2 J. Zhou, S. J. Lancaster, D. A. Walker, S. Beck, M. Thornton-Pett
allowed to ride on their corresponding carbon atoms with fixed
thermal parameters. An empirical absorption correction was
applied.25 The crystallographic data are summarised in Table 3.
In addition, refinement using full-matrix least squares on all
F 2 data26 was also performed for 3 and 7a. Both refinements
methods (either on F or on F 2) gave better results (lower R and
wR) for the model with the CN group N-bound to the metal
(K in case of 3, or Fe in case of 7a) than for the model where
this group is C-bond to the metal. The inspection of the param-
eters for the thermal ellipsoids also indicated that the model
containing NCB units are better solutions to the data sets than
those incorporating the CNB units. These results are consistent
with the observations from 11B{1H} NMR spectroscopy and the
previously reported data.2
and M. Bochmann, J. Am. Chem. Soc., 2001, 123, 223.
3 A. A. Danopoulos, J. R. Galsworthy, M. L. H. Green, S. Cafferkey,
L. H. Doerrer and M. B. Hursthouse, Chem. Commun., 1998,
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4 L. H. Doerrer, J. R. Galsworthy, M. L. H. Green, M. A. Leech and
M. Mueller, J. Chem. Soc., Dalton Trans., 1998, 3191.
5 L. H. Doerrer, J. R. Galsworthy, M. L. H. Green and M. A. Leech,
J. Chem. Soc., Dalton Trans., 1998, 2483.
6 L. H. Doerrer, A. J. Graham and M. L. H. Green, J. Chem. Soc.,
Dalton Trans., 1998, 3941.
7 L. H. Doerrer and M. L. H. Green, J. Chem. Soc., Dalton Trans.,
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8 J. L. Priego, L. H. Doerrer, L. H. Rees and M. L. H. Green,
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9 H. Jacobsen, H. Berke, S. Doering, G. Kehr, G. Erker, R. Froehlich
and O. Meyer, Organometallics, 1999, 18, 1724.
10 L. Li and T. J. Marks, Organometallics, 1998, 17, 3996.
11 C. Bergquist, B. M. Bridgewater, C. J. Harlan, J. R. Norton,
R. A. Friesner and G. Parkin, J. Am. Chem. Soc., 2000, 122,
10581.
CCDC reference numbers 204648–204650.
lographic data in CIF or other electronic format.
12 D. E. J. Arnold, S. Cradock, E. A. V. Ebsworth, J. D. Murdoch,
D. W. H. Rankin, D. C. J. Skea, R. K. Harris and B. J. Kimber,
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Computational details
All calculations were performed using density functional
methods of the Amsterdam Density Functional Package (ver-
sion 2000.2).27–30 The electronic configurations of the molecular
systems were described using type IV basis sets with triple ζ
accuracy sets of Slater type orbitals, with a single polarisation
function added to the main group atoms. The cores of the
atoms were frozen up to 2p for Fe, 4d for Hg, 1s for C, O and N,
2p for Si. First-order relativistic corrections were made to the
cores of all atoms using the ZORA formalism. The generalised
gradient approximation (GGA non-local) method was used,
using Vosko, Wilk and Nusair’s local exchange correlation31
with non-local exchange corrections by Becke32 and non-local
correlation corrections by Perdew.33 The non-local correction
terms were not utilised in calculating gradients during geometry
optimisations as better agreement with experimental structure
is normally achieved with a local density approximation.
18 (a) K. Sung, J. Org. Chem., 1999, 64, 8984; (b) C. Zanchini, Chem.
Phys., 2000, 254, 187.
19 T. S. Piper, F. A. Cotton and G. Wilkinson, J. Inorg. Nucl. Chem.,
1955, 1, 165.
20 J. L. W. Pohlmann and F. E. Brinckmann, Z. Naturforsch., Teil B,
1965, 20, 5.
21 Z. Otwinowski and W. Minor, Methods Enzymol., 1996, 276.
22 D. J. Watkin, C. K. Prout, J. R. Carruthers and P. W. Betteridge, in
CRYSTALS, Issue 10, Chemical Crystallography Laboratory,
Oxford, 1996.
23 D. J. Watkin, C. K. Prout and L. J. Pearce, in CAMERON, Chemical
Crystallography Laboratory, Oxford, 1996.
Acknowledgements
24 A. Altomare, G. Carascano, C. Giacovazzo and A. Guagliardi,
J. Appl. Crystallogr., 1993, 26, 343.
25 N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39,
158.
26 G. M. Sheldrick, in SHELXL93 - Program for Crystal Structure
Refinement, Göttingen, 1993.
27 E. J. Baerends, E. G. Ellis and P. Ros, Chem. Phys., 1973, 2, 41.
28 C. Fonseca Guerra, J. G. Snijider, B. te Velde and E. J. Baerends,
Theor. Chem. Acc., 1998, 99, 391.
29 B. te Velde and E. J. Baerends, J. Comput. Phys., 1992, 99, 84.
30 L. Verluis and T. Ziegler, J. Chem. Phys., 1988, 88, 322.
31 S. H. Vosko, L. Wilk and M. Nusair, Can. J. Phys., 1990, 58,
1200.
We thank Dr Neale G. Jones for helpful discussions, Drs David
J Watkin and Andrew R. Cowley for assistance with crystallo-
graphy, Balliol College Oxford for a Dervorguilla Scholarship
(S. I. P), the AG Leventis Foundation for a grant (to I.C.V) and
EPSRC for support (to G. D. W. A.). Part of this work was
carried out using the resources of the Oxford Super Computing
Centre and part using the EPSRC Columbus cluster at the
Rutherford Laboratory.
References
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33 J. Perdew, Phys. Rev. B, 1986, 33, 8822.
D a l t o n T r a n s . , 2 0 0 3 , 2 5 5 0 – 2 5 5 7
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