NT*; program(s) used to solve structure: *SHELXTL* (Sheldrick, 0000[@bb00]); program(s) used to refine structure: *SHELXL00* (Sheldrick, 0000[@bb00]); molecular graphics: *PLATON* (Spek, 0000[@bb00]); software used to prepare material for publication: *WinGX* (Farrugia, 0000[@bb0]) and *PLATON*.  Supplementary Material ======================  Crystal structure: contains datablocks global, I. DOI: [00.0000/S0000000000000000/hb0000sup0.cif](http://dx.doi.org/00.0000/S0000000000000000/hb0000sup0.cif)  Structure factors: contains datablocks I. DOI: [00.0000/S0000000000000000/hb0000Isup0.hkl](http://dx.doi.org/00.0000/S0000000000000000/hb0000Isup0.hkl)  Additional supplementary materials: [crystallographic information](http://scripts.iucr.org/cgi-bin/sendsupfiles?hb0000&file=hb0000sup0.html&mime=text/html); [0D view](http://scripts.iucr.org/cgi-bin/sendcif?hb0000sup0&Qmime=cif); [checkCIF report](http://scripts.iucr.org/cgi-bin/paper?hb0000&checkcif=yes)  Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: [HB0000](http://scripts.iucr.org/cgi-bin/sendsup?hb0000)).  