University Science Books, New York, 1987 ; C. Elschenbroich,
Organometallchemie, 4th Edn., Teubner, Stuttgart, 2003.
2 C. Amatore and A. Jutand, Acc. Chem. Res., 2000, 33, 314.
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A. R. Cowley and H. L. Anderson, J. Org. Chem., 2003, 68, 1089; H.
Furuta, H. Maeda and A. Osuka, Inorg. Chem. Commun., 2003, 6, 162;
M. Bröring and C. D. Brandt, Chem. Commun., 2001, 499; J. L. Sessler,
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nins, 2003, 7, 17.
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3920.
6 Spectroscopic data for 3: mp. 160 °C (decomp.); 1H NMR (CD2Cl2): d =
1.09 (t, 6H, 3J = 7.6 Hz, 2 3 CH2CH3), 1.18 (t, 6H, 3J = 7.6 Hz, 2 3
CH2CH3), 1.21 (t, 6H, 3J = 7.6 Hz, 2 3 CH2CH3), 1.33 [d, 9H, 2JPH
=
11.4 Hz, P(CH3)3], 2.42 (q, 4H, 3J = 7.6 Hz, 2 3 CH2CH3), 2.65 (q, 8H,
3J = 7.6 Hz, 4 3 CH2CH3), 2.69 (s, 6H, 2 3 terminal CH3), 6.92 (s, 2H,
2 3 meso-H), 7.58 (s, 4H, 4 3 para-H), 7.75 (s, 8H, 8 3 ortho-H); 13
C
Fig. 2 ORTEP plot of the molecular structure of 4. Selected bond lengths
[Å] and angles [°]: Pd–N1 2.0410(18), Pd–N2 2.298(2), Pd–N3 2.0354(18),
Pd–P1 2.3337(7), Pd–P2 2.3207(6), N1–Pd–N3 175.97(7), P1–Pd–P2
170.15(2), N2–Pd–P1 94.44(6), N2–Pd–P2 95.10(6).
NMR (CD2Cl2): d = 14.7, 16.9, 17.2, 17.6, 17.9, 18.0, 18.5, 20.8 [q, 1JCP
1
= 10.5 Hz, P(CH3)3], 117.9 (s, 4 3 para-C), 120.9, 125.0 (q, JCF
=
272.7 Hz, 8 3 CF3), 129.3 (qq, 2JCF = 31.5 Hz, 2JCF = 2.9 Hz, 8 3 meta-
C), 135.2 (s, 8 3 ortho-C), 138.0, 138.8, 139.0, 140.1, 150.9, 162.1 (q,
1JBC = 49.9 Hz, 4 3 ipso-C), 170.4; 19F NMR (CD2Cl2): d = 262.6; 31
P
NMR (CD2Cl2): d = 223.1; MS (FAB): m/z 598 [M 2 BArF]+; calc. for
palladium the Pd–N(2) bond is elongated by ~ 0.3 Å to 2.298
C
63H59BF24N3PPd 3 2 CH2Cl2: C 47.83, H 3.89, N 2.57; found: C 47.47,
Å.
H 3.63, N 2.47%.
The stepwise association of trimethylphosphine to the cation
7 Spectroscopic data for 4: mp. 129 °C (decomp.); 1H NMR (CD2Cl2): d =
0.71 (pseudotriplet, 18H, 6 3 PCH3), 1.08 (t, 6H, 3J = 7.6 Hz, 2 3
CH2CH3), 1.17, 1.20 (2 3 t, 12H, 3J = 7.6 Hz, 4 3 CH2CH3), 2.43 (q,
4H, 3J = 7.6 Hz, 2 3 CH2CH3), 2.66, 2.69 (2 3 q, 8H, 4 3 CH2CH3),
2.80 (s, 6H, 2 3 terminal CH3), 7.06 (s, 2H, 2 3 meso-H), 7.57 (s, 4H,
4 3 para-H), 7.73 (s, 8H, 8 3 ortho-H); 13C NMR (CD2Cl2): d = 13.6
[vt, N = 25.4 Hz, 2 3 P(CH3)3], 15.1, 17.6, 17.7, 18.1, 18.6, 18.8, 20.2,
117.9 (s, 4 3 para-C), 123.1, 125.0 (q, 1JCF = 272.6 Hz, 8 3 CF3), 129.4
(q, 2JCF = 31.5 Hz, 8 3 meta-C), 135.2 (s, 8 3 ortho-C), 135.7, 139.0,
2 in solution can easily be monitored by H- and 31P-NMR,
1
respectively. The 31P-NMR resonance shows a low-field shift
from 223.1 ppm to 218.8 ppm upon going from the tetra- to the
pentacoordinate species. The same process is indicated in the
proton NMR by a high-field shift and change in habitus of the
PMe3-proton resonance from 1.23 ppm (doublet, 3) to 0.71 ppm
(pseudotriplet, 4). No free phosphane was detected in either
spectra. These NMR results prove the five-coordinate structure
of 4 to be stable in solution.
Of particular interest is the seemingly paradoxical finding,
that the coordination number of a metal ion can be increased by
decreasing the number of accessible coordination sites. This
aspect is the major difference to the usual approach of blocking
coordination sites by large, bulky substituents, which always
renders higher coordination numbers sterically impossible. The
use of small, well-positioned substituents to introduce steric
repulsion only at very small segments of the coordination
sphere of a metal ion may be a generally applicable method for
the stabilisation of “reactive” intermediates. We are currently
investigating this opportunity in our laboratory.
140.1, 144.1, 152.4, 162.1 (q, 1JBC = 49.8 Hz, 4 3 ipso-C), 168.3; 19
F
NMR (CD2Cl2): d = 262.7; 31P NMR (CD2Cl2): d = 218.8; MS
(FAB): m/z 674 [M 2 BArF]+; calc. for C66H68BF24N3P2Pd 3 CH2Cl2:
C 48.83, H 4.22, N 2.59; found: C 49.10, H 4.16, N 2.47%.
8 Crystal data for C63H59BF24N3PPd 3: violet blocks, M = 1462.31,
monoclinic, space group P 21/c, a = 12.9944(11), b = 20.5527(17), c =
25.0962(21) Å, b = 104.331(1)°, U = 6493.9(9) Å3, Z = 4, Dc = 1.496
g cm23, m = 0.421 mm21, F(000) = 2960, 66958 reflections collected
(1.30 < q < 26.37°) at 173(2) K, 13271 independent (Rint = 0.0619),
10167 used in the structure refinement; R1 = 0.0630 [I > 2s(I)], wR2
=
0.1456 (all data), GOF = 1.099 for 1048 parameters and 6 restraints,
largest difference peak, hole = 0.847, 20.517 e Å23. CCDC 195926. See
in .cif or other electronic format.
This work was funded by the Deutsche Forschungsge-
meinschaft (Emmy-Noether-Programm) and the Fonds der
Chemischen Industrie. The authors thank Professor Helmut
Werner for his generous support.
9 Crystal data for C66H68BF24N3P2Pd 4: violet blocks, M = 1538.38,
¯
triclinic, space group P 1, a = 14.5341(11), b = 15.1714(11), c =
17.1442(12) Å, a = 95.9710(10), b = 97.2310(10), g = 105.8260(10)°,
U = 3570.0(4) Å3, Z = 2, Dc = 1.431 g cm23, m = 0.408 mm21, F(000)
= 1564, 67837 reflections collected (1.21 < q < 26.37°) at 173(2) K,
14572 independent (Rint
= 0.0257), 13891 used in the structure
refinement; R1 = 0.0423 [I > 2s(I)], wR2 = 0.1012 (all data), GOF =
1.143 for 1056 parameters and 0 restraints, largest difference peak, hole
=
suppdata/cc/b3/b305547g/ for crystallographic data in .cif or other
electronic format.
Notes and references
1 J. P. Collman, L. S. Hegedus, J. R. Norton and R. G. Finke, Principles
and Applications of Organotransition Metal Chemistry, 2nd Edn.,
0.652, 20.413 e Å23. CCDC 195925. See http://www.rsc.org/
CHEM. COMMUN., 2003, 2156–2157
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