Inorganic Chemistry
Article
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77.24; H, 5.92; N, 5.45; P, 11.62. 1H NMR (CDCl3, 500 MHz): δ 7.46
(m, 8H), 7.34 (m, 12H), 6.61 (m, 2H), 6.41 (m, 2H), 4.66 (s, 2H),
3.81 (d, J = 5.52 Hz, 4H). 13C NMR (CDCl3, 76 MHz): δ 142.14 (d, J
= 4.77 Hz, 2C), 137.32 (d, J = 12.79 Hz, 4C), 132.99 (d, J = 18.10 Hz,
8C), 129.08 (s, 4C), 128.74 (d, J = 6.60 Hz, 8C), 119.18 (s, 2C),
106.27 (s, 2C), 77.98 (t, J = 7.02 Hz, 1C), 50.73 (d, J = 7.69 Hz, 2C).
31P NMR (CDCl3, 146 MHz): δ −25.00 (s, 2P).
P, 11.60; Pd, 13.28. Found: C, 49.17; H, 3.75; N, 3.57; P, 11.30. H
NMR (CD3CN, 500 MHz): δ 7.99 (m, 8H), 7.71 (m, 2H), 7.67 (m,
4H), 7.61 (m, 8H), 7.58 (m, 2H), 5.45 (vt, J = 3.34 Hz, 4H). 13C
NMR (CD3CN, 126 MHz): δ 178.82 (t, J = 5.78 Hz, 1C), 134.37 (vt,
J = 7.31 Hz, 8C), 134.15 (t, J = 6.36 Hz, 2C), 133.68 (s, 4C), 130.53
(vt, J = 5.77 Hz, 8C), 127.99 (t, J = 25.22 Hz, 4C), 126.63 (s, 2C),
114.20 (s, 2C), 52.43 (vt, J = 17.67 Hz, 2C). 31P NMR (CD3CN, 203
MHz): δ 38.16 (s, 2P), −144.00 (sept, J = 706.89 Hz, 1P). 19F NMR
(CD3CN, 235 MHz): δ −72.89 (d, J = 706.26 Hz, 6F). ESI MS: m/z
647.3 ([C66H57ClN4OP4Pd2]2+, [(PCBImP)2Pd2Cl(OH)]2+), 656.2
([C33H28ClN2P2Pd]+, [PCBImPPdCl]+). FAB MS: m/z 655.4
([C33H28ClN2P2Pd]+, [PCBImPPdCl]+). HRMS. Calcd: m/z
655.04456. Found: m/z 655.04491 ([C33H28ClN2P2Pd]+,
[PCBImPPdCl]+).
1,3-Bis(diphenylphosphinomethylene)benzimidazolium
Hexafluorophosphate (5). To a colorless solution of 4 (710.0 mg,
1.35 mmol, 1.00 equiv) in 17 mL of degassed dry THF cooled to −78
°C was added in one portion triphenylcarbenium hexafluorophosphate
(510.0 mg, 1.31 mmol, 0.97 equiv). The mixture was stirred for 30 min
with warming to room temperature. After the reaction was complete,
the amount of THF was reduced in vacuo, and the product was
precipitated by the addition of 15 mL of degassed dry toluene. The
formed suspension was stirred overnight at room temperature and
filtered via cannula. The crude solid product was then redissolved in
THF, filtered through a syringe filter, and precipitated by the addition
of diethyl ether. Recrystallization of the precipitate from THF/Et2O
(2:8) at −40 °C yielded 790.0 mg (86%) of pure colorless crystalline
material 5. Anal. Calcd for C33H29F6N2P3: C, 60.01; H, 4.43; F, 17.26;
1,3-Bis(diphenylphosphinomethylene)benzimidazol-2-ylr-
hodium Carbonyl Hexafluorophosphate (8). A solution of 1,3-
bis(diphenylphosphinomethylene)benzimidazol-2-ylrhodium acetoni-
trile hexafluorophosphate (6b; 23.0 mg, 0.03 mmol, 1.00 equiv) in
0.5 mL of PO was pressurized with 2 bar of 13CO in a Young valve
NMR tube. After 2 h, the tube containing the reaction mixture was
flushed with degassed diethyl ether. Crystallization gave 20.0 mg
(98%) of 8 in the form of light-yellow needles. Anal. Calcd for
C34H28F6N2OP3Rh: C, 51.66; H, 3.57; F, 14.42; N, 3.54; O, 2.02; P,
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N, 4.24; P, 14.07. Found: C, 60.31; H, 4.62; N, 4.38; P, 14.06. H
NMR (CD3CN, 500 MHz): δ 8.69 (s, 1H), 7.67 (m, 2H), 7.53 (m,
2H), 7.41 (m, 20H), 5.15 (d, J = 5.35 Hz, 4H). 13C NMR (CD3CN,
126 MHz): δ 140.61 (t, J = 3.91 Hz, 1C), 134.47 (d, J = 12.27 Hz,
4C), 133.91 (d, J = 19.87 Hz, 8C), 132.30 (s, 2C), 131.24 (s, 4C),
130.13 (d, J = 7.18 Hz, 8C), 127.90 (s, 2C), 114.76 (s, 2C), 47.55 (d, J
= 20.95 Hz, 2C). 31P NMR (CD3CN, 202 MHz): δ −14.05 (s, 2P),
−144.00 (sept, J = 706.71 Hz, 1P). 19F NMR (CD3CN, 471 MHz): δ
−72.80 (d, J = 706.82 Hz, 6F).
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11.76; Rh, 13.02. Found: C, 51.28; H, 4.02; N, 3.21; P, 11.36. H
NMR (CD3CN, 300 MHz): δ 7.82 (m, 8H), 7.65 (m, 2H), 7.59 (dq, J
= 14.30 and 7.27 Hz, 12H), 7.50 (m, 2H), 5.37 (vt, J = 3.14 Hz, 4H).
13C NMR (CD3CN, 126 MHz): δ 197.21 (dt, J = 40.48 and 12.63 Hz,
1C), 195.96 (s, 1C), 134.71 (vt, J = 5.69 Hz, 2C), 134.00 (vt, J = 7.59
Hz, 8C), 132.90 (s, 4C), 132.01 (vt, J = 23.45 Hz, 4C), 130.45 (vt, J =
5.48 Hz, 8C), 126.09 (s, 2C), 125.74 (s, C, free CO), 113.85 (s, 2C),
54.31 (vt, J = 17.61 Hz, 2C). 31P NMR (CD3CN, 203 MHz): δ 55.41
(d, J = 138.49 Hz, 2P), −144.00 (sept, J = 707.27 Hz, 1P). 19F NMR
(CD3CN, 471 MHz): δ −72.60 (d, J = 706.73 Hz, 6F). ESI MS. m/z
617.4 ([C33H28N2P2Rh]+, [PCBImPRh]+), 633.3 ([C33H28N2OP2Rh]+,
[PCBImPORh]+), 645.4 ([C34H28N2OP2Rh]+, [PCBImPRhCO]+), 649.3
([C33H28N2O2P2Rh]+, [OPCBImPORh]+). IR: νC−O 1995.34 cm−1.
1,3-Bis(diphenylphosphinomethylene)benzimidazol-2-ylr-
hodium Ethylene Hexafluorophosphate (9). The ethylene gas
was introduced to the solution of 6b in a Young NMR tube.
Subsequently, the color of the mixture changed slightly to a maize
yellow; after 2 h, the 31P NMR spectra were recorded. Reaction of 6b
with ethylene leads to the reversible formation of 9 in PO, CH2Cl2,
and THF solutions at 25 °C. In all cases, the removal of volatile
components led to the formation of 6b, and complex 9 could not be
isolated. Crystallization directly from the reaction mixture did not give
the crystalline product 9.
Bis[1,3-bis(diphenylphosphinomethylene)benzimidazol-2-
ylrhodium] μ-Hydride Hexafluorophosphate (10). 6b (17.4 mg,
0.02 mmol, 1.00 equiv) was added to a biphasic solution of KHCO3
(62.6 mg, 0.62 mmol, 30.00 equiv) in 0.75 mL of degassed water and
3.5 mL of degassed THF. The autoclave was pressurized with 10 bar of
H2 and 30 bar of CO2 and thermostated at 60 °C. After 48 h, all
volatiles were removed in vacuo. The product was then redissolved in
acetone and filtered via a syringe filter. After the addition of diethyl
ether to an acetone solution, filtration, and drying of precipitate, the
terra-cotta-colored amorphous compound 10 (27.4 mg, 96%) was
obtained. Anal. Calcd for C66H57F6N4P5Rh2 (+1.00 equiv of C4H10O):
C, 57.78; H, 4.64; F, 7.83; N, 3.85; O, 1.10; P, 10.64; Rh, 14.15.
Found: C, 57.39; H, 5.06; N, 3.49; P, 10.27. Compound 10 can also be
synthesized by stirring of 6b in a THF suspension containing excess
1,3-Bis(diphenylphosphinomethylene)benzimidazol-2-ylr-
hodium Acetonitrile/Dimethyl Sulfoxide Hexafluorophos-
phate (6). 5 (480.0 mg, 0.7 mmol, 1.00 equiv) was added to the
solution of [μ-OCH3Rh(COD)]2 (170.0 mg, 0.35 mmol, 0.50 equiv)
in 10 mL of degassed THF at room temperature and stirred for 17 h.
After the reaction was complete, all volatiles were removed in vacuo.
The formed amorphous solid was then redissolved in DMSO (for 6a)
or in CH3CN (for 6b) and stirred for 3 h under a H2 atmosphere (0.5
bar over the atmospheric pressure). The reaction mixture was filtered
through a 0.20 μm syringe filter, and the solvent was partially reduced
in vacuo. The yellow needle-shaped crystals of substance 6a (450.0
mg, 76%) were obtained by the addition of diethyl ether after 10 days.
The yellow crystals of substance 6b (340.0 mg 61%) were obtained by
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the addition of diethyl ether. 6a. H NMR ((CD3)2SO, 300 MHz): δ
7.89 (m, 8H), 7.60 (m, 14H), 7.41 (m, 2H), 5.32 (m, 4H). 31P NMR
((CD3)2SO, 203 MHz): δ 48.23 (d, J = 151.08 Hz, 2P), −144.00
(sept, J = 711.40 Hz, 1P). 6b. Anal. Calcd for C35H31F6N3P3Rh (+0.20
equiv of C2H3N): C, 53.46; H, 4.00; F, 14.33; N, 5.63; P, 11.68; Rh,
12.94. Found: C, 53.44; H, 4.85; N, 5.24; P, 11.51. 1H NMR (CD3CN,
360 MHz): δ 7.80 (m, 8H), 7.54 (m, 12H), 7.40 (m, 2H), 7.30 (m,
2H), 4.97 (vt, J = 3.04 Hz, 4H). 13C NMR (CD3CN, 126 MHz): δ
198.96 (dt, J = 51.2 and 11.9 Hz, 1C), 134.93 (t, J = 6.0 Hz, 2C),
134.25 (t, J = 20.0 Hz, 4C), 133.76 (vt, J = 7.7 Hz, 8C), 131.97 (s,
4C), 130.13 (vt, J = 4.9 Hz, 8C), 124.39 (s, 2C), 111.97 (s, 2C), 51.43
(vt, J = 16.77 Hz, 2C). 31P NMR (CD3CN, 146 MHz): δ 45.84 (d, J =
152.79 Hz, 2P), −144.00 (sept, J = 706.37 Hz, 1P). 19F NMR
(CD3CN, 235 MHz): δ −72.86 (d, J = 706.26 Hz, 6F). ESI MS: m/z
585.6 ([C3 3 H2 8 KN2 O2 P2 ]+ , [OPCB I m POK]+ ), 617.5
([C33H28N2P2Rh]+, [PCBImPRh]+), 633.4 ([C33H28N2OP2Rh]+,
[PCBImPORh]+), 649.4 ([C33H28N2O2P2Rh]+, [OPCBImPORh]+).
1,3-Bis(diphenylphosphinomethylene)benzimidazol-2-yl-
palladium Chloride Hexafluorophosphate (7). 5 (104.3 mg, 0.15
mmol, 1.00 equiv) was added portionwise to a suspension of PdCl2
(26.9 mg, 0.15 mmol, 1.00 equiv) in 10 mL of degassed dry DMF at
room temperature and stirred for 8 h at 60 °C. After the reaction was
complete, all volatiles were removed in vacuo. The formed amorphous
solid was then redissolved in CH3CN and filtered. The colorless fine-
crystalline compound 7 (41.0 mg, 34%) was obtained after
crystallization from a CH3CN/Et2O mixture. Anal. Calcd for
C33H28ClF6N2P3Pd: C, 49.46; H, 3.52; Cl, 4.42; F, 14.22; N, 3.50;
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HCOOK within 24 h at 25 °C under an argon atmosphere. H NMR
((CD3)2CO, 360 MHz): δ 7.68 (m, 16H), 7.49 (m, 4H), 7.32 (m,
4H), 7.24 (vt, J = 7.39 Hz, 8H), 7.07 (vt, J = 7.56 Hz, 16H), 4.79 (s,
8H), −9.15 (m, 1H). 31P NMR ((CD3)2CO, 146 MHz): δ 55.90 (d, J
= 156.48 Hz, 4P), −144.00 (sept, J = 706.89 Hz, 1P).
Thermal Stability in Solutions. The thermal stability and
reactivity of the rhodium complex 6b in various solvents were
assessed according to the following procedure: 6b (3−7 mg) was
dissolved in 0.45 mL of a degassed solvent in a NMR tube at room
temperature in a glovebox. The NMR tube was placed in an oil bath;
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Inorg. Chem. 2015, 54, 9517−9528