[(1-Azulenyl)methanethiolato-κS](1,4,8,12-tetraazacyclopentadecane-κ4 N)zinc(II) perchlorate

In the title compound, [Zn(C11H26N4)(C11H9S)]ClO4, the ZnII atom is five-coordinated by four N atoms from a neutral 1,4,8,12-tetraazacyclopentadecane aza-macrocycle molecule, and one S atom from an azulenylmethanethiolate ligand. Only monomers are found in the crystal. The coordination geometry can be described as trigonal bipyramidal, with the thiolate group in an equatorial position. The Zn—N and Zn—S distances are in the usual ranges for this type of complex.

In the title compound, [Zn(C 11 H 26 N 4 )(C 11 H 9 S)]ClO 4 , the Zn II atom is five-coordinated by four N atoms from a neutral 1,4,8,12-tetraazacyclopentadecane aza-macrocycle molecule, and one S atom from an azulenylmethanethiolate ligand. Only monomers are found in the crystal. The coordination geometry can be described as trigonal bipyramidal, with the thiolate group in an equatorial position. The Zn-N and Zn-S distances are in the usual ranges for this type of complex.

Comment
The title compound belongs to a series of zinc thiolate complexes with azamacrocyclic ligands (Notni, Görls et al., 2006), which are potent model systems for a number of zinc enzymes (Schenk et al., 2006). These compounds possess nucleophilic p-methylthiolate or phenylmethylthiolate residues, the nucleophilicity of which is influenced by the nature of the macrocyclic ligand (Notni, Schenk et al., 2006;Notni et al., 2007). In order to gain insight into the electronic properties of the sulfur atom, azulenylmethyl derivatives were believed to allow a qualitative estimation of electron density at the thiolate sulfur employing VIS spectroscopy. However, the project failed since most of the desired complexes were elusive due to degradation processes during synthesis.
In crystalline form, the title compound is air-stable for several months. The crystal structure of the title compound contains a monovalent zinc(II) complex cation and a discrete perchlorate anion as shown in Fig. 1. Within the cation, the Zn II atom is coordinated by four N atoms and one S atom. Whether the coordination polyhedron can be assigned to tetragonal-pyramidal or trigonal-bipyramidal type is a question, which has been discussed in detail before (Notni, Görls et al., 2006). Following the argumentation given therein, we consider the title structure being trigonal-bipyramidal since pairs of opposing short Zn-N bond lengths [2.134 (4) and 2.139 (4) Å] as well as long Zn-N bond lengths [2.235 (3) and 2.272 (4) Å] are found. This is the largest difference between short and long Zn-N bond distances found for this type of zinc complexes (Notni, Görls et al., 2006;Salter et al., 2005). The pair of long N-Zn-N bonds is considered the axis of the trigonal bipyramid, the thiolate group thus being found in the equatorial position. The Zn-S bond length of 2.280 (1)Å is within the usual range for this kind of compounds (2.27-2.32 Å). The N atoms in these complexes are chiral in nature and the absolute configuration could be determined. In analogy to similar zinc-thiolate complexes of 1,4,8,12-tetraazacyclopentadecane, the N-bound H atoms are found in (+ ---) positions ('+' denotes the H atom being positioned at the thiolate side of the macrocycle and '-' at the opposite side).
This was filtered off, and from the remaining deep-blue solution, blue needle crystals of the title compound precipitated after 5 min which were collected on a filter funnel and dried in vacuum. Yield 66% ( supplementary materials sup-2 Refinement H atoms were positioned geometrically and refined as riding, with C-H = 0.95Å (CH) and 0.99Å (CH 2 ), and N-H = 0.93Å and U iso (H) = 1.2U eq (C, N). O atoms of the perchlorate group are disordered and they were refined isotropically. Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are drawn at the 40% probability level. The perchlorate anion was omitted for clarity. H atoms have been omitted except those attached to N atoms.

Figures
Crystal data [Zn(C 11