Iridium complexes supported by the PNP amidophosphine scaffold (PNP = [N(2-PiPr2-4-Me-C6H3)2]−) perform the selective double C−H activation of methyl amines to produce iridium(III) dihydrido aminocarbenes. The reactivity of these complexes is presented and contrasted with that observed for the previously reported iridium(I) alkoxycarbenes

Grubbs, Robert H.

Whited, Michael T.

English

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S1 
 
 
 
 
 
 
 
 
 
Supporting Information for 
 
Synthesis and Reactivity of Iridium(III) Dihydrido Aminocarbenes 
 
Matthew T. Whited and Robert H. Grubbs* 
 
Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering 
California Institute of Technology, Pasadena, CA 91125 
 
 
 
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Experimental Section 
All manipulations were carried out using standard Schlenk or glove-box techniques under 
a dinitrogen atmosphere. Unless otherwise noted, solvents were deoxygenated and dried by 
thorough sparging with Ar gas followed by passage through an activated alumina column.1 
Hexamethyldisiloxane and t-butyl methyl ether were distilled from CaH2 and degassed prior to 
use. (PNP)IrH22 and (PNP)Ir=C(H)OtBu (1)3 were prepared according to literature procedure. 
Other reagents were purchased from commercial vendors and used without further purification. 
Elemental analyses were carried out at Desert Analytics, Tucson, Arizona. NMR spectra were 
recorded at ambient temperature on Varian Mercury 300 MHz and 500 MHz spectrometers. 1H 
and 13C NMR chemical shifts were referenced to residual solvent. 31P NMR chemical shifts are 
reported relative to an external standard of 85% H3PO4. Infrared spectra were recorded using a 
Perkin Elmer Spectrum BXII spectrometer. X-ray diffraction studies were carried out in the 
Beckman Institute Crystallographic Facility on a Bruker KAPPA APEX II diffractometer. 
 
X-ray Crystallography Procedures. X-ray quality crystals were grown as indicated in the 
experimental procedures for each complex. The crystals were mounted on a glass fiber with 
Paratone-N oil. Structures were determined using direct methods with standard Fourier 
techniques using the Bruker AXS software package. In some cases, Patterson maps were used in 
place of the direct methods procedure. 
 
Preparation of Aminocarbene (2). To a solution of (PNP)IrH2 (139.7 mg, 0.2243 mmol) in 
N,N,N',N'-tetramethylethylenediamine (TMEDA, 10 mL) was added a solution of norbornene 
                                                 
1
 Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.; Timmers, F. J. Organometallics 1996, 15, 1518. 
2
 Fan, L.; Parkin, S.; Ozerov, O. V. J. Am. Chem. Soc. 2005, 127, 16772. 
3
 Whited, M. T.; Grubbs, R. H. J. Am. Chem. Soc. 2008, 130, 5874. 
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(24.3, mg, 0.258 mmol) in TMEDA (3 mL), causing a gradual lightening of the solution from red 
to yellow. The mixture was stirred at ambient temperature for 16 h and volatiles were removed in 
vacuo to afford an orange film (4:1 mixture of 2anti / 2syn by 31P NMR). The residues were 
dissolved as much as possible in pentane (ca. 3.5 mL), filtered, and large orange blocks of 2anti 
were recovered by slow evaporation of pentane at ambient temperature (58.1 mg, 35%). 
Characterization data for 2anti: 1H NMR  (C6D6): δ 12.80 (s, 1H, Ir=C(H)N), 7.88 (dt, J1 = 8.7 
Hz, J2 = 2.1 Hz, 2H, Ar–H), 7.03 (m, 2H, Ar–H), 6.78 (dd, J1 = 8.7 Hz, J2 = 1.8 Hz, 2H, Ar–H), 
3.12 (s, 3H, –NCH3), 2.76 (t, 3JHH = 6.3 Hz, 2H, –NCH2), 2.30 (s, 6H, Ar–CH3), 2.20 (m, 4H, –
CH(CH3)2), 1.90 (t, 3JHH = 6.3 Hz, 2H, –NCH2), 1.80 (s, 6H, –N(CH3)2), 1.30 – 1.09 (m, 24H, –
CH(CH3)2), –8.90 (br s, 2H, Ir–H). 13C{1H} NMR (C6D6): δ 209.1 (Ir=C(H)N), 162.6 (t, J = 9 
Hz), 131.0, 125.8, 125.6, 122.7, 115.8, 61.3, 57.4, 45.4, 42.8, 26.9 (t, J = 16 Hz), 21.1, 19.1, 
18.9. 31P{1H} NMR (C6D6): δ 49.1 (s). Anal. Calcd. for C32H56IrN3P2: C, 52.15; H, 7.66; N, 
5.70. Found: C, 52.43; H, 7.43; N, 5.60. 
Although 2syn could not be isolated, it was observed by NMR spectroscopy upon equilibration of 
2anti in solution: 1H NMR (C6D6): δ 12.76 (s, 1H, Ir=C(H)N). 31P{1H} NMR (C6D6): δ 47.2 (s). 
 
Preparation of Aminocarbene (3). (PNP)IrH2 (67.2 mg, 0.108 mmol) was dissolved in N-
methylmorpholine (7 mL) and norbornene (14.6 mg, 0.155 mmol) was added as a solution in N-
methylmorpholine (3 mL), causing a change in color from red to red-brown. The reaction was 
allowed to proceed 12 h, volatiles were removed in vacuo, and the residues were extracted into 
pentane, filtered, and dried to a reddish film. Analytically pure 3 was obtained as red-orange 
crystals by slow evaporation of pentane from a concentrated solution (10.0 mg, 13%). 1H NMR 
(C6D6): 12.70 (s, 1H, Ir=C(H)N), 7.85 (dt, J1 = 8.4 Hz, J2 = 2.4 Hz, 2H, Ar–H), 6.99 (m, 2H, Ar–
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H), 6.77 (dd, J1 = 8.4 Hz, J2 = 1.8 Hz, 2H, Ar–H), 4.08 (m, 2H, morpholine CH2), 3.30 (t, 3JHH = 
4.8 Hz, morpholine CH2), 3.02 (t, 3JHH = 4.8 Hz, morpholine CH2), 2.57 (t, 3JHH = 4.8 Hz, 
morpholine CH2), 2.28 (s, 6H, Ar–CH3), 2.15 (m, 4H, –CH(CH3)2), 1.18 (dvt, 12H, –CH(CH3)2), 
1.09 (dvt, 12H, –CH(CH3)2), –8.92 (br s, 2H, Ir–H). 13C{1H} NMR (C6D6): δ 207.9 (Ir=C(H)N), 
162.5 (t, J = 9.3 Hz), 131.2, 131.0, 125.3, 123.0, 115.8, 66.6, 66.2, 61.5, 53.4, 34.8, 26.7 (t, J = 
16 Hz), 23.1, 21.0, 19.0, 18.9, 14.6, 2.4. 31P{1H} NMR (C6D6): δ 49.5 (s). Anal. Calcd. for 
C31H51IrN2OP2: C, 51.58; H, 7.12; N, 3.88. Found: C, 52.30; H, 7.12; N, 3.89. 
 
Preparation of Complex (4). Aminocarbene 2 (28.1 mg, 0.0381 mmol) was dissolved in 
benzene (5 mL) and an excess of trimethylphosphine (500 µ, 1.0 M in toluene) was added. The 
solution was heated at 70 °C for 12 h in a sealed vial, causing lightening to a fluorescent yellow 
hue. Volatiles were removed in vacuo, leaving a pale yellow film. Analytically pure crystals of 4 
suitable for X-ray diffraction were obtained by slow evaporation of pentane from a concentrated 
solution (28.0 mg, 90%). 1H NMR (C6D6): δ 7.75 (d, J = 8.7 Hz, 2H, Ar–H), 7.12 (m, 2H, Ar–
H), 6.78 (d, J = 8.7 Hz, 2H, Ar–H), 3.21 (m, 2H, Ir–CH2), 2.78 (m, 2H, –NCH2), 2.67 (m, 4H, –
CH(CH3)2), 2.53 (m, 2H, –NCH2), 2.44 (s, 3H, –NCH3), 2.26 (s, 6H, –N(CH3)2), 2.25 (s, 6H, Ar–
CH3), 1.42 (dvt, 6H, –CH(CH3)2), 1.32 (m, 12H, –CH(CH3)2), 1.19 (dvt, 6H, –CH(CH3)2), 0.95 
(d, 2JPH = 6.6 Hz, 9H, –P(CH3)3), –11.61 (dt, 2JPH(trans) = 140 Hz, 2JPH(cis) = 19.8 Hz, 1H, Ir–H). 
13C{1H} NMR (C6D6): 162.5 (m), 131.7, 131.1, 129.7, 128.9, 126.0, 123.5, 115.9, 60.5, 60.1, 
46.8, 45.6, 30.4, 27.9, 21.2, 21.0, 19.9, 19.6, 19.4, 18.0, 17.8, 16.5. 31P{1H} NMR (C6D6): 14.9 
(d, 2JPP = 17 Hz, 2P, Ir–(PNP)), –53.8 (br, 1P, Ir–P(CH3)3). Anal. Calcd. for C35H65IrN3P3: C, 
51.70; H, 8.06; N, 5.17. Found: C, 51.59; H, 8.20; N, 5.11. 
 
S5 
Preparation of Complex (5). Aminocarbene 2 (ca. 10 mg) was dissolved in C6D6 (700 µL) and 
transferred to a resealable NMR tube. The solution was frozen and the headspace evacuated and 
backfilled with carbon monoxide (1 atm). The solution was warmed to room temperature and 
allowed to react for 12 h, then heated at 70 °C for 2 h to ensure complete conversion to 5. 
Complex 5 was not isolated, but its identity was confirmed by NMR, IR, and comparison to the 
analogous complex 4. 1H NMR (C6D6): δ 7.71 (dt, J1 = 8.1 Hz, J2 = 2.1 Hz, 2H, Ar–H), 6.94 (m, 
2H, Ar–H), 6.75 (dd, J1 = 8.7 Hz, J2 = 1.8 Hz, 2H, Ar–H), 3.25 (t, 3JPH = 4.2 Hz, 2H, Ir–CH2), 
2.74 – 2.66 (m, 2H, –NCH2), 2.58 – 2.40 (m, 6H, –CH(CH3)2 and –NCH2), 2.36 (s, 3H, –NCH3), 
2.21 (s, 6H, –N(CH3)2), 2.20 (s, 6H, Ar–H), 1.36 – 1.03 (m, 24H, –CH(CH3)2), –7.71 (t, 2JPH = 
18 Hz, 1H, Ir–H). 13C{1H} NMR (C6D6): δ 181.3 (t, 2JPC = 8.3 Hz, Ir–CO), 161.1, 131.4, 130.8, 
123.8, 115.6, 59.2, 59.0, 46.1, 44.8, 25.3 (m), 20.4, 18.6, 18.2, 17.7, 17.2. 31P{1H} NMR (C6D6): 
δ 27.0 (s). IR (C6D6, KBr, cm–1) υ(CO): 1976. 
 
Preparation of Complex (6). (PNP)Ir=C(H)OtBu (1) (54.4 mg, 0.0770 mmol) was dissolved in 
toluene (10 mL) and transferred to a resealable flask. The solution was frozen and the headspace 
evacuated and backfilled with carbon monoxide (1 atm). As the solution melted a color change 
from purple to yellow was observed, and the reaction was allowed to continue with stirring for 
16 h. Volatiles were removed in vacuo to afford a yellow film, and off-white crystals of 6 (26.2 
mg, 45%) were isolated by slow evaporation of pentane from a concentrated solution at -35 °C. 
1H NMR (C6D6): δ 7.42 (d, J = 6.9 Hz, 1H, Ar–H), 7.38 – 7.28 (m, 2H, Ar–H), 7.27 – 7.20 (m, 
1H, Ar–H), 6.90 (vt, 2H, Ar–H), 6.37 (dd, 3JPH = 16.8 Hz, 3JPH = 2.1 Hz, 1H, –NC(H)OtBu), 2.70 
(septet, 3JHH = 6.3 Hz, 1H, –CH(CH3)2), 2.31 (septet, 3JHH = 7.0 Hz, 1H, –CH(CH3)2), 2.19 (m, 
2H, –CH(CH3)2), 2.13 (s, 3H, Ar–CH3), 2.12 (s, 3H, Ar–CH3), 1.49 – 1.22 (m, 12H, –
S6 
CH(CH3)2), 1.09 (s, 9H, –OC(CH3)3), 0.94 – 0.72 (m, 12H, –CH(CH3)2). 13C{1H} NMR (C6D6): 
δ 188.1 (t, 2JPC = 37 Hz, Ir–CO), 184.8 (t, 2JPC = 8.7 Hz, Ir–CO). 31P{1H} NMR: δ 17.2 (d, 2JPP = 
95.3 Hz), 2.9 (d, 2JPP = 95.3 Hz). IR (THF, KBr, cm–1) υ(CO(symmetric)): 1981; 
υ(CO(antisymmetric)): 1924. Anal. Calcd for C33H50IrNO3P2: C, 51.95; H, 6.61; N, 1.84. Found: 
C, 53.11, 53.05; H, 6.67, 6.73; N, 1.70, 1.83. 
 
Thermal Isomerization of Aminocarbene (2). Aminocarbene 2 (ca. 10 mg) was dissolved in 
C6D6 and transferred to an NMR tube. The sealed sample was heated at 70 °C for 12 h and 
examined by NMR spectroscopy, revealing a mixture of 2anti, 2syn, and two cis-dihydrido isomers 
of 2. The 31P NMR chemical shifts of the cis-2 isomers were observed at δ 48.5 and 46.2 ppm. 
Each complex also exhibited a distinct carbene proton and two hydrides by 1H NMR 
spectroscopy.  
1H NMR (cis-2 (major), C6D6): δ 11.92 (s, 1H, Ir=C(H)N), –12.81 (dt, J1 = 21 Hz, J2 = 5.4 Hz, 
1H, Ir–H), –19.21 (br s, 1H, Ir–H).  
1H NMR (cis-2 (minor), C6D6): δ 11.87 (s, 1H, Ir=C(H)N), –12.46 (t, J1 = 21 Hz, J2 = 6 Hz, 1H, 
Ir–H), –19.38 (br s, 1H, Ir–H). 


Synthesis and Reactivity of Iridium(III) Dihydrido Aminocarbenes

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Synthesis and Reactivity of Iridium(III) Dihydrido Aminocarbenes

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