Organometallics
Article
(iPr-CH), 22.6 (iPr-CH3), 21.2 (Mes-CH3), 18.8 (Mes-CH3).
MS(FAB+): calculated m/z = 652.2886 for C36H47N5Rh [M −
OTf]+, observed 652.2885.
CH), 3.91−3.61 (m, 2H, cod-CH), 2.40 (s, 3H, Mes-CH3), 2.12 (s,
6H, Mes-CH3), 2.11−1.93 (m, 8H, iPr-CH and cod-CH2 overlapping),
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1.84−1.78 (m, 2H, cod-CH2), 1.20 (d, JHH = 6.8 Hz, 6H, iPr-CH3),
[Rh(I)(cod)(NHCMes-tzNHCBenz)]OTf (4b): orange powder (78 mg,
1.07 (d, 3JHH = 6.8 Hz, 6H, iPr-CH3). 13C NMR (75 MHz, CD2Cl2): δ
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0.089 mmol, 89%). H NMR (300 MHz, CDCl3): δ 7.72 (bs, 1H,
176.7 (d, JRh−C = 51.8 Hz, NCN), 146.3, 141.4, 140.2, 136.19, 135.7
CH), 7.48−7.28 (m, 4H, Benz-CH), 7.19−7.16 (m, 1H, Benz-CH),
6.97 (s, 2H, Mes-CH), 6.81 (bs, 1H, CH), 5.62 (bs, 2H, CH2), 5.55 (s,
2H, CH2), 4.89 (bs, 2H, cod-CH), 4.31 (s, 3H, N-CH3), 3.66 (bs, 2H,
cod-CH), 2.37 (s, 6H, CH3), 2.10 (s, 3H, CH3), 1.93−187 (m, 8H,
cod-CH2). 13C NMR (101 MHz, CD2Cl2): 182.1 (d, 1JRh−C = 42.2 Hz,
(Ar/tz-Cq), 132.8, 132.3 (DiPP-CH), 129.7 (Mes-CH), 126.6 (tz-CH),
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124.7 (DiPP-CH), 123.6, 123.2 (CH), 118.9 (OTf), 96.7 (d, JRh−C
=
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7.8 Hz, cod-CH), 79.6 (d, JRh−C = 12.3 Hz, cod-CH), 45.4 (CH2),
32.7 (cod-CH2), 29.5 (cod-CH2), 29.3 (DiPP-CH), 24.8, 23.4 (DiPP-
CH3), 21.4, 18.5 (Mes-CH3). MS(FAB+) for C35H46N5Rh: m/z
calculated 638.2730 [M − OTf]+, observed 638.2725.
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NCN) 166.7 (d, JRh−C = 48.5 Hz, CCN), 140.4, 139.5, 138.9, 135.0,
[Rh(I)(CO)2(NHCMes-tzNHCDiPP)]OTf (7). A pressure NMR tube
containing [Rh(I)(cod)(NHC-Trzl)+]OTf− 4a (9.2 mg) in CD2Cl2
(0.5 mL) was pressurized with syngas (5 bar). After shaking the tube a
color change from bright orange to a darker shade of orange was
observed. The NMR spectra showed complete conversion to the
carbonyl complex. 1H NMR (300 MHz, CD2Cl2): δ 8.03 (s, 1H, CH),
134.4 (tz/Ar-Cq), 129.0, 128.9, 128.2, 127.2 (Ar-CH) 122.4, 122.2
(CH), 119.1 (OTf), 95.9 (d, 1JRh−C = 7.7 Hz, cod-CH), 78.4 (d, 1JRh−C
= 12.2 Hz, cod-CH), 56.5, 55.3 (CH2), 36.9 (N-CH3), 29.5, 28.7 (cod-
CH2), 20.6, 18.0 (Mes-CH3). MS(FAB+): calculated m/z = 568.1947
for C30H35N5Rh [M − OTf − CH3]+, observed 568.1932.
[Rh(I)(cod)(NHCMes-tzNHC4‑C H ‑OMe)]BF4 (4c): orange powder (98.5
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mg, 0.14 mmol, 96%). H NMR (300 MHz, CDCl3): δ 7.80 (bs, 1H,
7.60 (t, JHH = 7.8 Hz, 1H, CH-DiPP), 7.36 (d, JHH = 7.8 Hz, 2H,
CH-DiPP), 7.10 (s, 1H, CH), 7.02 (s, 2H, Mes-CH), 5.92 (s, 2H,
CH2), 5.62−5.52 (m, 4H, free cod), 4.51 (s, 3H, N-CH3), 2.44−2.26
CH), 7.58 (d, 3JHH = 8.8 Hz, 2H, Ar-CH), 7.02 (d, J = 8.8 Hz, 4H, Ar-
CH and overlap Mes-CH), 6.77 (s, 1H, CH), 5.59 (bs, 2H, CH2), 4.39
(s, 3H, N-CH3), 4.02−3.76 (m, 2H, cod-CH), 3.90 (s, 3H, O-CH3),
3.49 (bs, 2H, cod-CH), 2.37 (s, 6H, CH3), 2.35−1.79 (m, 12H, cod-
CH2 and CH3 overlapping. 13C NMR (75 MHz, CDCl3): δ 181.1 (d,
1JRh−C = 53,3, NCN), 166.3 (d, 1JRh−C =47,25, CCN), 161.1 (Ar-C-O),
140.1, 139.2, 136.0, 131.8, 130.4 (tz/Ar-Cq), 129.3, 125.8, 123.2, 122.5,
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(m, 8H, free cod), 2.27−2.21 (m, JHH = 13.5, 6.7 Hz, 2H, iPr-CH),
2.03 (s, 6H, Mes-CH3), 1.27 (s, 3H, Mes-CH3) 1.22 (d, 3JHH = 6.8 Hz,
6H, iPr-CH3), 1.10 (d, JHH = 6.8 Hz, 6H, iPr-CH3). 13C NMR (101
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MHz, CD2Cl2): δ 185.3 (bs, CO), 173.7 (d, 1JRh−C = 47.5 Hz, NCN),
163.6 (d, 1JRh−C = 42.4, CCN), 145.7, 141.0, 140.2, 135.9, 135.7, 134.6
(tz/Ar-Cq), 131.9, 129.2, 124.2 (Ar-CH) 124.2 (CH) 123.0 (CH),
118.9 (OTf), 44.8 (CH2), 37.7 (N-CH3), 28.5 (iPr-CH), 24.7 (DiPP-
CH3), 22.4 (CH3), 20.7 (Mes-CH3), 17.9 (Mes-CH3). MS(FAB+) for
C30H37N5O2Rh: m/z calculated 602.2002 [M − OTf]+, observed
602.2038/C30H36N5O2Rh: m/z calculated 601.1924 [M − OTf − H]+,
observed 601.1929. IR ν(CO): 2064, 2005 cm−1.
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114.4 (Ar-CH and CH), 77.4 (d, JRh−C = 3.5 Hz, cod-CH), 55.9 (O-
CH3), 45.4 (CH2), 37.3 (N-CH3), 28.2, 22.0 (cod-CH2), 21.2, 17.7
(Mes-CH3). MS(FAB+) for C31H47N5ORh: m/z calculated 598.2053
[M − BF4]+, observed 598.2054.
General Procedure for the Synthesis of [M(cod)(NHC-
tz)]OTf. NaH (1 equiv, 60 wt %) was washed three times with
pentane. Subsequently [M(cod)Cl]2 (M = Ir, Rh, 0.5 equiv) in MeOH
(c = 20 mM) was added, and the resulting suspension was stirred for
half an hour at room temperature. After addition of the appropriate
triazolyl-imidazolium bromide (1 equiv), the mixture was stirred for 3
h at 50 °C, after which the resulting orange (rhodium) or red
(iridium) solution was concentrated, redissolved in dichloromethane,
and filtered over Celite. AgOTf (1.1 equiv) was added to the solution,
and the mixture was stirred in the dark for 2 h at room temperature,
during which it turned to a pale brown suspension. The reaction
mixture was filtered over Celite and concentrated to yield the product.
Alternative Procedure for the Synthesis of [M(cod)(NHC-tz)]OTf.
The triazolyl-imidazolium bromide salt (1 equiv) and [M(cod)Cl]2
(M = Ir, Rh, 0.5 equiv) were dissolved in THF. Potassium tert-
butoxide was added, and the mixture was stirred for 3 h, after which
the solution was filtered over Celite and concentrated. Subsequently a
solution of AgOTf (1.1 equiv) in DCM was added, and the resulting
mixture was stirred for another 2 h at room temperature in the dark,
during which it turned to a pale brown suspension. The reaction
mixture was filtered over Celite and concentrated to yield the product.
[Ir(I)(cod)(NHCMes-tzDiPP)]OTF (5): red solid (88 mg, 0.1 mmol,
[Ir(I)(CO)2(NHCMes-tzNHCDiPP)]OTf (8). A pressure NMR tube
containing [Ir(I)(cod)(NHC-Trzl)+]OTf− (3a) (40 mg) in CD2Cl2
(0.5 mL) was pressurized with carbon monoxide gas (5 bar). After
shaking the tube the color changed from red to bright yellow. The
NMR spectra showed complete conversion to the carbonyl complex.
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1H NMR (300 MHz, CD2Cl2): δ 8.08 (d, JHH = 1.9 Hz, 1H, CH),
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7.68−7.52 (t, JHH = 7.9 Hz, 1H, DiPP-CH), 7.37 (d, JHH = 7.9 Hz,
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2H, DiPP-CH), 7.13 (d, JHH = 2.0 Hz, 1H, CH), 7.02 (s, 2H, Mes-
CH), 6.00 (s, 2H, CH2), 5.62−5.52 (m, 4H, free cod), 4.53 (s, 3H, N-
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CH3), 2.44−2.26 (m, 8H, free cod), 2.23 (p, JHH = 6.8 Hz, 2H, iPr-
CH) 2.13 (s, 3H, Mes-CH3), 2.03 (s, 6H, Mes-CH3), 1.35−1.21 (m,
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18H, DiPP-CH3), 1.10 (d, JHH = 6.9 Hz, 6H, DiPP-CH3). 13C NMR
(126 MHz, CD2Cl2): δ 179.6, 178.9 (CO), 171.3 (NCN), 162.0
(CCN), 146.6, 141.9, 141.1, 136.7, 135.9, 134.6 (tz/Ar-Cq),132.8,
129.9, 127.7 (Ar-CH), 125.2 (CH), 125.0 (Ar-CH), 124.9 (CH), 124.0
(OTf), 45.6 (CH2), 38.5 (N-CH3), 29.2 (iPr-CH), 25.4 (DiPP-CH3),
23.1 (DiPP-CH3), 21.4 (Mes-CH3), 18.7 (Mes-CH3). MS(ESI+) for
C30H35N5O2Ir: m/z calculated 690.2416 [M − OTf]+, observed
690.2401. IR ν(CO): 2056, 1992 cm−1.
Alternative Synthesis for [Ir(I)(CO)2(NHCMes-tzNHCDiPP)]OTf (8).
Potassium tert-butoxide was added to a solution of Ir(CO)2(acac) (35
mg, 0.1 mmol) and 2a (671 mg, 0.1 mmol) in THF (5 mL), and the
resulting brown solution was stirred for 2 h at 50 °C. After the solution
was allowed to cool to room temperature, the mixture was filtered over
Celite. Then the solution was concentrated to 2 mL, and Et2O (10
mL) was added to precipitate the remaining ligand. The solution was
decanted and concentrated under vacuum to yield the product (50 mg,
0.06 mmol, 60%).
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76%). H NMR (300 MHz, CD2Cl2): δ 8.42 (s, 1H, tz-CH), 7.70 (d,
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3JHH = 2.0 Hz, 1H, CH), 7.59 (t, JHH = 7.7 Hz, 1H, DiPP-CH), 7.35
(d, 3JHH = 7.9 Hz, 2H, DiPP-CH), 7.03 (s, 2H, Mes-CH), 6.94 (d, 3JHH
= 2.0 Hz, 1H, CH), 5.75 (s, 2H, CH2), 4.59 (bs, 2H, cod-CH), 3.54
(bs, 2H, cod-CH), 2.37 (s, 3H, Mes-CH3), 2.07 (s, 6H, Mes-CH3),
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2.08−1.61 (m, 10H, cod-CH2 and iPr-CH overlapping), 1.19 (d, JHH
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= 6.8 Hz, 6H, DiPP-CH3), 1.06 (d, JHH = 6.8 Hz, 6H, DiPP, CH3).
13C NMR (75 MHz, CD2Cl2): δ 173.3 (NCN), 146.2, 141.2, 140.3,
135.8, 134.3 (Ar/tz-Cq), 132.4 (DiPP-CH), 129.6 (Mes-CH), 127.3
(tz-CH), 124.8 (DiPP-CH), 122.6, 123.3 (CH), 117.9 (OTf), 83.8
(cod-CH), 66.3 (cod-CH), 45.2 (CH2), 33.7 (cod-CH2), 30.1 (cod-
CH2), 29.4 (iPr-CH), 24.9, 23.4 (DiPP-CH3), 22.6, 18.6 (Mes-CH3).
MS(FAB+) for C35H47N5Ir: m/z calculated 728.3306 [M − OTf]+,
observed 728.3307.
[Ir(I)(CO)2(H)2(NHCMes-tzNHCDiPP)]OTf (9 and 9′). A pressure NMR
tube containing [Ir(I)(cod)(NHC-Trzl)+]OTf− (3a) in CD2Cl2 (0.5
mL) was pressurized with syngas (5 bar). After shaking the tube a
color change from bright red to yellow occurred. The NMR spectra
showed a mixture of [Ir(I)(CO)2(NHC-Trzl)+]OTf− (8) and two
different isomers of [Ir(I)(CO)2(H)2(NHC-Trzl)+]OTf− (9) in a
3.2:1:2.8 ratio. Alternatively, 9 could be obtained by stirring complex 8
in CD2Cl2 (1 mL) in a Schlenk connected to a balloon with hydrogen
gas and stirring for 10 min. Upon release of the pressure, complex 9
converts to 8 by losing H2, which prevented us from further
characterization. The mixture of products prevented us from assigning
[Rh(I)(cod)(NHCMes-tzDiPP)]OTF (6): bright orange solid (52 mg, 0.07
mmol, 73%). 1H NMR (300 MHz, CD2Cl2): 8.33 (s, 1H, tz-CH), 7.67
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(d, JHH = 1.9 Hz, 1H, CH), 7.58 (d, JHH = 7.8 Hz, 1H, DiPP-CH),
7.36 (d, 3JHH = 7.8 Hz, 2H, DiPP-CH), 7.08 (s, 2H, Mes-CH), 6.89 (d,
3JHH = 1.8 Hz, 1H, CH), 5.86 (s, 2H, CH2), 5.01−4.75 (m, 2H, cod-
G
dx.doi.org/10.1021/om5007038 | Organometallics XXXX, XXX, XXX−XXX