Syntheses, solid structures, and behavior in solution of [MI2(CO)3(pyrazole)2] complexes (M = Mo, W)

Abstract

[MI2(CO)3(pz*H)2] complexes (M = Mo, W; pz*H = pzH, dmpzH, indzH) have been synthesized and characterized in solid state and in solution. These heptacoordinated complexes present a capped octahedron geometry in the solid state where the azole ligands are always coordinated pseudo-cis, and the iodido ligands are coordinated either pseudo-trans (pzH complexes and molybdenum complex with indzH) or pseudo-cis (tungsten complex with dmpzH). Both isomers are found in the crystal structure of [WI2(CO)3(indzH)2]. The difference in energies between both isomers have been theoretically calculated and range between −2.9 and +1.0 kcal/mol. The complexes where the iodido ligands are coordinated pseudo-trans show unequivalent azoles in the NMR at low temperature while they undergo a dynamic process in solution which makes both heterocycles equivalent at room temperature. The other complexes display a dynamic behavior in solution where both heterocycles are equivalent both at room and at low temperatures.