Alkyne/methylene coupling at adjacent iridium/osmium centers: Facile carbon-carbon and carbon-oxygen bond formation

Article abstract of DOI:10.1021/om1009999

The methylene-bridged complex [IrOs(CO)₄(μ-CH ₂)(dppm)₂][CF₃SO₃] (dppm = μ-Ph₂PCH₂PPh₂) (3) can be synthesized by the addition of diazomethane to [IrOs(CO)₅(dppm)₂][CF ₃SO₃] (1) or [IrOs(CO)₄(dppm) ₂][CF₃SO₃] (2). Reaction of 3 with dimethyl acetylenedicarboxylate (DMAD) leads to the insertion of the alkyne into the iridium-carbon bond, yielding both [IrOs(CO)₄(μ- κ¹:κ¹-C(CO₂CH₃)= C(CO₂CH₃)CH₂)(dppm)₂][CF ₃SO₃] (5) and [IrOs(CO)₃(μ- κ¹:κ¹-C(CO₂CH₃)= C(CO₂CH₃)CH₂)(dppm)₂][CF ₃SO₃] (6), each of which can be obtained as the exclusive product under either CO or an Ar purge, respectively. Hexafluorobutyne (HFB) fails to react with 3, but reacts with [IrOs(CO)₃(μ-CH ₂)(dppm)₂][CF₃SO₃] (4) yielding [IrOs(CO)₃(μ-κ¹:κ¹-C(CF ₃)=C(CF₃)CH₂)(dppm)₂][CF ₃SO₃] (7). Reaction of 7 with diazomethane results in the insertion of a second methylene unit into the iridium-carbon bond, yielding [IrOs(CO)₃(μ-κ¹:κ¹-CH ₂(CF₃)C=C(CF₃)CH₂)(dppm) ₂][CF₃SO₃] (9), which can be characterized by NMR spectroscopy only at low temperatures owing to deinsertion of the iridium-bound methylene group at ambient temperature. Compound 6 also reacts with diazomethane but in this case results in the formation of a new carbon-oxygen bond between the newly introduced methylene unit and a carbonyl oxygen of the inserted DMAD fragment. This bond formation is accompanied by carbon-hydrogen bond activation of the original osmium-bound methylene group, yielding [IrOs(CO)₃(μ-H)(μ-κ¹: κ¹:κ¹-CH₂OC(OCH₃)= CC(CO₂CH₃)=CH)(dppm)₂][CF₃SO ₃] (8). Attempts to insert a methylene unit into the iridium-carbon bond of the alkyne-bridged complexes [IrOs(CO)₃(μ- κ¹:κ¹-RC=CR)(dppm)₂][CF ₃SO₃] (R = CO₂Me (12), CF₃ (13)) yields the C₃-bridged complex [IrOs(CO)₃(μ- κ¹:κ¹-CH₂(CF₃)C=CCF ₃)(dppm)₂][CF₃SO₃] (14) in the case of 13, but no further methylene incorporation is observed. Compound 12 reacts with diazomethane to give a number of unidentified products under a variety of conditions. The reactivities of the aforementioned complexes are compared to that of related late metal combinations.

Full text of DOI:10.1021/om1009999

952 Organometallics 2011, 30, 952–964
DOI: 10.1021/om1009999
Alkyne/Methylene Coupling at Adjacent Iridium/Osmium Centers: Facile
Carbon-Carbon and Carbon-Oxygen Bond Formation
Tiffany J. MacDougall, Angela Llamazares, Oliver Kuhnert, Michael J. Ferguson,‡
Robert McDonald,‡ and Martin Cowie*
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2.
‡X-ray Crystallography Laboratory.
Received October 20, 2010
The methylene-bridged complex [IrOs(CO)4(μ-CH2)(dppm)2][CF3SO3] (dppm=μ-Ph2PCH2PPh2) (3)
can be synthesized by the addition of diazomethane to [IrOs(CO)5(dppm)2][CF3SO3] (1) or [IrOs(CO)4-
(dppm)2][CF3SO3] (2). Reactionof3with dimethyl acetylenedicarboxylate (DMAD) leads to the insertion
of the alkyne into the iridium-carbon bond, yielding both [IrOs(CO)4(μ-κ1:κ1-C(CO2CH3)dC(CO2CH3)-
CH2)(dppm)2][CF3SO3] (5) and [IrOs(CO)3(μ-κ1:κ1-C(CO2CH3)dC(CO2CH3)CH2)(dppm)2]-
[CF3SO3] (6), each of which can be obtained as the exclusive product under either CO or an Ar purge,
respectively. Hexafluorobutyne (HFB) fails to react with 3, but reacts with [IrOs(CO)3(μ-CH2)(dppm)2]-
[CF3SO3] (4) yielding [IrOs(CO)3(μ-κ1:κ1-C(CF3)dC(CF3)CH2)(dppm)2][CF3SO3] (7). Reaction of 7
with diazomethane results in the insertion of a second methylene unit into the iridium-carbon bond,
yielding [IrOs(CO)3(μ-κ1:κ1-CH2(CF3)CdC(CF3)CH2)(dppm)2][CF3SO3] (9), which can be character-
ized by NMR spectroscopy only at low temperatures owing to deinsertion of the iridium-bound
methylene group at ambient temperature. Compound 6 also reacts with diazomethane but in this
case results in the formation of a new carbon-oxygen bond between the newly introduced methylene
unit and a carbonyl oxygen of the inserted DMAD fragment. This bond formation is accompanied
by carbon-hydrogen bond activation of the original osmium-bound methylene group, yielding
[IrOs(CO)3(μ-H)(μ-κ1:κ1:κ1-CH2OC(OCH3)dCC(CO2CH3)dCH)(dppm)2][CF3SO3] (8). Attempts
to insert a methylene unit into the iridium-carbon bond of the alkyne-bridged complexes
[IrOs(CO)3(μ-κ1:κ1-RCdCR)(dppm)2][CF3SO3] (R = CO2Me (12), CF3 (13)) yields the C3-bridged
complex [IrOs(CO)3(μ-κ1:κ1-CH2(CF3)CdCCF3)(dppm)2][CF3SO3] (14) in the case of 13, but no
further methylene incorporation is observed. Compound 12 reacts with diazomethane to give a
number of unidentified products under a variety of conditions. The reactivities of the aforementioned
complexes are compared to that of related late metal combinations.
Introduction
reactions,11-13 and the Fischer-Tropsch (FT) process.14,15
The majority of alkylidene complexes studied are of the form
LnMdCRR0, in which the unsaturated alkylidene ligand is
terminally bound to one metal center.16-20 Complexes in which
the alkylidene group bridges pairs of metal centers21,22 have been
much less studied and differ significantly from terminally bound
carbenes in having an approximately tetrahedral rather than
trigonal-planar geometry. As such, the bridging alkylidene unit
is formally saturated and is expected to have a lower reactivity
than the terminal unit. Nevertheless, the prototype alkylidene-
the methylene (CH2) group-has been implicated as the pivotal
Metal-alkylidene complexes play an important role in the
formation of carbon-carbon bonds, being involved in a number
of processes including olefin metathesis,1-10 cyclopropanation
*Corresponding author. E-mail: martin.cowie@ualberta.ca. Fax:
01 7804928231. Tel: 01 7804925581.
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Published on Web 01/05/2011
2011 American Chemical Society

Article
Organometallics, Vol. 30, No. 5, 2011 953
surface-bound species involved in carbon-carbon chain growth
in FT chemistry,14,15,23-28 in which this group is generally
accepted to bridge pairs of adjacent metals on the catalyst
surface. In binuclear complexes, bridging methylene groups
have shown a rich chemistry in carbon-carbon bond forma-
tion, in some ways mimicking FT reactivity.26,29-49
In attempts to determine the roles of the adjacent metals in
carbon-carbon bond formation involving methylene
groups that bridge pairs of different metals, we have pre-
viously investigated the Rh/Ru,41,42 Rh/Os,37,38 and Ir/Ru43
combinations of metals. The Rh/Os combination has dem-
onstrated a particularly rich chemistry in which the in-
corporation of up to four methylene groups has occurred,
generating either allyl and methyl, or butanediyl groups at
the metals.37,38 Labeling studies on this system implicated
the involvement of bridging hydrocarbyl intermediates in
these methylene-coupling reactions. However, these puta-
tive hydrocarbyl-bridged intermediates remained elusive,
so we sought to model these transformations via coupling
of methylene units with unsaturated substrates such as
olefins,50,51 alkynes,29,31,35,36,39,42,45-48,52-54 and cumu-
lenes55-59 as sources of C2 fragments.
In the present study we undertook an investigation into the
Ir/Os combination of metals with the goal of exploiting the
greater bond strengths involving these third-row metals, which
we assumed might stabilize species not observed with the other
metal combinations, allowing us to study them in greater detail.
We outline our attempts to generate C3- and C4-bridged
hydrocarbyl fragments, either by reactions of the methylene-
bridged (C1) complexes [IrOs(CO)n(μ-CH2)(dppm)2][X] (n =
3, 4; X = BF4, CF3SO3) with hexafluorobutyne and dimethyl
acetylenedicarboxylate or by reaction of the alkyne-bridged
(C2) precursors [IrOs(CO)n(μ-κ1:κ1-RCdCR)(dppm)2]-
[CF3SO3] (n = 3, 4; R = CF3, CO2Me) with diazomethane.
The reactivity of this system is also compared to the related
work involving the other metal combinations.37,38,41-43,54
Experimental Section
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General Comments. All solvents were dried using appropriate
desiccants, distilled before use, and stored under a nitrogen
atmosphere. Reactions were performed under an argon atmo-
sphere using standard Schlenk techniques. Diazomethane was
generated from Diazald, which was purchased from Aldrich, as
were the 13C-enriched Diazald, dimethyl acetylenedicarboxylate
(DMAD), and bis(triphenylphosphoranylidene)ammonium
chloride, while the hexafluorobutyne (HFB) was purchased from
PCR Inc. 13C-enriched N-methyl-N-nitroso-p-toluenesulfona-
mide was prepared by using a modified version of the procedure
for synthesizing the 14C-enriched radio-labeled analogue.60
The trimethylamine-N-oxide dihydrate was also purchased
from Aldrich and was dried either by sublimation or accord-
ing to the literature procedure,61 and the 13CO was purchased
from Isotech, Inc. The complexes [IrOs(CO)5(dppm)2][CF3SO3]
(1) and [IrOs(CO)4(dppm)2][CF3SO3] (2) were prepared using
modified versions of the published procedures.62
The 1H and 31P{1H} NMR spectra were recorded on a Varian
Inova 400 spectrometer operating at 399.9 and 161.8 MHz,
respectively. All low-temperature spectra and the heteronuclear
decoupling experiments (13C{1H} and 13C{1H,31P}) were re-
corded on a Varian Unity spectrometer operating at 161.9 MHz
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1
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also carried out in the departmental facility.
Preparation of Compounds. Spectroscopic data for the com-
pounds prepared are presented in Table 1.
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954 Organometallics, Vol. 30, No. 5, 2011
MacDougall et al.

Article
a. [IrOs(CO)5(dppm)2][CF3SO3] (1) and [IrOs(CO)4(dppm)2]-
[CF3SO3] (2). Compound 1 was prepared according to the
published procedure62 with the slight modification described herein.
The protonation step to generate [IrOs(CO)3(μ-H)2(dppm)2][X]
Organometallics, Vol. 30, No. 5, 2011 955
e. [IrOs(CO)3(μ-K1:K1-C(CO2CH3)dC(CO2CH3)CH2)(dppm)2]-
[CF3SO3] (6). Compound 4 (25 mg, 0.018 mmol) was dissolved in
5 mL of CH2Cl2, and to it was added DMAD (2.6 μL, 0.021 mmol),
resulting in a color change from red to yellow. The solvent was
evaporated to 2 mL, and 10 mL of diethyl ether and 20 mL of
pentane were added to precipitate a yellow-orange solid. The solid
was recrystallized from CH2Cl2/diethyl ether/pentane (1:3:5),
washed with 2 ꢀ 5 mL of pentane, and dried in vacuo (89% yield).
HRMS: m/z calcd for C60H52IrO7OsP4 (Mþ), 1393.1905; found,
1393.1902 (Mþ). Anal. Calcd for C61F3H52IrO10OsP4S: C, 47.56;
H, 3.40. Found: C, 47.73; H, 3.74.
was carried out using HOSO2CF3 (HOTf) instead of HBF4 Et2O
3
as follows. A solution of HOTf in Et2O (1 equiv in 10 mL of Et2O)
was added to an orange solution of [IrOs(H)2(CO)3(μ2-κ1:κ1:κ1-(o-
C6H4)PhPCH2PPh2)(dppm)]62 in benzene, resulting in the gradual
precipitation of a yellow powder. To ensure complete precipita-
tion of the product, excess diethyl ether was added. Furthermore,
instead of purging a solution of [IrOs(CO)3(μ-H)2(dppm)2][CF3-
SO3] in CH2Cl2, a slurry of the complex in THF and CH2Cl2 was
purged with CO(g) for 16 h to afford 1. Compound 2 was prepared
by the published procedure,62 using CH2Cl2 as solvent with
recrystallization from CH2Cl2/diethyl ether.
f. [IrOs(CO)3(μ-K1:K1-C(CF3)dC(CF3)CH2)(dppm)2][CF3-
SO3] (7). Compound 4 (55 mg, 0.039 mmol) was dissolved in
10 mL of CH2Cl2. Hexafluoro-2-butyne (HFB) was passed
vigorously through the solution for 2 min, resulting in a color
change from red to orange. The solvent was evaporated to 2 mL,
and 10 mL of diethyl ether and 20 mL of pentane were added to
precipitate an orange solid. The solid was recrystallized from
CH2Cl2/diethyl ether/pentane (1:3:3), washed with 2 ꢀ 5 mL of
pentane, and dried in vacuo (87% yield). HRMS: m/z calcd for
C59H46F6IrO3OsP4 (Mþ), 1413.1539; found, 1413.1541 (Mþ).
b. [IrOs(CO)4(μ-CH2)(dppm)2][CF3SO3] (3). Method (i).
Compound 1 (50 mg, 0.035 mmol) was dissolved in 5 mL of
CH2Cl2. Diazomethane, generated from 200 mg of Diazald, was
passed through the solution at ambient temperature, causing the
solution color to change from light yellow to bright yellow. The
solvent was evaporated to 2 mL, and 30 mL of diethyl ether was
added to precipitate a bright yellow solid. This solid was recrys-
tallized from CH2Cl2/diethyl ether, washed with 2 ꢀ 5 mL of
diethyl ether, and dried in vacuo (91% yield). HRMS: m/zcalcd for
C55H46IrO4OsP4 (Mþ), 1279.1585; found, 1279.1585 (Mþ). Anal.
Anal. Calcd for C59.25Cl0.5F9H46.5IrO6OsP4S (7 0.25 CH2Cl2):
3
C, 44.99; H, 2.96. Found: C, 44.80; H, 3.09. 1H NMR spectros-
copy in CDCl3 confirmed the presence of dichloromethane of
crystallization. 19F NMR: δ -47.0 (quartet, 3F, 5JFF = 13.8 Hz),
δ -61.7 (quartet of triplets, 3F, 5JFF = 13.7 Hz, 4JFH = 2.6 Hz),
δ -79.2 (singlet, 3F).
Calcd for C59F3H53.5IrO7.75OsP4S (3 0.75 C4H10O): C, 47.82; H,
3
3.64. Found: C, 47.83; H, 3.68. 1H NMR spectroscopy in CDCl3
confirmed the presence of ether of crystallization.
g. [IrOs(CO)3(μ-H)(μ-K1:K1:K1CH2OC(OCH3)dCC(CO2-
CH3)dCH)(dppm)2][CF3SO3] (8). An orange solution of 6 (34 mg,
0.023 mmol) in 5 mL of CH2Cl2 was cooled to -78 °C. Diazo-
methane, generated from 200 mg of Diazald, was passed through
the solution at this temperature, resulting in no observable color
change. The solution was slowly warmed to ambient temperature,
the solvent was evaporated to 2 mL, and to it was added 10 mL of
diethyl ether and 20 mL of pentane to precipitate a light orange solid,
which was recrystallized from CH2Cl2/diethyl ether/pentane (1:3:5)
and dried in vacuo (86% yield). HRMS: m/z calcd for C61H54Ir-
O7OsP4 (Mþ), 1407.2061; found, 1407.2059 (Mþ). Anal. Calcd for
C62F3H54IrO10OsP4S: C, 47.90; H, 3.50. Found: C, 47.85; H, 3.91.
h. [IrOs(CO)3(μ-K1:K1-CH2C(CF3)dC(CF3)CH2)(dppm)2]-
[CF3SO3] (9). An orange solution of 7 (40 mg, 0.026 mmol) in
5 mL of CH2Cl2 was cooled to -78 °C. Diazomethane, generated
from 200 mg of Diazald, was passed through the solution at this
temperature, resulting in a color change from orange to yellow.
The solution was kept at -78 °C, and the product was character-
ized by low-temperature NMR since it was not stable upon
warming to ambient temperature. 19F NMR (-78 °C): δ -49.9
(quartet of triplets, 3F, 5JFF = 15.8 Hz, 4JFH = 2.6 Hz), δ -59.8
(quartet of triplets, 3F, 5JFF = 16.5 Hz, 4JFH = 1.3 Hz), δ -79.6
(singlet, 3F).
Method (ii). Compound 2 (40 mg, 0.028 mmol) was dissolved
in 5 mL of CH2Cl2 and cooled to -78 °C. Diazomethane, gene-
rated from 200 mg of Diazald, was passed through the solution,
causing a color change from orange to bright yellow. The solvent
was evaporated to 2 mL, and 30 mL of diethyl ether was added to
precipitate a bright yellow solid, which was recrystallized from
CH2Cl2/diethyl ether, washed with 2 ꢀ 5 mL of diethyl ether, and
dried in vacuo (92% yield).
c. [IrOs(CO)3(μ-CH2)(dppm)2][CF3SO3] (4). Compound 3
(22 mg, 0.015 mmol) was dissolved in 5 mL of CH2Cl2, the
solution was cooled to 0 °C, and Me3NO (1.74 mg, 0.023 mmol,
1.50 equiv) was added, resulting in an immediate color change
from yellow to dark red. The solution was warmed to ambient
temperature, the solvent was evaporated to 2 mL, and 10 mL of
diethyl ether together with 30 mL of pentane were added to
precipitate a red solid, which was recrystallized from CH2Cl2/
diethyl ether/pentane (1:3:5), washed with 2 ꢀ 5 mL of pentane,
and dried in vacuo (78% yield). HRMS: m/z calcd for C54H46Ir-
O3OsP4 (Mþ), 1251.1635; found, 1251.1636 (Mþ). Due to the
instability of this compound, satisfactory elemental analyses could
not be obtained.
d. [IrOs(CO)4(μ-K1:K1-C(CO2CH3)dC(CO2CH3)CH2)(dppm)2]-
[CF3SO3] (5). Method (i). Compound 3 (50 mg, 0.035 mmol)
was dissolved in 10 mL of CH2Cl2, and to it was added dimethyl
acetylenedicarboxylate (DMAD; 5.5 μL, 0.045 mmol). The
solution was stirred at ambient temperature for 3 h, resulting
in a gradual color change from yellow to light orange. The
solution was purged with CO(g) for 3 min with no resulting color
change. The solvent was evaporated to 3 mL, and to it was added
10 mL of diethyl ether and 30 mL of pentane to precipitate a
light orange solid. The solid was recrystallized from CH2Cl2/
diethyl ether/pentane (1:3:5), washed with 2 ꢀ 5 mL of pentane,
and dried in vacuo (90% yield). HRMS: m/z calcd for C60H52Ir-
O7OsP4 (Mþ - CO), 1393.1902; found, 1393.1902 (Mþ - CO).
Anal. Calcd for C62F3H52IrO11OsP4S: C, 47.48; H, 3.34. Found:
C, 47.69; H, 3.64.
i. [IrOs(CO)4(μ-K1:K1-C(CO2CH3)dC(CO2CH3))(dppm)2]-
[CF3SO3] (10). A solution of DMAD (4.5 μL, 0.036 mmol) in 5 mL
of CH2Cl2 was cooled to -78 °C and was added dropwise via
cannula over 30 min to a solution of compound 2 (51 mg, 0.036
mmol) in 5 mL of CH2Cl2 at -78 °C. The mixture was stirred at this
temperature for 30 min and then slowly warmed to ambient
temperature. After an additional 2 h of stirring the solvent was
evaporated to 2 mL, and to it was added 10 mL of diethyl ether and
20 mL of pentane to precipitate a light orange solid. The solid was
recrystallized from CH2Cl2/pentane, washed with 2 ꢀ 5 mL of
pentane, and dried in vacuo (75% yield). HRMS: m/z calcd for
C59H50IrO7OsP4 (Mþ - CO), 1379.1741; found, 1379.1746 (Mþ -
CO). Anal. Calcd for C61F3H50IrO11OsP4S: C, 47.13; H, 3.24.
Found: C, 46.87; H, 3.06.
Method (ii). Compound 6 (20 mg, 0.013 mmol) was dissolved
in 0.7 mL of CD2Cl2 in an NMR tube to afford an orange
solution, which was purged by CO(g) for 1 min, resulting in a
slight lightening of the solution. Conversion of 6 to 5 was
monitored by 31P NMR spectroscopy and was observed to be
quantitative under the CO atmosphere.
j. [IrOs(CO)4(μ-K1:K1-C(CF3)dC(CF3))(dppm)2][CF3SO3] (11).
An orange solution of 2 (60 mg, 0.043 mmol) in 10 mL of CH2Cl2
was cooled to -78 °C. The argon headspace of the flask was
evacuated and replaced with a slight overpressure of HFB. The
reaction was stirred at -78 °C for 1 h and then slowly warmed to
ambient temperature and stirred for 12 h, resulting in a gradual color

956 Organometallics, Vol. 30, No. 5, 2011
MacDougall et al.
change to yellow. The solvent was evaporated to 2 mL, and to it was
added 20 mL of pentane to precipitate a light orange solid, which was
recrystallized from CH2Cl2/pentane, washed with 2 ꢀ 5 mL
of pentane, and dried in vacuo (94% yield). HRMS: m/z calcd
for C57H44F6IrO3OsP4 (Mþ - CO), 1399.1382; found, 1399.1384
(Mþ - CO). Anal. Calcd for C59.175Cl0.35F9H44.35IrO7OsP4S
collected using a Bruker APEX-II CCD detector/D8 diffractom-
eter63 with the crystals cooled to -100 °C (3, 7, 8-BF4) or with
an Enraf-Nonius CAD4 diffractometer63 with the crystals
cooled to -50 °C (12-BF4); all data were collected using Mo
˚
KR radiation (λ = 0.71073 A). The data were corrected for
absorption through Gaussian integration from indexing of the
crystal faces (3, 8-BF4, 12-BF4) or through use of a multiscan
model (SADABS63) (7). Structures were solved using Patterson
search/structure expansion (DIRDIF-200864) (3), direct methods/
structure expansion (SIR97) (7), or direct methods (SHELXS-9766)
(8-BF4, 12-BF4). Refinements were completed using the program
SHELXL-97.66 Hydrogen atoms attached to carbons were
assigned positions based on the sp2 or sp3 hybridization geom-
etries of their attached carbons and were given thermal
parameters 20% greater than those of their parent atoms
(the hydrido ligand of 8-BF4 was located from a difference
Fourier map and was assigned a fixed isotropic displacement
parameter while its coordinates were freely refined). See
Supporting Information (Tables S1-S4) for a listing of crys-
tallographic experimental data.
1
(9 0.175CH2Cl2): C, 44.30; H, 2.83. Found: C, 44.09; H, 2.76. H
3
NMR spectroscopy in CDCl3 confirmed the presence of dichloro-
=
methane of crystallization. 19F NMR: δ -52.7 (quartet, 3F, 5JFF
13.6 Hz), δ -53.1 (quartet, 3F, 5JFF = 13.6 Hz), δ -79.3 (singlet,
3F).
k. [IrOs(CO)3(μ-K1:K1-C(CO2CH3)dC(CO2CH3))(dppm)2]-
[CF3SO3] (12). A solution of anhydrous Me3NO (0.023 mmol,
1.7 mg) in 3 mL of CH2Cl2 was added dropwise over a period of
30 min to a stirred solution of 10 (30 mg, 0.019 mmol) in 5 mL of
CH2Cl2, resulting in a gradual darkening of the solution. The
solvent was evaporated to 2 mL, and to it was added 10 mL of
diethyl ether and 20 mL of pentane to precipitate an orange solid,
which was recrystallized from CH2Cl2/diethyl ether/pentane
(1:3:5), washed with 2 ꢀ 3 mL of pentane, and dried in vacuo
(86% yield). HRMS: m/z calcd for C59H50IrO7OsP4 (Mþ),
1379.1746; found, 1379.1739 (Mþ). Anal. Calcd for C60F3H50Ir-
O10OsP4S: C, 47.21; H, 3.30. Found: C, 47.20; H, 3.44.
(b) Special refinement conditions. (i) Compound 3: The metals
were found to be equally disordered over both positions, so each was
refined as 50% Ir and 50% Os sharing each site. (ii) Compound 7:
l. [IrOs(CO)3(μ-K1:K1-C(CF3)dC(CF3))(dppm)2][CF3SO3] (13).
Compound 11 (40 mg, 0.026 mmol) was dissolved in 3 mL of
CH2Cl2, and to the solution was added dropwise over a period of
30 min anhydrous Me3NO (2.3 mg, 0.031 mmol) in 2 mL of CH2-
Cl2, resulting in a gradual color change from orange to dark orange-
red. The solvent was evaporated to 2 mL, and to it was added 20 mL
of diethyl ether to precipitate an orange solid. The solid was
recrystallized from CH2Cl2/diethyl ether, washed with 2 ꢀ 3 mL
of diethyl ether, and dried in vacuo (82% yield). HRMS: m/z calcd
for C57H44F6IrO3OsP4 (Mþ), 1399.1384; found, 1399.1394 (Mþ).
Anal. Calcd for C58F9H44IrO6OsP4S: C, 45.05; H, 2.87. Found: C,
45.18; H, 2.97. 19F NMR: δ -45.9 (quartet, 3F, 5JFF = 11.2 Hz),
δ -51.2 (quartet, 3F, 5JFF = 11.2 Hz), δ -79.3 (singlet, 3F).
m. [IrOs(CO)3(μ-K1:K1-CH2C(CF3)dC(CF3))(dppm)2][CF3-
SO3] (14). A dark orange solution of 13 (33 mg, 0.021 mmol) in
5 mL of CH2Cl2 was cooled to -78 °C. Diazomethane, generated
from 200 mg of Diazald, was passed through the solution at low
temperature, resulting in a color change to yellow. This compound
was stable in solution at low temperature only and was character-
ized by NMR at -78 °C. 19F NMR (-78 °C): δ -51.5 (quartet,
3F, 5JFF = 16.6 Hz), δ -52.2 (quartet of triplets, 3F, 5JFF = 16.6
Hz, 4JFH = 2.5 Hz), δ -79.2 (singlet, 3F).
n. [IrOs(CO)3(PMe3)(μ-CH2)(dppm)2][CF3SO3] (15). Com-
pound 3 (100 mg, 0.070 mmol) was dissolved in 5 mL of CH2Cl2,
and to the solution was added neat PMe3 (14.5 μL, 0.140 mmol).
The solution was stirred at ambient temperature for 6 h, result-
ing in a lightening of the solution. The solvent was evaporated to
2 mL, and to it was added 10 mL of diethyl ether and 20 mL of
pentane to precipitate a light yellow solid, which was recrystal-
lized from CH2Cl2/diethyl ether/pentane (1:3:5) and dried in
vacuo (91% yield). Anal. Calcd for C58F3H55IrO6OsP5S: C,
47.25; H, 3.76. Found: C, 47.08; H, 3.79.
The Cl-C and Cl Cl distances within the disordered solvent
3 3 3
dichloromethane molecules were restrained to be 1.80(1) and
˚
2.80(1) A, respectively. (iii) Compound 8-BF4: Restraints were
applied to achieve idealized geometries within the two conformers
of the disordered tetrafluoroborate ion; F-B distances were con-
strained to be equal (within 0.03 A) during refinement, as were the
˚
F
F distances of F-B-F angles. (iv) Compound 12-BF4: Re-
3 3 3
straints were applied to distances within the two conformers of the
disordered tetrafluoroborate ion in the same manner as for 8-BF4
above. The Cl-C distances within the disordered solvent dichloro-
˚
methane molecule were constrained to be equal (within 0.03 A)
during refinement, as were the Cl Cl distances within each dis-
3 3 3
ordered moiety. (v) Assignments of metal centers in complexes 7, 8-
BF4, 12-BF4: For each of the complexes in which the metals have
dissimilar coordination environments, the final models were tested
by switching the identities of the metal atom centers (Ir for Os and
vice versa) and refining these to completion. In each case, the final
indices became subtly but noticeably worse for the “reversed-
metals” models (7: from R1 = 0.0262, wR2 = 0.0674 to R1 =
0.0264, wR2 = 0.0691; 8-BF4: from R1 = 0.0299, wR2 = 0.0792 to
R1 = 0.0306, wR2 = 0.0806; 12-BF4: from R1 = 0.0458, wR2 =
0.1489 to R1 = 0.0460, wR2 = 0.1498). For 8-BF4, the position of
the hydrido ligand (H(1)) could not be freely refined after reversing
the identities of the metals, and that model would only converge
˚
after distance restraints were applied (d(Ir-H(1)) = 1.61(1) A;
˚
d(Os-H(1)) = 1.85(1) A) that were based on the distances
observed for the freely refined hydrido ligand of the original model.
Results and Compound Characterization
a. Methylene-Bridged Precursor. The precursor methylene-
bridged complex, [IrOs(CO)4(μ-CH2)(dppm)2][CF3SO3] (3), is
o. Relative Rates for the Reactions of 3 and [IrRu(CO)4(μ-
CH2)(dppm)2][CF3SO3] with PMe3. Compound 3 (30 mg, 0.021
mmol) was dissolved in 0.7 mL of CD2Cl2 in an NMR tube.
[IrRu(CO)4(μ-CH2)(dppm)2][CF3SO3] (28 mg, 0.021 mmol)
was dissolved in 0.7 mL of CD2Cl2 in an NMR tube to yield a
solution of identical concentration to that of 3 in CD2Cl2. To
both tubes was added neat PMe3 (4.4 μL, 0.042 mmol) simulta-
neously (t = 0 h). The reaction was monitored each hour
(including t = 0 h) by 31P{1H} spectroscopy, monitoring the
relative rates of conversions of 3 and the Ir/Ru analogue to their
corresponding PMe3-substitution products.
(63) (a) For compounds 3, 7, and 8-BF4, programs for diffractometer
operation, data collection, data reduction, and absorption correction
were those supplied by Bruker. (b) For compound 12-BF4, programs for
diffractometer operation and data collection were those supplied by
Enraf-Nonius. The data were reduced using the program XCAD4
(Harms, K.; Wocadlo, S. University of Marburg, 1995). Absorption
corrections were applied using programs of the SHELXTL system (Bruker,
2008).
(64) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Smits, J. M. M.;
Garcia-Granda, S.; Gould, R. O. The DIRDIF-2008 program system;
Crystallography Laboratory, Radboud University: Nijmegen, The Netherlands,
2008.
X-ray Structure Determinations. (a) General. Crystals were
grown via slow diffusion of diethyl ether into an acetonitrile
solution of the compound (3) or diffusion of diethyl ether into a
CH2Cl2 solution of the compound (7, 8-BF4, 12-BF4). Data were
(65) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. J. Appl. Crystallogr. 1999, 32, 115.
(66) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.

Article
Organometallics, Vol. 30, No. 5, 2011 957
Scheme 1
Figure 1. Perspective view of the complex cation of [IrOs(CO)4-
(μ-CH2)(dppm)2][CF3SO3] (3). Thermal ellipsoids are shown at
the 20% probability level except for hydrogens, which are
shown artificially small. Only the ipso carbons of the phenyl
rings are shown.
Table 2. Selected Bond Lengths and Angles for Compound 3
˚
(a) Distances (A)
readily prepared by reaction of either [IrOs(CO)5(dppm)2]-
[CF3SO3] (1) or [IrOs(CO)4(dppm)2][CF3SO3] (2) with diazo-
methane at ambient temperature (see Scheme 1). One carbonyl
in compound 1 is labile and readily lost in the reaction,
generating the identical product as in the reaction of 2, under
identical conditions. Both reactions proceed instantly, even
at -78 °C. No incorporation of additional methylene groups
is observed when the reaction is carried out at ambient tem-
perature.
atom 1
atom 2
distance
atom 1
atom 2
distance
Ir
Ir
Ir
Ir
Os
Os
2.8345(1)
1.887(2)
1.919(3)
2.134(2)
1.919(3)
Os
Os
C(2)
C(3)
C(4)
C(5)
O(2)
C(3)
1.881(2)
2.150(2)
1.139(3)
1.144(3)
C(1)
C(2)
C(5)
C(3)
(b) Angles (deg)
angle atom 1 atom 2 atom 3 angle
C(1) 157.74(7)
Complex 3 produces the expected pattern in the 31P{1H}
NMR spectrum, characteristic of an AA0BB0 spin system,
corresponding to the Ir- and Os-bound ends of the dipho-
sphines. With both resonances (δ -5.8 and -6.9) so close in
chemical shift, which resonance corresponds to the Ir- or Os-
bound ends of the diphosphines is not clear. Through the use of
13C{1H,31P} NMR techniques in which the phosphorus reso-
nances are selectively decoupled, we can determine that two
carbonyls display spin-spin coupling with each end of the
disphosphine units, so are attached two to each metal, but
we are unable to identify which set of 31P resonances is which.
The two 13C resonances at δ 185.1 and 178.2 correspond to the
carbonyls on one metal, while those at δ 181.7 and 170.0
correspond to the carbonyls on the other; all carbonyls appear
to be terminally bound, as supported by the IR spectrum, in
which all carbonyl bands fall in the region above 1900 cm-1. A
13CH2-enriched sample of 3 shows the μ-CH2 carbon in the
13C{1H} NMR spectrum at δ 46.6 as a very broad multiplet
displaying couplings of 9.0 and 8.2 Hz to the chemically
atom 1 atom 2 atom 3
Os
Os
Ir
Ir
Ir
Ir
Ir
C(5)
Ir
Os
Os
Ir
48.82(5)
48.32(5)
C(2)
C(3)
97.50(10) C(5)
95.64(10) Ir
Os
Os
C(5)
C(2)
C(3)
O(2) 177.3(3)
O(3) 177.8(3)
C(4) 158.63(7)
Os 82.86(7)
Os
As is typical with these A-frame-like complexes, the dppm
ligands bridge both metals in a mutually trans arrangement.
˚
The Ir-Os separation of 2.8345(1) A is consistent with a metal-
metal bond and is significantly shorter than the intraligand
˚
P-P separation of ca. 3.00 A, indicating compression along the
Ir-Os axis due to mutual attraction of the metals. The geometry
at both metals is a distorted octahedron in which the distortion
in the equatorial plane arises from the acute angles formed by the
introduction of the methylene bridge (C(5)-Ir-Os = 48.82(5)°
and C(5)-Os-Ir = 48.32(5)°). There is no significant twisting
around the metal-metal axis in the complex cation, resulting in
an eclipsed conformation of both metals. Torsion angles relating
the eclipsed ligands are between ca. 3° and 6°. The disorder of the
metals, noted in the Experimental Section, presumably gives rise
to a slight, unresolved disorder of the carbonyl ligands, which
probably gives rise to the somewhat elongated thermal ellipsoids
for C(2)O(2) and C(3)O(3).
1
inequivalent 31P nuclei. In the H NMR spectrum of 3, two
signals at δ 4.77 and 3.36 represent the chemically inequivalent
CH2 protons of the dppm ligands, indicating the absence of
“front-back” symmetry on either side of the IrOsP4 plane.
These protons display mutual two-bond coupling of 14.0 Hz.
The protons of the newly introduced methylene bridge appear
The structure of 3 differs significantly from those of its
congeners, involving the Rh/Ru, Rh/Os, and Ir/Ru combina-
tions of metals, which all have a carbonyl ligand in a site
bridging the metals. The absence of a bridging carbonyl in the
Ir/Os species (3) is consistent with the lower tendency of third-
row metals to support bridging carbonyl ligands.67,68 As such,
compound 3 more closely resembles the monophosphine
1
as a multiplet at δ 4.75. Due to the overlap in the H NMR
spectrum between the methylene protons of the dppm ligands
and the newly introduced methylene group protons, a 2D
HSQC NMR experiment was used to correlate the carbon
signal at δ 46.6 to the proton signal at δ 4.75.
An X-ray structure determination of 3, as shown for the
complex cation in Figure 1, verifies the bridging arrangement of
the methylene group and the symmetrical ligand arrangement
having two carbonyls on each metal. Selected bond lengths and
angles are presented in Table 2. An ORTEP diagram that
includes all phenyl rings is given as Supporting Information.
(67) Housecroft, C. E.; Sharpe, A. G. In Inorganic Chemistry, 2nd ed.;
Prentice Hall: Harlow, England, 2005; p 713.
(68) Elschenbroich, C. In Organometallics, 3rd ed.; Wiley-VCH:
Weinheim, Germany, 2006; p 360.

958 Organometallics, Vol. 30, No. 5, 2011
MacDougall et al.
analogues [MM0(PMe3)(CO)3(μ-CH2)(dppm)2]þ (MM0 =
RhRu,41 RhOs,38 IrRu43), which also have two terminal
ligands on each metal.
The bonding in 3 can be described by either of the valence
bond formulations shown in Chart 1. In the Ir(II)/Os(I)
formulation the metals are connected by a conventional
metal-metal bond, while in the Ir(I)/Os(II) formulation
the coordinatively saturated Ir center forms a dative bond
to Os to give the latter its favored 18e- configuration. We
favor this latter description, in keeping with the favored
oxidation states of these metals.
b. C3-Bridged Species from [IrOs(CO)x(μ-CH2)(dppm)2]-
[CF3SO3] (x = 3 or 4). The addition of dimethyl acetylene-
dicarboxylate (DMAD) to the methylene-bridged tetracarbo-
nyl complex [IrOs(CO)4(μ-CH2)(dppm)2][CF3SO3] (3) under
ambient conditions results in the insertion of the alkyne into the
Ir-CH2 bond, yielding [IrOs(CO)4(μ-κ1:κ1-C(CO2CH3)dC-
(CO2CH3)CH2)(dppm)2][CF3SO3] (5) and [IrOs(CO)3(μ-
κ1:κ1-C(CO2CH3)dC(CO2CH3)CH2)(dppm)2][CF3SO3] (6)
(Scheme 2). The fourth carbonyl ligand of 5 is readily displaced
under an argon purge, converting it to 6, while addition of
CO(g) to the 5/6 mix yields only 5. Unlike the facile reaction
with DMAD, hexafluorobutyne (HFB) does not react with
3 at ambient temperature. However, decarbonylation of 3 by
reaction with sublimed anhydrous trimethylamine-N-oxide
(TMNO) generates the unstable complex [IrOs(CO)3(μ-CH2)-
(dppm)2][CF3SO3] (4), which undergoes facile alkyne insertion
of either DMAD or HFB to generate [IrOs(CO)3(μ-κ1:κ1-
C(R)dC(R)CH2)(dppm)2][CF3SO3] (R = CO2Me (6)) or
CF3 (7)), respectively (Scheme 2). The presence of adventitious
water, present in unsublimed TMNO, results in the formation
of unwanted hydroxide-containing byproducts.
employing selective 31P-decoupling, since coupling is only
observed between adjacent 31P and 13C moieties. The metal
having the greater number of carbonyls is identified as Os on
the basis of its greater tendency to be coordinatively satu-
rated. The structures shown in Scheme 2 are assigned on the
basis of these experiments. A 13CO-enriched sample of 5displays
four terminal CO resonances in the 13C{1H} NMR spectrum at
δ 184.4, 177.8, and 160.0, corresponding to the Os-bound CO
ligands with coupling to the Os-bound phosphorus nuclei of
between 5.5 and 7.0 Hz, while one at δ 174.8 corresponds to the
sole Ir-bound CO, displaying 10.4 Hz coupling to the Ir-bound
phosphorus atoms. A 13CH2-enriched sample of 5shows the Os-
bound CH2 carbon in the 13C{1H} NMR spectrum at approxi-
mately δ 47 as a very broad multiplet. This multiplet sharpens
noticeably (as seen in line width at 50% peak height) upon the
decoupling of the Os-bound phosphorus nuclei at δ -18.7, but
shows no effect upon decoupling the Ir-bound phosphorus
1
signal. In the H NMR spectrum of 5, two signals at δ 5.13
and δ 4.86 represent the chemically inequivalent CH2 protons of
the dppm ligands, while the Os-bound CH2 protons appear as a
triplet at δ 2.20 with 11.1 Hz coupling to only the two
phosphorus nuclei bound to this metal. The absence of coupling
of these μ-CH2 protons to the Ir-bound phosphorus nuclei is
consistent with alkyne insertion into the Ir-CH2 bond. In
addition to the above resonances, compound 5 displays two
separate resonances for the CH3 groups of the inserted DMAD
molecule at δ 2.38 and 1.29.
For compounds 6 and 7, 13CO-enriched samples each
display two resonances at ca. δ 185 and δ 180, corresponding
to the Os-bound CO ligands showing coupling to only the
Os-bound phosphorus atoms of ca. 9 Hz, while one at ca. δ
168 corresponds to the Ir-bound CO, coupling to only the Ir-
bound phosphorus atoms (2JCP = 9.5 Hz). Again, 13CH2-
enriched samples of 6 and 7 show the Os-bound CH2 carbons
in the 13C{1H} NMR spectra as broad multiplets at δ 10.3
In the case of compounds 5, 6, and 7, their unsymmetrical
carbonyl distribution allows the 31P resonances to be identi-
fied as Ir- or Os-bound on the basis of 13C NMR experiments
1
and 8.0, respectively. In the H NMR spectra of 6, the Os-
Chart 1
bound CH2 protons appear as a triplet at δ 1.53 with 11.4 Hz
coupling to the Os-bound 31P nuclei, while in 7 these protons
appear as a more complex triplet of quartets at δ 1.86 with
8.9 Hz coupling to phosphorus as well as coupling of 2.5 Hz
to one CF3 group. As above, the absence of coupling between
these CH2 protons and the Ir-bound phosphorus nuclei is
consistent with alkyne insertion into the Ir-CH2 bond. ln the
Scheme 2

Article
Organometallics, Vol. 30, No. 5, 2011 959
Scheme 3
Within the bridging C3 fragment the C(6)-C(7) bond length
of 1.344(5) A is characteristic of a double bond,69 while C(6)-
˚
2
˚
C(4) (1.512(4) A) is indicative of a single bond between sp and
sp3 carbons.69,70 All angles within the C3 fragment (Ir-C(7)-
C(6) = 122.3(2)°, C(4)-C(6)-C(7) = 122.1(3)°, and Os-
C(4)-C(6) = 115.5(2)°) are slightly larger than those predicted
for undistorted sp2 and sp3 angles and together with the acute
the Ir-Os-C(4) and Os-Ir-C(7) angles of 82.40(9)° and
85.88(9)°, respectively, suggest significant strain within the
dimetallacyclopentene moiety. Presumably, the staggered ar-
rangement of the two coordination spheres along the metal-
metal axis occurs to alleviate further strain; an eclipsed confor-
mation, while maintaining the observed metal-metal distance,
would exacerbate the strain within this moiety. This structure
closely resembles those of the related [RhM(CO)3(μ-κ1:κ1-C-
(CF3)dC(CF3)CH2)(dppm)2]þ (M = Ru,42 Os54).
Figure 2. Perspective view of the complex cation of [IrOs(CO)3-
(μ-κ1:κ1-C(CF3)dC(CF3)CH2)(dppm)2][CF3SO3] (7). Thermal
ellipsoids as described in Figure 1. Only the ipso carbons of the
phenyl rings are shown.
Table 3. Selected Bond Lengths and Angles for Compound 7
˚
(a) Distance (A)
Compounds 5 and 6 react with a second equivalent of
CH2N2; however, instead of the anticipated insertion into the
Ir-C bond of the strained bridging C3 unit, a new C-O bond
is formed to yield [IrOs(CO)3(μ-H)(μ-κ1:κ1:κ1-CH2OC-
(OCH3)dCC(CO2CH3)dCH)(dppm)2][CF3SO3] (8), as illu-
strated in Scheme 3. The reactions of compounds 5 and 6
with CH2N2 to generate 8 occur readily. Although 5 requires
prior CO loss to generate 6 before reacting to form 8, as
shown by 31P{1H} NMR spectroscopy at -78 °C, the relative
rates of reaction of 5 and 6 are comparable, attesting to the
extreme lability of the fourth CO in the former.
atom 1
atom 2
distance
atom 1
atom 2
distance
Ir
Ir
Ir
Os
Os
Os
2.7910(2)
1.876(4)
2.102(3)
1.937(3)
1.862(3)
Os
C(4)
C(6)
C(6)
C(7)
C(8)
2.185(3)
1.512(4)
1.515(5)
1.344(5)
1.511(5)
C(1)
C(7)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
(b) Angles (deg)
atom 1 atom 2 atom 3
angle
atom 1 atom 2 atom 3 angle
Os
C(1)
Ir
Ir
Ir
Ir
C(7)
C(7) 175.37(14) C(4)
C(4)
85.88(9)
Os
C(4)
C(6)
C(6)
C(6)
C(7)
C(6) 115.5(2)
C(5) 113.6(3)
C(7) 122.1(3)
C(7) 123.8(3)
C(8) 123.3(3)
The defining feature of the 1H NMR spectrum of 8 is the
hydride resonance at δ-18.91, appearing as a quintet with equal
coupling of 8.4 Hz to all four phosphorus nuclei of the dppm
ligands, confirming its bridging arrangement. The proton of the
CH group appears as a triplet at δ5.12, showing coupling to only
the Os-bound phosphorus nuclei of 11.2 Hz, while the Ir-bound
CH2 group appears at δ 4.10, with coupling to only the Ir-bound
phosphorus nuclei of 10.6 Hz. The protons of the dppm methy-
Ir
Os
82.40(9)
C(4)
C(5)
C(6)
C(7)
C(7)
C(6) 122.3(2)
C(8) 114.2(2)
case of compound 7, the 19F NMR spectrum displays two
resonances for the CF3 groups of the inserted HFB group.
An X-ray structure determination of 7, shown for the com-
plex cation in Figure 2, verifies that alkyne insertion into the
Ir-CH2 bond has occurred as was proposed on the basis of the
above spectroscopic studies. Selected bond lengths and angles
are presented in Table 3. The geometry at Os is shown to be a
rather undistorted octahedron, while that at Ir is best described as
a tetragonal pyramid in which the axial site corresponds to the
Ir-Os bond. Although the nature of the metal-metal bond
lene groups appear as two signals at δ 5.10 and 4.85 (2JHH
=
13.4 Hz). In a 13CO-enriched sample of 8 two signals for the
three CO ligands appear in the 13C{1H} NMR spectrum at δ
184.3 (1C) for the Ir-bound CO coupling to only the adjacent
phosphorus nuclei (2JCP = 4.7 Hz) and δ 174.4 (2C, coinciden-
tally overlapped) for the two Os-bound CO ligands, coupling to
the Os-bound phosphorus nuclei (2JCP =7.4Hz). Inasampleof
6 in which the Os-bound CH2 group was 13C-enriched, reaction
with 12CH2N2 resulted in 13C enrichment only at the Os-bound
methyne group (Scheme 3). This carbon appears at δ115.2 in the
13C{1H} NMR spectrum and is shown by APT to be bound to a
single proton. In addition, this proton, noted above, now dis-
plays coupling to the labeled carbon of 148.0 Hz in the 1H NMR
spectrum. Experiments in which 13CH2N2 was added to un-
labeled 6 gives rise to a 13C{1H} resonance at δ 60.4. In the 1H
NMR spectrum the added methylene resonance appears as a
˚
(2.7910(2) A) and the corresponding oxidation states of the
metals can be ambiguous in such complexes, we again favor an
Ir(I)/Os(II) formulation in which the occupied dz2 orbital of the
square-planar Ir forms a dative bond to Os, as is shown in
Scheme 2. Although the dppm ligands occupy the typical bridg-
ing positions, close to mutually trans at both metals, they are
significantly twisted with respect to each other, resulting in a
staggered conformation at both metals, in which the torsion
angles about the Ir-Os bond range from 23.48(3)° to 28.09(3)°.
(69) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
3
2
˚ ˚
(70) rc(sp ) = 0.77 A; rc(sp ) = 0.74 A.

960 Organometallics, Vol. 30, No. 5, 2011
MacDougall et al.
Scheme 4
The most significant distortions from octahedral geometries
result from the nonlinearity of the P(1)-Ir-P(3) (172.13(3)°)
and P(2)-Os-P(4) (158.81(4)°) units of the diphosphines,
which are bent toward the bridging hydrocarbyl fragment. This
bending occurs to minimize contacts between the almost ver-
tical dppm phenyl rings, on the same face as the bridging
hydride, and the carbonyl ligands and is aided by the phenyl
group orientations on the opposite face, which lie almost
parallel to the bridging “C3” moiety (see Figure S2 in Support-
ing Information). One carbonyl on Os lies opposite the bridging
hydride ligand, and another is trans to the methyne carbon of
the C3-bridging unit. Within the bridging hydrocarbyl fragment
the bond lengths are most consistent with the canonical form
shown in Scheme 3, in which the C(5)-C(6) and C(7)-C(8)
Figure 3. Perspective view of the complex cation of [IrOs(CO)3-
(μ-H)(μ-κ1:κ1:κ1-CH2OC(OCH3)dCC(CO2CH3)dCH)(dppm)2]-
[CF3SO3] (8). Only the ipso carbons of the phenyl rings are shown.
Thermal ellipsoids are as described in Figure 1.
Table 4. Selected Bond Lengths and Angles for Compound 8
˚
(a) Distance (A)
˚
atom 1
atom 2
distance
atom 1
atom 2
distance
bonds (1.348(6) and 1.344(6) A) are typical of double bonds,
while C(6)-C(7), a double bond in the precursor (6), has now
lengthened to 1.464(5) A, typical of a single bond between sp -
Ir
Ir
Ir
Ir
Os
Os
Os
Os
C(4)
C(1)
C(4)
C(6)
H(1)
C(2)
C(3)
C(8)
H(1)
O(4)
1.904(4)
2.128(4)
2.101(4)
1.61(5)
1.938(4)
1.879(4)
2.115(4)
1.84(5)
O(4)
C(5)
C(6)
C(7)
C(7)
C(9)
C(9)
O(7)
C(5)
C(6)
C(7)
C(8)
C(9)
O(6)
O(7)
C(20)
1.349(5)
1.348(6)
1.464(5)
1.344(6)
1.497(6)
1.201(5)
1.347(6)
1.455(6)
2
˚
hydridized carbons.69 ThelengthsofthenewlyformedC(4)-O-
˚
˚
(4) bond(1.447(5) A) andthe C(5)-O(4) bond(1.349(5) A) are
as expected, with the latter being typical for an enol ester.69 The
unsymmetrical metal-hydride distances (Ir-H(1)=1.61(5) A,
Os-H(1) = 1.84(5) A) suggest a stronger interaction with Ir,
˚
˚
1.447(5)
although the uncertainties in accurately defining the hydrogen
position by X-ray methods leave this interpretation in some
doubt, and certainly the equal spin-spin coupling of the hyd-
ride to both ends of the diphosphines in the 1H NMR spectrum
is suggestive of a close-to-symmetric hydride bridge in solution.
Incorporation of the hydride bridge results in a substantial
(b) Angle (deg)
angle atom 1 atom 2 atom 3 angle
atom 1 atom 2 atom 3
C(1)
C(4)
C(4)
O(4)
O(4)
Ir
Ir
C(4)
C(6)
89.21(18) C(5)
77.86(16) C(5)
C(5) 113.1(3)
O(5) 112.8(4)
C(6) 122.7(4)
O(5) C(10) 115.0(4)
˚
C(6)
C(7)
C(8)
C(7) 120.8(4)
C(8) 125.1(4)
Os
lengthening of the metal-metal separation to 3.2956(3) A from
approximately 2.8 A in the precursor (estimated from the
O(4)
C(5)
C(5)
C(6)
C(7)
Ir
˚
129.1(3)
145(4)
analogous species 7), as expected for a three-center two-electron
interaction.
H(1) Os
doublet of triplets at δ 4.10 with coupling to the 13C of 147.2 Hz.
These experiments confirm that C-H activation involves the
CH2 group of the original μ-C3 fragment and not the added CH2
group. Low-temperature NMR studies did not yield additional
information on the transformation of 6 to 8, since no additional
species were observed.
Although these NMR data clearly established the fate of
the original CH2 group in the precursor 6, it did not establish
how the newly added CH2 group was incorporated into the
complex. However, the connectivity was clearly established
by the X-ray structure determination of 8, and a representation
of the complex cation is shown in Figure 3. Clearly shown in this
figure are the C3-bridged unit (C(6)-C(7)-C(8)), in which the
original CH2 unit has been converted to CH and the bridging
hydride, together with the new five-membered ring involving
the added methylene group, the carbonyl group of the ester
functionality from the DMAD, and the Ir center (Ir-C(4)-
O(4)-C(5)-C(6)). Selected bond lengths and angles are pre-
sented in Table 4.
In a previous study on the related Rh/Os system we had
reported the conversion of the C3-bridged species [RhOs(CO)3-
(μ-κ1:κ1-RCdC(R)CH2)(dppm)2]þ (R = CO2Me), to the C4-
bridged product by methylene insertion into the Rh-carbon
bond of the bridging hydrocarbyl fragment and had been
surprised that the HFB analogue (R = CF3) had not reacted
similarly.54 We now find that the former proposal of methylene
insertion into the Rh-hydrocarbyl bond had been in error,
as is unambiguously shown in the current study, for which the
spectroscopy matches very closely to that in the Rh/Os study.
The hexafluorobutyne-containing analogue (7) also reacts
with diazomethane, but in this case yields a very different prod-
uct, [IrOs(CO)3(μ-κ1:κ1-CH2C(CF3)dC(CF3)CH2)(dppm)2]-
[CF3SO3] (9), which is only stable at temperatures below
-20 °C; upon warming to ambient temperature, quantitative
regeneration of 7 occurs, also generating ethylene, as seen in the
1H NMR spectrum (Scheme 4).
Compound 9 appears to be the originally anticipated
product, in which methylene insertion into the Ir-C bond
of the C3-bridged fragment has occurred. Both hydrocarbyl
Both metals display a pseudo-octahedral geometry, with
all angles between adjacent groups of approximately 90°.
1
methylene groups of 9 appear in the H NMR spectrum at

Article
Organometallics, Vol. 30, No. 5, 2011 961
Scheme 5
standard, it is evident that all of 9 is transformed back to the C3-
bridged species (7) via loss of the CH2 unit (Scheme 4). The
1
methylene unit lost from 7 is observed as ethylene in the H
NMR spectrum at δ 5.41. The conversion of 9 to 7 occurs even
in the absence of excess diazomethane, so incorporation of an
additional CH2 group is not necessary and does not precede
ethylene formation.
1
1
Figure 4. Select regions of the H and H{31P} NMR spectra
showing the resonances for the two CH2 groups of the C4 bridge
of compound 9.
c. C2-Bridged Species. Attempts to obtain isomers of 6
and 7 having an “Ir-CH2-(alkyne)-Os” core led us to
investigate CH2 insertion into alkyne-bridged Ir/Os species,
on the assumption that CH2 insertion into the Ir-alkyne bond
would occur. The alkyne-bridged precursors, [IrOs(CO)4(μ-
RCCR)(dppm)2][CF3SO3] (R = CO2Me (10), CF3 (11)), were
obtained by addition of the respective alkynes to the tetracar-
bonyl complex [IrOs(CO)4(dppm)2][CF3SO3] (2) (Scheme 5).
Again, the 31P resonances are not readily identified as Ir-
or Os-bound without the 13C{31P} experiments, which estab-
lish that the 13CO resonances at δ 180.0 (10) and 177.0 (11)
correspond to the lone Ir-bound carbonyl in each complex,
while the three other carbonyls in both compounds are
terminally bound to Os. The IR spectra of these compounds
δ 4.01 and 2.27. The former resonance appears as a triplet
(see Figure 4) for which selective decoupling of the Ir-bound
31P resonances leads to its collapse to a singlet, while no effect
is seen in the other resonance. The second CH2 signal appears
as a multiplet, which simplifies to a poorly resolved quartet,
displaying coupling to the adjacent CF3 group (4JHF = 2.5 Hz)
upon decoupling the Os-bound 31P nuclei; again, decoupling
of these 31P nuclei leads to no noticeable change in the other
CH2 resonance. The small fluorine-hydrogen coupling
noted is typical of what we would expect from four-bond
coupling71-73 and indicates that the C3 unit of the precursor (7)
has remained intact.
reveal the CO stretches in the range 2075 to 1957 cm-1
,
In a 13CO-enriched sample of 9 three resonances are
observed in the 13C{1H} NMR spectrum at δ 187.9, 184.0,
and 178.0. The two upfield resonances each appear as triplets
having ca. 9 Hz coupling to different pairs of phosphorus nuclei;
the one at δ 184.0 couples to the Ir-bound ends of the dipho-
sphines, while the one at δ 178.0 displays coupling to the Os
ends. The slightly downfield 13CO resonance displays ca. 8 Hz
coupling to the Os-bound 31P nuclei, but sharpens slightly upon
31P decoupling at the Ir end, suggesting a weak semibridging
interaction. When all carbonyls and both methylene groups are
13C-enriched, this low-field carbonyl resonance shows ca. 15 Hz
coupling to the Os-bound methylene group, suggesting a mu-
tually trans arrangement; however, no 13C-13C coupling is
observed for the Ir-bound methylene group and the carbonyl
resonating at δ 184.0, suggesting at least some deviation from a
rigorously trans arrangement.
offering further support that all are terminally bound. In the
1H NMR spectrum the dppm CH2 groups resonate between
ca. δ 4.7 and 4.2. In the case of 10, the CH3 protons on the
bridging alkyne fragment appear at δ 3.32 and 2.48. A car-
bonyl can be removed from both 10 and 11 by the addition of
TMNO or by refluxing in THF, yielding the C2-bridged
tricarbonyl species [IrOs(CO)3(μ-κ1:κ1-C(R)dCR)(dppm)2]-
[CF3SO3] (R = CO2Me (12), CF3 (13)), as shown in Scheme 5;
we propose that loss of an Os-bound CO is accompanied by
formation of an IrfOs dative bond. All spectroscopic param-
eters are in keeping with the A-frame nature of these species,
as is confirmed by the X-ray structure determination of 12,
which shows the bridging κ1:κ1 arrangement of the alkyne
(Figure 5). Selected bond lengths and angles are presented in
Table 5.
Complex 12 has a pseudo-octahedral Os center in which
the sixth coordination site is occupied by the dative IrfOs
bond from an otherwise square-planar Ir(I) center, much as
discussed earlier for compound 7. The Ir-Os bond length of
Compound 9 is stable only at low temperatures, and upon
warming to ambient temperature, its disappearance is accom-
panied by the re-formation of 7. Using bis(triphenylphos-
phoranylidene)ammonium chloride as an internal phosphorus
˚
2.8610(6) A is typical of a single bond and is significantly
shorter than the nonbonded P-P distances. The alkyne
bridges the two metals, almost parallel to the metal-metal
(71) Emsley, J. W.; Phillips, L.; Wray, V. Prog. Nucl. Magn. Reson.
Spectrosc. 1976, 10, 83.
(72) Foris, A. Magn. Reson. Chem. 2004, 42, 534.
(73) Wray, V.; Lincoln, D. N. J. Chem. Soc., Perkin Trans. 2 1976, 2,
1307.
˚
axis, in which the C(6)-C(7) bond length of 1.345(11) A is
typical of a double bond and the C(5)-C(6)-C(7) and
C(6)-C(7)-C(8) angles are all near the expected 120°.

962 Organometallics, Vol. 30, No. 5, 2011
MacDougall et al.
does not react with additional CH2N2. Compound 14 is unstable,
and warming to ambient temperature results in its disappearance,
accompanied by quantitative re-formation of 13. This loss of the
methylene unit, as ethylene, was also observed upon warming, as
was also noted in the transformation of 9 to 7.
Reaction of the DMAD-bridged species (12) with CH2N2
does not parallel the reaction with 13 but instead yields multiple
unidentified products, unchanged by varying the reaction con-
ditions. One of the products yielded a single crystal from
solution; however the badly disordered structure did not refine
acceptably. Nevertheless, the connectivity determined from the
preliminary structure determination indicates the formation of a
bond between the added methylene group and the carbonyl
oxygen of the adjacent end of the bridging DMAD group, much
as observed for compound 9, suggesting one reason for the
divergence in the reactivities of 12 and 13.
Discussion
Figure 5. Perspective view of the complex cation of [IrOs(CO)3-
(μ-κ1:κ1-C(CO2Me)dC(CO2Me))(dppm)2][CF3SO3] (12). Phe-
nyl hydrogens omitted. Thermal ellipsoids are as described in
Figure 1. The numbering of the phenyl carbons starts at the ipso
carbon and is sequential around the rings, which are numbered
1 through 8.
In many ways, the reactivity of the Ir/Os species, described
in this paper, parallels that described earlier for the analo-
gous Rh/Ru, Rh/Os, and Ir/Ru systems, although significant
differences are observed depending on the metal combination. In
the generation of the methylene-bridged precursor [IrOs(CO)4-
(μ-CH2)(dppm)2]þ by reaction of [IrOs(CO)4(dppm)2]þ with
diazomethane, the reactivity parallels that of the Rh/Ru and Ir/
Ru systems, while differing substantially from that of the Rh/Os
system. Whereas the three systems, [MM0(CO)4(dppm)2]þ
(MM0 = RhRu, IrRu, IrOs) incorporate only a single methy-
lene group, irrespective of temperature, the Rh/Os system is
much more reactive with diazomethane, incorporating up to
four methylene groups at temperatures above -60 °C, yield-
ing the monomethylene species, as the exclusive product, only
at temperatures below this.
Table 5. Selected Bond Lengths and Angles of Compound 12
˚
(a) Distance (A)
atom 1
atom 2
distance
atom 1
atom 2
distance
Ir
Ir
Ir
Os
Os
Os
Os
2.8610(6)
1.906(9)
2.110(8)
1.936(9)
1.858(8)
2.090(8)
C(6)
C(6)
C(5)
C(5)
O(4)
C(7)
C(5)
C(7)
O(5)
O(4)
C(4)
C(8)
1.516(11)
1.345(11)
1.203(11)
1.312(11)
1.447(10)
1.471(11)
C(1)
C(6)
C(2)
C(3)
C(7)
The structure of [IrOs(CO)4(μ-CH2)(dppm)2]þ (3), as noted,
is very different from tþhe structures of its congeners, [MM0-
(CO)4(μ-CH2)(dppm)2] (MM0=RhRu, RhOs, IrRu). Where-
as these latter three species have unsymmetrical structures,
having a bridging carbonyl, one terminal CO on Rh or Ir and
two terminal COs on Ru or Os, as shown for structure A in
Chart 2 (dppm groups not shown), compound 3 has a close-to-
symmetric structure having two carbonyls on each metal.
Although these different structure types should give rise to
different reactivity patterns, their reactivities with additional
diazomethane appear, at first glance, to bear little relationship
to their structures, recalling that, of these four compounds, only
the Rh/Os member reacted with additional diazomethane.37,38
We had previously rationalized the differing reactivities of the
Rh/Ru, Rh/Os, and Ir/Ru species (having similar structures) on
the basis of incipient coordinative unsaturation.38,43,74 Although
both metals in A are saturated, a comparison of the structures of
these three compounds showed that the only one to react further
with diazomethane (Rh/Os) had the bridging carbonyl interact-
ing the weakest with the group 9 metal. This led to the suggestion
that this weak Rh-(μ-CO) interaction was a source of incipient
unsaturation being readily displaced from Rh by nucleophilic
attack at the vacant coordination site, as shown in Chart 2. This
weaker interaction allowed even the weak nucleophile, diazo-
methane, to displace this bridging carbonyl, while presumably
for the Rh/Ru and Ir/Ru analogues, the stronger interactions of
the group 9 metal with the bridging carbonyl did not allow
diazomethane to displace this CO, resulting in no reactivity.
(b) Angle (deg)
atom 1 atom 2 atom 3 angle atom 1 atom 2 atom 3 angle
Os
Os
C(1)
Ir
Ir
Ir
Ir
Os
C(1) 115.4(2) Ir
C(6) 64.8(2) Ir
C(6) 179.1(3) Ir
C(2) 87.7(3) C(6)
Os
Os
C(6)
C(7)
C(3) 175.7(3)
C(7) 72.6(2)
C(7) 118.6(6)
Os 103.5(6)
Using the same methodology as discussed previously,
diazomethane can be used to introduce a CH2 group into the
Ir-carbon bond of the “IrOs(μ-RCCR)” moiety of 13 to give 14
(Scheme 5), as determined by the 8.8 Hz coupling between the
CH2 protons and the Ir-bound 31P nuclei. In this case, coupling
of the CH2 protons and the fluorine nuclei of the adjacent CF3
group is not observed in either the 1Horthe19FNMRspectrum,
although small couplings of 2 Hz or less could be masked by
the width of the observed peaks. The three carbonyl ligands are
terminally bound, as witnessed by their IR stretches in the range
1991 to 1910 cm-1, and in a 13CO-enriched sample of 14 the
three carbonyl resonances are observed between δ 177.1 and
195.2 in the 13C NMR spectrum. Selective 31P decoupling
identifies the downfield resonance as the lone Ir-bound carbonyl.
In a 13CH2-enriched sample the Ir-bound methylene unit ap-
pears in the 13C{1H} NMR spectrum at δ 67.8. Although
spin-spin coupling between the CH2 unit and the 31P nuclei
bound to Ir is not directly observed, owing to the breadth of the
signal, sharpening of the peak is observed upon 31P decoupling
of the Ir-bound 31P nuclei. This C3-bridged product, [IrOs-
(CO)3(μ-κ1:κ1-CH2(CF3)CdCCF3)(dppm)2][CF3SO3] (14),
(74) Cowie, M. Can. J. Chem. 2005, 83, 1043.

Article
Organometallics, Vol. 30, No. 5, 2011 963
Chart 2
Scheme 6
These ideas were supported by the relative rates of substitution
of a carbonyl by PMe3 at -25 °C, for which the rates decreased
in the order, rate(RhOs) ≈30 ꢀ rate(RhRu) ≈36 ꢀ rate(IrRu),74
paralleling the increasing strength of the group 9-(μ-CO)
interaction.
We can now extend these ideas to include the lack of
reactivity of 3 with diazomethane. As shown in Chart 2,
compound 3 is again saturated at both metals, and the all-
terminal-carbonyl arrangement observed should be less able to
transfer an Ir-bound CO to Os, making it the least susceptible
to nucleophilic attack at Ir. Furthermore, although structure A
is formally saturated, it has a vacant site opposite the bridging
carbonyl and adjacent to the methylene group, while com-
pound 3 has no accessible coordination site. In keeping with
this logic, 3 is unreactive toward diazomethane.
In order to test the above idea that Ir/Os should be the least
susceptible to nucleophilic attack of the series, we compared
its reactivity with PMe3 to that of the Ir/Ru analogue (the
slowest of the previous series). Under identical conditions at
ambient temperature, the rate of substitution of a carbonyl in
[IrRu(CO)4(μ-CH2)(dppm)2][CF3SO3] by PMe3 was found
to be approximately 1.5 times the rate of substitution in 3
(monitored by 31P{1H} NMR spectroscopy), consistent with
the ideas of coordinative saturation noted above.
These structural arguments, however, do not explain the
relative reactivities of this tetracarbonyl series with dimethyl
acetylenedicarboxylate (DMAD) nor the failure of hexa-
fluorobutyne (HFB) to react with any of the tetracarbonyl
precursors. The most reactive species with diazomethane and
PMe3 (Rh/Os) is unreactive toward DMAD,54 while both the
Ir/Os (3) and Rh/Ru analogues42 react readily with DMAD
at ambient temperature.
In most studies involving the insertion of unsaturated
substrates into a metal-CH2 bond of a bridging methylene
group, a vacant coordination site, adjacent to the bond into
which insertion occurs, is assumed.40,42,45,46,54 Certainly the
regioselectivity of these insertions in our MM0 series, which
always occurs into the group 9 metal-CH2 bond,42,54 is
consistent with incipient coordinative unsaturation at this
metal, and furthermore, insertion is significantly more facilþe
for the tricarbonyl analogues [MM0(CO)3(μ-CH2)(dppm)2]
than for the tetracarbonyl species. The reactivity trend in our
tetracarbonyl series and in particular the facile reactivity of the
saturated species 3 with DMAD, which can occur without
carbonyl loss, suggest that coordinative unsaturation is not
required to initiate the insertion. Furthermore, these electron-
deficient alkynes are not particularly nucleophilic.
The bridging methylene group in these late-metal species is
nucleophilic,54,75,76 so we suggest that nucleophilic attack of
this bridging group at the electron-deficient alkynes, HFB
and DMAD, may initiate the insertion; this reactivity is more
in line with the electrophilic nature of both alkynes. At first
glance, this proposal seems inconsistent with the higher
reactivity noted here and elsewhere,42,54,77,78 of DMAD
compared to HFB; on the basis of the higher group electro-
negativity of CF3,79 the opposite would be expected. How-
ever, we suggest that the potential for the carboxylate group
to offer additional resonance stabilization results in DMAD
being more electrophilic. In the tetracarbonyl complex 3 the
additional carbonyl (compared to 4) lowers the nucleophilic-
ity of the complex, lowering its reactivity toward the less
electrophilic alkyne, HFB, which reacts with 4 but not with 3.
We do not fully understand what subtle factors might give
rise to the differences in nucleophilicity of the μ-CH2 group
in this closely related series.
Differences in reactivity between DMAD and HFB, noted
above, are even more noticeable in the reactions of the C3-
bridged species [IrOs(CO)3(μ-κ1:κ1-RCdC(R)CH2)(dppm)2]þ
(R = CO2Me (6), CF3(7)) with diazomethane, which proceed
very differently. Whereas 7reacts with diazomethane to give the
anticipated C4-bridged product, shown in Scheme 4, com-
pound 6 yields the dimetallacycle 8 by C-O bond formation,
as shown in Scheme 3. We propose that the reaction involving 6
proceeds as outlined in Scheme 6, in which the carboxylate
carbonyl adjacent to the site of diazomethane coordination
(75) Samant, R. G.; Trepanier, S. J.; Wigginton, J. R.; Xu, L.;
Bierenstiel, M.; McDonald, R.; Ferguson, M. J.; Cowie, M. Organome-
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964 Organometallics, Vol. 30, No. 5, 2011
MacDougall et al.
displaces N2 via nucleophilic attack at the coordinated di-
azomethane, generating the O-CH2 bond, leading to the un-
observed intermediate C, having a terminal olefin moiety as
shown. Carbon-hydrogen bond activation of the R-olefin moiety
could then generate the final hydrido-bridged compound 8.
On this basis, the different reactivity of the HFB-inserted
product 7 with diazomethane is understandable. With no
adjacent carbonyl functionality, the favored reactivity in this
case is the anticipated insertion into the Ir-C(sp2) bonds of
the “μ-C3” fragment. The instability of this species, reverting
to the precursor and ethylene, must result from the more
favorable Ir-C(sp2) bond of the precursor (7) than the
Ir-C(sp3) bond of the product, and 7 is presumably also
favored, having the electronegative CF3 group on the R-
carbon, which further strengthens this Ir-C bond. We also
suggest that the additional strain within the six-membered
dimetallacycle of 9 further destabilizes this product.
Our second strategy for yielding C4-bridged species was
through double methylene insertion into the Ir-C(sp2) bond
of alkyne-bridged species. Although this again would lead to
replacement of an Ir-C(sp2) bond by a less favorable Ir-C-
(sp3) bond, we reasoned that the relief in strain, progressing
from a four-membered C2-bridged to a five-membered C3-
bridged species, might favor the insertion product. Certainly
this strategy had proven successful for the Rh/Os system.
However, in the current Ir/Os system the DMAD-bridged
precursor yields a mixture of uncharacterized products,
while the C3-bridged product obtained from the HFB-
bridged precursor, namely, [IrOs(CO)3(μ-κ1:κ1-CH2(CF3)-
CdCCF3)(dppm)2][CF3SO3] (14), is unstable at temperatures
above -20 °C, reverting to the HFB-bridged precursor; unlike
the analogous RhOs species, compound 14 failed to insert a
second methylene group.
Clearly, the factors involved in these transformations are
subtle, and changes in the metal combination can have a
significant effect on reactivity. These factors, which are not
fully understood, are more complex than in monometallic
systems and will need to be understood before the potential
of mixed-metal systems can be fully utilized.
Acknowledgment. We thank the Natural Sciences and
Engineering Research Council of Canada (NSERC) and
the University of Alberta for financial support for this
research and NSERC for funding the Enraf-Nonius
CAD4 diffractometer, the Bruker D8/APEX II CCD
diffractometer, and the Nicolet Avatar IR spectrom-
eter. We thank the Department’s Mass Spectrometry
Facility and the NMR Spectroscopy and Analytical
and Instrumentation Laboratories. Finally, we thank
NSERC and the Province of Alberta for funding sup-
port for T.J.M.
Supporting Information Available: Tables of crystallographic
experimental details for compounds 3, 7, 8, and 12 and ORTEP
diagrams for the complex cations of compounds 3 and 8,
showing all non-hydrogen atoms of phenyl groups in pdf
format. Atomic coordinates, interatomic distances and angles,
anisotropic thermal parameters, and hydrogen parameters for
compounds 3, 7, 8, and 12 in a CIF file. This material is available
free of charge via the Internet at http://pubs.acs.org.