Stereochemistry of seven-co-ordination: crystal structures of rac- and meso-tricarbonyldi-iodo[o-phenylenebis(methylphenylarsine)]molybdenum(II)

Abstract

The crystal structures of the title compounds (I)[rac–o–C₆H₄(AsMePh)₂Mo(CO)₃l₂], CHCl₃, and (II)[meso-o-C₆H₄(AsMePh)₂Mo(CO)₃l₂], have been determined from diffractometer data by the heavy-atom method and refined by least squares to R 0·08 [(I), 2809 reflections] and 0·11 [(II) 2371 reflections]. Crystals of both compounds are triclinic, space group P, with Z= 2 in unit cells of dimensions : (I), a= 14·985(5), b= 12·337(3), c= 9·654(1)Å, α= 110·78(2), β= 101·90(2), γ= 104·74(2)°; (II), a= 15·828(6), b= 10·505(1), c= 9·733(1)Å, α= 120·604(8), β= 98·99(2), γ= 97·69(2)°. Both complexes are comprised of discrete molecules with seven-co-ordinate molybdenum atoms, being of the type [M(bidentate)(unidentate)₅]. A theoretical description of this system has been developed in terms of repulsion theory, yielding four different possible stereochemical types of which examples are found for three among these and previously determined structures of this type.