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<inf>1</inf>/n [a = 14.7858(2), b = 16.9090(1), c = 26.2350(2) Å; β = 92.861(1)°], aquadi(o-sulfobenzimidato-N)bis(4-propylpyridine)-copper(II) (2) in the tetragonal space group P4<inf>2</inf>/n [a = 15.4127(1), c = 13.4604(1) Å], diaquatetrakis(3-(2-propenyl)imidazole)-copper(II) di-o-sulfobenzimidate (3b) in the monoclinic space group P2<inf>1</inf>/c [a = 9.3959(5), b = 28.029(2), c = 8.8763(3) Å; β = 111.175(1)°] and di(o-sulfobenzimidato)tetra(isoquinoline)copper(II) (4b) in the orthorhombic space group Pna2<inf>1</inf> [a = 23.2132(6), b = 11.5760(2), c = 17.6297(4) Å]. The copper atom in 1 is six-coordinate in a distorted trans-N<inf>4</inf>O<inf>2</inf>Cu octahedron with elongated copper-oxygen bonds [Cu-O<inf>water</inf> = 2.462(3), Cu-O<inf>sulfonyl</inf> = 2.567(3) Å]. This adduct represents the first example of a combined O<inf>sulfonyl</inf>/ionic coordination of the o-sulfobenzimidate ion in the same crystal. The copper atom in 2 is fivecoordinate in the form of a N<inf>4</inf>OCu square pyramid [Cu-O<inf>water</inf> = 2.238(5) Å]. In 3, the o-sulfobenzimidate anions are linked to the copper atom through the coordinated water molecule forming a distorted octahedral N<inf>4</inf>O<inf>2</inf>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.