Data collection: COLLECT (Hooft, 1998) ; cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008) ; program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) ; molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006) ; software used to prepare material for publication: publCIF (Westrip, 2010) . 