title: An unusual methylene aziridine refined in P2(1)/c and the nonstandard setting P2(1)/n.
abstract: The unusual methylene aziridine 6-tert-butyl-3-oxa-2-thia-1-azabicyclo[5.1.0]oct-6-ene 2,2-dioxide, C(9)H(15)NO(3)S, was found to crystallize with two molecules in the asymmetric unit. The structure was solved in both the approximately orthogonal and the oblique settings of space group No. 14, viz. P2(1)/n and P2(1)/c, respectively. A comparison of these results clearly displayed an increase in the correlation between coordinates in the ac plane for the oblique cell. The increase in the corresponding covariances makes a significant contribution to the standard uncertainties of derived parameters, e.g. bond lengths. Since there is yet no CIF definition for the full variance-covariance matrix, there are clear advantages to reporting the structure in the nonstandard space-group setting.
authors: Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, England.
authors: George C
authors: GC
authors: Feast
authors: James
authors: J
authors: Haestier
authors: Lee W
authors: LW
authors: Page
authors: Jeremy
authors: J
authors: Robertson
authors: Amber L
authors: AL
authors: Thompson
authors: David J
authors: DJ
authors: Watkin
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D001388:Aziridines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D010087:Oxides / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: C546050:6-tert-butyl-3-oxa-2-thia-1-azabicyclo(5.1.0)oct-6-ene 2,2-dioxide; D001372:Aza Compounds; D001388:Aziridines; D010087:Oxides