A [2 × 2] Cu4 molecular grid and a Mn5 cluster derived from a 1-(2-pyridyl)pyrazole based polytopic ligand – Synthesis, structure, magnetic properties and catalytic activity in the allylic oxidation of cyclohexene

Abstract The homoleptic [2 × 2] tetranuclear compound [Cu 4 (PyPzCAP) 4 ](NO 3 ) 4 ·8H 2 O ( 1 ) and the pentanuclear Mn(II) cluster [Mn 5 (PyPzCAP) 6 ](ClO 4 ) 4 ·4C 6 H 6 ( 2 ) are self-assembled from the ditopic pro-ligand HPyPzCAP [(5-methyl-1-(pyridin-2-yl)-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide)]. Complex 1 is almost a square grid, and all the Cu(II) centers show a distorted octahedral environment with an N 4 O 2 chromophore. Complex 2 has a pentanuclear core with a trigonal bipyramidal arrangement of the Mn(II) atoms. The axial Mn centers bear an N 3 O 3 chromophore and the equatorial centers have an N 4 O 2 distorted octahedral arrangement. Complex 1 shows a ferromagnetic exchange interaction ( J  = +4.62 cm −1 and g  = 2.05), whereas 2 shows weak an antiferromagnetic interaction ( J  = −2.73 cm −1 and g  = 2.02). Both complexes 1 and 2 catalyze the allylic oxidation of cyclohexene to cyclohex-2-ene-1-one with good selectivity and an excellent overall turnover number.