Crystal structures of two cross-bridged chromium(III) tetra-aza-macrocycles

Timothy J Prior; Danny L Maples; Randall D Maples; Wesley A Hoffert; Trenton H Parsell; Jon D Silversides; Stephen J Archibald; Timothy J Hubin

doi:10.1107/S1600536814019072

Crystal structures of two cross-bridged chromium(III) tetra-aza-macrocycles

Acta Crystallogr Sect E Struct Rep Online. 2014 Aug 30;70(Pt 9):148-52. doi: 10.1107/S1600536814019072. eCollection 2014 Sep 1.

Authors

Timothy J Prior¹, Danny L Maples², Randall D Maples², Wesley A Hoffert³, Trenton H Parsell³, Jon D Silversides¹, Stephen J Archibald¹, Timothy J Hubin²

Affiliations

¹ Department of Chemistry, University of Hull, Cottingham Road, Hull HU6 7RX, England.
² Department of Chemistry and Physics, Southwestern Oklahoma State University, Weatherford, OK 73096, USA.
³ Department of Natural Science, McPherson College, McPherson, KS 67460, USA.

Abstract

The crystal structure of di-chlorido-(4,10-dimethyl-1,4,7,10-tetra-aza-bicyclo-[5.5.2]tetra-deca-ne)chromium(III) hexa-fluorido-phosphate, [CrCl2(C12H26N4)]PF6, (I), has monoclinic symmetry (space group P21/n) at 150 K. The structure of the related di-chlorido-(4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-deca-ne)chromium(III) hexa-fluorido-phosphate, [CrCl2(C14H30N4)]PF6, (II), also displays monoclinic symmetry (space group P21/c) at 150 K. In each case, the Cr(III) ion is hexa-coordinate with two cis chloride ions and two non-adjacent N atoms bound cis equatorially and the other two non-adjacent N atoms bound trans axially in a cis-V conformation of the macrocycle. The extent of the distortion from the preferred octa-hedral coordination geometry of the Cr(III) ion is determined by the parent macrocycle ring size, with the larger cross-bridged cyclam ring in (II) better able to accommodate this preference and the smaller cross-bridged cyclen ring in (I) requiring more distortion away from octa-hedral geometry.

Keywords: chromium complexes; cross-bridged macrocycle; crystal structure.