Single Crystal X-ray Diffraction Determination Research Articles

Metal complexes of fluorophosphines: XIV. Structures of five zerovalent metal complexes of methylaminobis(difluorophosphine)

Details are presented of single crystal X-ray diffraction determinations of the structures of the five zerovalent metal complexes Cr[PF 2N(CH 3) 2] 4[(PF 2) 2NCH 3], Fe[(PF 2) 2NCH 3] 4, and [CH 3N(PF 2) 2] 3Co 2L 2 (L = CO, CH 3NHPF 2, and (CH 3) 2NPF 2). The chromium atom in Cr[PF 2N(CH 3) 2] 4[(PF 2) 2NCH 3] has a distorted octahedral coordination with four monodentate (CH 3) 2NPF 2 ligands and one bidentate CH 3N(PF 2) 2 ligand; the small bite of the latter ligand distorts one of the idealized 90° angles of the CrP 6 octahedron to 67°. The iron atom in Fe[(PF 2) 2NCH 3] 4 has a distorted trigonal bipyramidal coordination with three monodentate CH 3N(PF 2) 2 ligands and one bidentate CH 3N(PF 2) 2 ligand. The bidentate CH 3N(PF 2) 2 ligand in Fe[(PF 2) 2NCH 3] 4 is coordinated to an axial and an equatorial position of the FeP 5 trigonal bipyramid and because of its small bite squeezes the relevant P ax-Fe-P eq angle from the ideal value of 90° down to 69°. The structures of the binuclear cobalt complexes [CH 3N(PF 2) 2] 3Co 2L 2 (L = CO, (CH 3) 2NPF 2, and CH 3NHPF 2) may be regarded as consisting of two CoCoLP 3 trigonal bipyramids linked through a cobalt-cobalt bond. Further linking of the two trigonal bipyramids occurs through the three biligate bimetallic CH 3N(PF 2) 2 ligands, each of which bridges an equatorial position of one trigonal bipyramid with an equatorial position of the other trigonal bipyramid thereby leading to a [3.3.3]propellane structure in which the edge shared by the three five-membered chelate rings is the cobalt-cobalt bond. Significant deviations from three-fold symmetry occur in these trigonal bipyramids and in a given binuclear cobalt complex the two trigonal bipyramids are twisted by about 30° relative to each other.

Structural studies in the lepidopterene system

.A new, metastable phase of lepidopterene, (5,6,11,12-tetrahydro-4b,12[1',2']:6,10b[1",2"]-dibenzenochrysene) (1), has been obtained from methylene chloride solution, exhibiting a luminescence which differs from that of the stable form, having an absorption maximum at 580 nm rather than 560 nm. Single crystal X-ray diffraction determination of the structure of the new phase shows it to be orthorhombic, Pbcn, a 36.75(3), b 7.229(7), c 44.85(3) Ǻ, Z 24, the structure being refined to a residual of 0.065 for 2413 independent 'observed' reflections. Despite the relatively low precision of the determination, it is evident that in the metastable form, the gross molecular disposition is severely distorted. The crystal structure of dimethyllepidopterene (2) has also been determined, and refined by least squares to a residual of 0.041 for 632 'observed' reflections. Crystals are mono- clinic, P21/c, with a 9.607(4), b 11.564(7), c 10.576(6) Ǻ, β 107.72(4), Z 2; the molecules are centrosymmetric. Tetrachlorolepidopterene (31, formed by the dimerization of 1,5-dichloro-9-anthrylmethyl, yields two crystalline forms from xylene and methylene chloride solutions which differ in their crystal exciplex luminescence, showing emission maxima at 590 and 575 nrn respectively. Single- crystal X-ray structure determination confirms that the two crystalline forms, α- and β-, are polymorphs of the same centrosymmetric molecular species. For the α-form, crystals are triclinic, P1 , a 15.374(6), b 9.858(4), c 8.000(4) Ǻ, α 83.98(4), β 83.73(3), γ 71.53(3)°, Z 2, 2138 independent 'observed' reflections being refined to a residual of 0.037; the unit cell contains two independent centrosymmetric molecules. For the β-form, crystals are monoclinic, C2/c, a 11.03(2), b 13.67(2), c 16.32(3) Ǻ, β 1 1 1.13(12)°, Z 4; the residual for 1554 independent reflections was 0.053.