The crystal structure of methyltriphenylphosphonium permanganate, C₁₉H₁₈P⁺MnO₄⁻

Abstract

This work is part of a study of the properties of a series of quartenary ammonium and phosphonium permanganates. The title compound v1as recrystallized from a methylenechloride-carbon tetrachloride mixture. Two crystalline forms v1ere found. The first (a) is orthorhombic, space group Pbc2,, a= l2.626(3)A 0 , b = l4.832(26)A 0 , c = l9.806(7)A 0 , Z = 8. The second form (S) is monoclinic, space group P2,jc. Assuming Z = 4 for the S form, the calculated densities are identical (1 .42 g cm-3). The intensity data for the (a) form were collected with a Picker four-circle automated diffractometer controlled by the NRCC Diffractometer Control System (D.F. Grant, E.J. Gabe, Am. Cryst. Assoc. Abstracts, 2, 245, (1974)). The space group was assumed to be Pbcm (<E 2 -l) = 0.94, <E> = 0.81). However, the Patterson map did not show the expected peaks of the form (DOw), associated with the mirror plane. A solution was then attempted in the non-centrosymmetric space group Pbc2, using the version of the direct methods program MULTAN, contained in the NRCC program system. The structure \vas refined by block-diagonal least squares with anisotropic temperature factors to a conventional R factor of 0.086, using the 2110 independent reflections with sin B/A 5 0.60 and I/o(I) > 2.0. The structure contains two formula units in the form of ion pairs related by a local non-crystallographic center of symmetry. Each of the permanganate ions is found near the methyl group of a cation, which allows the closest approach of the permanganate ion to the positive charge centre. The B form is currently under investigation. The most unusual feature of the complex, the tr.vo 4-membered Co-N-C-N rings r.vith a coTILrnon nitrogen atom, shor.vs that two ring closures both using only one carbon atom occurred in the condensation. As a result, the angles subtended at tne metal by the donor nitrogens Nl, N3 and N4 are just.72 & 73°1 and the bridging carbon atoms Cll, Cl2 are only 2.47A from the metal. 08.2-44 SYNTHESIS !I.ND CRYSTAL STRUCTURES OF CAGEDAn expected nnitromethyln cap closes off the opposite side of the complex, r.vhich has in total very approximate mirror symmetry.The novelty of this structure has prompted a corrobative investigation into less suitable crystals of the minor product formed in the same reactions. !l~alysis and structural details of both compounds and of the synthetic mechanisms will be presented. 08.2-45PHASE RELATIONS AND CRYSTAL STRUCTURES IN THE SYSTEM WATER -HYDROGEN FLUORIDE.