Journal of the American Chemical Society
Article
experiments) or the characteristic resonances of the solvent nuclei
(13C NMR experiments) as internal standards, while 31P NMR was
referenced to external H3PO4. Spectral assignments were made by
routine one- and two-dimensional NMR experiments where
appropriate. The crystal structures were determined in a Bruker-
Nonius, X8Kappa diffractometer. Dimer [(η5-C5Me5)IrCl2]2,30
NaBArF,31 and [H(OEt2)2][BArF]32 were prepared according to
1-NCMe+: Anal. Calcd for C61H50BF24IrNP: C, 49.27; H, 3.39; N,
0.94. Found: C, 49.4; H, 3.6; N, 1.4. IR (Nujol): ν(CN) 2285 cm−1.
1H NMR (400 MHz, CD2Cl2, 25 °C): δ 7.44 (d, 1 H, Ha), 7.26, (m, 3
4
H each, Hb, Hd/f, He), 6.98 (m, 1 H, Hd/f), 6.94 (dd, 1 H, JHP = 3.5
2
Hz, Hc) 3.52 (d, 1 H, JHH = 15.0 Hz, IrCHH), 3.32 (dd, 1 H, 2JHH
=
15.0, 2JHP = 3.5 Hz, IrCHH), 2.65, 1.44 (s, 3 H each, Meβ, Meγ), 2.55
(s, 3H, NCMe), 2.26 (d, 3 H, 2JHP = 9.9 Hz, PMe), 2.03 (s, 3H, Mea),
1
1.55 (d, 15 H, JHP = 1.8 Hz, C5Me5). 13C{1H} NMR (100 MHz,
4
literature procedures. In the H NMR spectra all aromatic couplings
CD2Cl2, 25 °C): δ 155.9 (d, 2JCP = 30 Hz, C1), 142.0, 140.9 (d, 2JCP
=
were of ca. 7.5 Hz, and signals corresponding to the BArF counterion
were invariant for different complexes (CD2Cl2; δ 7.74 (s, 8H, Ho),
7.57 (s, 4H, Hp)).
1
8 Hz, C4, C6), 140.8 (C3), 139.4 (d, JCP = 63 Hz, C2), 131.0, 130.3
(CHb, CHe), 130.9, 130.5 (d, 3JCP = 9 Hz, CHd, CHf), 127.4 (d, 1JCP
=
51 Hz, C5), 128.6 (d, 3JCP = 7 Hz, CHc), 126.8 (d, 3JCP = 15 Hz, CHa),
Computational Details. DFT calculations were performed with
the Gaussian 09 package33 with Truhlar’s hybrid meta-GGA functional
M06.34 The Ir atom was represented by the Stuttgart/Dresden
effective core potential and the associated basis set35 as implemented
in Gaussian 09 (SDDALL). The remaining H, C, P, and Si atoms were
represented by means of the 6-31G(d,p) basis set.36−38 The
geometries for all species described were optimized in the gas phase
without symmetry restrictions. Frequency calculations were performed
on the optimized structures at the same level of theory to characterize
the stationary points, as well as for the calculation of gas-phase
enthalpies (H), entropies (S), and Gibbs energies (G) at 298.15 K.
The nature of the intermediates connected was determined by intrinsic
reaction coordinate calculations or by perturbing the transition states
along the TS coordinate and optimizing to a minimum. The solvent
effects (dichloromethane ε = 8.93) were modeled with the SMD
continuum model39 by single-point calculations on gas-phase-
optimized geometries (test free optimizations in solution of some
species gave analogous results). The relative free energies in solution
were calculated according to ΔGsolution = ΔEsolution + (ΔGgas − ΔEgas),
where ΔEsolution is the electronic energy plus the solvent entropy.40
Synthesis of Compound 1+. To a solid mixture of 1-Cl (100 mg,
0.16 mmol) and NaBArF (143 mg, 0.16 mmol) was added 5 mL of
CH2Cl2 under argon. The reaction mixture was stirred for 10 min at
room temperature, after which the solution turned from orange to
yellow. The mixture was filtered and the solvent evaporated under
reduced pressure to obtain a yellow solid (220 mg, 95%). For further
purification, the complex can be crystallized from a 1:2 mixture of
CH2Cl2:pentane. Anal. Calcd for C59H47BF24IrP: C, 49.01; H, 3.28.
2
3
118.6 (NCMe), 95.0 (d, JCP = 2 Hz, C5Me5), 25.6, 23.2 (d, JCP = 6
3
3
Hz, JCP = 8 Hz, respectively, Meβ, Meγ), 20.5 (d, JCP = 3 Hz, Meα),
19.4 (d, 1JCP = 39 Hz, PMe), 17.3 (IrCH2), 8.2 (C5Me5), 4.4 (NCMe).
31P{1H} NMR (160 MHz, CD2Cl2, 25 °C): δ 8.9.
The minor diastereomer of compound Ir-NCMe+ is characterized
1
by H NMR multiplets with δ 3.55 and 3.29 ppm, due to the IrCH2
protons, which are partly overlapped with the signals corresponding to
the IrCH2 group of the major diastereomer. A doublet at 1.76 ppm is
associated with the C5Me5 ligand. In the 31P{1H} NMR spectrum a
singlet is recorded with δ 5.8 ppm. Analytical and spectroscopic data
for the other Lewis base adducts are reported in the SI.
Synthesis of Bis(Hydride) 3+. To a solid mixture of 1-Cl (100
mg, 0.16 mmol) and NaBArF (143 mg, 0.16 mmol) placed in a thick-
wall vessel was added 3 mL of CH2Cl2. The reaction mixture was
stirred for 30 min at room temperature under 1 bar of H2, after which
the original solution with intense yellow color became almost
colorless. Addition of pentane under hydrogen atmosphere caused
precipitation of complex 3+ as a fine, pale yellow powder in
quantitative yield. Workup of the complex in the absence of hydrogen
led to release of H2 and formation of 1+. 1H NMR (500 MHz, CD2Cl2,
25 °C, H2 atmosphere): δ 7.39 (d, 1 H, Ha), 7.33−7.25 (m, 3 H, Hb,
Hd/f, He), 7.05 (dd, 1 H, 4JHP = 3.8 Hz, Hd/f), 6.98 (dd, 1 H, 4JHP = 4.7
2
Hz, Hc), 2.59, 1.50 (s, 3 H each, Meβ, Meγ), 2.55 (d, 3H, JHP = 10.5
4
Hz, PMe), 2.00 (s, 3 H, Meα), 1.79 (d, 15 H, JHP = 1.1 Hz, C5Me5),
1
−4.63 (br. s, 4 H, IrCH2, Ir−H2). H NMR (400 MHz, CD2Cl2, −80
°C, H2 atmosphere): δ 7.31 (d, 1 H, Ha), 7.22−7.10 (m, 3 H, Hb, Hd/f
,
2
He), 6.88 (m, 2 H, Hc, Hd/f), 3.93 (d, 1 H, JHH = 14.2 Hz, IrCHH),
3.38 (d, 1 H, 2JHH = 14.2, IrCHH), 2.45 (m, 6 H, Meβ/γ, PMe), 1.92 (s,
3 H, Meα), 1.60 (s, 15 H, C5Me5), 1.31 (s, Meβ/γ), −12.79 (s, 1 H,
1
Found: C, 49.1; H, 3.7. H NMR (500 MHz, CD2Cl2, −60 °C): δ
7.36 (m, 1 H, Hc), 7.28 (t, 1 H, Hb), 7.24 (t, 1 H, He), 7.04, 6.94 (m, 1
H each, Hd, Hf), 6.73 (dd, 1 H, 4JHP = 3.7 Hz, Ha), 2.98 (t, 1 H, 2JHH
=
2
IrHH), −13.37 (d, 1 H, JHP = 17.5 Hz, IrHH). 13C {1H} NMR (125
3JHP = 4.8 Hz, IrCHα), 2.50 (s, 3 H, Meγ), 2.44 (s, 3 H, Meα), 2.20 (d,
3 H, 2JHP = 12.8 Hz, PMe), 2.09 (s, 3 H, Meβ),1.63 (s, 15 H, C5Me5),
MHz, CD2Cl2, 25 °C, H2 atmosphere): δ 152.4 (d, 2JCP = 29 Hz, C1),
141.6, 140.4 (d, 2JCP = 9 Hz, 8 Hz, C4, C6), 140.1 (d, 2JCP = 3 Hz, C3),
136.4 (d, 1JCP = 62 Hz, C2), 132.4, 132.1 (CHb, CHe), 131.3, 130.8 (d,
2
3
1
1.15 (dd, 1 H, JHH = 4.8, JHP = 15.6 Hz, IrCHβ). H NMR (300
MHz, CD2Cl2, 25 °C): δ 7.36, (m, 2 H, Ha/b/c/d/e/f), 7.12 (br. s, 4 H,
Ha/b/c/d/e/f), 2.44 (br. s, 11 H, Meα, Meβ, Meγ, IrCH2), 2.28 (d, 3 H,
2JHP = 12.8 Hz, PMe), 1.63 (d, 15 H, 4JHP = 1.8 Hz, C5Me5). 13C{1H}
NMR (125 MHz, CD2Cl2, −60 °C): δ 142.2, 141.4 (s, d, 2JCP = 16 Hz,
C4, C6), 136.7 (C3), 132.7 (CHb), 132.1 (CHe), 131.2 (d, 3JCP = 4 Hz,
CHc), 129.2, 128.7 (d, 3JCP = 10 Hz, CHd, CHf), 126.8 (d, 3JCP = 6 Hz,
3JCP = 9 Hz, CHd, CHf), 129.9 (d, 3JCP = 8 Hz, CHc), 126.4 (d, 3JCP
=
1
17 Hz, CHa), 124.9 (br. s, C5), 104.2 (C5Me5), 29.6 (br. d, JCP = 57
3
Hz, PMe), 24.9, 23.4 (d, JCP = 5 Hz, 8 Hz, Meβ, Meγ), 20.3 (Meα),
11.7 (br. s, IrCH2), 8.8 (C5Me5). 31P{1H} NMR (200 MHz, CD2Cl2,
25 °C, H2 atmosphere): δ 3.7 (br. s).
Synthesis of Hydride−Phosphepine 4+. A solid mixture of 1-Cl
(100 mg, 0.16 mmol) and NaBArF (145 mg, 0.16 mmol) placed in a
Schlenk flask was suspended in CH2Cl2 (5 mL) under argon. A
saturated aqueous solution of NaHCO3 (5 μL) was added to the
reaction mixture, which was stirred for 16 h with intermittent
vacuum−argon cycles to pump out the produced molecular hydrogen.
The yellow solution was filtered and the solvent evaporated under
reduced pressure to obtain a pale yellow solid, which was washed with
pentane to yield compound 4+ (210 mg, 90%). For further purification
4+ can be recrystallized from a 1:1 mixture of CH2Cl2:pentane. Anal.
Calcd for C59H45BF24IrP: C, 49.08; H, 3.14. Found: C, 48.7; H, 3.1. IR
(Nujol): ν(Ir−H) 2135 cm−1. EM (ES) m/z calcd for M+: 581.19.
1
2
CHa), 116.8 (d, JCP = 65 Hz, C5), 95.6 (d, JCP = 15 Hz, C1), 92.7
1
(C5Me5), 67.5 (d, JCP = 28 Hz, C2), 27.0 (IrCH2), 22.7 (Meα), 22.1,
21.9 (d, s, 3JCP = 16 Hz, 7 Hz, Meβ, Meγ), 12.8 (d, 1JCP = 41 Hz, PMe),
8.5 (C5Me5). 31P{1H} NMR (200 MHz, CD2Cl2, −60 °C): δ −44.9.
Synthesis of Cationic Adducts 1-L+ (L = NCMe, C5H5N, NH3,
CO, PMe3). To a solid mixture of 1-Cl (50 mg, 0.08 mmol) and
NaBArF (72 mg, 0.08 mmol) placed in a Schlenk flask was added 5 mL
of CH2Cl2. The reaction mixture was stirred for 5 min at room
temperature under 1.5 bar of CO or NH3 (a thick-wall vessel instead
of a conventional Schlenk flask was employed in these cases), or
alternatively treated with 100 μL of NCMe or pyridine (for
corresponding NCMe or pyridine adducts, respectively) or with a
toluene solution of PMe3 (0.4 mL, 1 M) (for corresponding cationic
PMe3 complex). The solution was filtered, and the solvent was then
evaporated under reduced pressure to obtain pale white (Ir-NCMe+,
1
Expt.: 581.2. H NMR (500 MHz, CD2Cl2, 25 °C): δ 7.34 (m, 2 H,
Ha, Hd), 7.16 (m, 2 H, Hb, He), 6.95, 6.92 (dd, 1H, 4JHP = 3.9 Hz Hc,
Hf), 4.97 (dd, 1 H, 3JHH = 8.6, 4JHP = 2.8 Hz, CHα), 4.51 (d, 1 H, 3JHH
= 8.6 Hz, CHβ), 2.58 (d, 3 H, 2JHP4 = 13.2 Hz, PMe), 2.52, 2.50 (s, 3 H
each, Meα, Meβ), 1.97 (d, 15 H, JHP = 1.0 Hz, C5Me5), −13.03 (d, 1
H, 2JHP = 28.5 Hz, IrH). 13C{1H} NMR (100 MHz, CD2Cl2, 25 °C): δ
148.2 (d, 2JCP = 17 Hz, C4), 143.6 (d, 2JCP = 23 Hz, C1), 139.2, 138.8,
137.1, 136.0 (C2, C3, C5, C6), 131.3, 131.2, 131.1, 130.5 (CHb, CHc,
+
+
+
Ir-PMe3 , Ir-CO+) or yellow powders (Ir-NC5H5 , Ir-NH3 ) in ca.
+
95% yield. Complexes Ir-NCMe+ and Ir-NH3 were obtained as
mixtures of diastereomers (88:12, L = NCMe; 94:6, L = NH3). These
complexes can be recrystallized from a 1:2 mixture of CH2Cl2:pentane.
7173
dx.doi.org/10.1021/ja301759m | J. Am. Chem. Soc. 2012, 134, 7165−7175