Complementarity of anion-mediated hydrogen-bonding and alkyl substitution in the construction of two-dimensional rhombic (4,4) grids by bis(N-alkylamidino-O-alkylurea)copper(ii) nitrates and tetrafluoroborates

Suksangpanya, U., Blake, A. J., Hubberstey, P., Parker, D. J., Teat, S. J. and Wilson, C. (2004) Complementarity of anion-mediated hydrogen-bonding and alkyl substitution in the construction of two-dimensional rhombic (4,4) grids by bis(N-alkylamidino-O-alkylurea)copper(ii) nitrates and tetrafluoroborates. CrystEngComm, 5, pp. 23-33. (doi: 10.1039/b210627b)

Abstract

A series of co-ordination complexes containing bis(N-alkylamidino-O-alkylurea)copper(II) cations, [CuL2]2+, and either nitrate or tetrafluoroborate anions has been synthesised. Single crystal X-ray diffraction analysis of five products has revealed the presence of elegant supramolecular hydrogen-bonded networks in which the [CuL2]2+ cations act as four-connecting centres and the anions as two-connecting centres to form 2-D rhombic (4,4) grids. To generate this architecture, the pendant alkyl groups of the N-alkylamidino-O-alkylurea ligands have to be able to fit in the cavity formed within the grid. Ideal fits (complementarity) occur for [Cu(Lme)2]·2BF4 (Lme = N-methylamidino-O-ethylurea) and [Cu(Lem)2]·2NO3 (Lem = N-ethylamidino-O-methylurea) where the pendant alkyl groups are coplanar with the remainder of the cation. An enforced fit is indicated in [Cu(Lee)2]·2X (Lee = N-methylamidino-O-ethylurea; X = NO3 or BF4) and [Cu(L2m)2(ONO2)][Cu(L2m)2(OHMe)]·3NO3·Et2O (L2m = N-benzylamidino-O-methylurea) by some or all of the pendant groups being bent out of the plane of the cation. The four-fold connectivity of the [CuL2]2+ cations arises from the presence of four pairs of N–H donors, set at ca. 90° to each other, which form hydrogen bonds to four anions. The two-fold connectivity of the nitrate and tetrafluoroborate anions arises from two oxygens/fluorines acting as acceptors in an R22(8) motif and one oxygen/fluorine acting as an acceptor in an R12(6) motif. The resultant hydrogen-bonding assemblies are similar for both anions and are considered to be viable supramolecular synthons.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wilson, Dr Claire
• Authors: Suksangpanya, U., Blake, A. J., Hubberstey, P., Parker, D. J., Teat, S. J., and Wilson, C.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: CrystEngComm
• Publisher: Royal Society of Chemistry
• ISSN: 1466-8033
• ISSN (Online): 1466-8033
• Published Online: 15 January 2003