HOMOLEPTIC MESITYLS OF IRIDIUM(III,IV,V) AND RUTHENIUM(IV,V)

The interaction of IrCl3(tht)3, tht = tetrahydrothiophene, and mesityl (2,4,6-trimethylphenyl, mes)-magnesium bromide in diethyl ether gives Ir(mes), 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 [IrV(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), 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.