Coordination of Deprotonated Saccharin in Copper(II) Complexes. Structural Role of the Saccharinate Directed by the Ancillary N‐heterocyclic Ligands

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 P2₁/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 P4₂/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 P2₁/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 Pna2₁ 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‐N₄O₂Cu octahedron with elongated copper—oxygen bonds Cu—O_water = 2.462(3), Cu—O_sulfonyl = 2.567(3)Å]. 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 N₄OCu square pyramid Cu—O_water = 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 N₄O₂Cu 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.