STRUCTURAL CHARACTERIZATION OF 2 SOLID-STATE FORMS OF THE COMPLEX BIS[1,1'-BIS(DIPHENYLPHOSPHINO)FERROCENE] RHODIUM(I) TETRAPHENYLBORATE

This paper describes a work aimed at determining the molecular structu re of a rhodium(I) complex along an experimental track in which a conv entional X-ray single crystal structural analysis was accidentally pre ceded by a powder X-ray diffractometric investigation. The complex [Rh (dppf)(2)]BPh(4) (dppf=1,1'-bis(diphenylphosphino)ferrocene) was obtai ned from dichloroethane in two crystalline forms, hereafter referred t o as alpha and beta, which are different in colour and in the content of lattice-entrapped solvent. Conventional and synchrotron powder wide angle X-ray diffractometry (WAXS), FT-IR, P-31 and H-1 NMR spectrosco py demonstrate that alpha and beta are dimorphic forms of the same mol ecular entity. The observed WAXS spectrum of the alpha form was comput ationally fitted (R=11.3%) with that calculated for [Rh(dppf)(2)]BPh(4 ), upon assuming that the molecular geometry of the title complex was identical to that of the already determined iridium analogue, i.e. squ are-planar with a pronounced tetrahedral distortion. X-ray single crys tal structural analysis confirmed this conclusion. FT-IR, DSC and TG a nalyses have also been employed for a solid state characterization of the two species.