Organometallics
Article
0.0759 mmol) and NaOMe (4.1 mg, 0.0759 mmol) were dissolved in
deoxygenated ethanol (1.5 mL). The reaction mixture was stirred for 6
h at room temperature. The suspension was filtered through a plug of
Celite and concentrated under reduced pressure. The residue was
triturated with dichloromethane (1.5 mL) and decanted. The white
solid was redissolved in acetonitrile and filtered. Colorless crystals
were obtained at ambient temperature by vapor diffusion of hexanes
into a concentrated solution of the complex in a dichloromethane/
C27H42N5IrSb2F12 (1100.37): C, 29.47; H, 3.85; N, 6.36. Found: C,
29.32; H, 4.05; N, 6.42.
Synthesis of 6.
1
acetonitrile mixture: yield 25.2 mg (0.0403 mmol, 53%). H NMR
(400 MHz, CD3CN): δ 10.73 (br s, 2H, NH), 6.87 (d, 2H, 4JHH = 1.9
Hz, H-5), 5.75 (d, 1H, 2JHH = 12.7 Hz, NCH2N), 5.34 (d, 1H, 2JHH
=
Complex 5 (15.0 mg, 0.0136 mmol) was treated with ethylamine (27
μL, 2.0 M) in acetone-d6 at room temperature. The reaction mixture
was concentrated under reduced pressure, and the residue was
triturated with dichloromethane and ethyl ether. In air, the white solid
obtained was suspended in dichloromethane and filtered through a
plug of Celite. The white solid was recovered with acetone and
vacuum-dried: yield 9.6 mg (0.0087 mmol, 64%). We note that the
appearance of triplets for the ethylamine carbons (2JCD = 11.5 Hz and
3JCD = 4.5 Hz) can be taken as evidence that the NH2 undergoes an
H/D exchange process with traces of HOD in the NMR solvent to
form the monodeuterated amine ligand CH3CH2NHD. 1H NMR (400
MHz, (CD3)2CO): δ 11.74 (br s, 2H, NH), 7.40 (s, 2H, H-5), 6.49 (d,
1H, 2JHH = 13.4 Hz, NCH2N), 6.04 (d, 1H, 2JHH = 13.4 Hz, NCH2N),
4.46 (br s, 1H, NHD), 2.36 (m, 2H, CH3CH2NHD), 1.92 (s, 15H,
4
12.7 Hz, NCH2N), 2.04 (d, 15H, JHH = 0.6 Hz, C5(CH3)5), 1.28 (s,
18H, C(CH3)3), −15.89 (br s, 1H, IrH). A cross peak between the
NH and residual water was observed in the 2D EXSY NMR spectrum,
which is a consequence of an exchange process involving the NH of
both PNHCs and residual water. Exchange between both NHs and
[Ir]-H could not be determined due to the insolubility of 4a in
nonpolar NMR solvents. 13C{1H} NMR (100.6 MHz, CD3CN): δ
150.5 (C-2), 143.7 (C-4), 114.7 (C-5), 93.3 (C5(CH3)5), 62.6
(NCH2N), 31.3 (C(CH3)3), 29.5 (C(CH3)3), 10.8 (C5(CH3)5).
HRMS (ESI-TOF) m/z: [M+] calcd for C25H40N4Ir 589.2878;
found 589.2880. Anal. Calcd for C25H40N4ClIr (624.29): C, 48.10;
H, 6.46; N, 8.97. Found: C, 49.09; H, 6.80; N, 9.07. Although these
results are outside the range viewed as establishing analytical purity,
they are provided to illustrate the best values obtained to date.
Synthesis of 4b.
3
C5(CH3)5), 1.35 (s, 18H, C(CH3)3), 1.00 (t, 3H, JHH = 7.0 Hz,
CH3CH2NHD). 13C{1H} NMR (100.6 MHz, (CD3)2CO): δ 147.4
(C-2), 145.3 (C-4), 117.4 (C-5), 94.4 (C5(CH3)5), 62.8 (NCH2N),
2
45.2 (t, JCD = 11.5 Hz, CH3CH2NHD), 31.5 (C(CH3)3), 29.5
3
(C(CH3)3), 17.9 (t, JCD = 4.5 Hz, CH3CH2NHD), 9.6 (C5(CH3)5).
1
Complex 6 was also analyzed in acetone-d6 containing less HOD. H
NMR (400 MHz, (CD3)2CO): δ 11.61 (br s, 2H, NH), 7.41 (s, 2H,
H-5), 6.50 (d, 1H, 2JHH = 13.2 Hz, NCH2N), 6.06 (d, 1H, 2JHH = 13.6
Hz, NCH2N), 4.45 (br s, 2H, NH2), 2.31 (m, 2H, CH3CH2NH2), 1.92
3
(s, 15H, C5(CH3)5), 1.35 (s, 18H, C(CH3)3), 1.03 (t, 3H, JHH = 7.2
Complex 4b was prepared in the same manner as 3b, using 4a (15.0
mg, 0.024 mmol) and KPF6 (13.5 mg, 0.072 mmol) in acetone/2-
propanol. After filtration, the white solid was washed with dichloro-
Hz, CH3CH2NH2). 13C {1H} NMR (100.6 MHz, (CD3)2CO): δ 147.6
(C-2), 145.4 (C-4), 117.6 (C-5), 94.6 (C5(CH3)5), 63.0 (NCH2N),
45.5 (CH3CH2NH2), 31.6 (C(CH3)3), 29.6 (C(CH3)3), 18.1
(CH3CH2NH2), 9.7 (C5(CH3)5). Anal. Calcd for C27H46N5IrSb2F12
(1104.40): C, 29.36; H, 4.20; N, 6.34. Found: C, 29.51; H, 3.92; N,
6.16.
1
methane and dried in vacuo: yield 17.3 mg (0.023 mmol, 98%). H
NMR (400 MHz, (CD3)2CO): δ 11.15 (br s, 2H, NH), 7.10 (d, 2H,
2
4JHH = 1.6 Hz, H-5), 6.10 (d, 1H, JHH = 12.8 Hz, NCH2N), 5.62 (d,
1H, 2JHH = 12.8 Hz, NCH2N), 2.02 (s, 15H, C5(CH3)5), 1.30 (s, 18H,
C(CH3)3), −15.77 (br s, 1H, IrH). 13C{1H} NMR (100.6 MHz,
(CD3)2CO): δ 149.5 (C-2), 142.7 (C-4), 114.4 (C-5), 92.4
(C5(CH3)5), 61.9 (NCH2N), 30.5 (C(CH3)3), 28.8 (C(CH3)3), 9.9
(C5(CH3)5). 31P {1H} NMR (161.9 MHz, (CD3)2CO): δ −144.3
(sept, JPF = 707.5 Hz). HRMS (ESI-TOF) m/z: [M+] calcd for
C25H40N4Ir 589.2878; found 589.2888.
General Procedure for Transfer Hydrogenation Studies
Monitored by 1H NMR. Acetophenone (0.06 mmol), 1,3,5-
trimethylbenzene (2 μL) as internal standard, and 0.6 mL of 2-
1
propanol-d8 were transferred into a J. Young NMR tube, and a H
NMR spectrum was recorded. Then, the precatalyst (2 mol %) and
KOH (10 mol %) were added. The reaction mixture was heated at 95
°C for 24 h. The conversions were quantified by the integration of the
1H NMR signals of the alcohol and acetophenone. The value of the
Synthesis of 5.
integral for the singlet due to the aromatic protons of 1,3,5-
trimethylbenzene (internal standard) was set to 10 units in each case.
General Procedure for Transfer Hydrogenation Studies
Monitored by Gas Chromatography−Mass Spectrometry
(GC-MS). Alkenones. 6-Methyl-5-hepten-2-one or 5-hexen-2-one
(0.1 mmol) and precatalyst (2 mol %) were stirred in 2-propanol (1
mL) in a 2 mL vial at 70 °C for 1 h. Then KOH (10 mol %) was
added and the mixture was stirred at 95 °C for 6 h. An aliquot (0.1
mL) was taken and diluted to 1 mL with 2-propanol.
α,β-Unsaturated Ketones. To a 2-propanol solution (1 mL) of (E)-
chalcone (0.1 mmol) in a 2 mL vial were added the precatalyst (2 mol
%) and KOH (10 mol %). Then the mixture was stirred at 95 °C for
30 min. An aliquot (0.1 mL) was taken and diluted to 1 mL with 2-
propanol.
The analytical GC/MS system used was an Agilent 7890A GC
coupled to an Agilent Technologies 5975C mass detector, equipped
with a HP-5MS capillary column (30 m × 0.25 mm × 0.25 μm). An
Agilent Technologies 7693 autosampler was used to inject 1 μL of a
solution sample. The ionization energy was 70 eV with a mass range of
30−800 m/z. The temperature of the injector was set at 250 °C and
that of the detector to 230 °C. The flow rate of the carrier gas
(helium) was 1.0 mL/min injected with a gas dilution of 1:50.
AgSbF6 (15.9 mg, 0.0456 mmol) was added to a stirred solution of 3a
(15.0 mg, 0.0228 mmol) in dichloromethane at room temperature.
After 1 h, acetonitrile (75 μL, 1.4 mmol) was added dropwise until the
reaction mixture became colorless. The suspension was filtered and
concentrated under reduced pressure. Dichloromethane (3 × 1 mL)
and hexanes (1 × 1 mL) were added and then removed under high
vacuum to afford a pale pink solid: yield 22.3 mg (0.0202 mmol, 89%).
1H NMR (400 MHz, (CD3)2CO): δ 12.07 (br s, 2H, NH), 7.40 (d,
2H, 4JHH = 2.0 Hz, H-5), 6.51 (d, 1H, 2JHH = 13.8 Hz, NCH2N), 6.01
(d, 1H, 2JHH = 13.8 Hz, NCH2N), 2.70 (s, 3H, CH3CN), 1.97 (s, 15H,
C5(CH3)5), 1.35 (s, 18H, C(CH3)3). 13C {1H} NMR (100.6 MHz,
(CD3)2CO): δ 145.8 (C-4), 144.6 (C-2), 121.3 (CH3CN), 117.6 (C-
5), 96.4 (C5(CH3)5), 63.0 (NCH2N), 31.7 (C(CH3)3), 29.5
(C(CH3)3), 9.7 (C5(CH3)5), 3.9 (CH3CN). HRMS (ESI-TOF) m/z:
[M2+] calcd for C27H42N5Ir 314.6530; found 314.6520. Anal. Calcd for
E
Organometallics XXXX, XXX, XXX−XXX