Synthesis and characterisation of some main-group compounds with bulky electron-withdrawring substituents

Abstract

Several new group 13, 14 and 15 derivatives with the ligands 2,4,6-(CF(_3))(_3)C(_6)H(_2) (Ar), 2,6- (CF(_3))(_2)C(_6)H(_3) (Ar') and / or 2,4-(CF(_3))(_2)C(_6)H(_3) (Ar") have been prepared. They have been characterised by multinuclear NMR spectroscopy and, for all isolated compounds, by elemental analysis and, where possible, single crystal X-ray diffraction. Reaction of ArLi or the mixture Ar'Li/Ar"Li with BCI3 has led to the characterisation of several mono- and disubstituted compounds, but attempted substitution in AICI3 was unsuccessful. Reaction of EC1(_4) (E = Si, Ge, Sn) with the Ar'Li/Ar"Li mixture yielded predominantly the less sterically hindered disubstituted product Ar"(_2)ECl(_2) for E = Si and Ge but to Ar'(_2)ECl(_2) for E = Sn. In the case of B or Si, chlorine exchange is observed and Ar(_2)BF, Ar(_2)SiF(_2) and Ar'(_2)SiF(_2) have been synthesised. Ar(_2)SiF(_2) is the only product identified in the reaction of ArLi with SiC1(_4). Reaction of ArLi or the Ar'Li/Ar"Li mixture, in an appropriate ratio, with group 15 derivatives gave rise to several mono-or disubstituted compounds of the type ArEX(_2), Ar(_2)EX, Ar'EX(_2), Ar"EX(_2), Ar"(_2)EX and Ar'Ar"EX (E = P or As; X = H, CI or Br). (^19)F NMR spectra of Ar'Ar"EX show that, for the two ortho-CF(_3) groups of the Ar' moiety, there is free rotation of the aryl group around the central atom. A series of variable temperature studies has been carried out, and allowed the determination of the rotational energy barrier of the molecule. For the first time, the molecular structures of derivatives containing three fluoroxyl ligands have been determined (Ar"(_3)B and Ar'Ar"(_2)Sb).The synthesis of some new platinum complexes has been facilitated by reaction of phosphanes with the platinum dimer [(PtCl(_2)(Pet(_3))](_2) or [(PtBr(_2)(Pet(_3))](_2). Reactions of the platinum dimer with arsane derivatives have not been successful. Halogen exchange was observed between bromophosphane ligands and CI groups on the platinum. Attempts have been made to synthesise new P=E derivatives containing the electron- withdrawing substituents Ar or Ar' via reaction with the chlorine abstractor W(PMe(_3))(_6)- ArP=PAr and Ar'P=PAr' have been prepared. Synthesis of the first phosphaalkyne containing Ar or Ar' has been attempted by reacting a phosphaalkene with a Pt(0) species.