Article
Organometallics, Vol. 29, No. 24, 2010 6767
PPh3 to produce Cp*IrClH(PPh3) is much slower than origi-
nally described,29 requiring about 24 h for completion. 2-Hydro-
xypyridine, 6-methyl-2-hydroxypyridine, 2,6-dihydroxypyridine
hydrochloride, NaOMe, Et3N, and AgPF6 were purchased from
Aldrich. Racemic 1-phenylethanol was obtained from Alfa-Aesar.
Electrospray ionization-mass spectra (ESI-MS) were acquired
using a Micromass Quattro QHQ quadrupole-hexapole-quadru-
pole instrument. 1H, 19F, and 31P NMR spectra were acquired on
Varian UNITY INOVA TM 500NB and UNITY 500 NB in-
struments. Elemental analyses were performed by the School of
Chemical Sciences Microanalysis Laboratory utilizing a model
CE 440 CHN analyzer.
and κ1-2-hp groups appear as an average in the spectrum, as seen
previously for a related complex.17 1H NMR (500 MHz, CDCl3
25 °C): δ 1.68 (s, 15H, Cp*), 5.97 (d, 2H, 8.7 Hz, aryl-CH), 6.15
(d of d of d, 2H, 3.1 Hz, 10.4 Hz, 12.7 Hz aryl-CH), 7.13 (d of d of
d, 2H, 2.0 Hz, 6.8 Hz, 8.7 Hz, aryl-CH), 7.75 (d of d, 2H, 1.7 Hz,
5.9 Hz, aryl-CH).
Cp*Ir(2-hp)Cl(PPh3) (5). A solution of 329 mg (1.26 mmol) of
PPh3 in 5 mL of CH2Cl2 was transferred to a orange solution of
574 mg (1.26 mmol) of 1. After stirring for 10 min, the reaction
solution was concentrated under vacuum and diluted with hex-
anes to precipitate yellow crystals, which were dried under vacuum.
Yield: 721 mg (1.01 mmol, 81%). Alternatively, the product could
be obtained by reaction of Cp*IrCl2(PPh3) with Na2-hp in sim-
ilar yield. 1H NMR (500 MHz, CD2Cl2): δ 1.35 (d, 15H, 2.1 Hz,
Cp*), 5.60 (d of d, 1H, 1.5 Hz, 8.7 Hz, pyr-aryl-CH), 5.87 (t of d,
1H, 1.5 Hz, 6.5 Hz, pyr-aryl-CH), 6.78 (t of d, 1H, 2.2 Hz,
7.5 Hz, pyr-aryl-CH), 7.00 (m, 2H, Ph-CH), 7.14 (m, 3H, Ph-
CH), 7.33 (m, 4H, Ph-CH), 7.45 (m, 4H, Ph-CH), 7.97 (m, 2H,
Ph-CH), 8.12 (d of d, 1H, 2.2 Hz, 5.5 Hz, pyr-aryl-CH). 31P
NMR (202 MHz, CD2Cl2): δ 6.53 (s, Ir-PPh3). Anal. Calcd for
C33H34ClIrNOP (found): C, 55.10 (54.96); H, 4.76 (4.71); N,
1.95 (2.10).
[Cp*2Ir2H2( μ-2-hp)]X ([2]Cl and [2]PF6). A solution of 400 mg
(7.4 mmol) of NaOMe in 5 mL of MeOH was transferred to a
solution of 704 mg (7.4 mmol) of 2-hpH in 5 mL of MeOH to
give a colorless homogeneous solution. Solvent was removed
under vacuum at 60 °C overnight to give an air-stable hygro-
scopic white powder, assumed to be Na2-hp, which was stored in
a desiccator. Yield:774 mg (6.6 mmol,89%). 1H NMR(500 MHz,
CD3OD): δ 6.33 (t, 1H, 6.2 Hz, aryl-CH), 6.40 (d, 1H, 8.5 Hz,
aryl-CH), 7.35 (m, 1H, aryl-CH), 7.67 (d, 1H, 5.4 Hz, aryl-CH).
A solution of 24 mg (0.205 mmol) of Na2-hp in 2 mL of MeOH
was transferred to a blue solution of 150 mg (0.205 mmol) of
Cp*2Ir2H2Cl2 in 10 mL of CH2Cl2 to immediately give a red
solution. After stirring 5 min, the solvent was removed under
vacuum. The residue was extracted into 10 mL of CH2Cl2, and
the slurry was cannula-filtered to remove NaCl. The filtrate was
concentrated to ∼3 mL and diluted with hexanes to produce a
[Cp*Ir(K2-2-hp)(PPh3)]PF6 ([6]PF6). A solution of 40 mg
(0.158 mmol) of AgPF6 in 3 mL of CH2Cl2 was transferred to
an orange solution of 114 mg (0.158 mmol) of 5 in 4 mL of
CH2Cl2 to give an immediate colorless precipitate. The solu-
tion mixture was filtered to give a pale orange solution. Addi-
tion of hexanes to the filtrate gave yellow crystals, which were
1
1
brown powder. Yield: 138 mg (0.176 mmol, 86%). H NMR
dried under vacuum. Yield: 103 mg (0.125 mmol, 79%). H
(500 MHz, CD2Cl2): δ -14.10 (s, 2H, Ir-H-Ir) 1.92 (s, 15 H,
Cp*), 1.99 (s, 15 H, Cp*’), 6.57 (d of d of d, 1H, 5.0 Hz, 8.2 Hz,
13.7 Hz aryl-CH), 7.28 (m, 2H, aryl-CH, aryl-CH0), 8.33 (d, 1H,
6.1 Hz, aryl-CH). ESI-MS: m/z = 750.2 ([Cp*2Ir2H2(2-hp)]þ).
Red crystals of [Cp*2Ir2H2( μ-2-hp)]PF6 precipitated upon the
addition of 0.5 mL of a saturated aqueous solution of NaPF6 to
an acetone solution of [2]Cl. The solid was filtered off, washed
with water, and dried under vacuum overnight. Yield: 350 mg
NMR (500 MHz, CD2Cl2): δ 1.45 (d, 15H, 2.1 Hz, Cp*), 5.46
(d, 1H, 8.7 Hz, pyr-aryl-CH), 6.52 (d of d of d, 1H, 1.0 Hz,
5.8 Hz, 6.9 Hz, pyr-aryl-CH), 7.11 (t of d, 1H, 1.3 Hz, 7.9 Hz,
pyr-aryl-CH), 7.41 (m, 12H, Ph-CH), 7.49 (m, 3H, Ph-CH),
7.77 (d of d, 1H, 0.8 Hz, 5.8 Hz, pyr-aryl-CH). 31P NMR (202
MHz, CD2Cl2): δ 15.72 (s, Ir-PPh3), -145.2 (p, 710 Hz, PF6).
ESI-MS: m/z=684.4 ([Cp*Ir(2-hp)(PPh3)]þ), 625.3 ([Cp*Ir-
Cl(PPh3)]þ), 589.3 ([Cp*Ir(PPh3)]þ).
1
(0.39 mmol, 68%). H NMR (500 MHz, CD2Cl2): δ -14.10
Cp*IrCl(6-Me-2-hp) (7). The salt “Na6-Me-2-hp” was synthe-
sized analogously for Na2-hp. H NMR (500 MHz, CD3OD):
1
(s, 2H, Ir-H-Ir), 1.92 (s, 15 H, Cp*), 1.99 (s, 15 H, Cp*0), 6.57
(d of d, 1H, 5.3 Hz, 8.9 Hz aryl-CH), 7.28 (m, 2H, aryl-CH, aryl-
CH0), 8.33 (d, 1H, 6.3 Hz, aryl-CH). ESI-MS: m/z = 750.2
([Cp*2Ir2H2(2-hp)]þ). Anal. Calcd for C25H36F6Ir2NOP (found):
C, 33.51 (33.37); H, 4.05 (3.97); N, 1.56 (1.63). Crystals suitable
for X-ray diffraction were obtained by layering a solution of
60 mg of [3]PF6 in 2 mL of CH2Cl2 with 30 mL of Et2O. Crystals
grew over the course of 2 h at room temperature.
δ 2.24 (s, 3H, CH3), 6.18 (d, 1H, 6.9 Hz, aryl-CH), 6.24 (d, 1H,
8.7 Hz, aryl-CH), 7.30 (m, 1H, aryl-CH). A colorless solution of
110 mg (0.656 mmol) of Na6-Me-2-hp in 5 mL of MeOH was
transferred to an orange solution of 261 mg (0.328 mmol) of
Cp*2Ir2Cl4 in 10 mL of CH2Cl2. After the solution was stirred
for 1 h, the solvent was removed by vacuum. The product was
extracted into 5 mL of CH2Cl2, and this extract was filtered to
remove NaCl. The filtrate was concentrated to ∼2 mL and then
diluted with 10 mL of hexanes to produce a yellow precipitate.
Yield: 101 mg (0.213 mmol, 65%). 1H NMR (500 MHz,
CD2Cl2): δ 1.72 (s, 15H, Cp*), 2.28 (s, 3H, 6-CH3), 5.87 (d, 1H,
8.5 Hz, aryl-CH), 6.34 (d, 1H, 7.2 Hz, aryl-CH), 7.29 (d of d, 1H,
7.3 Hz, 8.4 Hz, 4-CH). Anal. Calcd for C16H21ClIrNO (found):
C, 40.81 (40.58); H, 4.49 (4.43); N, 2.97 (3.02). A CH2Cl2 solu-
tion of 7 was treated with 1 atm of H2 at room temperature over
24 h; 1H NMR analysis revealed ∼95% unreacted 7 as well as a
small amount of free 6-Me-hpH.
Cp*IrH(Cl)(2-hpH) (3) via Transfer Hydrogenation. A solu-
tion of 7.9 mg (0.017 mmol) of 1 in 0.8 mL of CD2Cl2 was treated
with 12.0 mg (0.017 mmol) of Cp*IrH(TsDPENH) at -27 °C.
After the addition, the mixture was immediately allowed to warm
to room temperature. 1H NMR analysis of the dark red solution
1
verified that the reaction was complete. H NMR (Figure S5)
(500 MHz, CD2Cl2): δ -15.8 (s, 1H, Ir-H), 1.54 (s, 15H, Cp*),
6.29 (t, 1H, 6.3 Hz, aryl-CH), 6.54 (d, 1H, 7.8 Hz, aryl-CH), 7.24
(m, 1H, aryl-CH), 8.03 (d of d, 1H, 1.8 Hz, 6.3 Hz, aryl-CH). For
catalytic hydrogenation see the Supporting Information.
Cp*Ir(2-hp)2. A colorless solution of 88.2 mg (0.753 mmol) of
Na2-hp in 6 mL of MeOH was transferred to an orange solution
of 150 mg (0.188 mmol) of Cp*2Ir2Cl4 in 5 mL of CH2Cl2. After
stirring 1 h the solvent was removed by vacuum. The product
was extracted into 5 mL of CH2Cl2 and filtered to remove NaCl.
The filtrate was diluted with 25 mL of hexanes, and this mixture
was concentrated under vacuum to 10 mL, producing a yellow
powder. The product was collected by filtration and washed
with 5 mL of hexanes. Yield: 142 mg (0.274 mmol, 73%). In the
(C5Me4R)IrCl(η3-C3H3-2,6-(CO)2NH) (R=Me (8) and R=Et).
A solution of 562 mg (10.41 mmol) of NaOMe in 5 mL of
MeOH was transferred to a solution of 768 mg (5.2 mmol) of
2,6-dihydroxypyridine HCl in 5 mL of MeOH to give a homo-
geneous colorless solution. Solvent was removed under vacuum
3
at 60 °C overnight to give an air-sensitve hygroscopic white
powder. Yield of “NaC5H4NO2 NaCl”: 945 mg (4.94 mmol,
3
95%). 1H NMR (500 MHz, CD3OD): δ 5.40 (d, 2H, 8.2 Hz, aryl-
CH), 7.23 (t, 1H, 8.2 Hz, aryl-4-CH). A solution of 151 mg
(0.791 mmol) of NaC5H4NO2 NaCl in 3 mL of MeOH was
1
room-temperature H NMR spectrum, signals for the κ2-2-hp
3
added to a solution of 300 mg (0.377 mmol) of Cp*2Ir2Cl4
in 3 mL of CH2Cl2. After stirring for 1 h, the solution was
concentrated under vacuum. The residue was extracted into
5 mL of CH2Cl2, and this extract was filtered to remove NaCl.
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(33) White, C.;Yates, A.;Maitlis, P. M. Inorg. Synth. 1992, 29, 228–234.