Mono(pentamethylcyclopentadienyl) complexes of cerium(III). Synthesis, molecular structure, thermal stability, and reactivity of (C5Me5)CeX2 (X = 2,6-di-tert-butylphenoxo, CH(SiMe3)2, and N(SiMe3)2) complexes

Article abstract of DOI:10.1021/om00113a020

Reaction of Ce(OAr)₃¹ (1) with LiR (R = C₅Me₅, 1,3-diphenyl-2-methylindene) affords novel RCe(OAr)₂ (R = C₅Me₅, 2; R = 1,3-diphenyl-2-methylindene, 3) compounds. Metathesis of the remaining aryloxide ligands in 2 with bulky main-group alkyl and amide compounds (LiCH(SiMe₃)₂ and NaN(SiMe₃)₂) provide neutral C₅Me₅CeR₂ complexes (R = CH(SiMe₃)₂,5; R = N(SiMe₃)₂,6). Compound 5 is a polymerization catalyst for ethylene but not for propylene. Compounds 2 and 6 disproportionate in solution with formation of equilibrium mixtures containing C₅Me₅CeX₂, (C₅Me₅)₂CeX, and CeX₃ complexes. Structural studies on 2, 5, and 6 show monomeric, formally five-coordinate compounds in the solid state. Compound 2 crystallizes in the monoclinic space group P2₁ with α = 9.575 (1) A?, b = 17.026 (2) A?, c = 11.530 (1) A?, β = 112.02 (1)°, and Z = 2. Compound 5 crystallizes in the hexagonal space group P6₃ with a = 18.477 (2) A?, c = 15.991 (3) A?, and Z = 6. Compound 6 crystallizes in the monoclinic space group P2₁/c with a = 19.252 (6) A?, b = 13.430 (4) A?, c = 12.503 (3) A?, β = 90.28 (2)°, and Z = 4. All compounds display interesting secondary interactions of the metal with C-H and/or Si-C bonds in the solid state.