Coordinative unsaturation versus oxophilicity: Ansa dimethylsilyl oxo-bridged uranium metallocenes. Synthesis, structures, and unexpected catalytic activity with alkynes and silanes

Jiaxi Wang, Ylia Gurevich, Mark Botoshansky, Moris S. Eisen

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The tetrachloride salt of uranium reacts with 1 equiv of the lithium ligand Li2[(C5Me4)2SiMe2] in DME to form the complex [η5-(C5Me4) 2SiMe2]UCl2 · 2LiCl · 2DME (1), which undergoes a rapid hydrolysis either in DME with equimolar amounts of water to give the coordinatively unsaturated bridged monooxide and monochloride uranium lithium salt complex {[η5-(C5Me 4)2SiMe2]UCl}2(μ-O)(μ-Cl) μLi(DME)3 μ DME (2) or in toluene to yield the dimeric bridged monochloride monooxide lithium salt complex [{[η5-(C 5Me4)2SiMe2]UCl}2(μ-O) (μ-Cl)·Li·1/2DME]2 (3). Alkylation of either complex 2 or 3 with BuLi in DME gives the monobridged dibutyl complex {[η5-(C5Me4)2SiMe 2]UBu}2(μ-O) (4). Complex 2 was characterized by solid state X-ray analysis. Complex 4 was found to be an active catalyst for the disproportionation metathesis of TMSC≡CH and the cross-metathesis of TMSC≡CH or TMSC≡CTMS with various terminal alkynes. To shed some light on the possible mechanistic scenario, different alkynes, TMSC≡CH, TMSC≡CTMS, or TMSC≡CPri, were reacted in the presence of complex 4 with PhSiH3, producing a myriad of products in addition to the unexpected TMSH and SiH4 (caution), indicating the cleavage of the trimethylsilyl group from the alkyne and the formation of a uranium-silyl intermediate. Complex 4 was also found to be an active catalyst for the phenyl cleavage metathesis of PhSiH3 to form Ph2SiH2 and Ph3SiH. In C6D6 solutions, the C-D activation of the aromatic ring takes place, forming C6D 5SiH3. Plausible mechanisms for all the catalytic processes are presented.

Original languageEnglish
Pages (from-to)4494-4504
Number of pages11
JournalOrganometallics
Volume27
Issue number17
DOIs
StatePublished - 8 Sep 2008
Externally publishedYes

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