Crystal structures of mono- and binuclear neodymium diarylphosphate complexes and their catalytic activity in 1,3-diene polymerization

Molecular structures of three neodymium tris(organophosphate) complexes of different types have been determined: mononuclear complex {Nd[(2,6-Me2C6H3-O)2PO2]3[(2,6-Me2C6H3-O)2PO2H]3} (1), binuclear complexes {Nd2[(2,6-Me2C6H3-O)2POO]6[(2,6-Me2C6H3-O)2PO2H]} (2) and {Nd2[(2,4-Cl2-6-MeC6H3O)2PO2]6(H2O)2(OCMe2)2} (3). Organophosphate ligands demonstrate κ1O and κ2O,O′ terminal, as well as μ2-κ1O:κ1O' bridging coordination modes. The complexes exhibit intramolecular H-bonding. The associates {[(2,6-Me2C6H3-O)2PO2]2(H)} in the inner coordination sphere of 1 and 2 display a very unusual nearly symmetrical O∙∙∙H∙∙∙O bonds. Complexes 1, 2, and {Nd2[(2,4-Cl2-6-MeC6H3O)2PO2]6} (3′) have been tested as precatalysts in polymerization of butadiene and isoprene. The system based on 3′ has demonstrated catalytic activity superior to neodymium tris[bis(2-ethylhexyl)phosphate] used in industry. The presence of additional acid molecules in precatalysts 1 and 2 decreases catalytic performance of corresponding catalytic systems.