d, 3J P-C ) 3 Hz, pyrCq), 146.1
(s, pyrCq), 146.3 (s, pyrCq), 151.7 (d, 5J P-C ) 4 Hz, pyrCq), 152.9
(s, pyrCq), 154.1 (s, pyrCq), CF3 not observed. 31P{1H} NMR
(161.9 MHz, CD2Cl2, 25 °C): δ -54.0. 19F NMR (376.5 MHz,
CD2Cl2, 25 °C): δ -75.5. 11B NMR (160 MHz, CD2Cl2, 25 °C):
space group
Z value
D
calc, g/cm3
1.695
1.938
1.516
F000
6056.00
-128
1608.00
-120
3032.00
-108
temp, °C
µ(Mo KR), cm-1
exposure time,
s/frame
23.52
51.77
55.86
1
δ -9.71 (d, J B-H ) 100 Hz). IR (KBr): 2979 (m), 2926 (m),
10.0
15.0
10.0
2556 (m), 1551 (s), 1448 (s), 1417 (s), 1384 (m), 1324 (s), 1229
(s), 1203 (s), 1179 (s), 1065 (m), 1008 (s), 960 (m), 863 (w), 826
(w), 782 (m), 691 (w), 637 (s), 518 (w). MS (EI): m/z 730 (M+),
715 (M+ - CH3). Anal. Calcd for C20H34N6BIrPO3SF3‚1/4CH2-
Cl2 (confirmed by 1H NMR spectroscopy): C, 32.40; H, 4.60;
N, 11.20. Found: C, 32.54; H, 4.71; N, 11.11.
2θmax, deg
no. of reflns measd
total
49.4
49.4
49.4
27 863
11 118
7014
13 173
4919
29 792
11 412
7156
880
8.13
unique
no. observations
no. variables
3087
785
342
reflns/param ratio 8.94
9.03
Ra; Rwb; Rall
0.045; 0.052;
0.077
1.52
0.030; 0.032;
0.067
0.95
0.030; 0.034;
0.054
1.20
Gen er a t ion of [Tp Me (P Me3)Ir Me(CD2Cl2)][BAr f] (3-
2
CD2Cl2) in CD2Cl2 Solu tion . Compound 3-CD2Cl2 was
always generated immediately prior to use. Typical proce-
dure: in a drybox, an NMR tube was charged with 7 (30.0
mg, 0.041 mmol) and NaBArf (36.0 mg, 0.041 mmol). The tube
was removed from the drybox and attached to a vacuum line,
and CD2Cl2 (∼0.6 mL) was added via vacuum-transfer tech-
niques. After thawing, the slurry was shaken for 10 min and
then the NaOTf was allowed to settle. The light yellow solution
GOF indicator
max. resid density, 1.22
0.93
0.72
e/Å3
min. resid density, -0.93
-1.11
-0.40
e/Å3
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fo|)2/∑w|Fo| ]1/2, w
) 1/σ2(Fo)
containing [TpMe (PMe3)IrMe(CD2Cl2)][BArf] is stable for ap-
3
155.2 (d, J P-C ) 4 Hz, pyrCq), 154.8 (s, pyrCq). 31P{1H} NMR
2
(161.9 MHz, CD2Cl2, 25 °C): δ -65.7. 11B NMR (160 MHz, CD2-
proximately 6 h at 298 K. Attempts to isolate this compound
were unsuccessful. 1H NMR (400 MHz, CD2Cl2, 25 °C): δ 7.72
(bs, 8H, o-BArf), 7.56 (bs, 4H, p-BArf), 6.05 (s, pyrCH), 5.92 (s,
pyrCH), 5.81 (s, pyrCH), 2.46 (s, 3H, pyrMe), 2.42 (s, 9H,
pyrMe), 2.35 (s, 3H, pyrMe), 2.30 (s, 3H, pyrMe), 2.00 (d, 3J P-H
1
Cl2, 25 °C): δ -9.86 (d, J B-H ) 104 Hz). IR (KBr): 3129 (w),
2960 (m), 2922 (m), 2551 (m), 1551 (s), 1449 (s), 1420 (s), 1380
(s), 1309 (m), 1288 (m), 1217 (s), 1065 (s), 1045 (m), 961 (s),
864 (m), 821 (s), 789 (s), 742 (m), 690 (m), 645 (m), 484 (w).
MS (EI): m/z 726 (M+). Anal. Calcd for C18H31BBr2IrN6: C,
29.81; H, 4.31; N, 11.59. Found: C, 29.99; H, 4.46; N, 11.42.
2
) 5 Hz, 3H, Ir-Me), 1.53 (d, J P-H ) 14 Hz, 9H, PMe3). 13C-
1
{1H} NMR (125 MHz, CH2Cl2, 25 °C): δ 161.9 (d, J B-C ) 50
3
Tp Me (P Me3)Ir Me(Br ) (6). To a stirred slurry of 5 (1.40 g,
Hz, i-BArf), 154.1 (s, pyrCq), 151.4 (d, J P-C ) 4 Hz, pyrCq),
2
150.7 (s, pyrCq), 148.2 (s, pyrCq), 146.4 (s, pyrCq), 146.1 (d,
0.0019 mol) in THF (20 mL) at -40 °C was added MeLi (0.0032
mol, 1.7 equiv, 1.4 M in Et2O) by syringe. After 2 h at 22 °C,
the homogeneous solution was run through a plug of alumina
(2 cm × 3 cm) and the solvent was removed under reduced
pressure to yield a yellow-orange solid. The solid was dissolved
in a minimum of CH2Cl2, and the resulting solution was
layered with pentane and cooled to -40 °C to afford yellow
2
3J P-C ) 3 Hz, pyrCq), 135.0 (s, o-BArf), 129.1 (qq, J F-C ) 31
Hz, 4J F-C ) 3 Hz, m-BArf), 124.8 (q, 1J F-C ) 270 Hz, BArfCF3),
3
117.7 (septet, J F-C ) 4 Hz, p-BArf), 110.9 (s, pyrCH), 109.5
4
(s, pyrCH), 109.3 (d, J F-C ) 4 Hz, pyrCH), 16.1 (s, pyrCH3),
1
16.0 (s, pyrCH3), 15.4 (d, J P-C ) 40 Hz, PMe3), 14.0 (s,
pyrCH3), 13.5 (s, pyrCH3), 12.6 (s, pyrCH3), 12.5 (s, pyrCH3),
2
-27.1 (d, J P-C ) 6 Hz, Ir-Me). 13C (125 MHz, CH2Cl2, -80
1
crystals of TpMe (PMe3)IrMe(Br). Yield: 740 mg, 60%. H NMR
(500 MHz, CD2Cl2, 25 °C): δ 5.84 (s, 1H, pyrCH), 5.80 (s, 1H,
pyrCH), 5.77 (s, 1H, pyrCH), 2.63 (s, 3H, pyrCH3), 2.57 (s, 3H,
pyrCH3), 2.43 (s, 3H, pyrCH3), 2.42 (s, 3H, pyrCH3), 2.33 (s,
2
1
°C): δ 62.4 (t, J C-H ) 186 Hz, CH2Cl2). 31P{1H} NMR (161.9
MHz, CD2Cl2, 25 °C): δ -52.3. 19F NMR (376.5 MHz, CD2Cl2,
25 °C): δ -61.0. 11B NMR (160 MHz, CD2Cl2, 25 °C): δ -8.7
1
(s, BArf), -11.0 (d, J B-H ) 97 Hz, TpMe ).
2
2
3H, pyrCH3), 2.33 (s, 3H, pyrCH3), 1.83 (d, J P-H ) 4 Hz, Ir-
2
) 10 Hz, PMe3). 13C{1H} (125 MHz, CD2-
[Tp Me (P Me3)Ir Me(N2)][BAr f] (3-N2). CH2Cl2 (10 mL) was
2
Me), 1.53 (d, J
P-H
Cl2, 25 °C): δ -27.5 (Ir-CH3, 2J P-C ) 6 Hz), 13.08 (s, pyrCH3),
13.2 (s, pyrCH3), 13.7 (s, pyrCH3), 15.0 (s, pyrCH3), 16.1 (d,
1J P-C ) 40 Hz, PMe3), 16.6 (s, pyrCH3), 17.2 (s, pyrCH3), 108.7
added to a vial containing 7 (90.3 mg, 0.12 mmol) and NaBArf
(110 mg, 0.12 mmol). The solution was stirred for 30 min and
filtered through glass fiber filter paper. The solvent was
removed under reduced pressure to afford 3-N2 as an off-white
solid. Crystallization from a concentrated CH2Cl2 solution
layered with pentane at -40 °C produced clear, blocklike
crystals of 3-N2. Yield: 126 mg, 67%. 1H NMR (500 MHz, CD2-
Cl2, 25 °C): δ 7.72 (bs, 8H, o-BArf), 7.56 (bs, 4H, p-BArf), 6.02
(s, 1H, pyrCH), 5.93 (s, 1H, pyrCH), 5.88 (s, 1H, pyrCH), 2.43
(s, 3H, pyrCH3), 2.36 (s, 6H, pyrCH3), 2.33 (s, 3H, pyrCH3),
4
(d, J P-C ) 5 Hz, pyrCH), 109.0 (s, pyrCH), 109.5 (s, pyrCH),
143.8 (s, pyrCq), 144.7 (s, pyrCq), 145.2 (s, pyrCq), 152.3 (s,
pyrCq), 152.7 (s, pyrCq), 153.5 (s, pyrCq). 31P{1H} NMR (161.9
MHz, CD2Cl2, 25 °C): δ -56.9. 11B NMR (160 MHz, CD2Cl2,
1
25 °C): δ -9.72 (d, J B-H ) 102 Hz). IR (KBr): 2954 (s), 2919
(s), 2527 (m), 1550 (s), 1444 (s), 1416 (s), 1380 (s), 1305 (w),
1285 (w), 1216 (s), 1134 (w), 1063 (s), 1037 (m), 958 (s), 858
(m), 815 (m), 786 (s), 734 (m), 693 (m). MS (EI): m/z 660 (M+),
645 (M+ - CH3). Anal. Calcd for C19H34BBrIrN6: C, 34.55; H,
5.19; N, 12.72. Found: C, 34.81; H, 5.36; N, 12.81.
3
2.31 (s, 3H, pyrCH3), 1.63 (d, 3H, J P-H ) 3 Hz, Ir-Me), 1.61
2
(d, 9H, J P-H ) 11 Hz, Ir-PMe3). 13C{1H} NMR (CD2Cl2, 125
MHz, 25 °C): δ -23.6 (d, 2J P-C ) 6 Hz, Ir-Me), 12.8 (s, pyrCH3),
12.9 (s, pyrCH3), 13.7 (s, pyrCH3), 14.0 (s, pyrCH3), 23.3 (d,
1J P-C ) 41 Hz, PMe3), 16.4 (s, pyrCH3), 16.8 (s, pyrCH3), 109.1
Tp Me (P Me3)Ir Me(OTf) (7). CH2Cl2 (20 mL) was added to
2
a vial containing 6 (1.30 g, 0.002 mol) and AgOTf (510 mg,

Cationic TpMe Ir(III) Complexes
Organometallics, Vol. 20, No. 23, 2001 4829
(q, J B-C ) 50 Hz, i-BArf). 31P{1H} NMR (161.9 MHz, CD2Cl2,
2
4
1
(d, J P-C ) 4 Hz, pyrCH), 109.7 (s, pyrCH), 111.6 (s, pyrCH),
3
1
118.1 (septet, J F-C ) 4 Hz, p-BArf), 125.2 (q, J F-C ) 270 Hz,
25 °C): δ -49.6. 19F NMR (376.5 MHz, CD2Cl2, 25 °C):
δ
2
4
BArfCF3), 129.48 (qq, J F-C ) 32 Hz, J F-C ) 3 Hz, m-BArf),
-60.9. 11B NMR (160 MHz, CD2Cl2, 25 °C): δ -7.3 (BArf), -9.5
3
2
135.4 (s, o-BArf), 146.1 (d, J P-C ) 3 Hz, pyrCq), 147.0 (s,
(d, 1J B-H ) 105 Hz, TpMe ). IR (KBr): 2969 (m), 2932 (m), 2561
3
pyrCq), 148.2 (s, pyrCq), 151.2 (d, J P-C ) 4 Hz, pyrCq), 151.6
(m), 2300 (vw), 2237 (vw), 2021 (vw), 1786 (w), 1728 (w), 1611
(m), 1553 (m), 1449 (s), 1421 (s), 1356 (s), 1277 (s), 1144 (vs),
956 (s), 888 (s), 839 (s), 790 (m), 713 (s), 682 (s), 671 (s). FAB/
MS (nitrobenzyl alcohol): m/z 622 (M+), 581 (M+ - CH3CN).
Anal. Calcd for C53H49N7PB2IrF24: C, 42.87; H, 3.33; N, 6.60.
Found: C, 43.21; H, 3.17; N, 6.25.
1
(s, pyrCq), 154.0 (s, pyrCq), 162.4 (q, J B-C ) 50 Hz, i-BArf).
31P{1H} NMR (161.9 MHz, CD2Cl2, 25 °C): δ -47.3. 19F NMR
(376.5 MHz, CD2Cl2, 25 °C): δ -61.0. 11B NMR (160 MHz, CD2-
Cl2, 25 °C): δ -9.54 (d, 1J B-H ) 106 Hz). 15N NMR (50.7 MHz,
CD2Cl2, 25 °C): δ -49.2 (NR), -144.4 (Nâ). IR (CH2Cl2): 2566
(m, B-H), 2225 (s, N2) cm-1. IR (KBr): 2975 (m), 2929 (m),
2565 (m, B-H), 2227 (s, N2), 1785 (w), 1611 (s), 1551 (s), 1450
(s), 1422 (s), 1357 (s), 1272 (vs), 1169 (vs), 959 (s), 888 (s), 839
(s), 793 (w), 714 (s), 671 (s). Anal. Calcd for C51H46B2-
PIrN8F24‚CH2Cl2 (confirmed by 1H NMR spectroscopy): C,
40.12; H, 3.11; N, 7.20. Found: C, 40.07; H, 2.98; N, 7.10.
2
[Tp Me (P Me3)Ir Me(AsP h 3)][BAr f] (3-AsP h 3). A CH2Cl2
2
(0.5 mL) solution of AsPh3 (7.0 mg, 0.021 mmol) was added to
a CH2Cl2 (1 mL) solution of [TpMe (PMe3)IrMe(N2)][BArf] (33
2
mg, 0.021 mmol) kept at -40 °C. After 12 h, the solution was
filtered through glass fiber filter paper and the solvent was
removed under reduced pressure to yield a light yellow foam.
Yield: 38 mg, 100%. This material was determined to be >95%
[Tp Me (P Me3)Ir Me(CO)][BAr f] (3-CO). Meth od A:
A
1
glass vessel sealed to a Kontes vacuum adapter was charged
with 3-N2 (56 mg, 0.038 mmol) and CH2Cl2 (3 mL). The
solution was degassed and placed under CO (1 atm). The
solution was stirred for 24 h, and the solvent was removed
under reduced pressure. Crystallization from CH2Cl2/pentane
afforded 3-CO. Yield: 43 mg, 77%. Meth od B: A glass vessel
sealed to a Kontes vacuum adapter was charged with 10 (40
mg, 0.026 mmol) and CH2Cl2 (3 mL). The bright orange
solution was heated at 75 °C. After 12 h, the light yellow
solution was filtered through glass fiber filter paper and
pure by H NMR spectroscopy. Material suitable for combus-
tion analysis was obtained by allowing hexane to diffuse into
a concentrated ether solution at 22 °C. Spectroscopic data were
obtained on noncrystallized material. 1H (500 MHz, CD2Cl2
25 °C): δ 7.75 (bs, 8H, o-BArf), 7.60 (bs, 4H, p-BArf),7.47 (m,
3H, AsPh3), 7.38 (bm, 12H, AsPh3), 5.86 (s, 2H, pyrCH), 5.54
(s, 1H, pyrCH), 2.59 (s, 3H, pyrCH3), 2.44 (s, 3H, pyrCH3), 2.43
3
(s, 3H, pyrCH3), 2.41 (s, 3H, pyrCH3), 2.02 (d, J P-H ) 3 Hz,
3H, IrMe), 1.47 (s, 3H, pyrCH3), 1.39 (s, 3H, pyrCH3), 1.22 (d,
2J P-H ) 10 Hz, 9H, PMe3). 13C{1H} (125 MHz, CH2Cl2, 25 °C):
δ -25.3 (s, Ir-Me), 13.3 (s, 2 pyrCH3), 13.6 (s, pyrCH3), 16.1
1
crystallized as described in method A. Yield: 27 mg, 70%. H
1
NMR (400 MHz, CD2Cl2, 25 °C): δ 7.72 (bs, 8H, o-BArf), 7.56
(bs, 4H, p-BArf), 6.02 (s, 2H, pyrCH), 5.88 (s, 1H, pyrCH), 2.43
(s, 3H, pyrCH3), 2.42 (s, 3H, pyrCH3), 2.40 (s, 3H, pyrCH3),
2.36 (s, 3H, pyrCH3), 2.31 (s, 3H, pyrCH3), 2.30 (s, 3H, pyrCH3),
(s, pyrCH3), 16.3 (s, pyrCH3), 17.3 (d, J P-C ) 39 Hz, PMe3),
19.3 (s, pyrCH3), 109.5 (s, pyrCH), 110.3 (d, J P-C ) 3 Hz,
3
pyrCH), 110.5 (d, J P-C ) 5 Hz, pyrCH), 118.1 (septet, J F-C
)
1
4 Hz, p-BArf), 125.2 (q, J F-C ) 270 Hz, BArfCF3), 129.4 (s,
AsPh3), 129.5 (qq, 2J F-C ) 31 Hz, 4J F-C ) 3 Hz, m-BArf), 131.4
(s, AsPh3), 132.1 (s, AsPh3), 133.2 (s, AsPh3), 134.4 (s, AsPh3),
135.4 (s, o-BArf), 146.3 (s, pyrCq), 147.2 (d, J P-C ) 2 Hz, pyrCq),
147.6 (s, pyrCq), 151.8 (s, pyrCq), 153.1 (d, J P-C ) 4 Hz, pyrCq),
2
3
1.70 (d, J P-H ) 11 Hz, 9H, PMe3), 1.39 (d, J P-H ) 3 Hz, 3H,
Ir-Me). 13C{1H} NMR (125 MHz, CD2Cl2, 25 °C): δ -22.6 (d,
J ) 5 Hz, Ir-CH3), 13.0 (s, pyrCH3), 13.0 (s, pyrCH3), 13.4 (s,
1
pyrCH3), 14.5 (s, pyrCH3), 16.6 (d, J P-C ) 35 Hz, PMe3), 16.7
4
1
(s, pyrCH3), 17.0 (s, pyrCH3), 108.8 (d, J P-C ) 4 Hz, pyrCH),
162.3 (q, J B-C ) 50 Hz, i-BArf). 11B NMR (160 MHz, CD2Cl2,
3
2
109.6 (s, pyrCH), 111.4 (s, pyrCH), 118.1 (septet, J F-C ) 4
25 °C): δ -7.2 (s, BArf), -9.1 (s, TpMe ). 19F NMR (376.5 MHz,
Hz, p-BArf), 125.2 (q, 1J F-C ) 270 Hz, BArfCF3), 129.5 (qq, 2J F-C
CD2Cl2, 25 °C): δ -60.9. 31P{1H} NMR (161.9 MHz, CD2Cl2,
25 °C): δ -60.0. IR (KBr): 3072 (w), 2977 (w), 2930 (w), 2565
(w), 1610 (m), 1554 (m), 1441 (m), 1420 (m), 1355 (s), 1280 (s),
1138 (s), 1038 (m), 957 (m), 887 (m), 840 (m), 791 (m), 743
(m), 713 (m). FAB/MS (NBA): m/z 887 (M+). Anal. Calcd for
C69H61N6F24PIrB2‚C6H14 (confirmed by 1H NMR spectros-
copy): C, 49.06; H, 4.12; N, 4.58. Found: C, 49.31; H, 4.06; N,
4.48.
4
) 31 Hz, J F-C ) 3 Hz, m-BArf), 135.4 (s, o-BArf), 146.4 (d, J
) 3 Hz, pyrCq), 147.6 (s, pyrCq), 147.7 (s, pyrCq), 151.5 (s, J )
1
3 Hz, pyrCq), 152.2 (s, pyrCq), 153.0 (s, pyrCq), 162.3 (q, J B-C
) 50 Hz, i-BArf), 163.3 (d, 2J P-C ) 11 Hz, Ir-CO). 31P{1H} NMR
(161.9 MHz, CD2Cl2, 25 °C): δ -43.8. 19F (376.5 MHz, CD2-
Cl2, 25 °C): δ -61.0. 11B NMR (160 MHz, CD2Cl2, 25 °C): δ
1
-7.2 (BArf), -9.5 (d, J B-H ) 105 Hz, TpMe ). IR (KBr): 2965
2
Tp Me (P Me3)Ir Me(Cl) (8). An NMR tube was charged with
(w), 2936 (w), 2568 (w, B-H), 2060 (vs, CO), 1610 (m), 1552
(m), 1449 (s), 1422 (s), 1355 (vs), 1278 (vs), 1126 (vs), 960 (m),
888 (m), 839 (m), 793 (w), 745 (w) 713 (w). Anal. Calcd for
52H46N6PB2IrOF24: C, 42.44; H, 3.15; N, 5.71. Found: C,
42.42; H, 3.16; N, 5.69.
2
[TpMe (PMe3)IrMe(N2)][BArf] (48 mg, 0.033 mmol) and CH2-
2
Cl2 (1 mL). The tube was degassed, and PMe3 (0.033 mmol)
was added by vacuum-transfer techniques. After 30 min, the
solvent was removed under reduced pressure. The resulting
orange foam was dissolved in C6H6 (0.5 mL), and over the
course of 15 min [Me3PCH2Cl][BArf] precipitated from solution
(spectroscopic and analytical data for [Me3PCH2Cl][BArf] are
listed below). The benzene solution was separated from the
precipitate and placed on a plug of silica gel (1 cm × 2 cm).
The light yellow band was eluted with CH2Cl2. The CH2Cl2
was then removed under reduced pressure. This material is
contaminated with small amounts (<5%) of [Me3PCH2Cl][BArf]
C
[TpMe (P Me3)Ir Me(CH3CN)][BAr f] (3-CH3CN). To a stirred
2
solution of [TpMe (PMe3)IrMe(N2)][BArf] (30.0 mg, 0.019 mmol)
2
in CH2Cl2 (5 mL) was added CH3CN (1.0 µL, 0.020 mmol).
After 1 h, the solution was concentrated, layered with pentane,
and cooled to -40 °C. Crystals of 3-CH3CN were isolated after
3 days. Yield: 26 mg, 83%. 1H NMR (400 MHz, CD2Cl2, 25
°C): δ 7.68 (bs, 8H, o-BArf), 7.52 (bs, 4H, p-BArf), 5.92 (s, 1H,
pyrCH), 5.81 (s, 1H, pyrCH), 5.80 (s, 1H, pyrCH), 2.63 (s, CH3-
CN), 2.38 (s, 3H, pyrCH3), 2.37 (s, 3H, pyrCH3), 2.28 (s, 3H,
pyrCH3), 2.26 (s, 6H, pyrCH3), 2.25 (s, 3H, pyrCH3), 1.47 (d,
1
that we were unable to remove. Yield: 17 mg, 84%. H (500
MHz, CD2Cl2 25 °C): δ 5.85 (s, 1H, pyrCH), 5.81 (s, 1H,
pyrCH), 5.77 (s, 1H, pyrCH), 2.60 (s, 3H, pyrCH3), 2.54 (s, 3H,
pyrCH3), 2.43 (s, 3H, pyrCH3), 2.36 (s, 3H, pyrCH3), 2.34 (s,
2J P-H ) 10 Hz, 9H, Ir-PMe3), 1.46 (d, J P-H ) 5 Hz, 3H, Ir-
3
Me). 13C{1H} NMR (125 MHz, CD2Cl2): δ -25.6 (d, J ) 6 Hz,
Ir-Me), 12.9 (s, pyrCH3), 12.9 (s, pyrCH3), 13.7 (s, pyrCH3), 13.9
3
2
6H, pyrCH3), 1.72 (d, J P-H ) 4 Hz, 3H, IrMe), 1.50 (d, J P-H
1
(s, pyrCH3), 15.4 (d, J P-C ) 40 Hz, PMe3), 16.2 (s, pyrCH3),
) 10 Hz, 9H, PMe3). 13C{1H} (125 MHz, CH2Cl2, 25 °C): δ
-26.7 (d, J P-C ) 5 Hz, Ir-Me), 13.0 (s, pyrCH3), 13.1 (s,
pyrCH3), 13.7 (s, pyrCH3), 14.1 (s, pyrCH3), 14.4 (s, pyrCH3),
4
2
16.6 (s, pyrCH3), 108.7 (d, J P-C ) 4 Hz, pyrCH), 109.1 (s,
pyrCH), 110.7 (s, pyrCH), 118.1 (septet, 3J F-C ) 4 Hz, p-BArf),
1
1
118.9 (s, CH3CN), 125.2 (q, J F-C ) 270 Hz, BArfCF3), 129.5
15.5 (d, J P-C ) 39 Hz, PMe3), 16.3 (s, pyrCH3), 16.5 (s,
2
4
(qq, J F-C ) 31 Hz, J F-C ) 3 Hz, m-BArf), 135.4 (s, o-BArf),
145.3 (s, pyrCq), 146.1 (s, pyrCq), 147.3 (s, pyrCq), 150.5 (d,
3J P-C ) 4 Hz, pyrCq), 150.8 (s, pyrCq), 153.8 (s, pyrCq), 162.4
pyrCH3), 108.4 (d, J P-C ) 5 Hz, pyrCH), 108.8 (s, pyrCH), 109.3
(s, pyrCH), 143.6 (d, J ) 3 Hz, pyrCq), 144.5 (s, pyrCq), 145.3
(s, pyrCq), 152.0 (d, J P-C ) 5 Hz, pyrCq), 152.5 (s, pyrCq), 152.8

4830 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
3
(s, pyrCq). 11B NMR (160 MHz, CD2Cl2, 25 °C): δ -9.7 (d, 100
(q, 1H, J H-H ) 4 Hz, CH3C(O)H), 7.73 (bs, 8H, o-BArf), 7.57
(bs, 4H, p-BArf), 5.96 (s, 1H, pyrCH), 5.85 (s, 1H, pyrCH), 5.79
(s, 1H, pyrCH), 2.43 (s, 3H, pyrCH3), 2.43 (s, 3H, pyrCH3), 2.41
Hz, TpMe B-H). 31P{1H} NMR (161.9 MHz, CD2Cl2, 25 °C): δ
2
-54.5. IR (KBr): 2956 (s), 2918 (s), 2532 (m), 1550 (s), 1442
(s), 1416 (s), 1381 (s), 1271 (s), 1215 (s), 1149 (w), 1115 (m),
1067 (m), 1033 (m), 960 (s), 860 (w), 824 (w), 779 (s), 725 (m),
3
(d, 3H, J H-H ) 4 Hz, CH3C(O)H), 2.32 (s, 6H, pyrCH3), 1.97
3
(s, 3H, pyrCH3), 1.94 (s, 3H, pyrCH3), 1.78 (d, 3H, J P-H ) 2
2
693 (m), 638 (m), 548 (w), 535 (m). HRMS (EI): m/z for [C19H34
-
Hz, Ir-Me), 1.48 (d, 9H, J P-H ) 10 Hz, PMe3). 13C{1H} NMR
BClN6PIr]+ (M+): calcd 616.1994, obsd 616.2008.
(125 MHz, CD2Cl2, 25 °C): δ 223.7 (s, CH3C(O)H), 162.4 (q,
3
[Me3P CH2Cl][BAr f]. See the synthesis of TpMe (PMe3)IrMe-
(Cl) (8) described above for preparative procedure. Yield: 19
mg, 58%. 1H (500 MHz, CD2Cl2 25 °C): δ 7.74 (bs, 8H, o-BArf),
2
1J B-C ) 50 Hz, i-BArf), 155.2 (s, pyrCq), 149.1 (d, J P-C ) 4
Hz, pyrCq), 148.8 (s, pyrCq), 148.0 (s, pyrCq), 146.3 (s, pyrCq),
145.9 (d, 5J P-C ) 2 Hz, pyrCq), 135.4 (s, o-BArf), 129.5 (qq, 2J F-C
4
1
2
) 31 Hz, J F-C ) 3 Hz, m-BArf), 125.2 (q, J F-C ) 270 Hz,
BArfCF3), 118.1 (septet, 3J F-C ) 4 Hz, p-BArf), 110.7 (s, pyrCH),
109.3 (s, pyrCH), 109.2 (d, 4J P-C ) 4 Hz, pyrCH), 32.2 (s, CH3C-
7.60 (bs, 4H, p-BArf), 3.99 (d, J P-H ) 6 Hz, 2H, ClCH2PMe3),
2
2.00 (d, J P-H ) 14 Hz, 9H, ClCH2PMe3). 13C{1H} (125 MHz,
1
CH2Cl2, 25 °C): δ 7.9 (d, J P-C ) 55 Hz, ClCH2PMe3), 33.3 (d,
1
3
1J P-C ) 55 Hz, ClCH2PMe3), 118.1 (septet, J F-C ) 4 Hz,
(O)H), 16.4 (s, pyrCH3), 15.7 (s, pyrCH3), 14.9 (d, J P-C ) 40
1
2
Hz, PMe3), 13.8 (s, pyrCH3), 13.7 (s, pyrCH3), 12.9 (s, pyrCH3),
12.8 (s, pyrCH3), -24.8 (d, J ) 6 Hz, Ir-Me). 31P{1H} NMR
(161.9 MHz, CD2Cl2, 25 °C): δ -43.8. 19F NMR (376.5 MHz,
CD2Cl2, 25 °C): δ -60.9.11B NMR (160 MHz, CD2Cl2, 25 °C):
p-BArf), 125.2 (q, J F-C ) 270 Hz, BArfCF3), 129.5 (qq, J F-C
4
1
) 31 Hz, J F-C ) 3 Hz, m-BArf), 135.4 (s, o-BArf), (q, J B-C
)
50 Hz, i-BArf). 11B NMR (160 MHz, CD2Cl2, 25 °C): δ -7.3 (s,
BArf). 19F NMR (376.5 MHz, CD2Cl2, 25 °C): δ -60.8. 31P{1H}
NMR (161.9 MHz, CD2Cl2, 25 °C): δ 30.9. IR (KBr): 3095 (w),
3013 (w), 2934 (w), 1788 (m), 1611 (m), 1426 (m), 1357 (s),
1278 (s), 1130 (s), 961 (m), 887 (m), 838 (m), 710 (m), 671 (m).
HRMS (FAB/NBA) m/z for [C4H11PCl]+ (M+): calcd 125.0287,
obsd 125.0284. Anal. Calcd for C36H23BClPF24: C, 43.73; H,
2.34. Found: C, 43.99; H, 2.12.
1
δ -7.2 (BArf), 9.5 (d, J B-H ) 108 Hz). IR (KBr): 2935 (w),
2560 (w), 1650 (m), 1610 (m), 1550 (m), 1447 (m), 1421 (m),
1355 (s), 1278 (s), 1278 (s), 1163 (s), 1073 (w), 950 (m), 890
(m), 849 (m), 792 (w), 714 (m), 683 (m), 671 (m). Anal. Calcd
for
C
53H50N6PB2IrOF24‚1/2CH2Cl2 (confirmed by 1H NMR
spectroscopy): C, 41.99; H, 3.36; N, 5.49. Found: C, 42.26; H,
3.28; N, 5.31.
[Tp Me (P Me3)Ir (N2)(P h )][BAr f] (9). To a solution of 3-N2
2
[Tp Me (P Me3)Ir Me(HC(O)C6H4CH3)][BAr f] (11). To a vial
2
(35 mg, 0.023 mmol) in CH2Cl2 (3 mL) was added a solution
of C6H6 (2 µl, 0.023 mmol) in CH2Cl2 (1 mL). After 15 h at
room temperature, the solution was filtered and the solvent
was removed under reduced pressure. Yield: 28 mg, 76%. This
containing a solution of [TpMe (PMe3)IrMe(N2)][BArf] (40.2 mg,
2
0.028 mmol) in CH2Cl2 (3 mL) was added p-tolualdehyde (3.3
µL, 0.028 mmol) via syringe. Upon addition the solution turned
bright orange. The solvent was removed under reduced pres-
sure after 30 min at 22 °C to yield a bright yellow solid. The
product was dissolved in a minimum of CH2Cl2, layered with
pentane, and cooled to -40 °C. Over the course of 5 days,
yellow needlelike crystals of 11 formed. Yield: 38 mg, 87%.
1
material was ∼90% pure as determined by H NMR spectros-
copy. Material suitable for single-crystal X-ray analysis was
obtained by slow diffusion of pentane into a concentrated
solution of [TpMe (PMe3)IrPh(N2)][BArf] in CH2Cl2 at -40 °C.
2
1H NMR (400 MHz, CD2Cl2, 25 °C): δ 7.69 (bs, 8H, o-BArf),
1H NMR (500 MHz, CD2Cl2, 25 °C): δ 1.55 (d, 9H, J P-H ) 10
Hz, PMe3), 1.86 (d, 3H, J P-H ) 4 Hz, Ir-Me), 1.90 (s, 3H,
pyrCH3), 1.91 (s, 3H, pyrCH3), 2.39 (s, 6H, pyrCH3), 2.47 (s,
3H, HC(O)C6H4CH3), 2.48 (s, 3H, pyrCH3), 2.54 (s, 3H,
pyrCH3), 5.85 (s, 1H, pyrCH), 5.86 (s, 1H, pyrCH), 5.98 (s, 1H,
2
1
7.52 (bs, 4H, p-BArf), 7.24 (d, H, J H-H ) 7 Hz, C6H5), 7.15 (t,
3
1
1H, J H-H ) 7 Hz, C6H5), 7.07 (t, H, J H-H ) 7 Hz, C6H5), 6.86
(t, 1H, J H-H ) 8 Hz, C6H5), 6.23 (d, 1H, J H-H ) 8 Hz, C6H5),
6.01 (s, 1H, pyrCH), 5.92 (s, 1H, pyrCH), 5.80 (s, 1H, pyrCH),
2.45 (s, 3H, pyrCH3), 2.43 (s, 3H, pyrCH3), 2.40 (s, 3H, pyrCH3),
3
2
pyrCH), 7.42 (d, J H-H ) 8 Hz, HC(O)C6H4CH3), 7.58 (bs, 4H,
2.34 (s, 3H, pyrCH3), 1.60 (d, 9H, J P-H ) 10 Hz, Ir-PMe3),
1.58 (s, 3H, pyrCH3), 1.38 (s, 3H, pyrCH3). 13C{1H} NMR (125
MHz, CD2Cl2): δ 12.9 (s, pyrCH3), 13.6 (s, pyrCH3), 13.8 (s,
p-BArf), 7.58 (d, HC(O)C6H4CH3, obscured by BArf resonance),
7.75 (bs, 8H, o-BArf), 9.18 (s, HC(O)C6H4CH3). 13C{1H} NMR
2
1
(125 MHz, CD2Cl2, 25 °C): δ -24.6 (d, J P-C ) 8 Hz, Ir-Me),
12.9 (s, pyrCH3), 13.0 (s, pyrCH3), 13.7 (s, pyrCH3), 13.9 (s,
pyrCH3), 16.2 (d, J P-C ) 40 Hz, PMe3), 16.4 (s, pyrCH3), 18.7
4
(s, pyrCH3), 109.3 (d, J P-C ) 4 Hz, pyrCH), 110.1 (s, pyrCH),
1
3
pyrCH3), 15.0 (d, J P-C ) 39 Hz, PMe3), 15.8 (s, pyrCH3), 16.4
111.2 (s, pyrCH), 118.1 (septet, J F-C ) 4 Hz, p-BArf), 125.2
3
1
(s, pyrCH3), 22.9 (s, HC(O)C6H4CH3), 109.1 (d, J P-C ) 4 Hz,
(q, J F-C ) 270 Hz, BArfCF3), 126.2 (s, C6H5), 128.9 (s, C6H5),
pyrCH), 109.2 (s, pyrCH), 110.5 (s, pyrCH), 118.1 (septet, 3J F-C
) 4 Hz, p-BArf), 125.2 (q, 1J F-C ) 270 Hz, BArfCF3), 129.5 (qq,
128.8 (s, C6H5), 129.5 (qq, 2J F-C ) 31 Hz, 4J F-C ) 3 Hz, m-BArf),
135.4 (s, o-BArf), 140.0 (s, C6H5), 138.0 (d, 3J P-C ) 5 Hz, C6H5),
2J F-C ) 31 Hz, J F-C ) 3 Hz, m-BArf), 131.6 (s, HC(O)C6H4-
4
2
3
142.2 (d, J P-C ) 9 Hz, C6H5), 146.0 (d, J P-C ) 4 Hz, pyrCq),
147.3 (s, pyrCq), 148.3 (s, pyrCq), 151.7 (s, pyrCq), 151.8 (d,
CH3), 132.3 (s, p-HC(O)C6H4CH3), 135.4 (s, o-BArf), 145.7 (d,
J ) 3 Hz, pyrCq), 146.2 (s, pyrCq), 147.8 (s, i-HC(O)C6H4CH3),
149.1 (s, pyrCq), 149.4 (s, pyrCq), 153.0 (s, pyrCq), 155.1 (s,
3J P-C ) 4 Hz, pyrCq), 153.6 (d, J P-C ) 1 Hz, pyrCq), 162.4 (q,
5
1J B-C ) 50 Hz, i-BArf). 31P{1H} NMR (161.9 MHz, CD2Cl2, 25
°C): δ -48.9. 19F NMR (376.5 MHz, CD2Cl2, 25 °C): δ -61.0.
11B NMR (160 MHz, CD2Cl2, 25 °C): δ -7.3 (BArf), -9.5 (d,
1
pyrCq), 162.3 (q, J B-C ) 50 Hz, i-BArf), 207.6 (s, HC(O)C6H4-
CH3). 31P{1H} NMR (161.9 MHz, CD2Cl2, 25 °C): δ -46.6. 19F
NMR (376.5 MHz, CD2Cl2, 25 °C): δ -61.0.11B NMR (160 MHz,
J B-H ) 102 Hz, TpMe ). IR (KBr): 3055 (w), 2970 (w), 2929
1
2
CD2Cl2, 25 °C): δ -7.3 (s, BArf), 9.6 (s, TpMe ). IR (KBr): 2973
2
(w), 2567 (m), 2236 (s), 1611 (m), 1551 (s), 1449 (s), 1421 (s),
1356 (s), 1278 (s), 1162 (s), 1073 (s), 959 (m), 888 (m), 839 (m),
794 (w), 713 (m), 682 (m), 671 (m). HRMS (FAB, nitrobenzyl
alcohol): m/z for [C24H36BN6PIr]+ (M+ - N2): calcd 643.2497,
obsd 643.2461.
(m), 2935(m), 2562 (w, B-H), 1610 (m), 1592 (s), 1562 (m),
1355 (s), 1278 (s), 1127 (s), 958 (m), 888 (m), 840 (m), 713 (m),
681 (m), 671 (m). FAB/MS (sulfolane): m/z 701 (M+). Anal.
Calcd for C59H54N6PB2IrOF24
Found: C, 44.90; H, 3.62; N, 5.00.
: C, 45.31; H, 3.48; N, 5.36.
[Tp Me (P Me3)Ir Me(HC(O)CH3)][BAr f] (10). A glass vessel
2
[Tp Me (P Me3)Ir (C6H4CH3)(CO)][BAr f] (12). A glass vessel
2
sealed to a Kontes vacuum adapter was charged with 3-N2
(64 mg, 0.043 mmol), a stir bar, and CH2Cl2 (2 mL). The
solution was degassed, and acetaldehyde (0.047 mmol) was
added via vacuum-transfer techniques. After stirring the
solution at 22 °C for 12 h, the reaction vessel was brought into
a glovebox. The solution was transferred to a 20 mL vial,
concentrated to ∼0.5 mL in vacuo, layered with pentane, and
sealed to a Kontes vacuum adapter was charged with [TpMe
-
2
(PMe3)IrMe(N2)][BArf] (43 mg, 0.027 mmol), p-tolualdehyde
(9.7 µL, 0.082 mmol), and CH2Cl2 (10 mL). The bright orange
solution was heated at 105 °C. After 36 h, the solution had
turned light yellow; it was filtered through glass fiber filter
paper, concentrated, layered with pentane, and cooled to -40
°C. Colorless crystals of 12 were isolated and washed with a
cold solution of pentane/CH2Cl2. Yield: 37 mg, 83%. The
pentane molecule of crystallization is not reported in the
cooled to -40 °C. Light-yellow crystals of [TpMe (PMe3)IrMe-
2
(HC(O)CH3)][BArf] were isolated and rinsed with cold pentane.
Yield: 40 mg, 60%. 1H NMR (400 MHz, CD2Cl2, 25 °C): δ 9.23

Cationic TpMe Ir(III) Complexes
Organometallics, Vol. 20, No. 23, 2001 4831
2
spectroscopic data. 1H NMR (500 MHz, CD2Cl2, 25 °C): δ 7.75
(bs, 8H, o-BArf), 7.60 (bs, 4H, p-BArf), 7.30 (d, 1H, J H-H ) 8
Hz, C6H4CH3), 7.00 (d, 1H, J H-H ) 6 Hz, C6H4CH3), 6.75 (d,
1H, J H-H ) 7 Hz, C6H4CH3), 6.20 (d, 1H, J H-H ) 7 Hz, C6H4-
CH3), 6.06 (s, 1H, pyrCH), 6.03 (s, 1H, pyrCH), 5.85 (s, 1H,
pyrCH), 2.50 (s, 3H, C6H4CH3), 2.47 (s, 3H, pyrCH3), 2.44 (s,
3H, pyrCH3), 2.38 (s, 3H, pyrCH3), 2.37 (s, 3H, pyrCH3), 2.31
(s, 3H, pyrCH3), 1.72 (d, 9H, 2J P-H ) 9 Hz, PMe3), 1.69 (s, 3H,
pyrCH3), 1.53 (s, 3H, pyrCH3). 13C{1H} NMR (125 MHz, CD2-
solution of [Cp*(PMe3)IrMe(CH2Cl2)][BArf] (15 mg, 0.011
mmol) was transferred to an NMR tube equipped with a 1/4
in. male Teflon cap. The tube was attached through the cap
to a nitrogen manifold fitted with a gauge, and the solution
was placed under N2 (8 atm). The tube was then removed from
the apparatus and shaken for ∼1 min. Caution: The tube was
agitated using a mechanical stirrer which was kept behind a
blast shield. 1H and 31P{1H} NMR spectra were then acquired.
1H NMR (500 MHz, CD2Cl2, 25 °C): δ 7.74 (bs, 8H, o-BArf),
4
Cl2, 25 °C): δ 13.0 (s, pyrCH3), 13.0 (s, pyrCH3), 13.5 (s,
7.50 (bs, 4H, p-BArf), 1.68 (d, J P-H ) 1 Hz, 15H, C5Me5, this
1
2
C6H4CH3), 14.3 (s, pyrCH3), 16.9 (s, pyrCH3), 17.2 (d, J P-C
)
differed by 0.02 ppm from 2-CH2Cl2), 1.57 (d, J P-H ) 17 Hz,
41 Hz, PMe3), 18.3 (s, pyrCH3), 20.9 (s, pyrCH3), 109.0 (d, 3J P-C
) 4 Hz, pyrCH), 109.8 (s, pyrCH), 111.1 (s, pyrCH), 115.9 (d,
9H, PMe3, this differed by 0.002 ppm from 2-CH2Cl2), 1.18 (d,
3J P-H ) 6 Hz, 3H, Ir-Me, this differed by -0.064 ppm from
2-CH2Cl2). 31P{1H} NMR (202.4 MHz, CD2Cl2, 25 °C): δ -27.9
(this differed by 1.20 ppm from 2-CH2Cl2). IR Sp ectr oscop y:
In a glovebox, a CH2Cl2 (5 mg) solution of [Cp*(PMe3)IrMe(CH2-
Cl2)][BArf] (30.1 mg, 0.053 mmol) was transferred to a high-
pressure infrared cell.100 The cell was sealed, removed from
the box, and pressurized with nitrogen. IR(CH2Cl2): 2207 (N2).
X-r a y Str u ctu r e Deter m in a tion s. The X-ray diffraction
measurements were made on a Siemens SMART diffractome-
ter101 with a CCD area detector. The crystal was mounted on
a glass fiber using Paratone N hydrocarbon oil. Cell constants
and an orientation matrix for data collection were obtained
from a least-squares refinement using the measured positions
of reflections in the range 3.00° < 2θ < 45.00°. Data were
integrated using the program SAINT.102 No decay correction
was applied. An empirical absorption correction based on
comparison of redundant and equivalent data and an el-
lipsoidal model of the absorption surface was applied using
2J P-C ) 8 Hz, C6H4CH3), 118.1 (septet, J F-C ) 4 Hz, p-BArf),
3
1
2
125.2 (q, J F-C ) 270 Hz, BArfCF3), 129.5 (qq, J F-C ) 31 Hz,
4J F-C ) 3 Hz, m-BArf), 130.1 (s, C6H4CH3), 130.5 (s, C6H4CH3),
135.4 (s, o-BArf), 136.2 (s, C6H4CH3), 139.0 (s, C6H4CH3), 140.1
3
3
(d, J P-C ) 5 Hz, C6H4CH3), 146.5 (d, J P-C ) 3 Hz, pyrCq),
147.7 (s, pyrCq), 148.0 (s, pyrCq), 152.0 (d, 3J P-C ) 3 Hz, pyrCq),
153.5 (s, pyrCq), 162.3 (q, 1J B-C ) 50 Hz, i-BArf), 162.9 (d, 2J P-C
) 11 Hz, Ir-CO). 31P{1H} NMR (161.9 MHz, CD2Cl2, 25 °C): δ
-45.3. 19F NMR (376.5 MHz, CD2Cl2, 25 °C): δ -61.0. 11B
NMR (160 MHz, CD2Cl2, 25 °C): δ -7.3 (s, BArf), -9.3 (s,
TpMe ). IR (KBr): 2967 (w), 2930 (w), 2570 (w), 2069 (s), 1611
2
(m), 1551 (m), 1450 (m), 1422 (m), 1355 (s), 1280 (s), 1129 (s),
1074 (m), 960 (m), 888 (m), 805 (w), 745 (w), 714 (m), 682 (m),
671 (m). FAB/MS (NBA): m/z 685 (M+). Anal. Calcd for
C
53H40N6PB2IrOF24‚CH3(CH2)3CH3‚CH2Cl2 (confirmed by 1H
NMR spectroscopy): C, 45.09; H, 3.78; N, 4.93. Found: C,
44.91; H, 3.63; N, 5.20.
the program XPREP103 or SADABS (7: Tmax ) 0.69, Tmin
0.0.56; 3-N2: Tmax ) 0.80, Tmin ) 0.46; 9: Tmax ) 0.74, Tmin
)
)
[Tp Me (P Me3)Ir H(N2)][BAr f] (13). A glass vessel (100 mL)
2
sealed to a Kontes vacuum adapter was charged with [TpMe
-
2
0.64).104 The structures were solved using methods described
previously.105 The function minimized in the full-matrix least-
squares refinement was ∑w(|Fo| - |Fc|)2. The weighting scheme
was based on counting statistics and included a factor to
downweight the intense reflections. Positional and thermal
parameters for the non-hydrogen atoms and the complete list
of intramolecular distances and angles for the complexes are
given in the Supporting Information.
(PMe3)Ir(C(N2)][BArf] (95 mg, 0.061 mmol), CH2Cl2 (10 mL),
and a stirbar. The solution was freeze-pump-thaw degassed
(3×), placed under H2 (1 atm), and allowed to stir. After 1.5 h,
the solvent was removed under reduced pressure to yield an
off-white solid. 1H NMR spectroscopic analysis (CD2Cl2) of the
solid revealed a 1:1 mixture of the desired product and [TpMe
-
2
(PMe3)IrH(H2)][BArf]. The powder was redissolved in CH2Cl2
(20 mL) and transferred to a Parr Bomb containing a stirbar.
The bomb was pressurized with N2 (40 atm), and the solution
was allowed to stir. After 12 h, the bomb was vented and
repressurized with N2 (40 atm). After an additional 12 h, the
bomb was vented, and the solvent was removed under reduced
(a ) [Tp Me (P Me3)Ir Me(N2)][BAr f] (3-N2). The compound
2
crystallizes in the space group C2/c (no. 15) with eight formula
units in the unit cell. The methyl and dinitrogen ligands are
disordered over the two coordination sites in a 47:53 ratio. The
dinitrogen was assumed to be linearly coordinated, and the
methyl group was assumed to lie on the same vector as
dinitrogen. Due to the close proximity of the atoms involved
in the disorder, the positions of only the terminal nitrogen
atoms of the N2 ligand (N7 and N8) were refined. The fluorine
atoms of some of the CF3 groups on the BArf anion were
disordered. The occupancies of the disordered fluorine atoms
in the BArf anion were adjusted so that the isotropic thermal
parameters of the disordered components were roughly equal;
the sum of the occupancies of the fluorine atoms of each CF3
group was equal to three. The non-hydrogen atoms (except for
the boron atoms and the partial occupancy chlorine, carbon,
fluorine, and nitrogen atoms) were refined anisotropically. The
pressure to yield [TpMe (PMe3)IrH(N2)][BArf]. White microc-
2
rystals of 13 are obtained after crystallization from CH2Cl2/
1
pentane at -40 °C. Yield: 60 mg, 64%. H (500 MHz, CD2Cl2
25 °C): δ 7.70 (bs, 8H, o-BArf), 7.60 (bs, 4H, p-BArf), 6.07 (s,
1H, pyrCH), 5.98 (s, 1H, pyrCH), 5.85 (s, 1H, pyrCH), 2.49 (s,
3H, pyrCH3), 2.43 (s, 3H, pyrCH3), 2.40 (s, 3H, pyrCH3), 2.29
2
(s, 3H, pyrCH3), 2.27 (s, 6H, pyrCH3), 1.65 d, J P-H ) 11 Hz,
9H, PMe3), -18.80 (d, 2J P-H ) 19 Hz, 1H, PMe3). 13C{1H} (125
MHz, CH2Cl2, 25 °C): δ 12.7 (s, pyrCH3), 12.8 (s, pyrCH3), 13.4
1
(s, pyrCH3), 14.9 (s, pyrCH3), 15.8 (s, pyrCH3), 17.5 (d, J P-C
3
) 41 Hz, PMe3), 18.0 (s, pyrCH3), 107.0 (d, J P-C ) 3 Hz,
pyrCH), 109.2 (s, pyrCH), 109.3 (s, pyrCH), 118.1 (septet, 3J F-C
) 4 Hz, p-BArf), 125.2 (q, 1J F-C ) 270 Hz, BArfCF3), 129.5 (qq,
4
2J F-C ) 31 Hz, J F-C ) 3 Hz, m-BArf), 135.4 (s, o-BArf), 146.5
(d, J ) 3 Hz, pyrCq), 147.1 (s, pyrCq), 149.5 (s, pyrCq), 151.0
(d, J ) 3 Hz, pyrCq), 151.9 (s, pyrCq), 154.1 (s, pyrCq), 162.3
(99) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992,
11, 3920-3922.
1
(q, J B-C ) 50 Hz, i-BArf). 11B NMR (160 MHz, CD2Cl2, 25
(100) Schultz, R. H.; Bengali, A. A.; Tauber, M. J .; Weiller, B. H.;
Wasserman, E. P.; Kyle, K. R.; Moore, C. B.; Bergman, R. G. J . Am.
Chem. Soc. 1994, 116, 7369-7377.
°C): δ -7.3 (s, BArf), -9.1 (d, 1J B-H ) 96 Hz, TpMe ). 19F NMR
2
(376.5 MHz, CD2Cl2, 25 °C): δ -61.0. 31P{1H} NMR (161.9
MHz, CD2Cl2, 25 °C): δ -46.7. IR (KBr): 2968 (w), 2925 (w),
2562 (w, B-H), 2231 (m, N2), 2205 (w, Ir-H), 1610.5 (m), 1550
(m), 1449 (m), 1423 (m), 1386 (m), 1355 (s), 1279 (s), 1129 (s),
960 (s), 839 (w), 796 (w), 714 (w), 671 (w). Anal. Calcd for
(101) SMART Area-Detector Software Package; Siemens Industrial
Automation, Inc.: Madison, WI, 1995.
(102) SAINT: SAX Area-Detector Integration Program, V4.024;
Siemens Industrial Automation, Inc.: Madison, WI, 1995.
(103) XPREP (v 5.03), Part of the SHELXTL Crystal Structure
Determination Package; Siemens Industrial Automation, Inc.: Madi-
son, WI, 1995.
(104) Sheldrick, G. SADABS Siemens Area Detector ABSorption
correction program; 1996. Advance copy, private communication.
(105) Kaplan, A. W.; Polse, J . L.; Ball, G. E.; Andersen, R. A.;
Bergman, R. G. J . Am. Chem. Soc. 1998, 120, 11649-11662.
C
50H44N8F24PIrB2: C, 41.20; H, 3.04; N, 7.69. Found: C, 40.85;
H, 2.83; N, 7.38.
Sp ectr oscop ic Obser va tion of [Cp *(P Me3)Ir Me(N2)]-
[BAr f] (2-N2). NMR Sp ectr oscop y. A CD2Cl2 (0.2 mL)

4832 Organometallics, Vol. 20, No. 23, 2001
Tellers and Bergman
partial occupancy fluorine atoms, the terminal N atoms of the
disordered dinitrogen ligand (N7, N8), and the partial oc-
cupancy carbon (C53) and chlorine atoms (Cl3, Cl5) of the
disordered CH2Cl2 molecules were refined isotropically.
atoms were modeled with isotropic thermal parameters con-
strained to be equal, and their occupancies were allowed to
refine.
Ack n ow led gm en t. This work was supported by the
Director, Office of Energy Research, Office of Basic
Energy Sciences, Chemical Sciences Division, U.S.
Department of Energy, under Contract No. DE-AC03-
76SF00098. The Center for New Directions in Organic
Synthesis is supported by Bristol-Myers Squibb as
Sponsoring Member. We thank Dr. Fred Hollander and
Dr. Dana Caulder of the UC Berkeley CHEXRAY
facility for the X-ray structure determinations, Profes-
sors D. M. Heinekey and Ernesto Carmona for helpful
discussions, and Dr. J ake Yeston and Dr. J effrey T.
Golden for assistance with high-pressure N2 experi-
ments. We also thank Boehringer-Ingelheim Pharma-
ceuticals, Inc. for a graduate fellowship to D.M.T.
(b) Tp Me (P Me3)Ir Me(OTf) (7). The compound crystallizes
2
in the space group P21/c (no. 14) with four formula units in
the unit cell. The non-hydrogen atoms, except for Cl(2) and
C(21) of the disordered solvent, were refined anisotropically.
The hydrogen atoms, Cl(2), and C(21) were refined isotropi-
cally.
(c) [Tp Me (P Me3)Ir P h (N2)][BAr f] (9). The compound crys-
2
tallizes in the space group P21/C (no. 14) with four molecules
in the unit cell. The asymmetric unit consists of the iridium
complex cation, a BArf anion, and a pentane of crystallization.
The non-hydrogen atoms (except the partial occupancy carbon
and fluorine atoms) were refined anisotropically. The partial
occupancy fluorine atoms (F(1)-F(3) and F(22)-F(36)) and
carbon atoms (C(58) and C(60)-C(65)) were refined isotropi-
cally. Two of the CF3 groups on the BArf anion show a three-
part rotational disorder, modeled with a 40:40:20% occupancy
ratio. Inspection of the Fourier map clearly shows that this is
a lightly hindered rotation of the CF3 groups. The pentane of
crystallization shows considerable disorder. The two terminal
carbons (C57 and C59) were refined with full occupancy and
anisotropic thermal motion parameters. The remaining carbon
Su p p or tin g In for m a tion Ava ila ble: ORTEP diagrams
and tables of atomic coordinates, anisotropic displacement
parameters, bond lengths and bond angles for compounds 3-N2,
7, and 9. These materials are available free of charge via the
Internet at http://pubs.acs.org.
OM010697C