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

摘要

Crystals of mononuclear tris[bis(2,6‐diisopropylphenyl) phosphato‐κ O ]pentakis(methanol‐κ O )lanthanide methanol monosolvates of lanthanum, [La(C 24 H 34 O 4 P) 3 (CH 3 OH) 5 ]·CH 3 OH, ( 1 ), cerium, [Ce(C 24 H 34 O 4 P) 3 (CH 3 OH) 5 ]·CH 3 OH, ( 2 ), and neodymium, [Nd(C 24 H 34 O 4 P) 3 (CH 3 OH) 5 ]·CH 3 OH, ( 3 ), have been obtained by reactions between LnCl 3 (H 2 O) 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 P 2 1 / c space group and have isomorphous crystal structures. All three bis(2,6‐diisopropylphenyl) phosphate ligands display a κ O ‐monodentate coordination mode. The coordination number of the metal atom is 8. Each [Ln{O 2 P(O‐2,6‐ i Pr 2 C 6 H 3 ) 2 } 3 (CH 3 OH) 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{O 2 P(O‐2,6‐ i Pr 2 C 6 H 3 ) 2 } 3 (CH 3 OH) 5 ]·CH 3 OH 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 tris[bis(2,6‐diisopropylphenyl) phosphato‐κ O ]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.