Organometallics
Article
solution. THF was removed under reduced pressure. The residue was
extracted with pentane (60 mL) and diethyl ether (60 mL) in turn to
give a red solution. Complex 4 was obtained as red crystals from the n-
pentane solution and diethyl ether solution at −10 °C, yield 0.71 g
(1.21 mmol, 74%). m.p.: 160−162 °C, C32H39CoNP3 (589.51 g/mol):
calcd. C 65.20, H 6.67, N 2.38; found C 65.55, H 7.03, N 2.12. IR
mode in complex 4 was destroyed because of the strong
coordination between the cobalt(I) center and the carbonyl
ligands caused by the strong π-backbonding. There is only
cobalt-Cbenzyl coordination among the three atoms of the (C-N-
C) moiety. The imine function with the phenyl group
orientates toward the direction away from the cobalt center.
The distance from the cobalt center to the nitrogen atom
(2.923 Å) indicates that there is no bonding interaction
between them. The distances N1−C22 (1.280(2) Å) and N1−
C21 (1.437(2) Å) explain that the former is a CN double
bond and the latter is a C−N single bond.
1
(Nujol mull, cm−1): 1583 ν(CC), 934 ρ(PMe3). H NMR (300
MHz, C6D6, 298 K, ppm): 8.60−7.12 (m, 19H, Ar-H), 3.11 (m, 1H,
2
azaallyl-H), 2.14 (d, J = 21.0 Hz, 1H, azaallyl-H),1.13 (d, JP,H = 6.0
2
Hz, 9H, PMe3), 0.77 (d, JP,H = 9.0 Hz, 9H, PMe3). 31P NMR (121.5
MHz, C6D6, 298 K, ppm): 72.04 (m, 1P, PPh2), 12.10 (s, 1P, PMe3),
10.83 (m, 1P, PMe3). 13C NMR (75 MHz, C6D6, 298 K, ppm): 154.0
(CAr), 147.8 (CAr), 141.8 (CAr), 138.2 (CAr), 132.9 (CAr), 131.8 (CAr),
123.6 (CAr), 73.7 (azaallyl-C), 65.2 (azaallyl-C), 21.2 (m, P(CH3)3),
19.7 (m, P(CH3)3).
CONCLUSIONS
■
In conclusion, three unsymmetrical η3-2-azaallyl cobalt(I)
complexes 4−6 were synthesized through sp3 C−H bond
activation under a mild condition without additives. A
diorganocobalt(III) coordination cation 7 could be obtained
from the reaction of complex 4 with iodomethane via C,N-
coupling. In the presence of HCl, complex 4 decomposed to
the free ligand 1 and CoCl(PMe3)3. A penta-coordinate
dicarbonylcobalt(I) complex 8 was isolated by the reaction of
complex 4 with carbon monoxide. The molecular structures of
4−8 were determined by single crystal X-ray diffraction.
Synthesis of Complex 5. A solution of ligand 2 (0.67 g, 1.61
mmol) in THF (30 mL) was added to a solution of CoMe(PMe3)4
(0.61 g, 1.61 mmol) in THF (30 mL) at −78 °C. The reaction mixture
was warmed to 25 °C and stirred for 24 h to get a red solution. THF
was removed under reduced pressure. The residue was extracted with
pentane (60 mL) and diethyl ether (60 mL) in turn to give a red
solution. Complex 5 was obtained as red crystals from the n-pentane
solution and diethyl ether solution at −10 °C, yield 0.61 g (0.97 mmol,
61%). m.p.: 154−157 °C, C32H38ClCoNP3 (623.96 g/mol): calcd. C
61.60, H 6.14, N 2.24; found C 62.01, H 6.02, N 2.41. IR (Nujol mull,
cm−1): 1578 ν(CC), 950 ρ(PMe3). 1H NMR (300 MHz, C6D6, 298
K, ppm): 8.40−7.13 (m, 18H, Ar-H), 2.95 (m, 1H, azaallyl-H), 2.12
2
EXPERIMENTAL SECTION
(d, J = 18.0 Hz, 1H, azaallyl-H), 1.12 (d, JP,H = 6.0 Hz, 9H, PMe3),
■
0.71 (d, 2JP,H = 9.0 Hz, 9H, PMe3). 31P NMR (121.5 MHz, C6D6, 298
K, ppm): 72.0 (m, 1P, PPh2), 10.2 (m, 2P, PMe3). 13C NMR (75
MHz, C6D6, 298 K, ppm): 154.3 (CAr), 146.7 (CAr), 141.6 (CAr), 137.8
(CAr), 132.9 (CAr), 131.7 (CAr), 126.9 (CAr), 73.4 (azaallyl-C), 63.6
(azaallyl-C), 21.1 (m, P(CH3)3), 19.7 (m, P(CH3)3).
General Procedures and Materials. Standard vacuum techni-
ques were used in the manipulations of volatile and air-sensitive
materials. Solvents were dried by distillation from Na-benzophenone
under nitrogen before use. CoMe(PMe3)4,54o-diphenylphosphino-
benzaldehyde,55and the Schiff base ligand 156 were prepared by the
literature methods. Infrared spectra (4000−400 cm−1), as obtained
from Nujol mulls between KBr disks, were recorded on a Bruker
Synthesis of Complex 6. A solution of ligand 3 (0.65 g, 1.58
mmol) in THF (30 mL) was added to a solution of CoMe(PMe3)4
(0.60 g, 1.58 mmol) in THF (30 mL) at −78 °C. The reaction mixture
was warmed to 25 °C and stirred for 24 h to get a red solution. THF
was removed under reduced pressure. The residue was extracted with
pentane (60 mL) and diethyl ether (60 mL) in turn to give a red
solution. Complex 6 was obtained as red crystals from the n-pentane
solution and diethyl ether solution at −10 °C, yield 0.71 g (1.14 mmol,
72%). m.p.: 166−169 °C, C33H41CoNOP3 (619.54 g/mol): calcd. C
63.98, H 6.67, N 2.26; found C 64.34, H 6.29, N 2.39. IR (Nujol mull,
cm−1): 1579 ν(CC), 947 ρ(PMe3). 1H NMR (300 MHz, C6D6, 298
1
ALPHA FT-IR instrument. H, 31P, and 13C {H} NMR spectra (300,
121.5, and 75 MHz, respectively) were recorded on a Bruker Avance
300 spectrometer with C6D6 or CDCl3 as the solvent without an
internal reference at room temperature. The 13C and 31P NMR
resonances were obtained with broad-band proton decoupling.
Elemental analyses were carried out on an ElementarVario ELIII.
Melting points were measured in capillaries sealed under nitrogen and
are uncorrected.
Synthesis of Ligand 2. Chlorobenzylamine (2.43 g, 17.24 mmol)
was added to a solution of o-diphenylphosphinobenzaldehyde (5.00 g,
17.24 mmol) in 10 mL of methanol. The mixed solution was stirred
for 10 min. Ligand 2 was afforded by the crystallization in methanol at
−10 °C, yield 6.76 g (16.38 mmol, 95%). IR (Nujol mull, cm−1): 1581
ν(CC), 1640 ν(CN). 1H NMR (300 MHz, CDCl3, 298 K, ppm):
K, ppm): 8.54−6.92 (m, 18H, Ar-H), 3.41 (s, 3H, OCH3), 3.16 (m,
2
1H, azaallyl-H), 2.18 (d, J = 21.0 Hz, 1H, azaallyl-H), 1.16 (d, JP,H
=
6.0 Hz, 9H, PMe3), 0.81 (d, JP,H = 6.0 Hz, 9H, PMe3). 31P NMR
(121.5 MHz, C6D6, 298 K, ppm): 71.1 (m, 1P, PPh2), 13.7 (s, 1P,
PMe3), 11.3 (m, 1P, PMe3). 13C NMR (75 MHz, C6D6, 298 K, ppm):
154.8 (CAr), 142.1 (CAr), 141.0 (CAr), 139.7 (CAr), 133.0 (CAr), 131.8
(CAr), 126.7 (CAr), 73.6 (azaallyl-C), 65.3 (azaallyl-C), 54.5 (OCH3),
21.2 (m, P(CH3)3), 19.8 (m, P(CH3)3).
2
4
8.88 (d, JP,H = 6.0 Hz, 1H, −HCN), 8.03−6.84 (m, 18H, Ar-H),
4.63 (s, 2H, CH2). 31P NMR (121.5 MHz, CDCl3, 298 K, ppm):
−13.31 (s). 13C NMR (75 MHz, C6D6, 298 K, ppm): 160.9 (m, CH
N), 139.2 (CAr), 137.4 (CAr), 134.2 (CAr), 132.5 (CAr), 129.3 (CAr),
128.6 (CAr), 127.8 (CAr), 64.3 (s, benzyl-C).
Synthesis of Complex 7. A solution of complex 4 (0.48 g, 0.81
mmol) in THF (20 mL) was added to a solution of iodomethane (0.12
g, 0.81 mmol) in THF (20 mL) at −78 °C. The reaction mixture was
warmed to 25 °C and stirred for 24 h to give a muddy orange solution.
The muddy solution was filtered to give a clear orange solution. The
residue was extracted with THF (180 mL) to give a clear orange
solution. Complex 7 was obtained as orange crystals from the THF
solution at −10 °C, yield 0.33 g (0.46 mmol, 56%). m.p.: 201−203 °C,
C33H42CoINP3 (731.45 g/mol): calcd. C 54.19, H 5.79, N 1.91; found
C 53.85, H 6.17, N 2.00. IR (Nujol mull, cm−1): 1593 ν(CC), 952
Synthesis of Ligand 3. Methoxybenzylamine (2.36 g, 17.24
mmol) was added to a solution of o-diphenylphosphinobenzaldehyde
(5.00 g, 17.24 mmol) in 10 mL of methanol. The solution was stirred
for 10 min. Ligand 3 was afforded by the crystallization in methanol at
−10 °C, yield 6.56 g (16.03 mmol, 93%). IR (Nujol mull, cm−1): 1612
ν(CC), 1633 ν(CN). 1H NMR (300 MHz, CDCl3, 298 K, ppm):
4
8.99 (d, JP,H = 3.0 Hz, 1H, −HCN), 8.06−6.73 (m, 18H, Ar-H),
4.61(s, 2H, CH2), 3.78 (s, 3H, −OCH3). 31P NMR (121.5 MHz,
CDCl3, 298 K, ppm): −13.85 (s). 13C NMR (75 MHz, C6D6, 298 K,
ppm): 160.2 (m, CHN), 158.5 (CAr), 139.4 (CAr), 136.3 (CAr),
133.1 (CAr), 130.3 (CAr), 128.9 (CAr), 127.7 (CAr), 113.8 (CAr), 64.5 (s,
benzyl-C), 55.29 (s, OCH3).
1
ρ(PMe3). H NMR (300 MHz, CO(CD3), 298 K, ppm): 8.03−7.06
(m, 19H, Ph-H),3.25 (d, J = 3.0 Hz, 3H, −CH3), 3.01 (dd, J = 6.0 Hz,
J = 3.0 Hz, 1H, NCH), 2.79 (s, 1H, NCH), 1.13 (d, 2JP.H = 6.0 Hz, 9H,
2
PMe3), 1.04 (d, JP.H = 6.0 Hz, 9H, PMe3). 31P NMR (121.5 MHz,
CO(CD3), 298 K, ppm): 73.1 (m, 1P, PPh2), 18.9 (m, 1P, PMe3), 10.1
(s, 1P, PMe3). 13C NMR (75 MHz, C6D6, 298 K, ppm): 138.1 (CAr),
137.9 (CAr), 136.0 (CAr), 134.5 (CAr), 133.0 (CAr), 131.8 (CAr), 72.4
(C-N), 44.4 (CH3), 23.7 (m, P(CH3)3), 22.8 (m, P(CH3)3).
Synthesis of Complex 4. A solution of ligand 1 (0.62 g, 1.60
mmol) in THF (30 mL) was added to a solution of CoMe-
(PMe3)4(0.62 g, 1.60 mmol) in THF (30 mL) at −78 °C. The
reaction mixture was warmed to 25 °C and stirred for 24 h to get a red
D
Organometallics XXXX, XXX, XXX−XXX