Organometallics
Article
m-C of PPh3), 121.2, 120.4, 119.5, 118.6, 117.1, 116.0, 112.4, 107.8,
14.4, 14.1. 31P{1H} NMR (DMSO-d6, 162 MHz, 23 °C) δ 33.4. IR
(KBr pellets, cm−1) ν 3427, 3131, 3051, 2921, 1958, 1605, 1550, 1501,
1478, 1458, 1435, 1408, 1354, 1325, 1280, 1217, 1185, 1155, 1093,
1048, 1032, 983, 844, 808, 793, 748, 698, 637, 620, 575, 527, 511, 462,
438. Anal. Calcd for C80H66Cl2N12P2Ru2: C, 62.78; H, 4.35; N, 10.98.
Found: C, 62.75; H, 4.37; N, 10.98.
initiates the catalytic reduction of the ketone substrates.
Unfortunately, the expected diruthenium(II) monohydride
and/or dihydride complex products were not successfully
isolated. The (CH2)3-linked bipyridine ligand may intensify the
cooperative interaction between the two Ru(II)-NNN
functionalities most effectively in the microenvironment,
remarkably enhancing the catalytic activity of complex 3d.
Synthesis of 3b. In a fashion similar to the synthesis of 3a, 1 (68.6
mg, 0.1 mmol) was reacted with 2b (8.5 mg, 0.05 mmol) afforded the
desired product as a dark orange solid (70 mg, 91%). Mp >300 °C dec.
1H NMR (DMSO-d6, 400 MHz, 23 °C) δ 8.48 (d, 4 H, 2‴-H), 8.09
(d, 2 H, 3-H), 7.60−7−65 (m, 4 H, 3‴-H), 7.55−7.58 (m, 2:2 H, 5″-H
and 8″-H), 7.45 (d, 2 H, 5-H), 7.40 (m, 2 H, 4-H), 7.20−7.24 (m, 2:18
H, 6″-H and Ph in PPh3), 7.01−7.08 (m, 14 H, 7″-H and Ph in PPh3),
6.38 (s, 2 H, 4′-H), 4.00 (s, 2 H, 7‴-H), 2.69 (s, 6 H, C3′-CH3), 2.53
(s, 6 H, C5′-CH3). 13C{1H} NMR (DMSO-d6, 100 MHz, 23 °C) δ
160.1, 156.7, 155.3, 146.1, 151.5, 146.9, 135.8, and 150.6 (Cq each),
149.8, 144.5, 133.0 (d, o-C of PPh3), 131.8 (d, i-C of PPh3), 129.3 (p-
C of PPh3), 127.6 (d, m-C of PPh3), 124.2, 120.5, 119.6, 118.7, 117.1,
116.1, 112.5, 107.9, 39.2, 14.5, 14.2. 31P{1H} NMR (DMSO-d6, 162
MHz, 23 °C) δ 33.4. IR (KBr pellets, cm−1) ν 3433, 3050, 2918, 1957,
1606, 1573, 1550, 1500, 1478, 1459, 1435, 1409, 1354, 1325, 1281,
1208, 1186, 1157, 1093, 1032, 1000, 982, 843, 791, 745, 626, 577, 527,
515, 499, 464, 435. Anal. Calcd for C81H68Cl2N12P2Ru2: C, 62.99; H,
4.44; N, 10.88. Found: C, 62.96; H, 4.40; N, 10.85.
Synthesis of 3c. In a fashion similar to the synthesis of 3a, 1 (68.6
mg, 0.1 mmol) was reacted with 2c (9.2 mg, 0.05 mmol) to afford the
desired product as an orange solid (70 mg, 90%). Mp >300 °C dec. 1H
NMR (DMSO-d6, 400 MHz, 23 °C) δ 8.45 (d, 4 H, 2‴-H), 8.08 and
7.57 (d each, 2:2 H, 3-H and 5-H), 7.63 (t, 2 H, 4-H), 7.44 and 7.32
(d each, 2:2 H, 5″-H and 8″-H), 7.20−7.24 (m, 22 H, 3‴-H and Ph in
PPh3), 7.05−7.09 (m, 14 H, 6″-H and Ph in PPh3), 6.98 (t, 2 H, 7″-
H), 6.38 (s, 2 H, 4′-H), 2.95 (s, 4 H, 7‴-H), 2.70 (s, 6 H, C3′-CH3),
2.53 (s, 6 H, C5′-CH3). 13C{1H} NMR (DMSO-d6, 100 MHz, 23 °C)
δ 160.1, 156.7, 155.3, 146.1, 151.5, 146.9, 135.8, and 149.7 (Cq each),
149.4, 144.5, 132.9 (d, o-C of PPh3), 131.8 (d, i-C of PPh3), 129.2 (p-
C of PPh3), 127.6 (d, m-C of PPh3), 123.9, 120.5, 119.5, 118.6, 117.1,
116.1, 112.4, 107.8, 34.5, 14.4, 14.1. 31P{1H} NMR (DMSO-d6, 162
MHz, 23 °C) δ 33.5. IR (KBr pellets, cm−1) ν 3424, 3052, 1962, 1606,
1573, 1551, 1500, 1477, 1458, 1435, 1410, 1355, 1326, 1280, 1226,
1186, 1157, 1093, 1048, 1032, 1000, 982, 844, 823, 792, 748, 698, 620,
578, 527, 499, 462, 435. Anal. Calcd for C82H70Cl2N12P2Ru2: C, 63.19;
H, 4.53; N, 10.78. Found: C, 63.25; H, 4.51; N, 10.77.
CONCLUSIONS
■
In summary, dinuclear ruthenium(II)-NNN pincer complexes
were constructed by assembly of a 16-electron coordinatively
unsaturated mononuclear Ru(II)-NNN pincer complex and the
4,4′-linked bipyridine ligands. The 4,4′-(CH2)3-bipyridine
ligand bestows the assembled diruthenium(II)-NNN pincer
complex with exceptionally high catalytic activity for the
transfer hydrogenation of ketones due to the cooperative
interaction between the two Ru(II)-NNN functionalities. The
present work provides a concise route to highly active transition
metal complex catalysts.
EXPERIMENTAL SECTION
■
General Considerations. All of the manipulations of air- and/or
moisture-sensitive compounds were carried out under nitrogen
atmosphere using standard Schlenk techniques. The solvents were
dried and distilled prior to use by literature methods. 1H and 13C{1H}
NMR spectra were recorded on a Bruker DRX-400 spectrometer, and
all chemical shift values refer to δTMS = 0.00 ppm, CDCl3 (δ(1H) =
7.26 ppm; δ(13C) = 77.16 ppm) and DMSO-d6 (δ(1H) = 2.50 ppm;
δ(13C) = 39.52 ppm). Elemental and HRMS analysis were achieved by
the Analysis Center, Dalian University of Technology and Dalian
Institute of Chemical Physics, Chinese Academy of Sciences. All
melting points were uncorrected. TLC analysis was performed using
glass-backed plates coated with 0.2 mm silica gel. Flash column
chromatography was performed on silica gel (200−300 meshes). All
chemical reagents were purchased from commercial sources and used
as received unless otherwise indicated. Compound 2b was prepared by
a literature method, and its spectroscopic features are in good
agreement with those reported in the literature.24
X-ray Crystallographic Studies. X-ray diffraction studies for
compound 3d were carried out on a SMART APEX diffractometer
with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). Cell
parameters were obtained by global refinement of the positions of all
collected reflections. Intensities were corrected for Lorentz and
polarization effects and empirical absorption. The structures were
solved by direct methods and refined by full-matrix least-squares on F2.
All non-hydrogen atoms were refined anisotropically. All hydrogen
atoms were placed in calculated positions. Structure solution and
refinement were performed using the SHELXL-97 package. The X-ray
crystallographic files, in CIF format, are available from the Cambridge
Crystallographic Data Centre upon quoting the deposition number
Synthesis of 3d. In a fashion similar to the synthesis of 3a, 1 (68.6
mg, 0.1 mmol) was reacted with 2d (9.9 mg, 0.05 mmol) to afford the
1
desired product as a red solid (72 mg, 92%). Mp >300 °C dec. H
NMR (DMSO-d6, 400 MHz, 23 °C) δ 8.45 (d, 4 H, 2‴-H), 8.12 and
7.61 (d each, 2:2 H, 3-H and 5-H), 7.67 (t, 2 H, 4-H), 7.47 and 7.36
(d each, 2:2 H, 5″-H and 8″-H), 7.20−7.26 (m, 22 H, 3‴-H and Ph in
PPh3), 7.16 (t, 2 H, 6″-H), 7.05−7.10 (m, 14 H, 7″-H and Ph in
PPh3), 6.39 (s, 2 H, 4′-H), 2.70 (s, 6 H, C3′-CH3), 2.63 (t, 4 H, 7‴-
H), 2.54 (s, 6 H, C5′-CH3), 1.93 (m, 2 H, 8‴-H). 13C{1H} NMR
(DMSO-d6, 100 MHz, 23 °C) δ 160.1, 156.7, 155.3, 146.1, 151.5,
146.9, 135.8 and 150.5 (Cq each), 149.5, 144.5, 132.9 (d, o-C of
PPh3), 131.8 (d, i-C of PPh3), 129.2 (p-C of PPh3), 127.6 (d, m-C of
PPh3), 123.9, 120.5, 119.6, 118.6, 117.1, 116.1, 112.4, 107.9, 33.7
(C7‴), 30.0 (C8‴), 14.4, 14.1. 31P{1H} NMR (DMSO-d6, 162 MHz,
23 °C) δ 33.3. IR (KBr pellets, cm−1) ν 3421, 3053, 2953, 1963, 1606,
1573, 1551, 1500, 1477, 1459, 1435, 1410, 1385, 1355, 1326, 1281,
1224, 1186, 1158, 1092, 1049, 1032, 1001, 981, 926, 888, 844, 798,
748, 698, 618, 598, 579, 527, 499, 435. Anal. Calcd for
C83H72Cl2N12P2Ru2: C, 63.39; H, 4.61; N, 10.69. Found: C, 63.35;
H, 4.65; N, 10.67.
Typical Procedure for the Synthesis of Complexes 3 and 5.
Synthesis of Complex 3a. Under a nitrogen atmosphere, a mixture of
complex 1 (68.6 mg, 0.1 mmol) and ligand 2a (7.8 mg, 0.05 mmol) in
3 mL of CH2Cl2/CH3OH (v/v, 5:1) was stirred at 25 °C for 5 h. All of
the volatiles were removed under reduced pressure, and the resultant
residue was subjected to purification by recrystallization in CH2Cl2/n-
hexane (v/v, 1:3) at ambient temperature, affording complex 3a as a
1
purple solid (71 mg, 93%). Mp >300 °C dec. H NMR (DMSO-d6,
400 MHz, 23 °C) δ 8.72 (d, 4 H, 2‴-H), 8.07 and 7.57 (d each, 2:2 H,
3-H and 5-H), 7.82 (d, 4 H, 3‴-H), 7.62 (t, 2 H, 4-H), 7.43 and 7.31
(d each, 2:2 H, 5″-H and 8″-H), 7.19−7.23 (m, 18 H, Ph in PPh3),
7.04−7.07 (m, 2:12 H, 6″-H and Ph in PPh3), 6.98 (t, 2 H, 7″-H), 6.37
(s, 2 H, 4′-H), 2.68 (s, 6 H, C3′-CH3), 2.52 (s, 6 H, C5′-CH3).
13C{1H} NMR (DMSO-d6, 100 MHz, 23 °C) δ 160.1, 156.6, 155.3,
146.1, 151.5, 147.0, 135.7 and 144.4 (Cq each), 150.5, 144.3, 132.9 (d,
o-C of PPh3), 131.7 (d, i-C of PPh3), 129.2 (p-C of PPh3), 127.5 (d,
Synthesis of 3e. In a fashion similar to the synthesis of 3a, 1 (68.6
mg, 0.1 mmol) was reacted with 2e (9.1 mg, 0.05 mmol) to afford the
desired product as a dark purple solid (72 mg, 93%). Mp >300 °C dec.
1H NMR (DMSO-d6, 400 MHz, 23 °C) δ 8.60 (d, 4 H, 2‴-H), 8.07
and 7.56 (d each, 2:2 H, 3-H and 5-H), 7.61 (m, 2:4 H, 4-H and 3‴-
H), 7.53 (s, 2 H, 7‴-H), 7.44 and 7.31 (d each, 2:2 H, 5″-H and 8″-
H), 7.19−7.24 (m, 18 H, Ph in PPh3), 7.04−7.11 (m, 2:12 H, 6″-H
F
Organometallics XXXX, XXX, XXX−XXX