Article
Organometallics, Vol. 29, No. 17, 2010 3751
-
their Br analogues, highlighting the importance of co-ligands
as well. Research in our laboratory is underway to develop this
halido-pseudohalido exchange reaction into a selective and
general methodology for the synthesis of catalytically useful cis-
configured transition metal complexes.
NCH
2 28 6 2
). Anal. Calcd for C28H N S Ni: C, 58.86; H, 4.94; N,
14.71. Found: C, 58.42; H, 4.80; N, 14.35. ESI (MS): m/z = 513 [M
-
cis-Diisothiocyanato-bis(1-propyl-3-methylbenzimidazolin-2-
þ
-1
NCS] . FT-IR (CH Cl ): ν~ (NCS) 2114 cm (w).
2 2
1
ylidene)nickel(II) (2e). Yield: 66%. H NMR (300 MHz,
CDCl ): major isomer (cis-anti), δ 7.42-7.34 (br m, 8 H, Ar-
3
H), 5.06-4.96 (br m, 2 H, NCH ), 4.72 (s, 6 H, NCH ), 4.53 (m,
Experimental Section
2
3
3
2 H, NCH
Hz, CH
2
2
), 1.96 (br m, 4 H, CH ), 0.93 (t, 6 H, J(H,H) = 6.9
3
); minor isomer (cis-syn), δ 7.80-7.66 (m, 8 H, Ar-H),
General Considerations. Unless otherwise noted, all opera-
tions were performed without taking precautions to exclude air
and moisture. All solvents and chemicals were used as received
without any further treatment if not noted otherwise. THF was
dried over sodium/benzophenone and distilled under nitrogen
4
1
.44 (s, 6 H, NCH ), 4.30 (m, 4 H, NCH ), 1.53 (br m, 4 H, CH ),
3 2 2
3
.09 (t, 6 H, J(H,H) = 6.9 Hz, CH ). Anal. Calcd for
3
C
24
H
28
6
N S
2
Ni: C, 55.08; H, 5.39; N, 16.06. Found: C, 54.91;
þ
H, 5.08; N, 16.34. ESI (MS): m/z = 464 [M - NCS] . FT-IR
-
1
1
13
(CH Cl ): ν~ (NCS) 2102 cm (w).
prior to use. H and C spectra were recorded on a Bruker ACF
00 spectrometer, and the chemical shifts (δ) were internally
referenced by the residual solvent signals relative to tetramethyl-
2 2
General Procedure for the Kumada-Corriu Coupling. In a
typical run, a Schlenk tube was charged with the appropriate
catalyst (0.01 mmol) and aryl halide (1 mmol). A THF solution
of the tolylmagnesium bromide (1.5 mL, 1 M, 1.5 mmol) was
added to the reaction mixture under nitrogen. The reaction
mixture was further stirred at ambient temperature for 12 or
3
1
13
silane ( H, C). Mass spectra were measured using a Finnigan
MAT LCQ (ESI) spectrometer. Infrared spectra were recorded
with a Varian 3100 FT-IR spectrometer. Elemental analyses
were performed on a Perkin-Elmer PE 2400 elemental analyzer
at the Department of Chemistry, National University of Singa-
pore. The dihalido-bis(carbene) nickel(II) complexes (1a-e)
24 h. Dichloromethane (10 mL) was added to the reaction mixture,
and the organic layer was washed with water (3 ꢀ 10 mL) and
2
a,b
dried over MgSO . The solvent was removed under reduced
4
were synthesized according to literature procedures.
pressure, and the product was isolated by column chromatog-
raphy and analyzed by H NMR spectroscopy.
General Procedure for the Preparation of Mixed Diisothiocya-
nato-bis(carbene) Ni(II) Complexes (2a-e). AgSCN (2.4 equiv)
and the appropriate trans-dihalido-bis(1,3-dialkylbenzimidazo-
lin-2-ylidene) Ni(II) complex (1 equiv) were suspended in
1
X-ray Diffraction Studies. X-ray data for 2a-e were collected
with a Bruker AXS SMART APEX diffractometer, using Mo
KR radiation at 223(2) K (for 2a, 2b, 2e), 293(2) K (for 2d), and
CH CN. The resulting mixture was stirred at 70 °C for 12 h
3
1
4
2
95(2) K (for 2b) with the SMART suite of programs. Data
shielded from light. The reaction mixture, initially a red suspen-
sion, turned yellow. The mixture was subsequently filtered
through a sintered funnel, and the residue was washed with
dichloromethane. The solvent of the filtrate was removed under
reduced pressure, and the resulting residue was subsequently
washed with methanol and dried under vacuum to afford
complexes 2a-e as greenish-yellow powders.
were processed and corrected for Lorentz and polarization
effects with SAINT and for absorption effect with SADABS.
Structural solution and refinement were carried out with the
1
5
16
1
7
SHELXTL suite of programs. The structure was solved by
direct methods to locate the heavy atoms, followed by difference
maps for the light, non-hydrogen atoms. All non-hydrogen
atoms were generally given anisotropic displacement para-
meters in the final model. All H atoms were put at calculated
positions. A summary of the most important crystallographic
data is given in the Supporting Information.
Computational Details. The DFT calculations were per-
formed by using the Gaussian 09 program. Geometry optimi-
zations for the trans- and cis-structures were carried out at the
trans-Diisothiocyanato-bis(1,3-diisopropylbenzimidazolin-2-
1
ylidene)nickel(II) (2a). Yield: 88%. H NMR (300 MHz,
CDCl ): δ 7.61 (dd, 4 H, Ar-H), 7.29 (dd, 4 H, Ar-H), 6.79 (m,
3
3
H, J(H,H) = 7.08 Hz, NCH), 2.04 (d, 24 H, J(H,H) = 7.08 Hz,
3
4
1
3
1
CH
s, NCS), 134.0, 123.6, 113.3 (s, Ar-C), 54.9 (s, NCH), 22.5 (s,
CH ). Anal. Calcd for C H N S Ni: C, 58.04; H, 6.26; N, 14.50.
3 3
). C{ H} NMR (75.4 MHz, CDCl ):δ173.1 (s, NCN), 142.4
1
8
(
3
28 36
6
2
19,20
hybrid B3LYP level of theory. The all-electron 6-31G(d)
basis sets were used for H, C, N, and S atoms, and LANL2DZ
Found: C, 58.22; H, 6.10; N, 14.35. ESI (MS): m/z = 520 [M -
NCS] . FT-IR (CH
2
1
þ
-1
2 2
Cl ): ν~ (NCS) 2106 cm (m).
trans-Diisothiocyanato-bis(1,3-diisobutylbenzimidazolin-2-yli-
1
dene)nickel(II) (2b). Yield: 91%. H NMR (300 MHz, CDCl
3
): δ
(
14) SMART version 5.628; Bruker AXS Inc.: Madison, WI, 2001.
3
.45 (dd, 4 H, Ar-H), 7.32 (dd, 4 H, Ar-H), 4.98 (d, 8 H, J(H,
7
H) = 8.04 Hz, CH
(15) SAINTþ version 6.22a; Bruker AXS Inc.: Madison, WI, 2001.
3
), 2.95 (m, 4 H, J(H,H) = 6.72 Hz, CH),
(16) Sheldrick, G. W. SADABS version 2.10; University of Gottingen,
2
3
.26 (d, 24 H, J(H,H) = 6.72 Hz, CH ). C{ H} NMR (75.4
13
1
2001.
17) SHELXTL version 6.14; Bruker AXS Inc.: Madison, WI, 2000.
18) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
1
MHz, CDCl
3
(
(
3
): δ 175.0 (s, NCN), 135.1, 124.0, 112.0 (s, Ar-C),
5
C H N S Ni: C, 60.47; H, 6.98; N, 13.22. Found: C, 60.29;
6.0 (s, CH
2 3
), 29.7 (s, CH), 21.4 (s, CH ). Anal. Calcd for
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;
Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.;
Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.;
Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo,
C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin,
A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma,
K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.;
Cioslowski, J.; Fox, D. J. Gaussian 09, Revision A.02; Gaussian, Inc.:
Wallingford, CT, 2009.
3
2
44
6 2
þ
H, 6.90; N, 13.55. ESI (MS): m/z = 576 [M - NCS] . FT-IR
CH
trans-Diisothiocyanato-bis(1,3-dibenzylbenzimidazolin-2-yli-
2 2
Cl
): ν~ (NCS) 2103 cm- (m).
1
(
1
dene)nickel(II) (2c). Yield: 89%. H NMR (300 MHz, CDCl ): δ
3
7
.50 (d, 4 H, Ar-H), 7.38-7.29 (br m, 16 H, Ar-H), 7.15-7.09
13 1
). C{ H} NMR (75.4 MHz,
(m, 8 H, Ar-H), 6.08 (s, 8 H, NCH
CDCl
2
3
): δ 176.9 (s, NCN), 135.7, 135.1, 129.9, 128.8, 127.6,
1
24.4, 111.9 (s, Ar-C), 52.2 (s, NCH ). Anal. Calcd for C H -
2 44 36
N
6
S
2
Ni: C, 68.49; H, 4.70; N, 10.89. Found: C, 68.42; H, 4.39; N,
þ
1
0.35. ESI (MS): m/z = 712 [M - NCS] . FT-IR (CH
2
Cl
2
):
-1
ν~ (NCS) 2100 cm (s).
cis-Diisothiocyanato-bis[1,3-bis(2-propenyl)benzimidazolin-2-
(19) Becke, A. D. J. Chem. Phys. 1993, 98, 5648–5652.
(20) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785–
1
ylidene]nickel(II) (2d). Yield: 73%. H NMR (300 MHz,
7
89.
(21) (a) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972,
56, 2257. (b) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213.
(c) Clark, T.; Chandrasekhar, J.; Spitznagel, G. W.; Schleyer, P. v. R.
J. Comput. Chem. 1983, 4, 294. (d) Rassolov, V. A.; Ratner, M. A.; Pople,
J. A.; Redfern, P. C.; Curtiss, L. A. J. Comput. Chem. 2001, 22, 976.
CDCl
4
3
): δ 7.42 (dd, 4 H, Ar-H), 7.32 (dd, 4 H, Ar-H), 6.34 (m,
3
H, CH), 5.75 (d, 4 H, J(H,H) = 5.25 Hz, NCH ), 5.49 (br m,
2
1
3
1
2 H, 4 H for NCH and 8 H for CH ). C{ H} NMR (75.4 MHz,
1
CDCl
2 2
3
): δ 175.4 (s, NCN), 134.3 (s, Ar-C), 131.9 (s, CHdCH
2
),
123.1 (s, Ar-C), 119.5 (s, CHdCH ), 111.4 (s, Ar-C), 50.6 (s,
2