Isomorphous rare‐earth tris[bis(2,6‐diisopropylphenyl) phosphate] complexes and their catalytic properties in 1,3‐diene polymerization and in the inhibited oxidation of polydimethylsiloxane

Crystals of mononuclear trisbis(2,6‐diisopropylphenyl) phosphato‐κO]pentakis(methanol‐κO)lanthanide methanol monosolvates of lanthanum, La(C₂₄H₃₄O₄P)₃(CH₃OH)₅]·CH₃OH, ( 1 ), cerium, Ce(C₂₄H₃₄O₄P)₃(CH₃OH)₅]·CH₃OH, ( 2 ), and neodymium, Nd(C₂₄H₃₄O₄P)₃(CH₃OH)₅]·CH₃OH, ( 3 ), have been obtained by reactions between LnCl₃(H₂O)_n (n = 6 or 7) and lithium bis(2,6‐diisopropylphenyl) phosphate in a 1:3 molar ratio in methanol media. Compounds ( 1 )–( 3 ) crystallize in the monoclinic P2₁/c space group and have isomorphous crystal structures. All three bis(2,6‐diisopropylphenyl) phosphate ligands display a κO‐monodentate coordination mode. The coordination number of the metal atom is 8. Each Ln{O₂P(O‐2,6‐ⁱPr₂C₆H₃)₂}₃(CH₃OH)₅] molecular unit exhibits four intramolecular O—H…O hydrogen bonds, forming six‐membered rings. The unit forms two intermolecular O—H…O hydrogen bonds with one noncoordinating methanol molecule. All six hydroxy H atoms are involved in hydrogen bonding within the Ln{O₂P(O‐2,6‐ⁱPr₂C₆H₃)₂}₃(CH₃OH)₅]·CH₃OH unit. This, along with the high steric hindrance induced by the three bulky diaryl phosphate ligands, prevents the formation of a hydrogen‐bond network. Complexes ( 1 )–( 3 ) exhibit disorder of two of the isopropyl groups of the phosphate ligands. The cerium compound ( 2 ) demonstrates an essential catalytic inhibition in the thermal decomposition of polydimethylsiloxane in air at 573 K. Catalytic systems based on the neodymium complex trisbis(2,6‐diisopropylphenyl) phosphato‐κO]neodymium, ( 3′ ), which was obtained as a dry powder of ( 3 ) upon removal of methanol, display a high catalytic activity in isoprene and butadiene polymerization.