Novel monopentamethylcyclopentadienyl alkoxides of La and Ce; X-ray crystal structure of (C5Me5Ce(OCMe3)2)2

Treatment of monomeric (C5Me5)2LnCH(SiMe3)2 (Ln = La and Ce) compounds with HOCMe3 gives the novel compounds (C5Me5Ln(OCMe3)2)2. An X-ray diffraction study of the cerium analogue reveals a dimeric structure with two symmetrically bridging and two terminal alkoxide ligands in a cis configuration. Crystal data: monoclinic space group P21/c, a 13.163(5), b 17.429(4), c 18.988(4) Å, β 100.75(2) °, V 4279.7 Å3 and Z = 4. Least-squares refinement leads to a final R (based on F) value of 0.044 for 4860 observed reflections. Treatment of (C5Me5)2CeCH(SiMe3)2 with an excess of 2,6-di-t-butylphenol at room temperature gives (C5Me5)2(2,6-di-t-butylphenoxo)cerium. Tris(2,6-di-t-butylphenoxo)cerium and C5Me5H are formed when the mixture is heated to 80 °C. The intermediate (C5Me5)bis(2,6-di-t-butylphenoxo)cerium is not observed under these conditions.