cis-(1,4,8,11-Tetraazacyclotetradecane-κN 4)bis(thiocyanato-κN)chromium(III) thiocyanate

The crystal structure of [Cr(NCS)2(cyclam)]NCS (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4) has been determined by using synchrotron radiation at 98 K. The CrIII atom is in a slightly distorted octahedral environment with four N atoms of the macrocyclic ligand and two N-coordinated NCS− anions in cis positions. The average Cr—N(cyclam) and Cr—NCS bond lengths are 2.085 (5) and 1.996 (15) Å, respectively. In the crystal, the uncoordinating SCN− anion is hydrogen bonded through N—H⋯S and N—H⋯N interactions to neighbouring complex cations.

The crystal structure of [Cr(NCS) 2 (cyclam)]NCS (cyclam = 1,4,8,11-tetraazacyclotetradecane, C 10 H 24 N 4 ) has been determined by using synchrotron radiation at 98 K. The Cr III atom is in a slightly distorted octahedral environment with four N atoms of the macrocyclic ligand and two N-coordinated NCS À anions in cis positions. The average Cr-N(cyclam) and Cr-NCS bond lengths are 2.085 (5) and 1.996 (15) Å , respectively. In the crystal, the uncoordinating SCN À anion is hydrogen bonded through N-HÁ Á ÁS and N-HÁ Á ÁN interactions to neighbouring complex cations.
In this communication, we report the structure of [Cr(cyclam)(NCS) 2 ]SCN in order to determine the mode of bonding of the thiocyanate group and to verify geometrical assignment made on the basis of spectroscopic measurements (Poon & Pun, 1980;Choi & Park (2003).
Counter anionic species play a very important role in coordination chemistry. This is another example of a cis-[Cr(cyclam) 2 (NCS) 2 ] + but with different counter anion (Friesen et al., 1997). The structural analysis shows that there is only one crystallographically independent Cr(III) complex cation where the nitrogen atoms of cyclam ligand occupy four adjacent sites and the two N-bonded NCS groups coordinate to the chromium centre in cis arrangement. The cyclam adopts the folded cis-V configuration with six-and five-membered chelate rings in chair and gauche conformation, respectively. The same conformational arrangement has been found in cis-[Cr(cyclam)(ONO) 2 ]NO 2 (Choi et al., 2004a).

Experimental
The free ligand cyclam was purchased from Stream Chemicals and used as provided. All chemicals were reagent grade materials and used without further purification. The cis-[Cr(cyclam)(NCS) 2 ]SCN was synthesized according to the literature (Ferguson & Tobe, 1970).

Refinement
Non-hydrogen atoms were refined anisotropically; hydrogen atoms were first located in a difference map; N-H hydrogen atoms were freely refined and C-H hydrogen atoms were constrained to ride on the parent carbon atom, with C-H = 0.98 Å and C-H = 0.99 Å and U iso (H) = 1.2U eq (C) for methylene groups.