Supporting information

Introduction of bulky tert-butyl substituents on the core of N,N’-diaryl

N-heterocyclic carbenes through the corresponding vicinal diamines

Ulrich Jacquemarda , Phoebe Harpaintera , and Sylvain Rolanda, ∗

Université P. et M. Curie – Paris 6, France

Table of contents

1. General information

2. Synthetic procedures

3. NMR spectra of new compounds

4. Crystal structure information

∗ Corresponding author. Tel.: +33 (0)1 44 27 55 67; fax: +33 (0)1 44 27 55 04; e-mail: sylvain.roland@upmc.fr

1. General information

Reagents were purchased from Acros, Sigma-Aldrich or Strem and used as received unless

stated otherwise. THF was distilled from sodium-benzophenone ketyl under nitrogen

atmosphere. Reactions involving organometallic species or air- or moisture-sensitive

compounds were carried out under an atmosphere of argon by using standard Schlenk

techniques. Analytical TLC was performed by using Merck Kieselgel 60 F254 silica gel

plates ; Visualisation : UV light (254 nm) and staining reagents (phosphomolybdic acid or

potassium permanganate solutions). Purifications by flash column chromatography were

performed on silica gel (Kieselgel 60 Merck, granulometry 40–63 or 15–40 µm). NMR spectra

were recorded on Bruker Nanobay spectrometers 250 or 400 MHz. Proton chemical shifts (δ)

are reported in ppm relative to TMS (tetramethylsilane). Carbon chemical shifts are reported

relative to the NMR solvent (CDCl3, 77.23 ppm ; C6D6, 128.39). Coupling constants are

reported in Hertz (Hz). The following abbreviations are used : s = singlet, d = doublet, t =

triplet, q = quadruplet, m = multiplet, br = broad). Melting point are uncorrected and were

determined using a Büchi 535 melting point apparatus. Elemental and HRMS analyses were

performed respectively at the I.C.S.N. (service de microanalyse) and in our Institute

(I.P.C.M., Groupe de Spectrométrie de masse). Given their high cytotoxicity, silver–NHCs

should be handled with caution.

2. Synthetic procedures

N,N’-bis(2,6-diisopropylphenyl)ethanediimine (1a)

N N C26H36N2

Mol. Wt.: 376.58

To a solution of 2,6-diisopropylphenylamine (15.0 g, 84.6 mmol) in n-propanol (60 mL) were

added at 20 °C a mixture of a 40% aqueous solution of glyoxal (6.1 g, 42.3 mmol), n-

propanol (18 mL) and water (9 mL). The mixture was stirred for 16 h at 20 °C then for 4 h at

60 °C. Upon addition of water (36 mL) a yellow solid precipitated which was collected by

filtration and dried (9 g, 77%). Mp 100–101 °C. 1H NMR (CDCl3): δ 1.52 (d, 24H, J = 7.5

Hz, CH3), 3.26 (m, 4H, J = 7.5 Hz, CH iPr), 7.45–7.54 (m, 6H, CHarom), 8.42 (s, 2H, N=CH). 13C NMR (CDCl3): δ 24.0 (CH3), 28.6 (CH iPr), 123.6 (CH Ar), 137.3 (C Ar), 148.6 (C Ar),

163.7 (HC=N). HRMS (ESI) m/z calcd. for C26H36N2Na [M+Na+] 399.27685; found

399.27707.

N,N’-bis(2,4,6-trimethylphenyl)ethanediimine (1b)

N N C20H24N2

Mol. Wt.: 292.42

To a solution of 2,4,6-trimethylphenylamine (15 g, 111 mmol) in n-propanol (60 mL) were

added at 20 °C a mixture of a 40% aqueous solution of glyoxal (8 g, 55 mmol), n-propanol

(24 mL) and water (12 mL). The mixture was stirred for 16 h at 20 °C then for 4 h at 60 °C.

Upon addition of water (48 mL) a yellow solid precipitated which was collected by filtration

and dried (14.1 g, 85%). Mp 156–157 °C. 1H NMR (CDCl3): δ 2.19 (s, 12H, CH3), 2.32 (s,

6H, CH3), 6.93 (s, 4H, CHarom), 8.13 (s, 2H, N=CH). 13C NMR (CDCl3): δ 18.3 (CH3), 20.9

(CH3), 126.7 (C Ar), 129.1 (CH Ar), 134.4 (C Ar), 147.6 (C Ar), 163.6 (HC=N). HRMS (ESI)

m/z calcd. for C20H25N2 [M+H+] 293.20123; found 293.20135.

N,N’-bis(2,6-diethylphenyl)ethanediimine (1c)

N NC22H28N2

Mol. Wt.: 320.47

To a solution of 2,6-diethylphenylamine (2.0 g, 13.4 mmol) in ethanol (27 mL) were added at

0° C a mixture of a 40% aqueous solution of glyoxal (1.0 g, 6.7 mmol), and three drops of

formic acid. The mixture was stirred for 18 h at 20 °C. The mixture was concentrated under

reduced pressure and the crude residue was purified by filtration on silica gel (pentane/Et2O ;

9:1) and crystallization in iPrOH/water to afford the title compound as yellow crystals (1.1 g,

51%). 1H NMR (CDCl3): δ 1.23 (t, 12H, J = 7.5 Hz, CH3), 2.58 (q, 8H, J = 7.5 Hz, CH2),

7.06–7.19 (m, 6H, CHarom), 8.18 (s, 2H, N=CH). 13C NMR (CDCl3): δ 14.7 (CH3), 24.8

(CH2), 125.1 (CH Ar), 126.6 (CH Ar), 132.4 (C Ar), 149.4 (C Ar), 163.3 (HC=N). Anal. calcd

for C22H28N2 (320.47) C 82.45, H 8.81, N 8.74; found C 82.05, H 8.63, N 8.71. HRMS (ESI)

m/z calcd. for C22H28N2Na [M+Na+] 343.21447 ; found 343.21358.

1-Amino-1-tert-butyl-N,N’-bis[2,6-diisopropylphenyl]-2-iminoethane (2a)

NH NC30H46N2

Mol. Wt.: 434.7

To a solution of 1a (1.5 g, 4.0 mmol) in THF (20 mL) was added dropwise at 0 °C a solution

of tert-butylmagnesium chloride 1.7 M in Et2O (3.1 mL, 5.2 mmol). The mixture was stirred at

0 °C for 1 h, quenched with saturated aqueous NH4Cl (20 mL) and stirred for 15 min. The

aqueous layer was separated and extracted with Et2O (3 x 20 mL). The combined organic

layers were washed with brine, dried over K2CO3, filtered and concentrated under reduced

pressure. The crude residue was purified by flash chromatography on silica gel (pentane/Et2O

; 99:1) to afford a white solid (1.63 g, 94%). Mp 89–90 °C. 1H NMR (C6D6): δ 1.03–1.06 (m,

12H, CH3 iPr), 1.15–1.28 (m, 21H, CH3 iPr + tBu), 2.47–2.54 (m, 2H, CH iPr), 3.45–3.50 (m,

2H, CH iPr), 3.88 (br s, 1H, NH), 4.14 (br s, 1H, HN–CH), 7.00–7.06 (m, 6H, CHarom), 7.54–

7.58 (m, 1H, N=CH). 13C NMR (C6D6): δ 23.2 (CH3 iPr), 23.6 (CH3 iPr), 24.1 (CH3 iPr), 24.2

(CH3 iPr), 27.0 (CH3 tBu), 27.6 (CH iPr), 28.4 (CH iPr), 35.6 (C(CH3)3), 71.8 (HN–CH),

123.0 (CH Ar), 123.3 (CH Ar), 124.0 (CH Ar), 124.4 (CH Ar), 128.2 (CH Ar) 137.5 (C Ar),

140.8 (C Ar), 141.5 (C Ar), 149.5 (C Ar) 167.4 (HC=N). Anal. calcd for C30H46N2 (434.7) C

82.89, H 10.67, N 6.44; found C 83.00, H 10.86, N 6.48. HRMS (ESI) m/z calcd. for C30H47N2

[M+H+] 435.37338; found 435.37358.

1-Amino-1-tert-butyl-N,N’-bis[2,4,6-trimethylphenyl]-2-iminoethane (2b)

NH NC24H34N2

Mol. Wt.: 350.54

To a solution of 1b (1.5 g, 5.1 mmol) in THF (20 mL) was added dropwise at 0 °C a solution

of tert-butylmagnesium chloride 1.7 M in Et2O (3.9 mL, 6.7 mmol). The mixture was stirred at

0 °C for 1 h, quenched with saturated aqueous NH4Cl (20 mL) and stirred for 15 min. The

aqueous layer was separated and extracted with Et2O (3 x 20 mL). The combined organic

layers were washed with brine, dried over K2CO3, filtered and concentrated under reduced

pressure. The crude residue was purified by flash chromatography on silica gel (pentane/Et2O

; 99:1) to afford a yellow oil (1.6 g, 90%). 1H NMR (CDCl3): δ 1.30 (s, 9H, tBu), 1.72 (s, 6H,

CH3 Mes), 2.27 (s, 6H, CH3 Mes), 2.35 (s, 6H, CH3 Mes), 3.57 (br s, 1H, NH), 4.04 (d, 1H, J

= 7.5 Hz, CH–tBu), 6.80 (s, 2H, CHarom), 6.82 (s, 2H, CHarom), 7.52 (d, 1H, J = 7.5 Hz,

N=CH). 13C NMR (CDCl3): δ 18.1 (CH3 Mes), 19.5 (CH3 Mes), 20.5 (CH3 Mes), 20.7 (CH3

Mes), 27.1 (CH3 tBu), 34.9 (C(CH3)3), 68.8 (HN–CH), 126.9 (C Ar), 128.4 (C Ar), 128.6 (CH

Ar), 129.8 (CH Ar), 130.7 (C Ar), 132.7 (C Ar), 141.3 (C Ar), 148.4 (C Ar), 168.4 (HC=N).

HRMS (ESI) m/z calcd. for C24H35N2 [M+H+] 351.27948 ; found 351.27854.

1-Amino-1-tert-butyl-N,N’-bis[2,6-diethylphenyl]-2-iminoethane (2c)

NH NC26H38N2

Mol. Wt.: 378.59

To a solution of 1c (0.20 g, 0.62 mmol) in THF (10 mL) was added dropwise at 0 °C a

solution of tert-butylmagnesium chloride 1.7 M in Et2O (0.44 mL, 0.75 mmol). The mixture

was stirred at 0 °C for 1 h, quenched with saturated aqueous NH4Cl (10 mL) and stirred for 15

min. The aqueous layer was separated and extracted with Et2O (3 x 20 mL). The combined

organic layers were washed with brine, dried over K2CO3, filtered and concentrated under

reduced pressure to afford a yellow oil (0.234 g, 99%). 1H NMR (CDCl3): δ 0.92 (t, 6H, J =

7.5 Hz, CH2CH3), 1.26 (s, 9H, tBu), 1.29 (t, 6H, J = 7.5 Hz, CH2CH3), 1.96 (q, 4H, J = 7.5 Hz,

CH2), 2.72 (q, 2H, J = 7.5 Hz, CH2), 3.74 (br s, 1H, HN–CH), 4.04 (d, 1H, J = 7.5 Hz, HN–

CH), 6.87–7.02 (m, 6H, CHarom), 7.51 (d, 1H, J = 7.5 Hz, N=CH). HRMS (ESI) m/z calcd. for

C26H39N2 [M+H+] 379.31078 ; found 379.30969. The compound decomposes in CDCl3 and on

silica gel. The crude product was used without further purification in the next step.

1-tert-butyl-1,2-bis{[2,6-diisopropylphenyl]amino}ethane (3a)

NH HNC30H48N2

Mol. Wt.: 436.72

To a solution of 2a (1.18 g, 3.38 mmol) in THF (20 mL) was slowly added at 0 °C lithium

aluminium hydride (0.270 g, 7.70 mmol). The mixture was stirred at 70 °C for 18 h, quenched

with water (20 mL) at 0 °C and stirred for 15 min. The aqueous layer was separated and

extracted with Et2O (3 x 20 mL). The combined organic layers were washed with brine, dried

over K2CO3, filtered and concentrated under reduced pressure. The crude residue was purified

by flash chromatography on silica gel (pentane/Et2O ; 99:1) to afford a white solid (1.24 g,

76%). Mp 72–73 °C. 1H NMR (CDCl3): δ 1.11 (s, 9H, tBu), 1.15 (d, 12H, J = 7.5 Hz, CH3

iPr), 1.30 (d, 12H, J = 7.5 Hz, CH3 iPr), 2.82–3.58 (m, 7H, CH iPr and CH2), 6.97–7.15 (m,

6H, CHarom). 13C NMR (CDCl3): δ 23.9 (CH3 iPr), 24.3 (CH3 iPr), 24.4 (CH3 iPr), 27.4 (CH3

tBu), 27.7 (CH3 iPr), 28.2 (CH3 iPr), 35.8 (C(CH3)3), 54.3 (HN–CH2), 68.5 (HN–CH), 122.1

(CH Ar), 123.5 (CH Ar), 123.6 (CH Ar), 142.7 (C Ar), 142.8 (C Ar), 144.1 (C Ar). HRMS

(ESI) calcd. for C30H49N2 [M+H+] 437.38846 ; found 437.38903.

1-tert-butyl-1,2-bis{[2,4,6-trimethylphenyl]amino}ethane (3b)

NH HN

C24H36N2

Mol. Wt.: 352.56

To solution of 2b (180 mg, 0.52 mmol) in THF (10 mL) was slowly added at 0 °C lithium

aluminium hydride (40 mg, 1.03 mmol). The mixture was stirred at 70 °C for 18 h, quenched

with water (10 mL) at 0 °C, and stirred for 15 min. The aqueous layer was separated and

extracted with Et2O (3 x 20 mL). The combined organic layers were washed with brine, dried

over K2CO3, filtered and concentrated under reduced pressure. The crude residue was purified

by flash chromatography on silica gel (pentane/Et2O ; 99:1) to afford a colorless oil (110 mg,

58%). 1H NMR (CDCl3): δ 1.07 (s, 9H, tBu), 2.13 (s, 6H, CH3 Mes), 2.26 (s, 6H, CH3 Mes),

2.41 (s, 6H, CH3 Mes), 2.74 (dd, 1H, J = 7.5 Hz and 12.5 Hz, CHH–NH), 3.22–3.29 (m, 5H,

CHH–NH and CH–NH), 3.65–3.68 (m, 1H, CH–NH), 6.83 (d, 4H, J = 2.5 Hz, CHarom). 13C

NMR (CDCl3): δ 18.2 (CH3 Mes), 20.0 (CH3 Mes), 20.5 (CH3 Mes), 20.6 (CH3 Mes), 27.2

(CH3 tBu), 35.8 (C(CH3)3), 51.6 (CH2), 64.7 (HN–CH), 126.5 (C Ar), 129.2 (C Ar), 129.4

(CH Ar), 130.1 (C Ar), 130.4 (CH Ar), 131.3 (C Ar), 143.3 (C Ar), 144.1 (C Ar). HRMS

(ESI) m/z calcd. for C24H37N2 [M+H+] 353.29442 ; found 353.29513.

1-tert-butyl-1,2-bis{[2,6-diethylphenyl]amino}ethane (3c)

NH HNC26H40N2

Mol. Wt.: 380.61

To a solution of 2c (158 mg, 0.42 mmol) in THF (10 mL) was slowly added at 0 °C lithium

aluminium hydride (33 mg, 0.88 mmol). The mixture was stirred at 70 °C for 18 h, quenched

with water (10 mL) at 0 °C, and stirred for 15 min. The aqueous layer was separated and

extracted with Et20 (3 x 20 mL). The combined organic layers were washed with brine, dried

over K2CO3, filtered and concentrated under reduced pressure. The crude residue was purified

by flash chromatography on silica gel (pentane/Et2O ; 98:2) to afford a yellow oil (68 mg,

43%). 1H NMR (CDCl3): δ 0.89–1.18 (m, 21H, tBu and CH3CH2), 2.36–2.51 (m, 4H,

CH2CH3), 2.76–2.82 (m, 4H, CH2CH3), 3.20–3.24 (m, 2H, CH2–NH), 3.64 (br s, 1H, CH–

NH), 6.87–7.08 (m, 6H, CHarom). 13C NMR (CDCl3): δ 14.4 (CH3CH2), 15.1 (CH3CH2), 24.2

(CH2), 25.4 (CH2), 27.3 (CH3 tBu), 35.8 (C(CH3)3), 53.4 (CH2–NH), 65.7 (CH–NH), 121.2

(CH Ar), 126.8 (CH Ar), 127.1 (CH Ar), 129.7 (C Ar), 133.3 (C Ar), 137.0 (C Ar), 144.5 (C

Ar). HRMS (ESI) m/z calcd. for C26H41N2 [M+H+] 381.32643 ; found 381.32635.

1,3-bis[2,6-diisopropylphenyl]-4-tert-butylimidazolinium chloride (4a)

Cl–

N NC31H46ClN2

Mol. Wt.: 482.16

To a solution of 3a (712 mg, 1.63 mmol) in triethylorthoformate (10 mL) was added slowly a

solution of HCl 4 M in dioxan (1.31 mL, 5.22 mmol). The mixture was stirred at 130 °C for 18

h and concentrated under reduced pressure. The crude residue was purified by flash

chromatography on silica gel (DCM/MeOH ; 9:1) to afford a white solid (674 mg, 85%). Mp

> 210 °C. 1H NMR (CDCl3): δ 0.91 (s, 9H, tBu), 1.27–1.42 (m, 24H, CH3 iPr), 2.69 (br s, 1H,

CH iPr), 2.79–2.87 (m, 1H, CH iPr), 3.07 (br s, 1H, CH iPr), 3.18–3.26 (m, 1H, CH iPr), 4.01

(t, 1H, J = 10.0 Hz, CH–N), 4.75–4.97 (m, 2H, CH2–N), 7.14–7.24 (m, 4H, CHarom), 7.36-

7.44 (m, 2H, CHarom), 9.68 (s, 1H, HC=N+). 13C NMR (CDCl3): δ 23.0 (CH3 iPr), 23.7 (CH3

iPr), 24.0 (CH3 iPr), 25.0 (CH3 iPr), 25.5 (CH3 iPr), 25.7 (CH3 iPr), 26.5 (CH3 tBu), 26.6 (CH3

iPr), 29.0 (CH iPr), 29.3 (CH iPr), 29.4 (CH iPr), 29.7 (CH iPr), 35.1 (C(CH3)3), 56.1 (CH2–

N), 75.6 (CH–N), 124.7 (CH Ar), 125.2 (CH Ar), 125.3 (CH Ar), 125.8 (CH Ar), 129.6 (C

Ar), 130.9 (C Ar), 131.1 (CH Ar), 131.5 (CH Ar), 145.3 (C Ar), 145.9 (C Ar), 146.5 (C Ar),

162.0 (HC=N+). HRMS (ESI) m/z calcd. for C31H47N2 447.37194 ; found 447.37338.

1,3-bis[2,4,6-trimethylphenyl]-4-tert-butylimidazolinium chloride (4b)

N N

Cl–

C25H35ClN2

Mol. Wt.: 399.01

To a solution of 3b (100 mg, 0.28 mmol) in triethylorthoformate (2 mL) was added slowly a

solution of HCl 4 M in dioxan (0.23 mL, 0.91 mmol). The mixture was stirred at 130 °C for 18

h and concentrated under reduced pressure. The crude residue was triturated in diethyl ether to

afford a white solid (80 mg, 71%). Mp > 210 °C. 1H NMR (CDCl3): δ 0.96 (s, 9H, tBu), 2.27

(s, 6H, CH3 Mes), 2.43 (s, 9H, CH3 Mes), 2.57 (s, 3H, CH3 Mes), 4.03 (t, 1H, J = 10.0 Hz,

CHH–N or CH–N), 4.42 (t, 1H, J = 10.0 Hz, CHH–N or CH–N), 4.88 (t, 1H, J = 10.0 Hz,

CHH–N or CH–N), 6.90–6.96 (m, 4H, CHarom), 10.39 (s, 1H, HC=N+). 13C NMR (CDCl3): δ

17.6 (CH3 Mes), 18.7 (CH3 Mes), 19.0 (CH3 Mes), 20.1 (CH3 Mes), 20.2 (CH3 Mes), 25.4

(CH3 tBu), 34.3 (C(CH3)3), 52.7 (H2C-N+), 71.2 (HN–CH), 130.2 (CH Ar), 130.4 (C Ar),

130.7 (CH Ar), 130.9 (CH Ar), 131.8 (C Ar), 133.9 (C Ar), 134.4 (C Ar), 134.6 (C Ar), 135.0

(C Ar), 139.6 (C Ar), 140.4 (C Ar), 162.7 (HC=N+). HRMS (ESI) m/z calcd. for C25H35N2

363.27839 ; found 363.27948.

1,3-bis[2,6-diethylphenyl]-4-tert-butylimidazolinium chloride (4c)

Cl–

N N

C27H39ClN2

Mol. Wt.: 427,07

To a solution of 3c (1.02 g, 2.69 mmol) in triethylorthoformate (10 mL) was added slowly a

solution of HCl 4 M in dioxan (2.15 mL, 8.61 mmol). The mixture was stirred at 130 °C for 18

h, and concentrated under reduced pressure. The crude residue was triturated in diethyl ether

to afford a white solid (0.777 g, 68%). Mp > 210 °C. 1H NMR (CDCl3): δ 0.93 (s, 9 H, tBu),

1.27–1.35 (m, 12H, CH3CH2), 2.58–2.80 (m, 8H, CH2CH3), 4.10 (t, 1H, J = 10.0 Hz, CHH–N

or CH–N), 4.70 (t, 1H, J = 10.0 Hz, CHH–N or CH–N), 5.02 (t, 1H, J = 10.0 Hz, CHH–N or

CH–N), 7.19–7.26 (m, 4H, CHarom), 7.34–7.40 (m, 2H, CHarom), 10.02 (s, 1H, HC=N+). 13C

NMR (CDCl3): δ 14.7 (CH3CH2), 14.9 (CH3CH2), 15.0 (CH3CH2), 15.4 (CH3CH2), 24.3

(CH2CH3), 24.7 (CH2CH3), 25.4 (CH2CH3), 26.5 (CH3 tBu), 35.1 (C(CH3)3), 55.2 (CH2–NH),

73.6 (CH–NH), 127.3 (CH Ar), 127.4 (CH Ar), 127.6 (CH Ar), 130.2 (CH Ar), 130.9 (CH

Ar), 131.5 (C Ar), 132.8 (C Ar), 140.2 (C Ar), 140.3 (C Ar), 140.6 (C Ar), 141.3 (C Ar),

162.4 (HC=N+). HRMS (ESI) m/z calcd. for C27H39N2 391.31078 ; found 391.31044.

1,3-bis[2,6-diisopropylphenyl]-4-tert-butylimidazolin-2-ylidene silver(I) chloride (5a)

N N

Ag

Cl

C31H46AgClN2Mol. Wt.: 590.03

The imidazolinium chloride 4a (50 mg, 0.10 mmol) was dissolved in DCM (5 mL) and Ag2O

(14 mg, 0.06 mmol) was added. The mixture was stirred at room temperature with exclusion

of light for 18 h, filtered through Celite and concentrated under reduced pressure to afford a

white solid (54 mg, 88%). Mp 182–183 °C. 1H NMR (CDCl3): δ 0.88 (s, 9 H, tBu), 1.24–1.37

(m, 24H, CH3 iPr), 2.93–3.04 (m, 3H, CH iPr), 3.53 (m, 1H, J = 7.5 Hz, CH iPr), 3.81 (t, 1H, J

= 12.5 Hz, CHH–N), 4.04 (t, 1H, J = 12.5 Hz, CHH–N), 4.35 (t, 1H, J = 12.5 Hz, CH–N),

7.16–7.25 (m, 4H, CHarom), 7.28-7.44 (m, 2H, CHarom). 13C NMR (CDCl3): δ 23.6 (CH3 iPr),

23.8 (CH3 iPr), 24.0 (CH3 iPr), 24.3 (CH3 iPr), 25.3 (CH3 iPr), 25.7 (CH3 iPr), 26.2 (CH3 iPr), 26.8

(CH3 tBu), 27.3 (CH3 iPr), 28.4 (CH iPr), 28.6 (CH iPr), 28.9 (CH iPr), 29.5 (CH iPr), 34.8

(C(CH3)3), 56.3 (CH2–N), 76.5 (CH–N), 124.7 (CHarom), 124.9 (CHarom), 125.2 (CHarom),

125.5 (CHarom), 129.6 (CHarom), 129.7 (CHarom), 130.2 (CHarom), 134.7 (Carom), 136.5

(Carom), 145.9 (Carom), 146.2 (Carom), 146.5 (Carom), 146.6 (Carom), 211.9 (d+d, J{13C–109Ag}

= 257 Hz, J{13C–107Ag} = 223 Hz, Ccarbene). HRMS (ESI) m/z calcd. for C31H46N2ClAgNa [M

+ Na+] 611.22927 ; found 611.22863.

1,3-bis[2,4,6-trimethylphenyl]-4-tert-butylimidazolin-2-ylidene silver(I) chloride (5b)

N N

Ag

Cl

C25H34AgClN2Mol. Wt.: 505.87

The imidazolinium chloride 4b (125 mg, 0.31 mmol) was dissolved in DCM (10 mL) and

Ag2O (43 mg, 0.19 mmol) was added. The mixture was stirred at room temperature with

exclusion of light for 18 h, filtered through Celite and concentrated under reduced pressure to

afford a white solid (156 mg, 98%, mixture of isomers). Mp 111–112 °C. Major isomer : 1H

NMR (CDCl3): δ 0.85 (s, 9H, tBu), 2.26–2.29 (m, 15H, CH3 Mes), 2.47 (s, 3H, CH3 Mes), 3.77

(t, 1H, J = 12.5 Hz, CHH–N), 3.96 (t, 1H, J = 12.5 Hz, CHH–N), 4.41 (t, 1H, J = 12.5 Hz,

CH–N), 6.86–6.91 (m, 4H, CHarom). 13C NMR (CDCl3): δ 18.1 (CH3 Mes), 18.3 (CH3 Mes), 19.1

(CH3 Mes), 20.0 (CH3 Mes), 20.9 (CH3 Mes), 21.1 (CH3 Mes), 26.7 (CH3 tBu), 34.8 (C(CH3)3), 53.6

(CH2–N), 73.0 (CH–N), 130.1 (CHarom), 130.5 (CHarom), 130.8 (CHarom), 134.2 (Carom), 135.0

(Carom), 135.2 (Carom), 135.3 (Carom), 137.2 (Carom), 137.9 (Carom), 138.9 (Carom), 210.6 (d+d,

J{13C–109Ag} = 257.5 Hz, J{13C–107Ag} = 223.1 Hz, Ccarbene). HRMS (ESI) m/z calcd. for

C50H68N4Ag 831.44876 ; found 831.44894.

N,N’-Bis[2,4,6-trimethylphenyl]-1,2-diamino-1,2-di-tert-butylethane (6)

NH HN

C28H44N2

Mol. Wt.: 408.66

To a solution of 1b (2.00 g, 6.84 mmol) in THF (40 mL) was added dropwise at –78 °C a

solution of tert-butyllithium 1.6 M in hexane (9.40 mL, 15.05 mmol). The mixture was stirred

at –78 °C for 1 h and at 20 °C for 3 h, quenched with saturated NH4Cl (40 mL) and stirred for

15 min. The aqueous layer was separated and extracted with Et2O (3 x 40 mL). The combined

organic layers were washed with brine, dried over K2CO3, filtered and concentrated under

reduced pressure. The crude residue was purified by flash chromatography on silica gel

(pentane/Et2O ; 99:1) to afford a white solid (2.22 g, 80%). Single crystals suitable for RX

analysis were obtained by slow evaporation in acetonitrile. Mp 155–156 °C. 1H NMR

(CDCl3): δ 1.02 (s, 18H, tBu), 2.24 (s, 6H, CH3 Mes), 2.28 (s, 6H, CH3 Mes), 2.56 (s, 6H, CH3

Mes), 3.95 (d, 2H, J = 7.5 Hz, NH), 4.10 (d, 2H, J = 7.5 Hz, CH–NH), 6.76 (s, 2H, CHarom),

6.82 (s, 2H, CHarom). 13C NMR (CDCl3): δ 19.5 (CH3 Mes), 20.2 (CH3 Mes), 23.4 (CH3 Mes),

27.6 (CH3 tBu), 38.5 (C(CH3)3), 58.7 (CH–NH), 120.8 (C Ar), 123.2 (C Ar), 126.3 (C Ar),

129.9 (CH Ar), 132.7 (CH Ar), 143.7 (C Ar). Anal. calcd for (C28H44N2)(Et2O)0.2 C 81.68, H

10.95, N 6.61; found C 81.59, H 10.87, N 6.77. HRMS (ESI) m/z calcd. for C28H45N2 [M+H+]

409.35773 ; found 409.35746.

1,3-Bis[2,4,6-trimethylphenyl]-4,5-di-tert-butylimidazolinium chloride (7)

N N

Cl–C29H43ClN2

Mol. Wt.: 455.12

To a solution of 6 (100 mg, 0.24 mmol) in THF (2 mL) was added slowly a preformed

solution of (HCHO)n (11 mg, 0.36 mmol, 1.5 equiv) in HCl 3.42 M in dioxane (112 µL, 0.38

mmol, 1.6 equiv). The mixture was stirred at 100 °C for 18 h, and concentrated under reduced

pressure. The crude residue was purified by flash chromatography on silica gel (DCM/MeOH;

9:1) to afford a beige solid (32 mg, 29%). Mp 181–182 °C. 1H NMR (CDCl3): δ 0.95 (s, 18H,

tBu), 2.23 (s, 6H, CH3 Mes), 2.40 (s, 6H, CH3 Mes), 2.59 (s, 6H, CH3 Mes), 4.51 (s, 2H, CH–

tBu), 6.85 (s, 2H, CHarom), 6.96 (s, 2H, CHarom), 10.65 (s, 1H, HC=N+). 13C NMR (CDCl3): δ

20.8 (CH3 Mes), 21.2 (CH3 Mes), 28.1 (CH3 tBu), 36.4 (C(CH3)3), 73.2 (CH–tBu), 130.9

(CHarom), 131.9 (CHarom), 132.4 (Carom), 132.6 (Carom), 134.5 (Carom), 139.2 (Carom), 162.7

(HC=N+). HRMS (ESI) m/z calcd. for C29H43N2 419.34208 ; found 419.34173.

1,3-Bis[2,4,6-trimethylphenyl]-4,5-di-tert-butylimidazolin-2-ylidene silver(I) chloride (8)

N N

Ag

Cl

C29H42AgClN2Mol. Wt.: 561.98

The imidazolinium chloride 7 (186 mg, 0.41 mmol) was dissolved in DCM (10 mL) and

Ag2O (57 mg, 0.24 mmol) was added. The mixture was stirred at room temperature with

exclusion of light for 18 h, filtered through Celite and concentrated under reduced pressure to

afford a white solid (218 mg, 94%, mixture of isomers). Mp 160–161 °C. 1H NMR (CDCl3),

isomer A : δ 0.90 (s, 18H, tBu), 2.25 (s, 6H, CH3 Mes), 2.35 (s, 6H, CH3 Mes), 2.53 (s, 6H, CH3

Mes), 4.17 (s, 2H, CH–N), 6.85 (s, 2H, CHarom), 6.93 (s, 2H, CHarom); isomer B : δ 0.79 (s,

18H, tBu), 1.47 (s, 6H, CH3 Mes), 2.25-2.35 (m, 12H, CH3 Mes), 4.05 (s, 2H, CH–N), 6.67 (s,

2H, CHarom), 6.94 (s, 2H, CHarom). 13C NMR (CDCl3), isomer B (isolated after silica gel

chromatography, DCM then DCM/MeOH; 9:1): δ 20.8 (CH3 Mes), 21.2 (CH3 Mes), 21.6 (CH3

Mes), 29.0 (CH3 tBu), 35.8 (C(CH3)3), 73.9 (CH–N), 130.6 (CHarom), 131.5 (CHarom), 133.7

(Carom), 134.6 (Carom), 137.5 (Carom), 138.5 (Carom), 213.7 (d+d, J{13C–109Ag} = 260 Hz, J{13C–107Ag} = 225 Hz, Ccarbene). HRMS (ESI) m/z calcd. for C58H84N4Ag 943.57414; found

943.57398.

3. NMR spectra (new compounds)

1c, 1H NMR :

13C NMR :

2a, 1H NMR :

13C NMR :

2b, 1H NMR :

13C NMR :

2c, 1H NMR :

13C NMR :

3a, 1H NMR :

13C NMR :

3b, 1H NMR :

13C NMR :

3c, 1H NMR :

13C NMR :

4a, 1H NMR :

13C NMR :

4b, 1H NMR :

13C NMR :

4c, 1H NMR :

13C NMR :

5a, 1H NMR :

13C NMR :

5b, 1H NMR :

13C NMR :

Compound 6, 1H NMR :

13C NMR :

Compound 7, 1H NMR :

13C NMR :

Compound 8, 1H NMR :

13C NMR :

4. Crystal structure information (diamine 6) : ============================== Formula C28H44N2 Crystal Class monoclinic Space Group P 21/c a 11.9285(16) alpha 90 b 13.777(3) beta 96.199(11) c 15.453(2) gamma 90 Volume 2524.7(7) Z 4 Radiation type Mo K� Wavelength 0.710730 � 1.08 Mr 408.67 � 0.062 Temperature (K) 200(2) Size 0.12x 0.14x 0.24 Colour colourless Shape block Cell from 225 Reflections Theta range 4 to 22 Diffractometer type KAPPA CCD Scan type PHI-OMEGA Absorption type multi-scan Transmission range 0.99 0.99 Reflections measured 7282 Independent reflections 7282 Theta max 30.00 Hmin, Hmax -16 16 Kmin, Kmax -19 19 Lmin, Lmax -21 21 Refinement on Fsqd R[I>2� (I)] 0.050 Weighted R-factor 0.120 Max shift/su 0.0052 Delta Rho min -0.23 Delta Rho max 0.28 Reflections used 4533 Number of parameters 273 Goodness of fit 0.997

TableI:Interatomicdistances(Å)forC28H44N2 C(1) - C(2) 1.4098(19) C(1) - C(6) 1.4174(19) C(1) - N(1) 1.3984(17) C(2) - C(3) 1.392(2) C(2) - C(7) 1.510(2) C(3) - C(4) 1.376(2) C(4) - C(5) 1.383(2) C(4) - C(8) 1.507(2) C(5) - C(6) 1.383(2) C(6) - C(9) 1.502(2) C(10) - C(11) 1.5653(19) C(10) - C(21) 1.559(2) C(10) - N(1) 1.4615(17) C(11) - C(25) 1.559(2) C(11) - N(2) 1.4642(17) C(12) - C(13) 1.4065(19) C(12) - C(17) 1.4133(19) C(12) - N(2) 1.4100(17) C(13) - C(14) 1.394(2) C(13) - C(18) 1.503(2) C(14) - C(15) 1.378(2) C(15) - C(16) 1.384(2) C(15) - C(19) 1.503(2) C(16) - C(17) 1.384(2) C(17) - C(20) 1.502(2) C(21) - C(22) 1.529(2) C(21) - C(23) 1.525(2) C(21) - C(24) 1.531(2) C(25) - C(26) 1.535(2) C(25) - C(27) 1.527(2) C(25) - C(28) 1.524(2) Table II :Bond angles (°) for C28H44N2 C(2) - C(1) - C(6) 117.91(12) C(2) - C(1) - N(1) 126.48(12) C(6) - C(1) - N(1) 115.43(12) C(1) - C(2) - C(3) 118.59(13) C(1) - C(2) - C(7) 125.25(12) C(3) - C(2) - C(7) 116.16(13) C(2) - C(3) - C(4) 124.01(14) C(3) - C(4) - C(5) 116.78(13) C(3) - C(4) - C(8) 121.36(16) C(5) - C(4) - C(8) 121.86(16) C(4) - C(5) - C(6) 122.20(14) C(1) - C(6) - C(5) 120.45(13) C(1) - C(6) - C(9) 120.36(12) C(5) - C(6) - C(9) 119.18(13) C(11) - C(10) - C(21) 114.61(11) C(11) - C(10) - N(1) 108.34(11) C(21) - C(10) - N(1) 113.28(12) C(10) - C(11) - C(25) 113.79(11) C(10) - C(11 - N(2) 108.91(10) C(25) - C(11) - N(2) 113.30(11) C(13) - C(12) - C(17) 118.29(12) C(13 - C(12) - N(2) 125.15(12) C(17) - C(12) - N(2) 116.35(12) C(12 - C(13) - C(14) 118.72(13) C(12) - C(13) - C(18) 125.03(13) C(14) - C(13) - C(18) 116.25(13) C(13) - C(14) - C(15) 123.68(14) C(14) - C(15) - C(16) 116.76(13) C(14) - C(15) - C(19) 121.67(15) C(16) - C(15) - C(19) 121.56(15) C(15) - C(16) - C(17) 122.35(14) C(12) - C(17) - C(16) 120.18(13) C(12) - C(17) - C(20) 121.06(13) C(16) - C(17) - C(20) 118.76(13) C(10) - C(21) - C(22) 112.64(13) C(10) - C(21) - C(23) 109.82(13) C(22) - C(21) - C(23) 110.04(14) C(10) - C(21) - C(24) 108.82(12) C(22) - C(21) - C(24) 107.90(15) C(23) - C(21) - C(24) 107.47(14) C(11) - C(25) - C(26) 109.14(12) C(11) - C(25) - C(27) 109.64(13) C(26) - C(25) - C(27) 107.51(14) C(11) - C(25) - C(28) 113.01(12) C(26) - C(25) - C(28) 107.89(15) C(27) - C(25) - C(28) 109.48(13) C(1) - N(1) - C(10) 130.98(11) C(11) - N(2) - C(12) 128.63(11)

Table III : Fractional atomic coordinates for C28H44N2 Atom x/a y/b z/c U(eqv) C(1) -0.01913(11) 0.77112(10) 0.04964(9) 0.0207 C(2) -0.01732(12) 0.80611(10) 0.13551(9) 0.0238 C(3) -0.11945(13) 0.82635(11) 0.16758(9) 0.0296 C(4) -0.22330(13) 0.81122(13) 0.12156(11) 0.0342 C(5) -0.22392(12) 0.77367(12) 0.03854(10) 0.0321 C(6) -0.12559(12) 0.75439(10) 0.00183(9) 0.0253 C(7) 0.08758(13) 0.82236(13) 0.19769(10) 0.0335 C(8) -0.33090(16) 0.83329(18) 0.16065(14) 0.0560 C(9) -0.13294(13) 0.71414(13) -0.08895(11) 0.0365 C(10) 0.19217(11) 0.77447(10) 0.02192(9) 0.0219 C(11) 0.26810(11) 0.68630(10) 0.00203(9) 0.0212 C(12) 0.26456(11) 0.57656(10) -0.13435(8) 0.0203 C(13) 0.36533(11) 0.59922(10) -0.16949(9) 0.0235 C(14) 0.39961(12) 0.54013(11) -0.23496(9) 0.0273 C(15) 0.34042(13) 0.45975(11) -0.26743(10) 0.0291 C(16) 0.24228(13) 0.43784(10) -0.23123(10) 0.0296 C(17) 0.20323(12) 0.49404(10) -0.16657(9) 0.0247 C(18) 0.44083(13) 0.68361(12) -0.14211(11) 0.0349 C(19) 0.38072(16) 0.39849(13) -0.33837(11) 0.0411 C(20) 0.09413(14) 0.46646(12) -0.13280(12) 0.0353 C(21) 0.21626(14) 0.86974(11) -0.02729(10) 0.0314 C(22) 0.19044(17) 0.86001(13) -0.12597(12) 0.0435 C(23) 0.33873(16) 0.90012(13) -0.00416(13) 0.0433 C(24) 0.14189(18) 0.95088(13) 0.00292(13) 0.0482 C(25) 0.30072(13) 0.61932(11) 0.08212(10) 0.0295 C(26) 0.37398(18) 0.53545(15) 0.05480(12) 0.0501 C(27) 0.37110(14) 0.67650(15) 0.15315(11) 0.0436 C(28) 0.19864(15) 0.57559(13) 0.11915(11) 0.0381 N(1) 0.07430(10) 0.74387(9) 0.00785(8) 0.0251 N(2) 0.21403(9) 0.63411(8) -0.07383(7) 0.0224