´
139
B.Ð. Glišic et al. / Polyhedron 105 (2016) 137–149
room temperature and made alkaline with a solution of 20 g of
NaOH in 33 mL of water.
2.3.1. Mixture of 1,7,11,11-tetramethyl-1,2,3,4-tetrahydro-1,4-
methanophenazine (L1) and 1,8,11,11-tetramethyl-1,2,3,4-
tetrahydro-1,4-methanophenazine (L2)
M.p. 59.4 °C; Rf = 0.22, Hex:Et2O (4:1, v/v); RI(HP-5MS) = 2008
(L2) and 2010 (L1); EI-MS (70 eV), m/z (rel. int.): 252 [M]+Å (91),
237 [MꢀCH3]+ (48.5), 223 (18.3), 209 (100), 195 (34.9), 182 (4.9),
168 (2.5), 143 (2.8), 128 (1.2), 111 (5.4), 104 (6), 89 (9.9), 77
(3.9), 65 (3.5), 51 (1.8), 41 (3.9). FTIR-ATR (neat) cmꢀ1: 2955
The reduction product of compound 4b, 3-methylbenzene-1,2-
diamine (5b), was isolated from the reaction mixture by steam dis-
tillation. Compound 5b was ‘‘salted out” by saturating the distillate
with NaCl and extracted with Et2O. Combined ethereal layers were
dried over anhydrous MgSO4 and concentrated under reduced
pressure. Since it was impossible to separate 4-methylbenzene-
1,2-diamine (5a) by steam distillation, this diamine was directly
‘‘salted out” from the reaction mixture and extracted with Et2O.
After the evaporation of the solvent, the crude 5a was purified by
sublimation. The yield was 83.5% (6.72 g) and 85.8% (6.92 g) for
compound 5a and 5b, respectively.
(
m
as(CH3)), 2924 (
1513 ( (Car@Car) and
1382, 1367 (ds(CH3)), 1332, 1264, 1174, 1106, 1074, 834, 802. UV
kmax (CH3CN) nm (log ): 316 (3.93), 242 (4.40), 206 (4.70). Anal.
m
as(CH2)), 2877 (
ms(CH3)), 2866 (ms(CH2)), 1601,
m
m(Car@N)), 1451 (das(CH3) and dsc(CH2)),
e
Calc. for the mixture = C17H20N2 (Mr = 252.35); C, 80.91; H, 7.99;
N, 11.10. Found: C, 80.62; H, 8.03; N, 11.35%.
2.2.3. ( )-Camphorquinone (7)
2.3.2. 1,9,11,11-Tetramethyl-1,2,3,4-tetrahydro-1,4-
A modified procedure of White and coworkers was applied [29].
methanophenazine (L3)
A
mixture of ( )-camphor (6; 20.0 g, 0.13 mol), SeO2 (8.0 g,
Rf = 0.26, Hex:Et2O (4:1, v/v); RI(HP-5MS) = 1959; EI-MS
(70 eV), m/z (rel. int.): 252 [M]+Å (80.2), 237 [MꢀCH3]+ (41.5), 223
(17.5), 209 (100), 195 (32.8), 182 (4.5), 168 (2.3), 143 (1.9), 128
(1.3), 116 (3.9), 104 (4.5), 89 (9.6), 77 (3.4), 65 (3.2), 51 (1.5), 41
0.07 mol) and Ac2O (14.0 mL) was stirred under reflux for 1 h. Then
the reaction mixture was cooled to room temperature, and an addi-
tional portion of SeO2 (8.0 g, 0.07 mol) was added. The mixture was
again heated to reflux, and two further batches of SeO2 (8.0 g,
0.07 mol) were added at 2.5-h and 6-h intervals. After the reaction
mixture was refluxed for additional 4 h, during that time precipita-
tion of Se was observed, it was cooled to ambient temperature and
subsequently 200 mL of EtOAc were added. The gray precipitate
was removed by filtration, and the filtrate was diluted with
100 mL of toluene. The filtrate was concentrated under reduced
pressure and that yielded crude ( )-camphorquinone as a yellow-
orange solid which was then dissolved in 200 mL of EtOAc, and
the solution was filtered by vacuum filtration through CeliteÒ.
The filtrate was successively washed with 200 mL of 10% aq. NaOH
and 100 mL of saturated aq. NaCl solution. The organic layer was
dried over anhydrous MgSO4, filtered, and concentrated in vacuo
to afford a reasonably pure (according to GC–MS) yellow crys-
talline ( )-camphorquinone (14 g, 64.1%) which was used in the
following reactions without purification.
(3.6). FTIR-ATR (neat) cmꢀ1: 2958 (
2871 ( s(CH3) and
(Car@N)), 1451 (das(CH3) and dsc(CH2)), 1391, 1371 (ds(CH3)),
1329, 1263, 1173, 1110, 1079, 796, 762; UV kmax (CH3CN) nm
(log ): 316 (3.86), 243 (4.52), 204 (4.64). Anal. Calc. for
m
as(CH3)), 2925 (
mas(CH2)),
m
m
s(CH2)), 1587, 1513, 1474 ( (Car@Car) and
m
m
e
L3 = C17H20N2 (Mr = 252.35); C, 80.91; H, 7.99; N, 11.10. Found: C,
80.73; H, 7.95; N, 11.32%.
2.3.3. 1,6,11,11-Tetramethyl-1,2,3,4-tetrahydro-1,4-
methanophenazine (L4)
M.p. 82.9 °C; Rf = 0.36, Hex:Et2O (4:1, v/v); RI(HP-5MS) = 1973;
EI-MS (70 eV), m/z (rel. int.): 252 [M]+Å (92.7), 237 [MꢀCH3]+ (50.4),
223 (18.4), 209 (100), 195 (34.6), 182 (4.7), 168 (2.6), 143 (2.2), 128
(1.3), 116 (4), 104 (4.6), 89 (9.6), 77 (3.3), 65 (2.9), 51 (1.4), 41 (3.2).
FTIR-ATR (neat) cmꢀ1: 2956 (
s(CH3) and s(CH2)), 1587, 1513 (
1474, 1449 (das(CH3) and ds(CH2)), 1389, 1370 (ds(CH3)), 1264,
1171, 1118, 1093, 1069, 793, 760. UV kmax (CH3CN) nm (log ):
mas(CH3)), 2925 (
mas(CH2)), 2868
(m
m
m
(Car@Car) and
m
(Car@N)),
e
2.3. 1,x,11,11-Tetramethyl-1,2,3,4-tetrahydro-1,4-methanophenazine
(x = 7, 8, 9 and 6 for L1–L4, respectively)
316 (3.93), 244 (4.58), 204 (4.71). Anal. Calc. for L4 = C17H20N2
(Mr = 252.35); C, 80.91; H, 7.99; N, 11.10. Found: C, 81.04; H,
7.85; N, 11.11%.
A modified procedure of Fitchett and Steel was applied [30].
Camphorquinone (7; 3.32 g, 20 mmol) and the corresponding dia-
mine (5a or 5b; 2.44 g, 20 mmol) were refluxed in glacial AcOH
(40 mL) for 1 h. The reaction mixture was then neutralised with
10% aq. NaOH and extracted with Et2O. The combined ethereal
extracts, dried over anhydrous MgSO4, were concentrated under
Retention data for all synthetic intermediates are given in
Table S1.
2.4. Synthesis of the gold(III) complexes 1–4
Gold(III) complexes with ligands L1–L4 were synthesized
according to the modified procedure published in the literature
for the preparation of [AuCl3(N-heterocycle)] complexes (heterocy-
cle is the monodentate pyridazine, pyrimidine, pyrazine, quinoxa-
line and phenazine) [25,26].
reduced pressure to give
standing.
a brown oil, which solidified on
The products of condensation of 7 with diamine 5b (4.30 g,
85.31%), ligands L3 and L4, were separated by column chromatog-
raphy on SiO2 applying a Hex:Et2O (4:1) mixture as the mobile
phase. Ligand L4 was obtained as a colorless crystalline solid, while
ligand L3 formed a pale yellow semi-solid.
Ligands L1 and L2 (4.26 g, 84.56%) obtained by the condensa-
tion of 7 with diamine 3a almost completely co-eluted on both
the used GC column (HP5-MS) and TLC (SiO2) plate. TLC was
run with a number of mobile phases of varying polarity but with
no success in better separating the two ligands. Thus, L1 and L2,
were only separated from the unreacted camphorquinone (7)
and diamine 3a by ‘‘dry-flash” column chromatography using a
gradient of Et2O and Hex (from pure Hex to 10% Et2O in Hex
with an increment step of 5%, v/v). The inseparable mixture of
ligands L1 and L2 was obtained in the form of a pale yellow
powder.
The solution of 0.5 mmol of a solid mixture, which contained
approximately equal amounts of L1 and L2 (0.55:0.45 M ratio,
according to a 1H NMR analysis), as well as, separately, of ligands
L3 and L4 (126.2 mg) in 10.0 mL of ethanol was added slowly
under stirring to the solution containing an equimolar amount of
K[AuCl4] (188.9 mg in 10.0 mL of ethanol). The resulting yellow
solution was stirred in the dark at ambient temperature for 24 h.
The yellow precipitate, formed after standing of this solution in a
refrigerator overnight, was filtered off, washed with water and
then recrystallized from dichloromethane to form yellow crystals
of gold(III) complexes. These crystals were collected from the solu-
tion and dried in the dark at ambient temperature. The pure com-
plexes of L1 and L2 with Au(III), [AuCl3(L1)] (1) and [AuCl3(L2)] (2),
were isolated by the means of a fractional crystallization from