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

TY - JOUR

T1 - Coordinative unsaturation versus oxophilicity

T2 - Ansa dimethylsilyl oxo-bridged uranium metallocenes. Synthesis, structures, and unexpected catalytic activity with alkynes and silanes

AU - Wang, Jiaxi

AU - Gurevich, Ylia

AU - Botoshansky, Mark

AU - Eisen, Moris S.

PY - 2008/9/8

Y1 - 2008/9/8

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=52649173226&partnerID=8YFLogxK

U2 - 10.1021/om800418u

DO - 10.1021/om800418u

M3 - 文章

AN - SCOPUS:52649173226

SN - 0276-7333

VL - 27

SP - 4494

EP - 4504

JO - Organometallics

JF - Organometallics

IS - 17

ER -