R. J. M. Klein Gebbink et al.
FULL PAPER
1181 (w), 1097 (w), 1084 (w), 1048 (m), 1034 (m), 1018 (m), 1004
absorption correction based on multiple measured reflections was
1
(m), 990 (m), 948 (w), 834 (s), 770 (m), 742 (m), 666 (w) cm–1. H
applied (µ = 1.00 mm–1, 0.77–0.89 correction range). Unique reflec-
NMR (300.1 MHz, [D6]acetone, 25 °C): δ = 1.64–1.68 (m, 6 H, tions; 9936 (Rint = 0.025). Non-hydrogen atoms were refined with
C*CH2CHH ring, C*CH2 ring), 2.04–2.09 (m, 2 H, C*CH2CHH
ring), 3.05–3.12 (m, 2 H, NCHH ring), 3.28–3.42 (m, 2 H, C*H),
3.83 (quintet, 3JH,H = 5.1 Hz, 2 H, NCHH ring), 3.91 (d, AB, 2JH,H
anisotropic displacement parameters. All hydrogen atoms were lo-
cated in the difference Fourier map. OH hydrogen atoms were kept
fixed on their located positions, CH hydrogen atoms were refined
with a riding model. One PF6 anion was orientationally disordered.
Number of parameters refined with 415 restraints: 605. R1/wR2
[IϾ2σ(I)]: 0.0203/0.0449. R1/wR2 (all refl.): 0.0246/0.0463. S =
1.040. Flack parameter[10] x = –0.031(15). Residual electron density
between –0.34 and 0.44 e/Å3.
2
= 11.7 Hz, 1 H, CHHOH), 4.20 (d, AB, JH,H = 11.7 Hz, 1 H,
2
CHHOH), 3.96 (d, AB, JH,H = 11.4 Hz, 1 H, CHHOH), 4.16 (d,
AB, 2JH,H = 11.4 Hz, 1 H, CHHOH), 3.92 (d, AX, 2JH,H = 14.7 Hz,
2 H, ArCH2N), 4.69 (d, AX, 2JH,H = 14.7 Hz, 2 H, ArCH2N), 5.79
3
3
(br. s, 1 H, OH), 6.84 (d, JH,H = 7.5 Hz, 2 H), 7.01 (t, JH,H
=
8.1 Hz, 1 H) ppm. 13C{1H} NMR (75.5 MHz, [D6]acetone, 25 °C):
δ = 21.22 (C*CH2CH2), 24.17 (C*CH2 ring), 60.48 (NCH2), 66.37
(ArCH2N), 68.55 (C*), 69.95 (CH2OH), 120.71 (Cmeta to Cipso),
125.23 (Cpara to Cipso), 146.83 (ArCCH2N) 150.92 (Cipso) ppm.
Acknowledgments
The work described here was financially supported by the National
Research School Combination-Catalysis (NRSC-C) (S.G.) and the
Council for Chemical Sciences of the Netherlands Organization for
Scientific Research (CW-NWO) (M.L., A.L.S.).
General Procedure for Aldol Condensation of Methyl α-Isocy-
anoacetate with Aldehydes: To a solution of the palladium complex
(0.016 mmol, 1 mol-%) in CH2Cl2 (5 mL) was sequentially added
methyl α-isocyanoacetate (145 µL, 1.6 mmol), aldehyde (1.6 mmol),
and diisopropylethylamine (28 µL, 0.16 mmol). The reaction mix-
ture was stirred at ambient temperature for 24 h. Subsequently, the
solvent was evaporated in vacuo, and 1H NMR samples and HPLC
samples were prepared. The yield and ratio of cis- and trans-iso-
mers was determined by 1H NMR and the enantiomeric excess
by HPLC. The configurations of the trans- and cis-product were
determined after separation of the trans/cis mixture (column
chromatography, SiO2, ethyl acetate/hexane = 1:2) by 1H NMR
analysis of the spectrum with the use of Eu(dcm)3 as the chiral
shift reagent.[23]
[1] For reviews on pincer complexes, see a) M. Albrecht, G.
van Koten, Angew. Chem. Int. Ed. 2001, 40, 3750–3781; b)
M. E. van der Boom, D. Milstein, Chem. Rev. 2003, 103, 1759–
1792; c) J. T. Singleton, Tetrahedron 2003, 59, 1837–1857; for a
general review on palladacycles, see d) J. Dupont, C. S. Con-
sorti, J. Spencer, Chem. Rev. 2005, 105, 2527–2571.
[2] For the NCN-pincer complexes, see a) J. G. Donkervoort, J. L.
Vicario, J. T. B. H. Jastrzebski, W. J. J. Smeets, A. L. Spek, G.
van Koten, J. Organomet. Chem. 1998, 551, 1–7; b) M. Al-
brecht, B. M. Kocks, A. L. Spek, G. van Koten, J. Organomet.
Chem. 2001, 624, 271–286; c) E. Diez-Barra, J. Guerra, I. Lo-
pez-Solera, S. Merino, J. Rodrigues-Lopez, P. Sanchez-Verdu,
J. Tejeda, Organometallics 2003, 22, 541–547.
[3] For the PCP complexes see a) F. Gorla, A. Togni, L. M. Ven-
anzi, A. Albinati, F. Lianza, Organometallics 1994, 13, 1607–
1616; b) J. M. Longmire, X. Zhang, Tetrahedron Lett. 1997, 38,
1725–1728; c) J. M. Longmire, X. Zhang, M. Shang, Organo-
metallics 1998, 17, 4374–4379; d) P. Dani, M. Albrecht,
G. P. M. van Klink, G. van Koten, Organometallics 2000, 19,
4468–4476.
[4] For the NCN-pincer complexes, see a) J. A. M. van Beek, G.
van Koten, M. J. Ramp, N. C. Coenjaarts, D. Grove, K. Goub-
itz, M. C. Zoutberg, C. H. Stam, W. J. J. Smeets, A. L. Spek,
Inorg. Chem. 1991, 30, 3059–3068; b) L. van Kuil, Y. S. J. Veld-
huizen, D. Grove, J. W. Zwikker, J. W. Jenneskens, W. Drenth,
W. J. J. Smeets, A. L. Spek, G. van Koten, Recl. Trav. Chim.
Pays-Bas 1994, 113, 267–277; c) I. G. Jung, S. U. Son, K. H.
Park, K.-C. Chung, J. W. Lee, Y. K. Chung, Organometallics
2003, 22, 4715–4720.
[5] For the Phebox-pincer complexes, see a) Y. Motoyama, N.
Makihara, Y. Mikami, K. Aoki, H. Nishiyama, Chem. Lett.
1997, 951–952; b) S. E. Denmark, R. A. Stavenger, A.-M.
Faucher, J. P. Edwards, J. Org. Chem. 1997, 62, 3375–3389; c)
M. A. Stark, C. J. Richards, Tetrahedron Lett. 1997, 38, 5881–
5884; d) Y. Motoyama, Y. Mikami, H. Kawakami, K. Aoki,
H. Nishiyama, Organometallics 1999, 18, 3584–3588; e) Y. Mo-
toyama, H. Narusawa, H. Nishiyama, Chem. Commun. 1999,
131–132; f) M. A. Stark, G. Jones, C. J. Richards, Organometal-
lics 2000, 19, 1282–1291; g) M. Gerisch, J. R. Krumper, R. G.
Bergman, T. D. Tilley, J. Am. Chem. Soc. 2001, 123, 5818–5819;
h) Y. Motoyama, M. Okano, H. Narusawa, N. Makihara, K.
Aoki, H. Nishiyama, Organometallics 2001, 20, 1580–1591; i)
Y. Motoyama, Y. Koga, H. Nishiyama, Tetrahedron 2001, 57,
853–860; j) Y. Motoyama, K. Shimozono, K. Aoki, H. Nishi-
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X-ray Crystal Structure Determinations: X-ray intensities were mea-
sured with a Nonius Kappa CCD diffractometer with a rotating
anode (graphite monochromator, λ = 0.71073 Å) up to a resolution
of (sin θ/λ)max = 0.65 Å–1 at a temperature of 150 K. The structures
were solved with automated Patterson methods[21] ([3]BF4) or Di-
rect Methods[22] ([3]PF6) and refined with SHELXL-97[23] against
F2 of all reflections. Geometry calculations and checks for higher
symmetry were performed with the PLATON[13] program. CCDC-
605998 (for [3]BF4) and -605999 (for [3]PF6) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
X-ray
Crystal
Structure
Determination
of
[3]BF4:
C18H27N2O2Pd·BF4, FW = 496.63, yellowish hexagonal plate,
0.30×0.30×0.06 mm3, monoclinic, C2 (no. 5), a = 18.5640(1), b =
10.7289(1), c = 20.6534(2) Å, β = 108.8572(3)°, V = 3892.78(6) Å3,
Z = 8, Dx = 1.695 g/cm3. Number of reflections measured: 37429.
An absorption correction based on multiple measured reflections
was applied (µ = 1.01 mm–1, 0.72–0.94 correction range). Unique
reflections: 8777 (Rint = 0.052). Non-hydrogen atoms were refined
with anisotropic displacement parameters. All hydrogen atoms
were located in the difference Fourier map. OH hydrogen atoms
were refined freely with isotropic displacement parameters; CH hy-
drogen atoms were refined with a riding model. Number of param-
eters refined with one restraint: 521. R1/wR2 [IϾ2σ(I)]: 0.0277/
0.0620. R1/wR2 (all refl.): 0.0301/0.0647. S = 1.033. Flack param-
eter[10] x = –0.043(16). Residual electron density between –0.57 and
0.58 e/Å3.
X-ray
Crystal
Structure
Determination
of
[3]PF6:
C18H27N2O2Pd·PF6·0.5H2O, FW
=
563.79, colorless block,
0.30×0.24×0.12 mm3, monoclinic, P21 (no. 4), a = 10.9459(10), b
= 9.2189(3), c = 21.5229(9) Å, β = 94.430(7)°, V = 2165.4(2) Å3, Z
= 4, Dx = 1.729 g/cm3. Number of reflections measured: 59398. An
4606
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Eur. J. Inorg. Chem. 2006, 4600–4607