Magnetic interaction between d1 [MOR4]-units of Molybdenum and Tungsten

Five-coordinate oxo-derivatives [NBu 4 ][MO(C 6 F 5 ) 4 ] (1) have been prepared for the heavier Group 6 elements: 1-Mo and 1-W. The magnetic properties of that salts have been studied by a combination of Electron paramagnetic resonance (EPR), calorimetric and magnetochemical techniques, pointing out the existence of weak ferromagnetic interactions. These have been correlated with the arrangement of the magnetic units in the crystal.