Cobalt(III) complexes with a tetradentate chelating system and a monodentate tertiary phosphine

Abstract

Novel cobalt(III) complexes of tetradenate chelating agents (chel) and monodentate tertiary phosphines of the type [Co^III(chel)PR₃]⁺ClO₄^– and [Co^III(chel)PR₃(H₂O)]⁺ClO₄^– are reported. A five-co-ordinate square pyramidal structure is suggested for both types of compound in non-complexing solvents. The thermodynamic trans-effect of PR₃ is indicated by the stoicheiometric formation constants of [Co^III(chel)(PR₃)(NO₂)]⁰ which can be correlated with σ* Taft constants of the phosphines. The trend of the trans-effect of L in [Co^III(chel)-L(H₂O)]⁺ is found to be PR₃ > organic group > OH^– > H₂O.