Homoleptic mesityls of iridium(III,IV,V) and ruthenium(IV,V)

Abstract

The interaction of IrCl₃(tht)₃, tht = tetrahydrothiophene, and mesityl (2,4,6-trimethylphenyl, mes)-magnesium bromide in diethyl ether gives Ir(mes)₃ as a very air-sensitive crystalline solid. Interaction of partially dehydrated IrCl₃ with mesityllithium in Et₂O gives the air-stable, paramagnetic Ir(mes)₄. Interaction of RuCl₃(tht)₃ with Mg(mes)₂(thf)₂(thf = tetrahydrofuran) gives Ru(mes)₄. The tetramesityls can be oxidised by AgO₃SCF₃ or NOPF₆ to give, respectively [Ir^V(mes)₄]O₃SCF₃ and [Ru^V(mes)₄]PF₆, the former being diamagnetic and the latter paramagnetic. Cyclic voltammetric and some chemical studies have been made and nuclear magnetic and electron paramagnetic resonance spectra recorded. The NMR spectra of the diamagnetic compounds show that there is synchronous rotation of mesityl groups about the M–C bond. The X-ray crystal structures of Ir(mes)₃, [Ir(mes)₄]O₃SCF₃ and Ru(mes)₄ have been determined; the tris(mesityl) is similar to that of Rh(mes)₃ described earlier while the tetramesityl compounds are tetrahedral or slightly distorted tetrahedral.