Coordination of deprotonated saccharin in copper(II) complexes. Structural role of the saccharinate directed by the ancillary N-heterocyclic ligands

Abstract

Four different coordination patterns were observed following the partial or complete thermodynamically-controlled ligand substitution of the hydrated tetraaquabis(o-sulfobenzimidato-N)copper(II) complex with heterocyclic bases as examined by X-ray diffraction. The N-heterocycle directs the o-sulfobenzimidate (saccharinate) anion into the immediate coordination polyhedron of the metal by any of the imido, carbonyl or sulfonyl functionalities, or as a lattice counter-ion in the crystal lattice. Aqua(o-sulfobenzimidato-O)tetrakis(4-methylpyridine)copper(II) o-sulfobenzimidate hemihydrate (1) crystallizes in the monoclinic space group P2(1)/n [a = 14.7858(2), b = 16.9090(1), c = 26.2350(2)Angstrom; beta = 92.861(1)degrees], aquadi(o-sulfobenzimidato-N)bis(4-propylpyridine)copper(II) (2) in the tetragonal space group P4(2)/n [a = 15.4127(l), c = 13.4604(1) Angstrom], diaquatetrakis(3-(2-propenyl)imidazole)copper(II) di-o-sulfobenzimidate (3b) in the monoclinic space group P2(1)/c [a = 9.3959(5), b = 28.029(2), c = 8.8763(3) Angstrom; beta = 111.175(1)degrees] and di(o-sulfobenzimidato)tetra(isoquinoline)copper(II) (4b) in the orthorhombic space group Pna2(1) [a = 23.2132(6), b = 11.5760(2), c = 17.6297(4) Angstrom]. The copper atom in 1 is six-coordinate in a distorted trans-N(4)O(2)Cu octahedron with elongated copper-oxygen bonds [Cu-O(water) = 2.462(3), Cu-O(sulfonyl) = 2.567(3) Angstrom]. This adduct represents the first example of a combined O(sulfonyl)/ionic coordination of the o-sulfobenzimidate ion in the same crystal. The copper atom in 2 is five-coordinate in the form of a N(4)OCu square pyramid [Cu-O(water) = 2.238(5) Angstrom]. In 3, the o-sulfobenzimidate anions are linked to the copper atom through the coordinated water molecule forming a distorted octahedral N(4)O(2)Cu environment. In 4, the copper atom is nearly octahedrally coordinated by four nitrogen atoms and a pair of o-sulfobenzimidate carbonyl oxygen atoms. The structural details of the o-sulfobenzimidate coordination pattern correspond well with the 298 and 77 K FT IR spectra of the adducts. The structures of two other solid adducts, tris(3-(2-propenyl)imidazole)copper(II) di-o-sulfobenzimidate trihydrate (3a) and diaquabis(o-sulfobenzimidato-N)bis(isoquinoline)copper(II) (4a) have been predicted by their spectral features. Alteration of the o-sulfobenzimidate coordination mode upon changing the heterocycle ligand shows that this moiety is as a convenient polyfunctional structural tool for the construction of functional solids.