N. Raja, B. Therrien / Journal of Organometallic Chemistry 765 (2014) 1e7
5
Scheme 4. Proposed mechanism for the catalytic rearrangement of aldoximes to amides (left cycle) from complexes 1e3 (M ¼ Ru, Rh, Ir; Ln ¼ ligands), showing the release and
reinsertion of an imine intermediate (right cycle).
used as received. The starting materials [(
Cl)2Cl2), [( -Cl)2Cl2] and [(
5-C5Me5)2Rh2( 5-C5Me5)2Ir2(
were prepared according to published methods [33,34]. The 1H, 13
h
6-p-cymene)2Ru2(
-Cl)2Cl2]
m
-
yellowered powder was filtered and washed with hexane, and
purified using column chromatography.
h
m
h
m
C
Complex 1, yellow solid (silica gel, chloroform:methanol,
{1H} and 2D NMR spectra were recorded with a Bruker Avance II
400 MHz spectrometer. Infrared spectra were recorded in the range
of 4000e400 cmꢀ1 as KBr pellets with a PerkineElmer FTIR 1720 X
spectrometer. Electrospray mass spectra were obtained in positive
ion mode with a LCQ Finnigan mass spectrometer. Microanalyzes
were carried out by the Mikroelementaranalytisches Laboratorium,
ETH Zürich (Switzerland). UVevisible absorption spectra were
recorded with an Uvikon 930 spectrophotometer (10ꢀ4 M in
CH2Cl2).
9.9:0.1). Yield: 84%. IR (KBr,
n
, cmꢀ1): 1562 (CH]N), 1350 (CeO). 1H
NMR (400 MHz, MeOD, 25 ꢁC):
d
(ppm) ¼ 7.49 (d, 3JHH ¼ 8.0 Hz, 2H,
Har), 7.39 (s, 4H, Har), 7.23 (d, 2H, Har), 6.00 (s, 2H, CH), 5.46 (d,
3JHH ¼ 4.8 Hz, 4H, Hp-cym), 5.06 (d, 2H, Hp-cym), 4.24 (d, 2H, Hp-cym),
4.17 (s, 2H, CH2), 2.56 (sept, 3JHH ¼ 6.8 Hz, 2H, CH(CH3)2), 2.14 (s, 6H,
CH3), 2.12 (s, 6H, CH3), 1.92 (s, 6H, CH3), 1.16 (d, 6H, CH(CH3)2), 1.09
(d, 6H, CH(CH3)2). 13C{1H} NMR (100 MHz, MeOD, 25 ꢁC):
d
(ppm) ¼ 178.0 (CeO), 170.2 (C]N), 165.2 (C]O), 161.6 (Car), 153.8
(Car), 139.6 (Car), 129.5 (Car), 128.8 (Car), 105.9 (Clactone), 102.6 (Cp-
cym), 100.4 (Cp-cym), 95.3 (Cp-cym), 85.9 (Cp-cym), 84.6 (Cp-cym), 80.5
(Cp-cym), 40.2 (CH2), 30.1 (CH(CH3)2), 22.7 (CH3), 21.3 (CH3), 20.2
(CH3), 17.8 (CH3), 16.8 (CH3). MS (ESI positive mode): m/z 1003.4
[M ꢀ Cl]þ. Anal. Calcd for C49H52Cl2N2O6Ru2: C, 56.70; H, 5.05; N
2.70. Found: C, 56.70; H, 5.05; N 2.81.
General procedure for the synthesis of the ligand precursor (LH2)
The
ligand
precursor
3,30-[(1E,10E)-{(methylenebis(4,1-
phenylene))bis(azanylyli-dene)}bis(ethan-1-yl-1-ylidene)]bis(4-
hydroxy-6-methyl-2H-pyran-2-one) (LH2) was synthesized by
treating a methanolic solution of 4,40-methylenedianiline and 2
equivalents of 3-acetyl-2-hydroxy-6-methyl-4H-pyran-4-one at
reflux for 2 h. The product was obtained as a white solid, and pu-
rified using column chromatography (silica gel, hexane:chloroform,
Complex 2, reddish-brown solid (silica gel, chlor-
oform:methanol, 9.5:0.5). Yield 85%. FTIR (KBr, n
, cmꢀ1): 1554
(CH]N), 1347 (CeO). 1H NMR (400 MHz, MeOD, 25 ꢁC):
d
(ppm) ¼ 7.41 (d, 3JHH ¼ 8.0 Hz, 2H, Har), 7.33 (d, 4H, Har), 7.24 (d,
2H, Har), 6.06 (s, 2H, CH), 4.07 (d, 2H, CH2), 2.18 (s, 6H, CH3), 2.17 (s,
6H, CH3), 1.31 (s, 30H, Hcp*). 13C{1H} NMR (100 MHz, MeOD, 25 ꢁC):
3:1). Yield: 80%. 1H NMR (400 MHz, CDCl3, 25 ꢁC):
d
(ppm) ¼ 7.27 (d,
d
(ppm) ¼ 178.9 (CeO), 172.0 (C]N), 165.7 (C]O), 161.6 (Car), 149.4
3JHH ¼ 8.4 Hz, 4H, Har), 7.12 (d, 4H, Har), 5.76 (s, 2H, CH), 4.05 (s, 2H,
(Car), 139.9 (Car), 129.7 (Car), 128.7 (Car), 125.3 (Car), 124.56 (Car),
107.2 (Clactone), 106.7 (Clactone), 94.2 (Ccp*), 40.2 (CH2), 24.3 (CH3),
22.2 (CH3), 19.2 (CH3), 17.9 (CH3), 7.2 (Ccp*). MS (ESI positive mode):
m/z 1007.9 [M ꢀ Cl]þ. Anal. Calcd for C49H54Cl2O6Rh2$0.5H2O: C,
55.91; H, 5.27; N 2.66. Found: C, 55.85; H, 5.22; N 2.72.
CH2), 2.60 (s, 6H, CH3), 2.16 (s, 6H, CH3). 13C{1H} NMR (100 MHz,
CDCl3, 25 ꢁC):
d
(ppm) ¼ 184.9 (CeO), 175.3 (C]N), 163.4 (C]O),
140.4 (Car), 134.7 (Car), 130.0 (Car), 125.8 (Car), 107.1 (Clactone), 97.4
(Clactone), 40.9 (CH2), 20.3 (CH3), 19.9 (CH3). MS (ESI positive mode):
m/z 521.6 [M þ Na]þ.
Complex 3, yellow solid (silica gel, chloroform). Yield 70%. FTIR
(KBr,
n
, cmꢀ1): 1554 (CH]N), 1347(CeO). 1H NMR (400 MHz, CDCl3,
3
General procedure for the synthesis of complexes 1e3
25 ꢁC):
d
(ppm) ¼ 7.96 (s, 2H, Har), 7.17 (d, JHH ¼ 7.2 Hz, 4H, Har),
6.75 (d, 2H, Har), 5.93 (s, 2H, CH), 4.01 (d, 2H, CH2), 2.22 (d, 6H, CH3),
A
dichloromethane solution of the ligand precursor LH2
2.09 (s, 6H, CH3), 1.26 (s, 30H, Hcp*). 13C{1H} NMR (100 MHz, CDCl3,
(1 mmol) was stirred with triethylamine (1 mL) for 1 h. Then to the
solution, the corresponding chloro bridged dimeric complex
(1 mmol) was added and the mixture was stirred for another 11 h at
room temperature. A color change of the solution from dark red to
yellow was observed. The solution was concentrated to 2 mL, and
hexane was added to initiate precipitation of the complex. The
25 ꢁC):
d
(ppm) ¼ 177.3 (CeO), 169.8 (C]N), 164.4 (C]O), 161.2
(Car), 150.5 (Car), 139.5 (Car), 129.8 (Car), 125.6 (Car), 106.9 (Clactone),
102.4 (Clactone), 85.6 (Ccp*), 40.2 (CH2), 25.6 (CH3), 19.6 (CH3), 8.5
(Ccp*). MS (ESI positive mode): m/z 1205.4 [M ꢀ Cl þ H2O]þ. Anal.
Calcd for C49H54Cl2Ir2N2O6$2H2O: C, 46.77; H, 4.65; N 2.23. Found:
C, 46.47; H, 4.41; N 2.25.