“…of the subunit 3 in co-crystallized 2 and 3, Zr-Cl distance is somewhat longer than observed for the pure 3 (vide supra) due to the disordering of the chlorine atom in the crystal of the co-crystallized 2 and 3. It is a known fact that the Group 4 metallocene dihalides, if treated with an appropriate reagent in presence of a side ligand that exhibits both n-donor and, at least weak, p-acidic properties (CO, tertiary phosphanes or even N 2 ) can be reduced to the divalent metal complexes [15][16][17][18][19][20]. However, in absence of such stabilizer and even in case of its low concentration, complexes of the divalent metal eagerly convert to the M(III) compounds [3,4,21].…”