Unusual Reactivity of a Tm-Pyrrolide/Aluminate Complex with a Metallocene-Type Structural Motif

Reaction of in situ generated (Me4Al)3Tm with 2,3,4,5-tetramethylpyrrole afforded Tm(Me){μ-CH2AlMe2(η5-NC4Me4)]2} (1), containing a terminally bonded CH3 group. The two pyrrolide rings confer the bent-metallocenic motif to the lanthanide by adopting a fairly symmetrical π-bonding mode. Each of the N atoms of the pyrrolide rings is bonded to one AlMe2 residue, which in turn bridges the lanthanide through a CH2 unit of an Al2(μ-CH2)Tm moiety. The reactivity of the terminal Me group of 1 was examined with both H2 and PhSiH3. Reaction with H2 under high pressure and room temperature caused loss of the terminal methyl group and major redistribution of the pyrrolyl moieties, yielding Tm[AlMe2(η5-NC4Me4)2][(μ-Me)(AlMe2)][(μ3-CH2)(AlMe3)] (2), with a stable ansa-metallocene type of structure and intacting Al2(μ-CH2)Tm unit. Reaction of 1 with PhSiH3 under mild conditions afforded an even more complex transformation accompanied by evolution of CH4 and formation of toluene. The resulting Tm[AlMe2(η5-NC4Me4)2](AlMe3)(μ3-CH2)(μ3-SiH3)(AlMe2)[Al Me2(NC4Me4)] (3) complex provides a rare example of SiH3 unit trapping.