RhI and AgI Complexes of N-heterocyclic Carbene (NHC) Precursors
reflux condenser, 8 (1033 mg, 3.0 mmol) and pentafluorobenzaldehyde
(588 mg, 3.0 mmol; 1.0 equiv.) were dissolved in anhydrous chloro-
form (12 mL). At room temperature, p-toluenesolfonic acid (10 mg)
and anhydrous MgSO4 (50 mg) were added. The mixture was refluxed
for 2 d. The product was subsequently isolated by liquid chromatog-
raphy from silica (height: 20 cm, diameter: 6 cm) with hexane/chloro-
form (1:4) as eluent. Additional recrystallization from ethanol afforded
9. Yield: 72%. HRMS: m/z: calcd. for C29H23F5N4: 522.1837 [M]+;
Experimental Procedures
2,3-Bis(mesitylamino)acrylonitrile (6): In a 100 mL three-necked
flask with magnetic stirrer and reflux-condenser,
5 (1080 mg,
3.7 mmol) was added to methanol (30 mL). To the suspension, acetone
cyanohydrin (630 mg, 7.4 mmol; 2.0 equiv.) and potassium cyanide
(10 mg) were added at room temperature and the mixture was refluxed
for 3 h. The mixture was reduced to half its original volume at a rotary
vaporator and chloroform was added until the residue was completely
dissolved. The organic layer was extracted with water, followed by
extraction of the aqueous layer with chloroform. The chloroform layers
were collected, dried with MgSO4, and filtered. After removing the
solvent in vacuo, crude 6 was recrystallized from ethanol to give yel-
low crystals. Yield: 91%. HRMS: m/z: calcd. for C21H25N3: 319.2043
1
found: 523.2392 [M + H]+. H NMR (300 MHz, CDCl3): δ [ppm, J
(Hz)] = 7.10 (s, 1 H, H-C2), 6.92 (s, 2 H, HMes–Aryl), 6.81, (s, 2 H,
HMes–aryl), 2.50 (s, 6 H, HMes–methyl), 2.24 (s, 6 H, HMes–methyl), 2.10 (s,
6 H, HMes–methyl). 13C NMR (75 MHz (CDCl3): δ (ppm) = 139.2,
138.7, 136.8, 131.9), 130.76, 130.5, 112.8 (CN), 110.5 (CCN),
78.5 (C2), 20.8, 19.2, 17.9, 17.8. 19F NMR (282 MHz, CDCl3), δ
[ppm, J (Hz)] = –132.9 to –133.2 (m, 1F), –147.2 to –147.5 (m, 1F),
–149.1 to –149.3 (m, 1F), –159.4 to –159.9 (m, 2F). FT-IR (KBr): ν˜
= 2989, 2963, 2927, 2213 (CN), 1734, 1651, 1593, 1523, 1509, 1480,
1418, 1361, 1304, 1213, 1166, 1140, 1128, 996, 937, 852, 799, 772,
733, 647, 557, 479 cm–1.
[M]+; found: 320.2035 [M + H]+. H NMR (300 MHz, CDCl3): δ =
1
[ppm, J (Hz)]: 6.90 (s, 2 H, HMes–aryl); 6.86 (s, 2 H, HMes–aryl); 6.66
(d, J = 12.7 Hz, 1 H, HCHNH); 6.27 (d, J = 12.7 Hz, 1 H, HCHNH); 4.06
(s, 1 H, HNH); 2.31 (s, 6 H, HMes–methyl); 2.28 (s, 3 H, HMes–methyl);
2.25 (s, 9 H, HMes–methyl). 13C NMR (75 MHz, CDCl3): δ (ppm) =
142.5, 138.3, 135.5, 132.6, 132.1, 129.8, 129.6, 129.4; 127.5 (CN);
119.6 (CCN); 88.3 (C-NHMes); 20.7, 20.6, 18.5, 18.2. FT-IR (KBr):
ν˜ = 3364, 3311, 3025, 2969, 2914, 2852, 2726, 2187 (CN), 1792, 1733,
1642, 1482, 1378, 1341, 1314, 1283, 1235, 1182, 1157, 1036, 1013,
899, 854, 726, 670, 585, 571, 553, 513, 498, 448 cm–1.
2-(Neopentylamino)-3-(neopentylidenimino)maleonitrile (12): In a
250 mL flask with magnetic stirrer, pivalaldehyde (860 mg, 10 mmol)
and 11 (1900 mg, 10 mmol; 1.0 equiv.) were dissolved in methanol
(60 mL). After adding three drops sulfuric acid (96%), the mixture
was refluxed for 2 h. After cooling to room temperature, the mixture
was poured into 200 mL cold water and stirred for 2 h. The resulting
precipitate was filtered through a glass frit, washed three times with
ice cold methanol, and recrystallized from n-hexane to afford 12.
Yield: 85%. HRMS: m/z: calcd. for C14H22N4: 246.1839 [M]+; found:
2,3-Bis(mesitylimino)propionitrile (7): In a 50 mL three-necked flask
with magnetic stirrer, Dean-Stark-trap and reflux condenser, manga-
nese(IV)oxide (900 mg, 10.4 mmol; 4.7 equiv.) were added to benzene
(25 mL) and the suspension was refluxed for 8 h. Afterwards, 6
(692 mg, 2.2 mmol) was added and the mixture was refluxed for ad-
ditional 8 h. The hot solution was filtered through a G3-frit filled with
celite 500. The celite was washed three times with dichloromethane
(10 mL) and the organic layers were collected. The collected organic
layer was dried with anhydrous MgSO4, filtered and evaporated under
vacuo. Recrystallization from 2-propanol gave 7 (orange plates). Yield:
85%. HRMS: m/z: calcd. for C21H23N3: 317.1886 [M]+; found:
1
247.2023 [M + H]+. H NMR (300 MHz, CDCl3): δ [ppm), J (Hz)] =
7.76 (s, 1 H, HNp–CH), 3.25 (s, 2 H, HNp–CH2), 1.19 (s, 9 H, HNp–methyl),
0.99 (s, 9 H, HNp–methyl). 13C NMR (75 MHz, CDCl3): δ (ppm) = 171.6
(C imine), 130.3, 114.6, 113.8), 104.2, 58.6, 38.1, 34.3, 27.3, 27.2. FT-
IR (KBr): ν˜ = 3359, 3313, 2962, 2904. 2868, 2235 (CN), 2207 (CN),
1624, 1596, 1480, 1448, 1388, 1367, 1340, 1301, 1248, 1211, 980,
943, 914, 742, 644, 564 cm–1.
1
318.1975 [M + H]+. H NMR (300 MHz, CDCl3): δ [ppm, J (Hz)] =
8.24 (s, 1 H, HCH=N), 6.98 (s, 2 H, HMes–aryl), 6.96 (s, 2 H, HMes–Aryl),
2.33 (s, 6 H, HMes–methyl), 2.26 (s, 6 H, HMes–methyl), 2.15 (s, 6 H,
H
145.6, 144.1, 136.0, 135.7, 129.3, 129.2, 127.5, 125.2, 121.5 (CN),
109.4 (CCN), 20.8, 18.4, 17.9. FT-IR (KBr): ν˜ = 3368, 3319, 2963,
2913, 2854, 2729, 2231 (CN), 1721, 1622, 1609, 1476, 1376, 1353,
1246, 1201, 1139, 1054, 1016, 955, 935, 581, 830, 814, 730, 658, 582,
559, 500, 476, 419 cm–1.
N,NЈ-Dineopentyldiaminomaleonitrile (13): In a 250 mL two necked
flask, 12 (2100 mg, 8.5 mmol) was dissolved in methanol (60 mL). To
the solution, NaBH4 (450 mg, 8.5 mmol; 1 equiv.) was added in four
portions within 10 min and the mixture was stirred for half an hour.
The mixture was poured into ice cold water (200 mL). After warming
to room temperature, the precipitate was filtered through a glass frit
and recrystallized from diethyl ether to afford 13. Yield: 94%. HRMS:
m/z: calcd. for C14H24N4: 248.1995 [M]+; found: 249.2084 [M + H]+.
Mes–methyl). 13C NMR (75 MHz, CDCl3): δ (ppm) = 158.3 (C-imine),
1H NMR (300 MHz, CDCl3): δ [ppm, J (Hz)] = 3.35 (br. s, 2 H, HNH
)
N,NЈ-Dimesityldiaminomaleonitrile (8): In a 100 mL round bot-
tomed flask with magnetic stirrer and reflux condenser, 7 (3020 mg,
9.5 mmol) was added to methanol (10 mL). To the suspension, acetone
cyanohydrin (1210 mg, 14.3 mmol; 1.32 mL; 1.5 equiv.) and potas-
sium cyanide (10 mg) were added at room temperature. The mixture
was stirred overnight at 55 °C and then cooled in an ice bath. The
crude product was filtered through a glass frit and washed with 5 mL
ice cold methanol to yield 8 as an off white solid. Yield: 82%. HRMS:
m/z: calcd. for C22H24N4: 344.1995 [M]+; found: 345.2036 [M + H]+.
1H NMR (300 MHz, CDCl3): δ [ppm, J (Hz)] = 6.90 (s, 4 H,
HMes–Aryl), 4.80 (s, 2 H, HAmino), 2.26, (s, 6 H, HMes–p–Methyl), 2.25 (s,
12 H, HMes–o–methyl). 13C NMR (75 MHz, CDCl3): δ (ppm): = 136.7,
133.9, 129.7, 114.0 (CN), 111.6 (CCN), 20.8, 18.2. FT-IR (KBr): ν˜ =
3367, 3322, 3014, 2980, 2944, 2922, 2861, 2735, 2206 (CN), 1742,
1602, 1484, 1457, 1448, 1437, 1352, 1227, 1158, 1038, 1010, 891,
857, 822, 777, 706, 564, 502, 419 cm–1.
2.88 (d, J = 6.9 Hz, 4 H, HNp–Methylen), 0.94 (s, 18 H, HNp–methyl). 13C
NMR (75 MHz (CDCl3): δ (ppm) = 114.5 (C 5), 114.3 (C 4), 58.4
(C 3), 32.3 (C 2), 27.1 (C 1). FT-IR (KBr): ν˜ = 3361, 2956, 2867,
2200 (CN), 1596, 1486, 1384, 1340, 1298, 1209, 1141, 955, 911, 889,
742, 994, 559, 504 cm–1.
4,5-Dicyano-1,3-dineopentyl-2-(pentafluorophenyl)-2,3-dihydro-
imidazole (14): In a 4 mL screw cap vial with magnetic stirrer, 13
(1020 mg, 4.1 mmol) and pentafluorobenzaldehyde (1130 mg,
5.8 mmol; 1.4 equiv.) were added to glacial acetic acid (1 mL). The
vial was sealed and the mixture was stirred for 48 h at room tempera-
ture. The crude product was filtered through a glass frit, washed with
20 mL water and 5 mL of ice cold methanol. The product was dried
in high vacuo to afford 14. Yield: 91%. HRMS: m/z: calcd. for
C21H23F5N4: 426.1837 [M]+; found: 427.2657 [M + H]+. 1H NMR
(300 MHz, CDCl3): δ [ppm, J (Hz)] = 6.62 (s, 1 H, H–C2), 2.86 (d, 2
4,5-Dicyano-1,3-dimesityl-2-(pentafluorophenyl)-2,3-dihydro-imid- H, J = 15.0, HNp–methylen), 2.50 (d, J = 15.1 Hz, 2 H HNp–methylen),
azole (9): In a 25 mL three-necked flask with magnetic stirrer and 0.90 (s, 18 H, HNp–methyl). 13C NMR (75 MHz, CDCl3): δ (ppm) =
Z. Anorg. Allg. Chem. 2013, 1731–1739
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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