Addition of amines to a carbonyl ligand: Syntheses, characterization, and reactivities of iridium(iii) porphyrin carbamoyl complexes

Article abstract of DOI:10.1021/om500189a

Treatment of (carbonyl)chloro(meso-tetra-p-tolylporphyrinato)iridium(III), (TTP)Ir(CO)Cl (1), with excess primary amines at 23°C in the presence of Na₂CO₃ produces the trans-amine-coordinated iridium carbamoyl complexes (TTP)Ir(NH₂R)[C(O)NHR] (R = Bn (2a), n-Bu (2b), i-Pr (2c), t-Bu (2d)) with isolated yields up to 94%. The trans-amine ligand is labile and can be replaced with quinuclidine (1-azabicyclo[2.2.2]octane, ABCO), 1-methylimidazole (1-MeIm), triethyl phosphite (P(OEt)₃), and dimethylphenylphosphine (PMe₂Ph) at 23°C to afford the hexacoordinated carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (for R = Bn: L = ABCO (3a), 1-MeIm (4a), P(OEt)₃ (5a), PMe₂Ph (6a)). On the basis of ligand displacement reactions and equilibrium studies, ligand binding strengths to the iridium metal center were found to decrease in the order PMe₂Ph > P(OEt)₃ > 1-MeIm > ABCO > BnNH ₂ ? Et₃N, PCy₃. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH₂ (2a,b), 1-MeIm (4a)) undergo protonolysis with HBF₄ to give the cationic carbonyl complexes [(TTP)Ir(NH₂R)(CO)]BF₄ (7a,b) and [(TTP)Ir(1-MeIm)(CO)] BF₄ (8), respectively. In contrast, the carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = P(OEt)₃ (5a), PMe₂Ph (6a,c)) reacted with HBF₄ to afford the complexes [(TTP)Ir(PMe ₂Ph)]BF₄ (9) and [(TTP)IrP(OEt)₃]BF₄ (10), respectively. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH ₂ (2a-d), 1-MeIm (4a), P(OEt)₃ (5b), PMe₂Ph (6c)) reacted with methyl iodide to give the iodo complexes (TTP)Ir(L)I (L = RNH₂ (11a-d), 1-MeIm (12), P(OEt)₃ (13), PMe₂Ph (14)). Reactions of the complexes [(TTP)Ir(PMe₂Ph)]BF₄ (9) and [(TTP)IrP(OEt)₃]BF₄ (10) with [Bu₄N]I, benzylamine (BnNH₂), and PMe₂Ph afforded (TTP)Ir(PMe ₂Ph)I (14), (TTP)Ir[P(OEt)₃]I (13), [(TTP)Ir(PMe ₂Ph)(NH₂Bn)]BF₄ (16), and trans-[(TTP) Ir(PMe₂Ph)₂]BF₄ (17), respectively. Metrical details for the molecular structures of 4a and 17 are reported.

Full text of DOI:10.1021/om500189a

Article
pubs.acs.org/Organometallics
Addition of Amines to a Carbonyl Ligand: Syntheses,
Characterization, and Reactivities of Iridium(III) Porphyrin Carbamoyl
Complexes
Taiwo O. Dairo, Arkady Ellern, Robert J. Angelici, and L. Keith Woo*
Department of Chemistry, Iowa State University, Ames, Iowa 50011-3111, United States
S
* Supporting Information
ABSTRACT: Treatment of (carbonyl)chloro(meso-tetra-p-tolylporphyrinato)iridium-
(III), (TTP)Ir(CO)Cl (1), with excess primary amines at 23 °C in the presence of
Na2CO3 produces the trans-amine-coordinated iridium carbamoyl complexes (TTP)Ir-
(NH2R)[C(O)NHR] (R = Bn (2a), n-Bu (2b), i-Pr (2c), t-Bu (2d)) with isolated yields
up to 94%. The trans-amine ligand is labile and can be replaced with quinuclidine (1-
azabicyclo[2.2.2]octane, ABCO), 1-methylimidazole (1-MeIm), triethyl phosphite
(P(OEt)3), and dimethylphenylphosphine (PMe2Ph) at 23 °C to afford the
hexacoordinated carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (for R = Bn: L =
ABCO (3a), 1-MeIm (4a), P(OEt)3 (5a), PMe2Ph (6a)). On the basis of ligand
displacement reactions and equilibrium studies, ligand binding strengths to the iridium
metal center were found to decrease in the order PMe2Ph > P(OEt)3 > 1-MeIm > ABCO
> BnNH2 ≫ Et3N, PCy3. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L =
RNH2 (2a,b), 1-MeIm (4a)) undergo protonolysis with HBF4 to give the cationic
carbonyl complexes [(TTP)Ir(NH2R)(CO)]BF4 (7a,b) and [(TTP)Ir(1-MeIm)(CO)]BF4 (8), respectively. In contrast, the
carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = P(OEt)3 (5a), PMe2Ph (6a,c)) reacted with HBF4 to afford the complexes
[(TTP)Ir(PMe2Ph)]BF4 (9) and [(TTP)IrP(OEt)3]BF4 (10), respectively. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR]
(L = RNH2 (2a−d), 1-MeIm (4a), P(OEt)3 (5b), PMe2Ph (6c)) reacted with methyl iodide to give the iodo complexes
(TTP)Ir(L)I (L = RNH2 (11a−d), 1-MeIm (12), P(OEt)3 (13), PMe2Ph (14)). Reactions of the complexes
[(TTP)Ir(PMe2Ph)]BF4 (9) and [(TTP)IrP(OEt)3]BF4 (10) with [Bu4N]I, benzylamine (BnNH2), and PMe2Ph afforded
(TTP)Ir(PMe2Ph)I (14), (TTP)Ir[P(OEt)3]I (13), [(TTP)Ir(PMe2Ph)(NH2Bn)]BF4 (16), and trans-[(TTP)Ir(PMe2Ph)2]-
BF4 (17), respectively. Metrical details for the molecular structures of 4a and 17 are reported.
Kinetic studies involving the reaction of amines with trans-
[M(CO)4L2]PF6 (where M = Mn, Re and L = PPh3, PMePh2,
PMe2Ph), have revealed that the rate of formation of carbamoyl
complexes has a second order dependence on the amine
concentration. To rationalize this rate dependence, a
mechanism involving amine assisted nucleophilic attack at the
carbonyl carbon atom was proposed (Scheme 1).7
Subsequently, metal carbamoyl complexes were either
observed or suggested to be involved in several catalytic and
stoichiometric chemical transformations. For example, the
catalytic oxidative carbonylation of n-butylamine to the 1,3-
substituted urea, using [(CO)2W(NPh)I2]2 as a catalyst, was
INTRODUCTION
■
Metal carbonyl complexes play a significant role in industrial
and organometallic chemistry, serving as important starting
materials and catalysts.1 A key reaction for these complexes is
the addition of nucleophiles to the carbonyl ligand. This
reactivity provides access to useful organic molecules such as
dimethylformamide, methanol, etc.2 Furthermore, the nucleo-
philic addition of the hydroxide anion to the CO ligand in
metal carbonyl complexes has been identified as a key step in
the water-gas shift reaction.3
Addition of amines to a transition-metal-bound carbonyl
ligand is a convenient route to the synthesis of metal carbamoyl
(or carboxamido) complexes (eq 1).4 In general, metal carbonyl
Scheme 1. Carbamoyl Complexes via Nucleophilic Attack of
Amine on M−CO
complexes that are susceptible to nucleophilic amine addition
to form metal carbamoyl complexes have υ(CO) above 2000
cm−1, an indication of the electrophilicity of the CO ligand.5,6
Some of the earliest reported examples of carbamoyl complexes
prepared by this route include those of Mn, Ru, Pt, and Fe.4
Received: February 21, 2014
© XXXX American Chemical Society
A
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proposed to involve the tungsten carbamoyl complex (CO)-
W[C(O)NHBu](NH2R)2(NPh)I as an intermediate.8 This was
supported further by IR spectroscopic studies with stoichio-
metric reactions of excess secondary and primary amines with
[(CO)2W(NPh)I2]2, which produced formamides and 1,3-
disubstituted ureas, respectively, in the presence of air as an
oxidizing agent.9 In addition, treatment of palladium carbamoyl
complexes with halogens or other oxidizing agents produced
isocyanates, in quantitative yields (eq 2).10
Scheme 2. Syntheses of Carbamoyl Complexes
(TTP)Ir(NH2R)[C(O)NHR] (2a−d)
a
PdClL2[C(O)NHR] + X2 ⎯⎯⎯⎯→ PdClXL2 + RNCO
a
meso-tolyl groups are omitted.
−HX
X = Cl, I
(2)
Na2CO3, workup resulted in some contamination with
(TTP)Ir(CO)Cl, presumably due to reversion of the reaction.
Similar observations were reported in the syntheses of the
carbamoyl complexes cis-Mn(CNR)[C(O)NHMe]-
(CO)2(bipy) from fac-[Mn(CNR)(CO)3(bipy)]+ and
MeNH2.17
Despite the diversity of metal carbamoyl complexes that
exist,11−17 reports on the synthesis and isolation of metal-
loporphyrin carbamoyl complexes are rare. One example
involves the formation of the carbamoyl complex (TPP)Rh-
[C(O)NEt2] from the reaction of (TPP)Rh(CO)Cl with
LiNEt2 in HNEt2. Treatment of the Rh carbamoyl product with
HCl re-formed the starting chlorocarbonyl complex.18 In
addition, octaethyl- and tetraphenylporphyrinato rhodium
carbamoyl complexes, (OEP)Rh[C(O)NHR] and (TPP)Rh-
[C(O)NHR], were observed as trace products in reactions of
the bis(isocyanide) porphyrinato rhodium(III) complexes
[(OEP)Rh(CNR)2]PF6 and [(TPP)Rh(CNR)2]PF6 with nu-
cleophiles, such as methanol, to form the cationic rhodium
diaminocarbene species [(OEP)Rh{C(NHR)2}]PF6 and
[(TPP)Rh{C(NHR)2}]PF6.19 Furthermore, Wayland and
co-workers20 isolated pentacoordinate carbamoyl complexes of
rhodium octaethylporphyrin, (OEP)Rh[C(O)NHR], by treat-
ing [(OEP)Rh]2 with CO and primary amines (eq 3). In this
case, the reaction was proposed to proceed via a hydrox-
yaminocarbene complex, [(OEP)RhC(OH)NHR]+.
Formation of the carbamoyl complexes was readily followed
1
spectroscopically, as evidenced by the replacement of the H
NMR β-pyrrole signal of (TTP)Ir(CO)Cl (1) with the β-
pyrrole signal of the corresponding carbamoyl products 2a−d.
The 1H NMR spectra also showed upfield shifts for the
carbamoyl and the trans-amine ligands, relative to the free
amine chemical shifts. These upfield shifts of the axial ligand
signals are attributed to the well-known ring current effect of
the porphyrin macrocycle.19,22 For example, the methylene
protons of free benzylamine resonate at 3.55 ppm, in C6D6. In
comparison, the methylene signal of the N-benzylcarbamoyl
ligand in complex 2a appeared as a two-proton doublet at 2.00
ppm, while the methylene protons of the trans-benzylamine in
2a resonated at −1.78 ppm (2H, br), also in C6D6. Generally,
the proton signals of the amine ligand are shifted more upfield
than those of the carbamoyl fragment, due to the closer
proximity of the amine to the porphyrin macrocycle. This is
1
/2[(OEP)Rh]2 + CO + RNH2
i
illustrated by (TTP)Ir(NH2 Pr)[C(O)NHPri] (2c), in which
⎯⎯⎯⎯⎯⎯→ (OEP)RhC(O)NHR
−1/2H2
(3)
the isopropyl methyl signal of the amine ligand resonated at
−2.31 ppm, in comparison to the isopropyl methyl signal of the
carbamoyl ligand at −0.75 ppm.
Although the isolation and characterization of the
pentacoordinate octaethylporphyrinato rhodium carbamoyl
complexes were described, the reactivities of these metal-
loporphyrin carbamoyl complexes were not explored. We
report herein the syntheses, characterization, and reactivities of
novel hexacoordinate porphyrinato iridium carbamoyl com-
plexes.
At 26 °C, the amine proton signals in the carbamoyl
compounds 2a−d were notably broadened relative to all other
signals (Figures S1, S5, S7, and S9, Supporting Information),
suggesting that the amine ligand was labile. Cooling an NMR
sample of 2a (in CDCl3) to 0 °C resulted in a sharpening of
these signals (Figure S2, Supporting Information). Further
evidence of this lability was demonstrated by 1H NMR
experiments with added amine. When ∼1.5 equiv of benzyl-
RESULTS AND DISCUSSION
■
1
Reactions of (TTP)Ir(CO)Cl with Amines. Generally,
carbonyl groups react with amines, to give carbamoyl ligands,
when ν(CO) is greater than 2000 cm−1.5,6 The ν(CO) value of
(TTP)Ir(CO)Cl (2056 cm−1)21 suggested that the carbonyl
ligand should be susceptible to nucleophilic attack. Thus,
treatment of THF solutions of (TTP)Ir(CO)Cl (1) with
primary amines, at 23 °C, immediately resulted in a color
change from red to brown. 1H NMR monitoring of the
reactions revealed that product formation was complete within
3 min. Amine-coordinated iridium carbamoyl complexes,
(TTP)Ir(NH2R)[C(O)NHR], were isolated from the reaction
mixtures in 73−94% yields (Scheme 2). Use of 2 equiv of the
amine resulted in quantitative reactions, as monitored by NMR.
In order to facilitate product isolation, both excess amine (up to
67 equiv) and excess sodium carbonate were needed. Without
amine was added to a C6D6 solution of 2a at 26 °C, the H
NMR spectrum exhibited broad methylene signals for both the
coordinated (−1.78 ppm) and free (3.55 ppm) amines. When
the temperature of the NMR sample was increased to 45 °C,
these signals coalesced into the baseline. Restoring the sample
temperature to 26 °C produced the original spectrum, in which
separate free and coordinated amine signals became visible
again.
Ligand Replacement Reactions. The lability of the
coordinated amines was further demonstrated by their ease of
substitution at 23 °C, by the ligands L = quinuclidine (1-
azabicyclo[2.2.2]octane, ABCO), 1-methylimidazole (1-MeIm),
triethyl phosphite (P(OEt)3), dimethylphenylphosphine
(PMe2Ph), leading to the isolation of the complexes (TTP)-
Ir(L)[C(O)NHR] (3−6) (Scheme 3). Benzylamine in (TTP)-
B
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a
Scheme 3. Substitution of Amine Ligands in
(TTP)Ir(NH2R)[C(O)NHR]
Table 2. 13C NMR Data for the α-C of the Carbamoyl
Ligands in (TTP)Ir(L)[C(O)NHR] (L = P(OEt)3 (5a,b),
PMe2Ph (6a−c))
a
complex
R
δ carbamoyl α-C
2
5a
5b
6a
6b
6c
Bn
nBu
Bn
nBu
iPr
162.72 (d, JP−C = 270.3 Hz)
2
162.73 (d, JP−C = 267.3 Hz)
2
163.87 (d, JP−C = 184.2 Hz)
2
163.87 (d, JP−C = 182.7 Hz)
2
163.39 (d, JP−C = 184.2 Hz)
a
In CDCl3.
a
Relative Binding Strengths of the Ligands. A series of
meso-tolyl groups are omitted.
substitution reactions to determine the relative binding
affinities of the BnNH2, ABCO, 1-MeIm, and P(OEt)3 ligands
to the iridium center in the (TTP)Ir(L)[C(O)NHBn]
Ir(NH2Bn)[C(O)NHBn] (2a) was completely displaced by 1
equiv of 1-methylimidazole within 3 min. Coordination of the
imidazole in (TTP)Ir(1-MeIm)[C(O)NHBn] (4a) was estab-
lished by the appearance of sharp proton singlets at 0.43 (3H),
1.63 (1H), 1.74 (1H), and 3.70 ppm (1H), assigned to the
methyl and ring protons of the bound 1-MeIm, which are
shifted upfield from 2.51 (methyl protons), 6.26, 6.99, and 7.22
ppm (ring protons), respectively, in the free 1-MeIm. The N-
benzylcarbamoyl ligand remained bound to the metal center, as
1
complexes was monitored by H NMR (eq 4). Equilibrium
constants determined for ligand exchange reactions in C6D6 at
25 °C are given in Table 3.
1
evidenced by H NMR signals of the carbamoyl NH (−1.13
ppm, t) and CH2 (2.07 ppm, d) in complex 4a, which were
shifted downfield, in comparison with the carbamoyl NH and
CH2 proton signals (−1.34 and 2.00 ppm, respectively) of
complex 2a.
Table 3. Equilibrium Constants for Ligand Exchange
Reactions Involving (TTP)Ir(L)[C(O)NHBn] at 25 °C (Eq
4)
In complex 6a, the 31P NMR signal of PMe2Ph shifted
downfield from −46.61 to −41.23 ppm upon coordination to
iridium (Table 1). A similar downfield shift in the 31P NMR
a
entry
L1
L2
K
1
2
3
4
5
6
7
8
9
BnNH2
ABCO
ABCO
9.4 0.2
0.11 0.01
0.06 0.02
1.9 0.1
BnNH2
BnNH2
1-MeIm
ABCO
a
Table 1. 31P NMR Data for P(OEt)3 and PMe2Ph as Free
1-MeIm
ABCO
Ligands and Coordinated to Carbamoyl Complexes,
(TTP)Ir(L)[C(O)NHR] (L = P(OEt)3 (5a,b), PMe2Ph (6a−
c))
1-MeIm
ABCO
0.58 0.05
14.4 1.0
0.07 0.004
5.7 0.5
P(OEt)3
ABCO
31P (δ) free ligand
(TTP)Ir(L)[C(O)NHR]
31P (δ) bound L
P(OEt)3
1-MeIm
P(OEt)3
P(OEt)3
1-MeIm
138.06 (P(OEt)3)
R = Bn (5a)
72.06
72.88
0.18 0.01
n
R = Bu (5b)
a
Reactions were carried out in C6D6 in air, with 1,3,5-mesitylene as an
−46.61 (PMe2Ph)
R = Bn (6a)
−41.23
−41.32
−41.27
1
internal standard, and monitored by H NMR (600 MHz).
n
R = Bu (6b)
i
R = Pr (6c)
a
With C6D6 solution of PPh3 (31P NMR δ −5.53 ppm) as an external
The data in Table 3 show that P(OEt)3 is more strongly
bound to the iridium than 1-MeIm, on the basis of the values of
the equilibrium constants shown in entries 8 and 9, and 1-
MeIm is more strongly bound to the metal center than ABCO,
as indicated by the equilibrium constants in entries 4 and 5.
In general, the more basic amines (conjugate acid pKa values
given in parentheses) n-butylamine (10.59), benzylamine
(9.34), isopropylamine (10.63), and tert-butylamine (10.55)25
were readily replaced by the less basic 1-MeIm (7.2),26 P(OEt)3
(3.31),27 and PMe2Ph (6.50).27 Moreover, only 1 equiv of
P(OEt)3 or PMe2Ph was required to completely displace 1-
MeIm from the Ir carbamoyl complexes (TTP)Ir(1-MeIm)[C-
(O)NHR]. This indicates that factors other than the ligand
basicity, such as π acidity and softness, influence ligand binding.
Thus, the d6 Ir(III) center, a soft acid28 and electron-rich π-
donor, prefers 1-methylimidazole and phosphorus ligands (soft
bases) over amines (hard bases). Other studies (see below)
indicate that the order of neutral ligand binding to (TTP)Ir-
(L)[C(O)NHBn] decreases in the order PMe2Ph > P(OEt)3 >
1-MeIm > ABCO > BnNH2 ≫ Et3N, PCy3. The stronger
standard.
signal for phosphine ligand coordination to the rhodium
tetraphenylporphyrin complex, (DPAP)2RhIIITPP, where
DPAP is diphenyl(phenylethynyl)phosphine, was observed
earlier by Stulz and co-workers.23 In contrast, coordination of
P(OEt)3 to Ir in 5a,b resulted in a large upfield shift of the
phosphite signal (Table 1). An analogous large upfield shift in
the compound (η-MeCp)(CO)2Mn(P(OEt)3) was rationalized
by metal d-electron back-donation to the π-acid P(OEt)3
ligand.24
The 13C chemical shifts for the α-C of the carbamoyl ligands
were readily assigned in the P(OEt)3 and PMe2Ph complexes
(5a,b and 6a−c, respectively), due to two-bond 31P−13C
coupling. For example, in 5a, a low-field 13C doublet appeared
at 162.72 ppm (2JP−C = 270.3 Hz), while a low-field 13C doublet
appeared at 163.87 ppm (2JP−C = 184.2 Hz) for 6a (Table 2).
C
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binding of PMe2Ph in comparison to P(OEt)3 is based on the
observation that 5 equiv of P(OEt)3 failed to displace PMe2Ph
from the carbamoyl complex 6a at 23 °C. These results are in
accord with the higher σ-donating ability of PMe2Ph, relative to
P(OEt)3.24 In addition to electronic factors, steric hindrance
also influences the binding of axial ligands to the iridium center.
The reaction with tricyclohexylphosphine, PCy3 (pKa 9.70,
cone angle 170°),27 illustrates the importance of steric
hindrance. When 1.5 equiv of PCy3 was added to a C6D6
solution of 2a at 23 °C, no reaction occurred after 12.5 h, as
amides (1.231 Å).31 The C(53)−N(7) bond distance (1.355(8)
Å) of the carbamoyl ligand is also analogous to that (1.341(5)
Å)20 reported for the pentacoordinate rhodium complex
[(OEP)Rh[C(O)NH(C6H3Me2)] and that (1.34(1) Å)32 for
the hexacoordinate ruthenium bis-carbamoyl complex [Ru-
(dppe)(CO)2[C(O)NHCHMe2]2. However, the Ir−N(5)
bond distance of 2.208(5) Å in the 1-methylimidazole complex
is longer than that reported for Ir−NMe3 in Ir(TTP)Cl(NMe3)
(2.174(2) Å).33 The Ir−C(53) length of 2.026(6) Å is
comparable to the Ir−C length reported for the pentacoordi-
nate Ir(TTP)[C(O)Ph] (2.038(12) Å)34 but is longer than the
Rh−C bond length (1.988(5) Å) in (OEP)Rh[C(O)NH-
(C6H3Me2)].20
1
monitored by H NMR. Other less basic and less sterically
hindered tertiary phosphines, such as P(n-Bu)3 (pKa 8.43, cone
angle 136°) and PPh3 (pKa 2.73, cone angle 145°),27 readily
displaced BnNH2 from complex 2a. Steric bulk also affects the
binding of amines. This was apparent during an attempt to
replace the benzylamine ligand (pKa 9.34; cone angle 106°)25,29
in complex 2a with Et3N (pKa 10.65; cone angle 150°)25,29 in
C6D6, at 23 °C. Although Et3N is more basic than BnNH2, no
reaction was observed, even after heating the reaction mixture
to 90 °C for almost 9 h with 2 equiv of Et3N. However, when
an excess of the more basic but less sterically hindered tertiary
amine quinuclidine (pKa 11.0°,30 cone angle 132°29) was added
at ambient temperature to a C6D6 solution of complex 2a,
complete displacement of BnNH2 was observed, affording
complex 3a in less than 7 min. All of these results indicate that
both electronic and steric properties of the L ligand contribute
to the overall trend in binding strengths in the (TTP)Ir(L)-
[C(O)NHBn] complexes.
Reactions of the Carbamoyl Ligand with Electro-
philes. Reactions with HBF4. Metal carbamoyl complexes
generally react with acids to form metal carbonyl complexes, a
process that also serves as a supporting test for the presence of
a carbamoyl ligand4 (eq 5). When 2 equiv of HBF4·Et2O was
added at 23 °C to benzene solutions of the amine-coordinated
carbamoyl complexes (TTP)Ir(NH2R)[C(O)NHR] (2a,b), the
corresponding cationic amine-coordinated carbonyl complexes
[(TTP)Ir(NH2R)(CO)]BF4 (7a,b) were produced, as shown
in Scheme 4. The carbonyl ligands of complexes 7a,b exhibited
CO stretching frequencies at 2075 and 2078 cm−1, respectively.
The molecular structure for (TTP)Ir(1-MeIm)[C(O)-
NHBn] (4a) was solved by single-crystal X-ray diffraction
analysis (Figure 1). The benzyl group of the N-benzylcarba-
Scheme 4. Reaction of Carbamoyl Complexes
a
(TTP)Ir(L)[C(O)NHR] (2−4) with HBF4
a
meso-tolyl groups are omitted.
The characterization of complex 7a was representative of
these new cationic carbonyl compounds. A low-intensity peak
at 138.96 ppm was assigned as the carbonyl 13C NMR
resonance (Figure S33 Supporting Information). This is similar
to the assignment for the carbonyl of [(TTP)Ir(CO)]BF4
(131.3 ppm) reported by Chan.34 Moreover, the parent ion
peak (m/z 996.3275) observed by HRMS for [(TTP)Ir-
(NH2Bn)(CO)]+ and satisfactory elemental analysis provided
confirmation of the composition and purity of complex 7a. This
represents the second account of a cationic iridium
porphyrinato carbonyl complex. The first report was for an
inseparable mixture of cations, [(TTP)Ir(CO)]BF4/[(TTP)-
Ir]BF4, described by Chan and co-workers.34 While a similar
reaction between 2 equiv of HBF4·Et2O and the 1-MeIm-
coordinated carbamoyl complex (4a) led to the formation of
the cationic 1-MeIm-coordinated carbonyl complex [(TTP)Ir-
(1-MeIm)(CO)]BF4 (8) (Scheme 4), the quinuclidine-
coordinated carbamoyl complex (3a) reacted with acid (eq 6)
to give the cationic benzylamine-coordinated carbonyl complex
[(TTP)Ir(NH2Bn)(CO)]BF4 (7a), as the major porphyrin
Figure 1. Molecular structure of (TTP)Ir(1-MeIm)[C(O)NHBn]
(4a) with 30% probability ellipsoids. Selected bond distances (Å) and
angles (deg): Ir−C(53) = 2.026(6), Ir−N(5) = 2.208(5), C(53)−
O(1) = 1.217(7), C(53)−N(7) = 1.355(8); C(53)−Ir−N(5) =
178.86(19), N(3)−Ir−N(1) = 178.92(18), N(2)−Ir−N(4) =
178.44(18), O(1)−C(53)−N(7) = 119.0(6), O(1)−C(53)−Ir =
124.3(5), N(7)−C(53)−Ir = 116.7(4).
moyl ligand [C(O)NHBn] is anti to the iridium. The sum of
the angles at the carbonyl carbon, C(53), is 360.0°, consistent
with a trigonal-planar carbon atom. In addition, the N-
benzylcarbamoyl and axial 1-MeIm ligands are collinear with
a C(53)−Ir−N(5) bond angle of 178.86(19)°. The C(53)−
N(7) bond distance (1.355(8) Å) of the carbamoyl ligand is
similar to that of secondary organic amides, RC(O)NHR′
(1.334 Å),31 and the CO bond distance (1.217(7) Å) of the
carbamoyl ligand is comparable to that of secondary organic
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ments.36,37 A bound BF4 anion was established in mer-(cis-
PMe3)(trans-NO)(CO)3W(μ-F)BF3 through a 31P NMR
doublet at 192 K, as a result of 31P−19F coupling. When a
CD2Cl2 solution of mer-(cis-PMe3)(trans-NO)(CO)3W(μ-
F)BF3 was warmed to 262 K, the doublet 31P NMR signal
became a pentet, due to exchange of the four fluorine atoms of
the BF4 into the bridging position.36 However, solution 31P
−
product (56%, by 1H NMR), with the coformation of a mixture
of other unidentified porphyrin products. The formation of 7a,
and not [(TTP)Ir(ABCO)(CO)]BF4, is in accord with the
higher basicity of quinuclidine in comparison with benzylamine
and its thermodynamic preference for the ammonium form.
In contrast to the reactions of the amine (2a,b) and 1-MeIm
(4a) complexes, the ambient-temperature reactions between
excess HBF4·Et2O (3−4 equiv) and each of the two PMe2Ph-
coordinated carbamoyl complexes 6a,c resulted in loss of the
entire carbamoyl ligand, as monitored by IR and NMR. The
NMR spectra of [(TTP)Ir(PMe2Ph)]BF4 (9) acquired in
CD2Cl2 at 223, 200, and 190 K revealed only a 31P NMR singlet
−
peak at −39.61 ppm. This suggests that the BF4 anion is not
coordinated to the metal center in complex 9 or is rapidly
dissociating on the NMR time scale.
Reactions with Methyl Iodide. When a C6D6 solution of a
carbamoyl complex (2a−d, 4a, 5b, or 6c) was heated to ∼85
°C with 3−6 equiv of MeI for 12−96 h, the iodo complex
(TTP)Ir(L)I was produced as the main porphyrin product with
1
1
purities ranging from 88 to 94% (eq 9), as identified by H
formation of [(TTP)Ir(PMe2Ph)]BF4 (9) was observed by H
NMR in each case (eq 7). The appearance of 9 was manifested
by a β-pyrrole proton signal at 8.83 ppm (in C6D6) and the
upfield shift of the methyl resonance of the phosphine ligand
from −2.66 ppm in the carbamoyl complex 6a to −3.23 ppm in
9. Moreover, the ortho and meta aryl proton signals of the
phosphine ligand (in C6D6) were shifted upfield from 4.07
(2H) and 6.34 (2H) ppm in 6a to 3.57 (2H) and 6.13 (2H)
ppm in 9, respectively. Temperature was an important factor in
the protonolysis of the P(OEt)3-coordinated carbamoyl
complex 5a. When a C6D6 solution of 5a was treated with 2
equiv of HBF4·Et2O, at 23 °C, the formation of [(TTP)IrP-
(OEt)3]BF4 (10) was accompanied by two other unidentified
porphyrin products (5.5% and 11.5%), neither of which
contained a CO ligand, as revealed by IR analysis. However,
when the same reaction was carried out in toluene at 0 °C,
complex 10 was formed as the only porphyrin product (eq 8).
NMR. For example, the β-pyrrole signal of the tert-butylamine-
coordinated carbamoyl complex 2d at 8.88 ppm was replaced
by a new resonance at 8.94 ppm, upon formation of the iodo
complex (TTP)Ir(NH2But)I (11d). In addition, the complete
loss of the proton resonances for the tert-butylcarbamoyl ligand
was observed. Of the amine carbamoyl complexes (2a−d), the
n-butyl analogue (2b) reacted with MeI the fastest (12 h), an
indication that a less sterically bulky carbamoyl substituent
increases the reaction rate.
In the reactions of 2a,b and 6c with MeI, ammonium iodide
coproducts were detected in the precipitate from the reaction
mixtures. For example, the only ammonium salt produced from
the reaction of (TTP)Ir(PMe2Ph)[C(O)NHiPr] (6c) with
methyl iodide was identified as [i-PrNMe3]I. This character-
ization was accomplished by comparing the 1H NMR spectrum
(in D2O) and 13C NMR spectrum (in CDCl3) of the
precipitate from the reaction mixture with that of an authentic
sample of [i-PrNMe3]I (see Figures S69 and S70, Supporting
Information), prepared by treating (i-Pr)NMe2 with a 2-fold
excess of methyl iodide at 23 °C. Similarly, [n-BuNMe3]I was
the only ammonium salt produced from the treatment of
The failure of the phosphine-coordinated complexes 6a,c to
form the cationic carbonyl complex [(TTP)Ir(PMe2Ph)(CO)]-
BF4 is presumably due to the trans influence of the PMe2Ph
ligand. In an analogous case, the trans effect of PPh3 was
proposed as a reason for the failure to isolate phosphine-
coordinated ruthenium(II) tetraarylporphyrinato carbonyl
complexes of the form (PR3)RuII(CO)(DPP), which were
only observed in solution by IR spectroscopy.35 Similarly, the π
(TTP)Ir(NH2 Bu)[C(O)NHnBu] (2b) with MeI. In the
n
reaction of (TTP)Ir(NH2Bn)[C(O)NHBn] (2a) with 2
equiv of MeI, three ammonium salts were identified:
[BnNMe3]I (66%), [BnNH3]I (25%), and [Me(Bn)NH2]I
(9%). One-bond 13C−14N coupling was observed for the N−
Me carbon atoms in the 13C NMR spectra of [BnNMe3]I, [n-
BuNMe3]I, and [i-PrNMe3]I. Similar coupling in the 13C NMR
spectra of quaternary ammonium halide salts was reported
earlier.38,39 Increasing the scale of reaction 9, up to 3-fold, failed
to provide cleanly isolable iodo products. However, complexes
13 and 14 were conveniently synthesized by an independent
method (vide infra). Although the formation of the (TTP)Ir-
(L)I complexes could proceed via a transient [(TTP)Ir(L)-
CO]+ intermediate, treatment of a C6D6 solution of the cationic
24
acidity of P(OEt)3 may have contributed to the dissociation
of the CO ligand (eq 8).
It is not clear whether complexes 9 and 10 are
pentacoordinate with a noncoordinating counteranion or
−
whether the BF4 is coordinating to the iridium metal center
through a fluoride atom. Examples of metal ligation by weakly
−
−
−
coordinating ligands such as BF4 , SbF6 , and PF6 have been
studied by variable-temperature solution NMR experi-
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iridium carbonyl complex [(TTP)Ir(NH2Bn)(CO)]BF4 (7a)
with [Bu4N]I, for 3.5 h under reflux conditions resulted in a
mixture that contained 63% (TTP)Ir(NH2Bn)I (11a), 36%
(TTP)Ir(CO)I,33 and 1% (TTP)Ir(NH2Bn)[C(O)NHBn]
1
(2a), as revealed by H NMR, rather than pure 11a.
Reactions of [(TTP)Ir(L)]BF4 and [(TTP)Ir(L)CO]BF4 with
Other Ligands. Reactions with [Bu4N]I. Treatment of a
CH2Cl2 solution of [(TTP)Ir(PMe2Ph)]BF4 (9) with ∼2 equiv
of [Bu4N]I at 23 °C for 8 min yielded the iodo complex 14 in
formulation of 16 was supported by the presence of a peak at
m/z 1106.3899, corresponding to [16 − BF4]+, in the high-
resolution mass spectrum. Moreover, the coordination of
BnNH2 in complex 16 was established by 1H NMR
spectroscopy, with the appearance of upfield multiplet signals
at −3.42 (2H) and −1.72 (2H) ppm, assigned to the NH2 and
CH2 protons, respectively. In addition, a doublet at −3.17 ppm
1
69% isolated yield (eq 10). The H NMR spectrum (in C6D6)
2
(6H, CH3, JP−H = 12 Hz) was assigned to the methyl protons
of the PMe2Ph ligand.
Reactions of [(TTP)Ir(PMe2Ph)]BF4 (9) with PMe2Ph. The
addition of 1.1 equiv of PMe2Ph to a CDCl3 solution of the
monophosphine complex [(TTP)Ir(PMe2Ph)]BF4 (9) resulted
of (TTP)Ir(PMe2Ph)I (14) exhibited a β-pyrrole proton
resonance at 8.84 ppm and a doublet peak at −3.06 ppm for
the methyl protons of the coordinated PMe2Ph. These spectral
properties matched those for the product of the reaction of MeI
with (TTP)Ir(PMe2Ph)[C(O)NHPri] (6c) (eq 9). In addition,
the 31P NMR signal for (TTP)Ir(PMe2Ph)I (14) appeared at
−43.55 ppm, which is different from the 31P NMR signal
(−41.28 ppm) for [(TTP)Ir(PMe2Ph)]BF4 (9). Similarly, a 2.2
mg scale synthesis of the P(OEt)3 analogue (13) was carried
out by treating a C6D6 solution of [(TTP)Ir(P(OEt)3)]BF4
(10) with ∼3 equiv of [Bu4N]I (eq 10). The formation of
(TTP)Ir[P(OEt)3]I (13) (43.5% isolated yield) was observed
by 1H NMR, as evidenced by the shifts of the CH3 and CH2 1H
NMR signals (in C6D6) from −0.53 and 0.55 ppm to −0.38
and 0.70 ppm, respectively, in going from reactant 10 to
product 13. The 31P NMR signal of the reactant 10 at 35.16
ppm was also replaced by a signal at −0.01 ppm upon
formation of the product 13. An independent synthesis was
carried out by treating a benzene solution of [(TTP)Ir(P-
(OEt)3)(NH2Bn)]BF4 (15) with 5 equiv of [Bu4N]I, resulting
in a 49% isolated yield of (TTP)Ir[P(OEt)3]I (13).
1
in a rapid reaction. The most notable change in the H NMR
spectrum, observed 10 min after initial addition of PMe2Ph, was
the replacement of the 6-H methyl doublet of the mono-
phosphine ligand at −2.75 ppm with a 12-H virtual triplet at
−2.77 ppm assigned to the bis-phosphines in trans-[(TTP)Ir-
(PMe2Ph)2]BF4 (17). This virtual coupling is diagnostic of a
trans arrangement of methylphosphines.40−44 The apparent
JP−H value measured for 17 was 4.0 Hz and is similar to the
values for the coupling constants in trans-PdI2(PMe2Ph)2 (4.4
Hz), and for the trans-PMe2Ph ligands in IrCl3(PMe2Ph)3 (4.5
Hz).45 Analogous rhodium and ruthenium porphyrinato bis-
phosphine complexes have also been reported, including
[(DPAP)2RhIII(TPP)]I and (DPPA)2RuII(DPP), where DPAP
is diphenyl(phenylethynyl)phosphine and DPPA is bis-
(diphenylphosphino)acetylene.23,35 The composition of com-
plex 17 was confirmed further by the m/z peak at 1137.3752
for [17 − BF4]+ by HRMS. The 31P NMR signal (in C6D6) for
17 (−32.35 ppm) was also markedly different from that for 9
(−41.28 ppm).
The molecular structure of 17 was confirmed by single-
crystal X-ray diffraction (Figure 2). The two axial PMe2Ph
ligands are collinear with a P(1)−Ir−P(2) bond angle of
179.20(11)°. The iridium−phosphorus bond distances of Ir−
P(1) = 2.354(3) Å and Ir−P(2) = 2.348(3) Å are comparable
to the Ir−P distances reported for nonporphyrinic mono-, bis-,
tris-, and tetrakis-phosphino iridium complexes (2.2044−
2.3927 Å).46−51 However, the iridium−phosphorus bonds in
Reactions of [(TTP)Ir(L)CO]BF4 and [(TTP)Ir(L)]BF4 with
Primary Amines. The cationic CO complexes could be used in
alternative syntheses of carbamoyl compounds. When C6D6
solutions of each of the cationic CO complexes 7a and 8 were
treated with 1 equiv of BnNH2, in the presence of Na2CO3, the
carbamoyl complexes 2a and 4a were formed quantitatively
(Scheme 5).
Scheme 5. Reactions of [(TTP)Ir(L)CO]BF4 (L = BnNH2
(7a), 1-MeIm (8)) with Primary Amines RNH2
An amine Ir phosphine complex, [(TTP)Ir(PMe2Ph)-
(NH2Bn)]BF4 (16), was prepared by treatment of a C6H6
solution of phosphine complex 9 with BnNH2. After the
reaction mixture was stirred at 23 °C for 30 min, complex 16
was isolated in 90% yield (eq 11). The 31P NMR signal for
[(TTP)Ir(PMe2Ph)(NH2Bn)]BF4 (16), which appeared at
−41.49 ppm, was very similar to that of the starting complex
[(TTP)Ir(PMe2Ph)]BF4 (9) (−41.28 ppm). However, the
Figure 2. Molecular structure of trans-[(TTP)Ir(PMe2Ph)2]BF4 (17)
with 30% probability ellipsoids. Selected bond distances (Å) and
angles (deg): Ir−P(1) = 2.354(3), Ir−P(2) = 2.348(3); P(1)−C(49)
= 1.783(13), P(1)−C(50) = 1.800(12), P(1)−C(51) = 1.794(12),
P(2)−C(57) = 1.822(13), P(2)−C(58) = 1.805(13), P(2)−C(59) =
1.808(12); P(1)−Ir−P(2) = 179.20(11).
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purification. NMR spectra were collected using Varian VXR 300 MHz,
Varian VXR 400 MHz, Bruker DRX 400 MHz, Varian MR 400 MHz,
and Bruker AVIII 600 MHz spectrometers. IR spectra were acquired in
the solid state on NaCl plates, using a Bruker IFS66 V FTIR
complex 17 are both shorter than the Ir−P bond distance
(2.537 Å) reported for the porphyrinic iridium phosphine
complex (OEP)Ir(C3H7)(PPh3).52 This unusually long Ir−P
bond length was attributed to the trans influence of the alkyl
ligand and to steric repulsion between the bulky PPh3 ligand
and the octaethylporphyrin ligand.
1
instrument. H NMR peak positions were referenced against residual
proton resonances of deuterated solvents (δ (ppm): CDCl3, 7.26;
C6D6, 7.15; D2O, 4.79), while 13C NMR peaks were referenced to
CDCl3 (δ 77.36 ppm). When multiple porphyrin products were
obtained in NMR-tube reactions, the purity of the major product was
determined by the ratio of its β-pyrrole proton area to that of the total
β-pyrrole integration. A solution of PPh3 in C6D6 (31P NMR: δ −5.53
ppm) was used as an external standard during 31P NMR data
collection.
CONCLUSIONS
■
The reaction (Scheme 2) of (TTP)Ir(CO)Cl (1) with primary
amines readily generates the amine-coordinated carbamoyl
complexes (TTP)Ir(NH2R)[C(O)NHR] (2a−d) under am-
bient conditions. A possible first step in the mechanism of this
reaction is amine attack on the CO ligand to give a carbamoyl
group (eq 1); such a reaction is expected, on the basis of the
high CO stretching frequency (2056 cm−1) in 1. Also
supporting this step is the known reaction33 of 1 with O−
NMe3 to give (TTP)Ir(Cl)(NMe3) and CO2, which presum-
ably involves nucleophilic attack of O−NMe3 on the CO ligand
in 1. This is a reaction typical of O−NMe3 with CO ligands in a
variety of metal carbonyl complexes.53−55 Following carbamoyl
ligand formation in the first step, the Cl− ligand could be
rapidly substituted by an amine to give the (TTP)Ir(NH2R)-
[C(O)NHR] product. Although this mechanism for the
reactions of 1 with amines is entirely plausible, it is not
possible to exclude an alternate pathway in which the first step
involves amine substitution of the Cl− ligand to give the
cationic (TTP)Ir(NH2R)(CO)+, which would be expected to
react rapidly with amine to give the final carbamoyl product 2.
The amine ligand in 2 is labile on the NMR time scale at 23
°C, allowing substitution with a variety of ligands. This has led
to the preparation of phosphine-, phosphite-, 1-MeIm-, and
ABCO-coordinated (TTP)Ir(L)[C(O)NHR] carbamoyl com-
plexes. Equilibrium studies of ligand displacement reactions of
these complexes show that the binding affinities of the L ligands
decrease in the order PMe2Ph > P(OEt)3 > 1-MeIm > ABCO >
BnNH2 ≫ Et3N, PCy3. Reactions of these carbamoyl
complexes (TTP)Ir(L)[C(O)NHR] with HBF4 either at
room temperature (for L = RNH2, 1-MeIm (Scheme 4) and
L = PMe2Ph (eq 7)) or at 0 °C (for L = P(OEt)3) (eq 8) give
products that depend on the nature of the axial L ligand. When
this ligand is an amine (2a,b, 4a), the reactions produce
cationic Ir carbonyl complexes of the form [(TTP)Ir(L)-
(CO)]BF4 (7a,b, 8). With complexes containing phosphite
(5a) or phosphine (6a,c) ligands, treatment with HBF4 results
in complete loss of the carbamoyl ligand and production of
complexes 9 and 10 ([(TTP)Ir(L)]BF4, L = PMe2Ph,
P(OEt)3), respectively. Reactions of MeI with all of the
carbamoyl complexes require a higher temperature (85 °C) and
afford the neutral iodo complexes (TTP)Ir(L)I (11a−d, 12−
14), regardless of the L ligand. All of these results demonstrate
that carbamoyl complexes of Ir(III) porphyrin complexes are
easily formed and show a broad range of reactivity.
(TTP)Ir(NH2Bn)[C(O)NHBn] (2a). In a nitrogen-filled glovebag, a
100 mL round-bottomed flask was charged with (TTP)Ir(CO)(Cl)
(1; 91 mg, 0.099 mmol), Na2CO3 (682 mg, 6.43 mmol), a stir bar, and
30 mL of THF. Benzylamine (610 μL, 5.6 mmol, 57 equiv) was added
by syringe into the flask, the flask was capped with a rubber septum,
and the mixture was stirred under N2 for 6 h. The reaction mixture was
then opened to air, and solids were removed via filtration. Solvent and
excess benzylamine were removed under reduced pressure. The
residue was washed with 60 mL of hexanes, and 2a was obtained.
Yield: 87% (95 mg, 0.086 mmol). Anal. Calcd for C63H53IrN6O·
0.7H2O: C, 67.87; H, 4.91; N, 7.54. Found: C, 67.90; H, 4.74; N, 7.37.
1H NMR (299 K, 300 MHz, C6D6): δ −5.14 (br, 2H, NH2), −1.78
(br, 2H, amine CH2), −1.34 (t, 1H, J = 6 Hz, carbamoyl NH), 0.41 (s,
1.40H, H2O), 2.00 (d, 2H, J = 6 Hz, carbamoyl CH2), 2.38 (s, 12H,
-C6H4-CH3), 4.52 (br, 2H, amine o-H), 5.27 (d, 2H, J = 6 Hz,
carbamoyl o-H), 6.22 (br, 2H, amine m-H), 6.39 (br, 1H, amine p-H),
6.79 (m, 3H, carbamoyl m,p-H), 7.21 (dd, 4H, J = 6 Hz, 3 Hz, -C6H4-
CH3), 7.28 (dd, 4H, J = 6 Hz, 3 Hz, -C6H4-CH3), 7.94 (dd, 4H, J = 6
Hz, 3 Hz, -C6H4-CH3), 8.15 (dd, 4H, J = 9 Hz, 3 Hz, -C6H4-CH3),
8.91 (s, 8H, pyrrole-H). 1H NMR (273 K, 400 MHz, CDCl3): δ −5.01
(t, 2H, J = 8 Hz, NH2), −2.00 (t, 2H, J = 8 Hz, amine CH2), −1.83 (t,
1H, J = 8 Hz, carbamoyl NH), 1.76 (d, 2H, J = 8 Hz, carbamoyl CH2),
2.68 (s, 12H, −C6H4CH3), 5.03 (d, 2H, 8 Hz amine o-H), 5.17 (d, 2H,
J = 8 Hz, carbamoyl o-H), 6.52 (t, 2H, J = 8 Hz, amine m-H), 6.65 (t,
1H, J = 8 Hz, amine p-H), 6.83 (t, 2 H, J = 8 Hz, carbamoyl m-H), 6.93
(t, 1 H, J = 8 Hz, carbamoyl p-H), 7.49 (dd, 8H, J = 16 Hz, 8 Hz,
−C6H4CH3), 7.85 (dd, 4H, J = 8 Hz, 4 Hz, -C6H4-CH3), 7.99 (dd, 4H,
J = 8 Hz, 4 Hz, -C6H4-CH3), 8.62 (s, 8H, pyrrole-H). 13C NMR (151
MHz, CDCl3): δ 21.87, 40.36, 41.64 (low intensity peak assigned by
2D HSQC), 122.91, 125.89, 126.03, 127.17, 127.47, 127.82, 127.84,
128.30, 128.60, 128.92, 131.83, 133.82, 134.68, 137.40, 139.19, 139.56,
142.80, 143.64 (CO Carbon). UV−vis (C6H6): λmax (log ε) 414
(5.24), 521 nm (4.21). HRMS (+ESI): calcd for [MH]+
(C63H54IrN6O)+ m/z 1103.3988; found m/z 1103.3921.
(TTP)Ir(ABCO)[C(O)NHBn] (3a). In a nitrogen-filled glovebag, a 20
mL scintillation vial was charged with complex 2a (71 mg, 0.064
mmol), quinuclidine (ABCO; 112 mg, 1.0 mmol, 15.6 equiv), and 10
mL of C6H6. After the mixture was stirred at 23 °C for 20 min, volatile
materials were removed under reduced pressure and the residues were
washed with 50 mL of hexanes to remove free benzylamine. Additional
treatment under reduced pressure at 85 °C for 2.5 days was needed to
remove excess quinuclidine, affording complex 3a. Yield: 52% (37 mg,
1
0.034 mmol). H NMR (400 MHz, C6D6): δ −2.73 (br t, 6H, J = 8
Hz, ABCO NCH2), −1.56 (t, 1H, J = 8 Hz, carbamoyl NH), −0.8 (br,
6H, ABCO CCH2), −0.27 (br, 1H, ABCO CH), 1.90 (d, 2H, J = 8 Hz,
carbamoyl CH2), 2.37 (s, 12H, −C6H4CH3), 5.22 (d, 2H, J = 8 Hz,
carbamoyl o-H), 6.77 (m, 3H, carbamoyl m/p-H), 7.20 (d, 4H, J = 8
Hz, −C6H4CH3), 7.32 (d, 4H, J = 8 Hz, −C6H4CH3), 7.92 (dd, 4H, J
= 8 Hz, 4 Hz, −C6H4CH3), 8.20 (dd, 4H, J = 8 Hz, 4 Hz, −C6H4CH3),
8.87 (s, 8H, pyrrole H). 13C NMR (101 MHz, CDCl3) δ: 17.94, 21.87,
24.20, 40.47, 43.73, 123.26, 125.89, 126.00, 127.36, 127.80, 127.83,
131.79, 134.00, 134.41, 137.37, 137.68, 139.26, 139.36, 142.78. UV−
vis (C6H6): λmax (log ε) 415 (5.19), 519 nm (4.19). HRMS (+ESI):
calcd for [MH]+ (C63H58IrN6O)+ m/z 1107.4301; found m/z
1107.4299.
EXPERIMENTAL SECTION
■
All manipulations were performed under a dry nitrogen atmosphere in
a glovebag or glovebox or using Schlenk techniques, except where
otherwise stated. Ir(TTP)Cl(CO) (1) was prepared according to a
literature procedure.56 Benzylamine and isopropylamine were distilled
from CaH2 and stored over 4 Å molecular sieves prior to use.
Dimethylphenylphosphine was stored in an inert-atmosphere glove-
box. Tetrahydrofuran and toluene were deoxygenated and dried by
passage through columns of reduced copper and alumina, respectively.
All other chemicals were reagent grade and were used without further
(TTP)Ir(1-MeIm)[C(O)NHBn] (4a). In air, a 20 mL scintillation vial
was charged with complex 2a (85 mg, 0.077 mmol), 1-
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methylimidazole (40 μL, 0.50 mmol, 6.5 equiv), and 15 mL of THF.
After the solution was stirred at 23 °C for 1 h, volatile materials were
removed under reduced pressure. Recrystallization was then done by
adding hexanes to a concentrated THF solution of the dried product,
to afford complex 4a. Yield: 89% (74 mg, 0.069 mmol). Anal. Calcd for
C60H50IrN7O·1.25H2O: C, 65.52; H, 4.81; N, 8.91. Found: C, 65.36;
porphyrin product by adding excess hexanes to a concentrated
benzene solution of the dried product, 7a was obtained. Yield: 36%
(18 mg, 0.017 mmol). Anal. Calcd for C56H45BF4IrN5O: C, 62.10; H,
4.19; N, 6.47. Found: C, 62.03; H, 4.10; N, 6.29. 1H NMR (400 MHz,
C6D6): δ −2.98 (br, 2H, amine NH2), −1.89 (t, 2H, J = 8 Hz, amine
CH2), 2.41 (s, 12H, −C6H4CH3), 4.76 (d, 2H, J = 8 Hz, amine o-H),
6.25 (t, 2H, J = 8 Hz, amine m-H), 6.39 (t, 1H, J = 8 Hz, amine p-H),
7.25 (d, 4H, J = 8 Hz, −C6H4CH3), 7.34 (d, 4H, 8 Hz, −C6H4CH3),
7.92 (d, 4H, J = 8 Hz,−C6H4CH3), 8.37 (d, 4H, J = 8 Hz,
−C6H4CH3), 9.09 (s, 8H, pyrrole H). 13C NMR (151 MHz, CDCl3):
δ 21.84, 40.52, 123.03, 125.77, 127.43, 127.80, 127.99, 128.40, 132.92,
133.08, 134.12, 134.98, 137.55, 138.48, 138.96 (CO Carbon), 141.63.
IR (NaCl, cm−1): ν(CO) 2078 (s). UV−vis (C6H6): λmax (log ε)
420 (5.33), 529 (4.33), 564 nm (3.73). HRMS (+ESI): calcd for [M −
BF4]+ ([C56H45IrN5O]+) m/z 996.3253; found m/z 996.3275.
1
H, 4.35; N, 8.63. H NMR (300 MHz, C6D6): δ −1.13 (t, 1H, J = 6
Hz, carbamoyl NH), 0.40 (s, 1.40H, H2O peak), 0.43 (s, 3H; 1-MeIm
Me), 1.63 (s, 1H, 1-MeIm aryl H), 1.74 (s, 1H, 1-MeIm aryl H), 2.07
(d, 2H, J = 6 Hz, carbamoyl CH2), 2.35 (s, 12H, −C6H4CH3), 3.70 (s,
1H, 1-MeIm aryl H), 5.32 (d, 2H, J = 3 Hz, carbamoyl o-H), 6.79 (m,
3H, carbamoyl m/p-H), 7.22 (d, 4H, J = 9 Hz, −C6H4CH3), 7.25 (d,
4H, J = 9 Hz, −C6H4CH3), 7.98 (d, 4H, J = 9 Hz, −C6H4CH3), 8.13
(d, 4H, J = 9 Hz, −C6H4CH3), 8.91 (s, 8H, pyrrole-H). 13C NMR
(151 MHz, CDCl3): δ 21.76, 32.93, 39.99, 117.76, 122.60, 122.98,
125.63, 125.92, 127.15, 127.60, 127.67, 131.35, 131.62, 133.74, 134.55,
137.06, 139.39, 139.78, 142.48, 146.83 (CO carbon). UV−vis (C6H6):
λmax (log ε) 416 (5.23), 523 nm (4.22). HRMS (+ESI): calcd for
[MH]+ (C60H51IrN7O)+ m/z 1078.3784; found m/z 1078.3780.
(TTP)IrP(OEt)3[C(O)NHBn] (5a). In air, a 20 mL scintillation vial
was charged with complex 2a (85 mg, 0.077 mmol), triethyl phosphite
(70 μL, 0.40 mmol, 5.2 equiv), and 15 mL of THF. After the solution
was stirred at 23 °C for 40 min, volatile materials were removed under
reduced pressure. After washing with hexanes and further drying under
reduced pressure, 5a was obtained. Yield: 46% (42 mg, 0.036 mmol).
1H NMR (400 MHz, C6D6): δ −1.48 (t, 1H, J = 8 Hz, carbamoyl
NH), −0.18 (t, 9H, J = 8 Hz, PCH2Me), 0.85 (p, 6H, J = 8 Hz, PCH2),
1.93 (d, 2H, J = 8 Hz, carbamoyl CH2), 2.38 (s, 12H, −C6H4-CH3),
5.18 (d, 2H, J = 8 Hz, carbamoyl o-H), 6.77 (m, 3H, carbamoyl m,p-
H), 7.21 (d, 4H, J = 8 Hz, −C6H4CH3), 7.33 (d, 4H, J = 8 Hz,
−C6H4CH3), 7.96 (dd, 4H, J = 8 Hz, 4 Hz, −C6H4CH3), 8.20 (dd, 4H,
J = 8 Hz, 4 Hz, −C6H4CH3), 8.93 (s, 8H, pyrrole H). 13C NMR (151
MHz, CDCl3): δ 15.50 (d, J = 4.5 Hz), 21.77, 39.32 (d, J = 4.5 Hz),
56.66 (d, J = 4.5 Hz), 122.25, 125.64, 125.94, 127.17, 127.59, 127.65,
[(TTP)Ir(CO)(1-MeIm)]BF4 (8). This compound was prepared
similarly to 7a, using complex 4a (33 mg, 0.031 mmol), 5 mL of C6H6,
and HBF4·Et2O (7.4 μL, 0.062 mmol, 2 equiv). Recrystallization from
CH2Cl2−hexanes afforded complex 8. Yield: 58% (19 mg, 0.018
1
mmol). H NMR (400 MHz, CDCl3): δ 0.19 (s, 1H, Im H), 0.97 (s,
1H, Im H), 2.19 (s, 3H, ImMe), 2.73 (s, 12H, −C6H4CH3), 4.96 (s,
1H, Im-H), 7.62 (m, 8H, −C6H4CH3), 8.09 (m, 8H,−C6H4CH3), 9.06
(s, 8H, pyrrole H). 13C NMR (101 MHz, CDCl3): δ 21.91, 34.13,
119.00, 120.33, 123.21, 128.13, 128.49, 129.95, 133.04, 134.38, 134.81,
137.42, 138.85, 139.65 (CO carbon), 141.52. IR (NaCl, cm−1): ν(C
O) 2079 (s). UV−vis (CH2Cl2): λmax (log ε): 416 (5.61), 528 (4.39),
564 nm (3.75) . HRMS (+ESI): calcd for [M − BF4]+
+
([C53H42IrN6O] ) m/z 971.3049; found m/z 971.3050.
[(TTP)Ir(PMe2Ph)]BF4 (9). In a nitrogen-filled glovebag, a 20 mL
scintillation vial was charged with complex 6a (35 mg, 0.030 mmol), 6
mL of C6H6, and HBF4·Et2O (14.5 μL, 0.12 mmol, 4 equiv). After it
was stirred at 23 °C for 20 min, the reaction mixture was decanted, to
separate it from the precipitates. Volatile materials were then removed
from the mother liquor under reduced pressure. Recrystallization by
adding excess hexanes to a concentrated benzene solution of the dried
product afforded the product 9. Yield: 81% (27 mg, 0.024 mmol). 1H
NMR (400 MHz, CDCl3): δ −2.75 (d, 6H, J = 12 Hz, PMe), 2.71 (s,
12H, −C6H4CH3), 3.84 (m, 2H, o-PPh), 6.53 (t, 2H, J = 8 Hz, m-
PPh), 6.96 (t, 1H, J = 8 Hz, p-PPh), 7.57 (t, 8H, J = 8 Hz,
−C6H4CH3), 7.91 (d, 4H, J = 8 Hz, −C6H4CH3), 8.12 (d, 4H, J = 8
Hz, −C6H4CH3), 8.78 (s, 8H, pyrrole H). 13C NMR (151 MHz,
CDCl3): δ 5.05 (d, J = 45.3 Hz), 21.90, 123.41, 125.90 (d, J = 7.6 Hz),
127.58, 127.71 (d, J = 12.1 Hz), 128.45, 130.43, 132.44, 133.64,
135.03, 138.17, 138.26, 142.27. 31P{1H} NMR (162 MHz, C6D6): δ
−41.28 ppm. UV−vis (CH2Cl2): λmax (log ε) 414 (5.38), 520 (4.41),
551 nm (3.66). HRMS (+ESI): calcd for [M − BF4]+
([C56H47IrN4P]+) m/z 999.3168; found m/z 999.3141.
[(TTP)IrP(OEt)3]BF4 (10). A nitrogen-purged 5 mL round-
bottomed flask containing a 1 mL toluene solution of complex 5a
(2.7 mg, 0.0023 mmol) at 0 °C was charged with 0.8 μL of HBF4·
Et2O. While the solution was stirred at 0 °C for 3 min, the reaction
mixture quickly changed from brown-black to bright red. After volatile
materials were removed under reduced pressure, the residues were
washed with hexane and further dried under reduced pressure to afford
10 (88%, 2.2 mg, 0.0020 mmol). 1H NMR (400 MHz, C6D6): δ −0.53
(t, 9H, J = 8 Hz, PCH2−Me), 0.55 (p, 6H, J = 8 Hz, PCH2), 2.42 (s,
12H, −C6H4CH3), 7.31 (d, 4H, 8 Hz, −C6H4CH3), 7.36 (d, 4H, 8 Hz,
−C6H4CH3), 8.05 (d, 4H, J = 8 Hz, −C6H4CH3), 8.30 (d, 4H, J = 8
Hz, −C6H4CH3), 8.98 (s, 8H, pyrrole H). 31P{1H} NMR (162 MHz,
C6D6): δ 35.16 ppm (s). HRMS (+ESI): calcd for [M − BF4]+
([C54H51IrN4O3P]+) m/z 1027.3328; found m/z 1027.3326.
131.36, 133.89, 134.60, 137.07, 139.56, 139.61, 142.28, 162.72 (2JP−C
=
270.3 Hz, CO Carbon). 31P{1H} NMR (162 MHz, C6D6): δ 72.06
ppm. UV−vis (C6H6): λmax (log ε) 396 (5.07), 429 (4.75), 546 (3.96),
593 nm (3.80). HRMS (+ESI): calcd for [MH]+ (C62H60IrN5O4P)+
m/z 1162.4012; found m/z 1162.4009.
(TTP)Ir(PMe2Ph)[C(O)NHBn] (6a). In a glovebox, a 20 mL
scintillation vial was charged with complex 2a (101 mg, 0.091
mmol), dimethylphenylphosphine (70 μL, 0.49 mmol, 5.4 equiv), and
15 mL of THF. After the solution was stirred at 23 °C for 30 min,
volatile materials were removed under reduced pressure. After washing
with hexanes and further drying under reduced pressure, 6a was
obtained. Yield: 45% (46 mg, 0.041 mmol). Anal. Calcd for
C64H55IrN5OP·2.5H2O: C, 65.23; H, 5.13; N, 5.94. Found: C,
65.05; H, 4.82; N, 5.78. 1H NMR (400 MHz, C6D6): δ −2.66 (d, 6H, J
= 8 Hz, PMe), −1.38 (t, 1H, J = 8 Hz, carbamoyl NH), 0.44 (s, 5H,
H2O), 1.97 (d, 2H, J = 8 Hz, carbamoyl CH2), 2.40 (s, 12H,
−C6H4CH3), 4.07 (t, 2H, J = 8 Hz, o-PPh), 5.20 (d, 2H, J = 8 Hz,
carbamoyl o-H), 6.34 (t, 2H, J = 8 Hz, m-PPh), 6.58 (t, 1H, J = 8 Hz,
p-PPh), 6.76 (m, 3H, carbamoyl m/p-H), 7.20 (d, 4H, J = 8 Hz,
−C6H4CH3), 7.37 (d, 4H, J = 8 Hz, −C6H4CH3), 7.92 (d, 4H, J = 8
Hz, −C6H4CH3), 8.02 (d, 4H, J = 8 Hz, −C6H4CH3), 8.80 (s, 8H,
pyrrole H). 13C NMR (151 MHz, CDCl3): δ 5.34 (d, J = 18.1 Hz),
21.87, 39.62, 122.37, 125.75, 126.05, 126.41 (d, J = 10.6 Hz), 127.18
(d, J = 7.6 Hz), 127.24, 127.70, 127.76, 127.81, 130.94 (d, J = 30.2
Hz), 131.60, 133.97, 134.67, 137.26, 139.37, 139.80, 142.19, 163.87 (d,
2JP−C = 184.2 Hz, CO carbon). 31P{1H} NMR (162 MHz, C6D6): δ
−41.23 ppm. UV−vis (C6H6): λmax (log ε) 398 (5.09), 419 (4.80), 440
(4.62), 548 (3.86), 601 nm (3.81). HRMS (+APCI): calcd for [MH]+
(C64H56IrN5OP)+ m/z 1134.3852; found m/z 1134.3852.
(TTP)Ir(NH2Bn)I (11a). In the glovebox, 0.65 mL of C6D6 was
added to an NMR tube containing 2a (6 mg, 0.0056 mmol). This was
followed by the addition of 11 μL (0.011 mmol, 2 equiv) of a C6D6
stock solution containing 0.11 mM of MeI. The NMR tube was sealed
with a rubber septum and heated to 85 °C for 72 h, while the reaction
[(TTP)Ir(CO)(NH2Bn)]BF4 (7a). In a nitrogen-filled glovebag, a 20
mL scintillation vial was charged with complex 2a (51 mg, 0.047
mmol), 6 mL of C6H6, and HBF4·Et2O (11 μL, 0.092 mmol, 2 equiv).
After the solution was stirred at 23 °C for 20 min, the reddish
porphyrin product solution was separated, via vacuum filtration, from
the insoluble precipitate. Thereafter, volatile materials were removed
from the filtrate under reduced pressure. After recrystallization of the
1
was monitored by H NMR spectroscopy for the consumption of 2a.
The reaction mixture was filtered through Celite to remove insoluble
precipitates. Removal of volatile components from the filtrate under
reduced pressure yielded 11a (61%, 3.8 mg, 0.0035 mmol, 92%
H
dx.doi.org/10.1021/om500189a | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
purity). 1H NMR (300 MHz, C6D6): δ −4.87 (t, 2H, J = 6 Hz, NH2),
−2.32 (t, 2H, J = 9 Hz, CH2), 2.38 (s, 12H, −C6H4CH3), 4.21 (d, 2H,
J = 6 Hz, amine o-H), 6.05 (t, 2H, J = 6 Hz, amine m-H), 6.28 (t, 1H, J
= 6 Hz, amine p-H), 7.20 (d, 4H, J = 9 Hz,−C6H4CH3), 7.30 (d, 4H, J
= 9 Hz, −C6H4CH3), 8.02 (d, 4H, J = 9 Hz, −C6H4CH3), 8.16 (d, 4H,
J = 9 Hz, −C6H4CH3), 8.96 (s, 8H, pyrrole H). 13C NMR (101 MHz,
CDCl3): δ 21.89, 42.68, 122.95, 126.31, 127.48, 128.00, 128.11,
128.54, 132.32, 133.74, 134.37, 135.05, 137.62, 139.09, 142.89. UV−
vis (C6H6): λmax (log ε): 418 (5.42), 528 (4.27), 562nm (3.65).
HRMS (+ESI): calcd for [M + H]+ ([C55H46IrN5I])+ m/z 1096.2427;
found m/z 1096.2448.
135.15, 137.52, 139.20, 142.05. 31P{1H} NMR (162 MHz, C6D6): δ
−43.55 ppm. UV−vis (C6H6): λmax (log ε) 385 (4.82), 439 (5.14), 545
(4.18), 582 nm (4.02). HRMS (+ESI): calcd for [M − I]+
([C56H47IrN4P]+) m/z 999.3168; found m/z 999.3139.
[i-PrNMe3]I. 1H NMR (400 MHz, D2O): 1.38 (dt, 6H, CHMe, J = 8
Hz, 4 Hz)), 3.04 (s, 9H, NMe), 3.64 (h, 1H, CH, J = 8 Hz). 13C NMR
1
(101 MHz, CDCl3): 17.50, 51.64 (t, JC−N = 4 Hz), 67.81.
[(TTP)Ir(PMe2Ph)(NH2Bn)]BF4 (16). In air, a 20 mL scintillation
vial was charged with complex 9 (30 mg, 0.028 mmol), benzylamine
(7.5 μL, 0.068 mmol, 2.4 equiv), and 10 mL of C6H6. After the mixture
was stirred at 23 °C for 30 min, volatile materials were removed under
reduced pressure. Recrystallization of the residues from THF−hexanes
afforded complex 16 (90%, 30 mg, 0.025 mmol). 1H NMR (400 MHz,
C6D6): δ −3.42 (m, 2H, amine NH2), −3.17 (d, 6H, J = 12 Hz, PMe),
−1.72 (m, 2H, amine CH2), 2.44 (s, 12H, −C6H4CH3), 3.64 (m, 2H,
PPh o-H), 4.89 (d, 2H, J = 8 Hz, amine o-H), 6.17 (t, 2H, J = 8 Hz,
PPh m-H), 6.25 (t, 2H, J = 8 Hz, amine m-H), 6.37 (t, 1H, J = 8 Hz,
PPh p-H), 6.51 (t, 1H, J = 8 Hz, amine p-H), 7.32 (d, 4H, J = 8 Hz,
−C6H4CH3), 7.41 (d, 4H, J = 8 Hz, −C6H4CH3), 7.95 (dd, 4H, J = 8
Hz, 4 Hz, −C6H4CH3), 8.34 (dd, 4H, J = 8 Hz, 4 Hz, −C6H4CH3),
8.86 (s, 8H, pyrrole H). 13C NMR (151 MHz, CDCl3): δ 4.90 (d, J =
42.3 Hz), 21.92, 41.37, 123.18, 125.15 (d, J = 58.9 Hz), 125.96, 126.06
(d, J = 9.1 Hz), 127.32, 127.71 (d, J = 10.6 Hz), 127.78, 128.13,
128.38, 130.00, 132.76, 133.97, 134.91, 135.15, 138.03, 138.29, 142.19.
31P{1H} NMR (162 MHz, C6D6): δ −41.49 ppm. UV−vis (C6H6):
λmax (log ε) 419 (5.36), 528 (4.32), 561 nm (3.71). HRMS (+ESI):
calcd for [M − BF4]+ ([C63H56IrN5P]+) m/z 1106.3903; found m/z
1106.3899.
[BnNMe3]I. 1H NMR (400 MHz, D2O): δ 3.08 (s, 9H, N-Me), 4.48
(s, 2H, CH2), 7.53−7.59 (m, 5H, C6H5). 13C NMR (101 MHz,
1
1
CDCl3): 53.29 (t, JC−N = 4 Hz), 69.31 (t, JC−N = 2 Hz), 127.42,
129.70, 131.37, 133.44. HRMS (+ESI): calcd for [M − I]+
([C10H16N]+) m/z 150.1283; found m/z 150.1281.
(TTP)Ir(1-MeIm)I (12). In a glovebox, a 20 mL scintillation vial was
charged with 4a (27 mg, 0.025 mmol), 5 mL of C6H6, and MeI (3.4
μL, 0.055 mmol, 2.2 equiv). After the contents of the vial were refluxed
at 80 °C for 36 h, the solution was vacuum-filtered through Celite on a
fritted funnel. After removal of volatile components from the filtrate
under reduced pressure, followed by recrystallization of the residue
from C6H6−hexanes, 12 was obtained in 88% purity, as determined by
1
1H NMR. Yield: 61% (16 mg, 0.015 mmol). H NMR (400 MHz,
C6D6): δ 0.16 (s, 3H, 1-MeIm Me), 1.14 (t, 1H, J = 4 Hz, 1-MeIm aryl
H), 1.28 (t, 1H, J = 4 Hz, 1-MeIm aryl H), 2.35 (s, 12H, −C6H4CH3),
3.39 (t, 1H, J = 4 Hz, 1-MeIm aryl H), 7.19 (dd, 4H, J = 8 Hz, 4 Hz,
−C6H4CH3), 7.27 (d, 4H, J = 8 Hz, 4 Hz, −C6H4CH3), 8.06 (dd, 4H,
J = 8 Hz, 4 Hz, −C6H4CH3), 8.17 (dd, 4H, J = 8 Hz, 4 Hz,−
C6H4CH3), 8.97 (s, 8H, pyrrole H). 13C NMR (151 MHz, CDCl3): δ
21.88, 33.67, 117.61, 122.25, 122.72, 127.25, 127.86, 130.45, 131.86,
133.76, 135.02, 137.36, 139.44, 142.62. UV−vis (C6H6): λmax (log ε)
420 (5.38), 528 (4.27), 563 nm (3.71). HRMS (+ESI): calcd for [M]·+
([C52H42IrN6I])+ m/z 1070.2145; found m/z 1070.2162.
trans-[(TTP)Ir(PMe2Ph)2]BF4 (17). In a glovebox, an NMR tube
was charged with 20 mg (0.0185 mmol) of 9, 1.0 mL of CDCl3, and
1
2.9 μL (0.020 mmol, 1.1 equiv) of PMe2Ph. Analysis, by H NMR,
after 6.5 h showed quantitative formation of 17. After the volatile
components were removed under reduced pressure, compound 17 was
1
obtained. Yield: 80% (18 mg, 0.015 mmol). H NMR (400 MHz,
(TTP)Ir[P(OEt)3]I (13). In air, a 20 mL scintillation vial was charged
with 28 mg of crude (∼60% pure) compound 15 (0.013 mmol), 6 mL
of benzene, and 24.5 mg (0.065 mmol, 5 equiv) of [Bu4N]I. The
mixture was then stirred at 23 °C for 30 h. The n-butylammonium
salts were extracted from the organic layer, using water. After the
volatile components were removed under reduced pressure, followed
by a hexane wash, complex 13 was obtained. Yield: 49% (8 mg, 0.0065
mmol). 1H NMR (400 MHz, C6D6): δ −0.38 (t, 9H, J = 8 Hz,
PCH2Me), 0.70 (p, 6H, J = 8 Hz, PCH2), 2.38 (s, 12H, −C6H4CH3),
7.19 (d, 4H, J = 8 Hz, −C6H4CH3), 7.36 (d, 4H, J = 8 Hz,
−C6H4CH3), 8.03 (dd, 4H, J = 8 Hz, 4 Hz,−C6H4CH3), 8.19 (dd, 4H,
J = 8 Hz, 4 Hz, −C6H4CH3), 8.99 (s, 8H, pyrrole H). 13C NMR (151
MHz, CDCl3): δ 15.22 (d, J = 6.0 Hz), 21.87, 59.39 (d, J = 7.6 Hz),
122.80, 127.29, 127.96, 131.67, 133.75, 135.17, 137.45, 139.56, 142.29.
31P{1H} NMR (162 MHz, C6D6): δ −0.01 ppm. UV−vis (CH2Cl2):
λmax nm (log ε) 370 (4.55), 433 (5.17), 539 (4.20), 576 (3.89). HRMS
(+ESI): calcd for [M − I]+ ([C54H51IrN4O3P]+) m/z 1027.3328;
found m/z 1027.3302.
CDCl3): δ −2.77 (t, 12H, J = 4 Hz, PMe), 2.73 (s, 12H, −C6H4CH3),
3.82 (m, 4H, o-PPh), 6.51 (t, 4H, J = 8 Hz, m-PPh), 6.91 (t, 2H, J = 8
Hz, p-PPh), 7.60 (d, 8H, J = 8 Hz, −C6H4CH3), 7.87 (d, 8H, J = 8 Hz,
−C6H4CH3), 8.73 (s, 8H, pyrrole H). 13C NMR (151 MHz, CDCl3):
δ 4.20 (t, J = 16.6 Hz), 21.89, 123.23, 125.34 (t, J = 24.2 Hz), 126.35
(t, J = 4.5 Hz), 127.80 (t, J = 4.5 Hz), 128.22, 129.86, 132.92, 134.33,
137.63, 138.66, 141.92. 31P{1H} NMR (162 MHz, C6D6): δ −32.35
ppm. UV−vis (CH2Cl2): λmax (log ε): 312 (sh, 4.13), 333 (sh, 4.33),
356 (4.50), 432 (5.21), 541 (4.14), 578 nm (4.09). HRMS (+ESI):
calcd for [M − BF4]+ ([C64H58IrN4P2]+) m/z 1137.3766; found m/z
1137.3752.
General Procedure for the Determination of Equilibrium
Constants. Stock solutions of each carbamoyl complex (2a−5a) were
made up in 5.0 mL of C6H6, with concentrations ranging between 3.9
and 6.4 mM. Additional stock solutions of the free ligands were made
up in 5.0 mL of C6D6. A single 5.0 mL C6D6 stock solution (91.7 mM)
of mesitylene was used for the internal standard in all the reactions. A
known volume of the carbamoyl complex solution was added to an
NMR tube equipped with a high-vacuum Teflon stopcock, and the
C6H6 was removed under reduced pressure. A known volume
(typically 0.6 mL) of C6D6 was added to the solid carbamoyl complex,
followed by either 10 μL (0.92 μmol) or 20 μL (1.83 μmol) of the
(TTP)Ir(PMe2Ph)I (14). In air, a 20 mL scintillation vial was
charged with complex 9 (34 mg, 0.031 mmol), [Bu4N]I (23.1 mg,
0.061 mmol, 2 equiv), and CH2Cl2 (5 mL). After the mixture was
stirred at 23 °C for 8 min, the n-butylammonium salts were extracted
from the organic phase using water. Volatile components were then
removed from the organic phase under reduced pressure. After
washing with hexanes and drying under reduced pressure, complex 14
was obtained. Yield: 69% (24 mg, 0.021 mmol) Anal. Calcd for
C56H47IrN4PI·0.12C6H14: C, 59.95; H, 4.32; N, 4.93. Found: C, 60.25;
1
internal standard solution. After analysis of the mixture by H NMR,
the actual molarity of the metal carbamoyl complex was calculated
from its β-pyrrole peak integration versus the mesitylene aliphatic
proton peak integration. The actual molarity of the stock solution of
each free ligand was similarly determined by the 1H NMR analysis of a
mixture of a known volume of the ligand and internal standard. For the
equilibrium measurements, a fresh volume of the free ligand solution
was transferred by syringe into the NMR tube containing a C6D6
solution of both the complex and the internal standard. Each reaction
was then monitored by NMR, over a period of up to 1 h (note that the
reaction of 5a with quinuclidine took 10 h to reach equilibrium).
Concentrations of reactants and products were determined by 1H
NMR analysis, monitored at 10−15 min intervals for each mixture.
1
H, 4.16; N, 4.79. H NMR (400 MHz, C6D6): δ −3.06 (d, 6H, J = 8
Hz, PMe), 0.89 (t, 0.73H, C6H14), 1.24 (m, 0.96H, C6H14), 2.40 (s,
12H, −C6H4CH3), 3.86 (m, 2H, PPh o-H), 6.23 (td, 2H, J = 8 Hz, 4
Hz, PPh m-H), 6.57 (m, 1H, PPh-pH), 7.18 (d, 4H, J = 8 Hz,
−C6H4CH3), 7.39 (d, 4H, J = 8 Hz, −C6H4CH3), 7.95 (dd, 4H, J = 8
Hz, 4 Hz, −C6H4CH3), 8.04 (dd, 4H, J = 8 Hz, 4 Hz, −C6H4CH3),
8.84 (s, 8H, pyrrole H). 13C NMR (151 MHz, CDCl3): δ 3.69 (d, J =
37.8 Hz), 21.88, 122.93, 125.27 (d, J = 55.9 Hz), 126.36 (d, J = 9.1
Hz), 127.27, 127.42 (d, J = 9.1 Hz), 127.95, 129.55, 131.93, 133.66,
I
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X-ray Crystal Structure Determination of Complexes 4a and
17. X-ray-quality crystals of (TTP)Ir(1-MeIm)[C(O)NHBn] (4a)
and trans-[(TTP)Ir(PMe2Ph)2]BF4 (17) were obtained by layering a
saturated THF solution of the complex with hexanes and allowing the
hexane to slowly diffuse into the THF solution at −21 °C over a
period of 24 h (for 4a) and 10 days (for 17).
(6) Angelici, R. J.; Blacik, L. J. Inorg. Chem. 1972, 11, 1754.
(7) Angelici, R. J.; Brink, R. W. Inorg. Chem. 1973, 12, 1067.
(8) McCusker, J. E.; Logan, J.; McElwee-White, L. Organometallics
1998, 17, 4037.
(9) McCusker, J. E.; Abboud, K. A.; McElwee-White, L. Organo-
metallics 1997, 16, 3863.
A red needlelike single crystal of 4a and brown platelike crystal of
17 were selected under the microscope and covered with PARATONE
oil. The samples were mounted in a Bruker APEX2 diffractometer
under a stream of cold nitrogen. Full sphere X-ray intensity data were
measured to a resolution of 0.71 Å (0.5° width ω-scan, 15 s per frame,
Mo Kα radiation. λ = 0.71073 Å, graphite monochromator). The
frames were integrated using a narrow-frame algorithm. Data were
corrected for absorption effects using the multiscan method.57,58
Structures were solved by direct methods. All non-hydrogen atoms
were refined in a full-matrix anisotropic approximation based on F2. All
expected hydrogen atoms were placed on calculated positions and
were refined in an isotropic approximation using a “riding” model. The
Uiso(H) values were set at 1.2−1.5 times the Ueq value of the carrier
atom. All calculations were performed using the APEX II software
suite.59
One molecule of 4a and three THF solvent molecules were found
in the asymmetric unit of the triclinic cell. Although additional THF
molecules may partially occupy observed voids, attempts to apply
SQUEEZE were not able to improve the refinement significantly.
Thus, the original data set was used for final results. Similarity
constraints on geometrical parameters and on displacement
parameters were used to treat solvent molecules.
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3995.
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ASSOCIATED CONTENT
* Supporting Information
■
S
Text, figures, tables, and CIF files giving preparative details, 1H,
13C, 31P and 2-D NMR spectra for compounds 2−17, and
single-crystal X-ray structural refinement data for compounds
4a and 17. This material is available free of charge via the
Internet at http://pubs.acs.org. CCDC files 977996−977997
also contain supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
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AUTHOR INFORMATION
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
We thank the U.S. Department of Energy (award
DESC0002142) for partial support of this work.
■
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Chem. 2013, 51, 701.
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