Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2004
Supplementary material
X-ray data for crystals of 2[Co2(L1)3(NO3)](NO3)4(ClO4)2·4MeCN were extremely weak resulting in
poor structure refinement (see supplementary material) and thus detailed structural analysis of the bond
lengths and angles cannot be made due to large errors associated with the extremely weak data.
However, the presence of a HHH isomer in the solid state is both unambiguous and consistent with
solution studies. The structure was treated as follows:
Many non-hydrogen atoms were unstable when refined with anisotropic thermal parameters, thus only
a selection of the heavier atomic mass atoms [all Co, S and Cl atoms, nitrogen atoms N(101), N(121),
N(131), N(151), N(161), N(171), N(181), N(191), N(201), N(211), N(301), N(311), N(321), N(331),
N(341), N(361), N(371), N(381), N(391), N(401), N(411) (of the helicate ligand strands), N(1) and
N(2) (of the nitrate guest ions) and O(1A), O(1B), O(1C), O(2A), O(2B), O(2C), O(3A), O(3B), O(3C),
O(4A), O(4B), O(4C) (of the nitrate counter ions)] were assigned anisotropic displacement parameters
and refined without positional constraints. Isotropic thermal parameters were retained for a majority of
remaining non-hydrogen atoms, though for atoms C(515)-O(520), C(525)-O(528), C(530)-C(532),
C(610), O(617)-C(619), C(628)-C(632) (in the alkyl and ester groups attached to amide residues),
O(7A)-(7C), N(8), O(8A)-(8C) (in discreet nitrate anions) and C(768) (in a disordered acetonitrile
solvent molecule) thermal parameters were fixed at 150 Å2. All hydrogen atoms were constrained to
ideal geometries and refined with fixed isotropic displacement parameters in calculated positions.
DFIX constraints were used to model three poorly resolved ester (-CO2Me) and four alkyl (-CH(Me)2)
substituents attached to terminal amide residues, (S)-CONHCH(CH(Me)2)(CO2Me), on the ligand
chain. Thus C-C single bonds were constrained to a target value of 1.50(3) Å, C=O double bonds to
1.20(3) Å, and C-O single bonds to 1.40(3) Å. Further DFIX constraints (between non-bonded atoms in
the offending groups) and FLAT restraints were imposed to maintain reasonable ester/alkyl geometries.
Two disordered nitrate anions and an acetonitrile solvent molecule were treated similarly with target NO bond lengths of 1.23(3) Å, C-C bonds of 1.40(3) Å and C-N bonds of 1.20(3) Å. As mentioned
above, the thermal parameters for many of these atoms were fixed at values of 150 Å 2.
The crystal sustained rapid solvent loss on removal from the mother liquor resulting in several poorly
defined solvent molecules in the asymmetric unit. As attempts at modeling the disordered molecules
were unsuccessful a diffuse solvent correction was employed using the SQUEEZE routine in
PLATON.
Finally, as the oscillation of calculated hydrogens on disordered/poorly resolved parent atoms
prevented complete least squares convergence a DAMP 1000 0.05 constraint was used in the final
stages of refinement.