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Abstract. (C30H20N2)n, monoclinic, P2Jc, a = 12.865 (5), b = 4.907 (4), c = 17.403 (5) .h, fl = I08.3 (4) ° , Z = 2/n, M r = n(408.5), Dob s = 1.30, Dealt = 1.301 g cm -3. Intensity data collected on a twocircle diffractometer using graphite-monochromated Cu K~t radiation were refined by full-matrix least squares to an R factor of 0-086. Single-crystal structure analyses show that the polymer backbone has the alternating double-single-triple-single bonding pattern and is a planar conjugated system. The carbazolyl groups are planar and make angles of 43.3 and 81° with the b axis and the plane of the polymer backbone, respectively.Introduction. Intensity data were collected on a HewlettPackard-Canberra controlled Supper diffractometer of Weissenberg geometry, using graphite-monochromated Cu K~t (2 = 1.54178 ,~) radiation and a pulseheight analyser. A fixed-counter moving-crystal technique with variable step scans was used (Hanson & Nordman, 1975) (scan range = 9 to 12°; rate = 2 to 8 ° min-~; sin 20ma× = 1.0). 880 reflections were measured;

T h e title compounds crystallize in the orthorhombic system, the 2-methoxy compound (I) in the space group Pnma, and the 2-tert-butyl material (11) in space group Pmcn. Lattice parameters are: (I) a = 6.123 (41, b = 10.02 ( l ) , c = 17.65 (1) A, z = 4: (11) a = 10.077 ( 3 ) , b = 10.662 (3), c = 12.703 (3) A, z = 4. Compounds I and I1 both havechair-form ring conformations with the 5-tert-butyl group axial in both. For I the methoxy on phosphorus is axial and the phosphoryl oxygen is equatorial. The 2-tert-butyl is equatorial in I1 with the thiophosphoryl sulfur axial. In comparison to the structures of a large number of other phosphoranes, these rings systems, especially 11, appear to be somewhat flattened about the C(5) end of the molecule. This apparently results from steric interactions involving the axial tert-butyl groups and the ring atoms C(4), O ( l j , and O ( 3 ) and hydrogens bonded thereto. Bond angle deformations within the 5-tert-butyl and a t its point of attachment to the ring also attest t o this fact. T h e phosphorus end of the ring associated with I1 is highly puckered. This property is shown to be a general one for lJ.2-dioxaphosphorinanes with double-bonded 0, S, or Se axial. For I1 the ring pucker is unusually large. Explanations based on nonbonded interactions of the 2-tert-butyl with ring oxygens O(1) and O ( 3 ) or across the ring with the axial

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