Hydride derivatives of Group 4 metals with the ansa-( SiMe2)2(η5-C5H3)2 ligand

Preparation and Characterization of Monomeric and Dimeric Group IV Metallocene Dihydrides Having Alkyl-Substituted Cyclopentadienyl Ligands

“…Thus, for example, the molecular weight indicates that Cp* 2 ZrH 2 is monomeric, and accordingly a single resonance at δ 7.46 is observed at room temperature in benzene-d 6 for the equivalent ZrH 2 . Similarly, monomeric Cp*(η 5 -C 5 HMe 4 )ZrH 2 (12), Cp*{η 5 -C 5 H 3 -1,3-(CMe 3 ) 2 }ZrH 2 (9), and {η 5 -C 5 H 3 -1,3-(CMe 3 ) 2 } 2 ZrH 2 (13) exhibit singlets at δ 7.45, δ 7.09, and δ 7.36, respectively, for their ZrH 2 .…”

“…19 Taken together, these observations suggest that the methyl groups that are most accessible for formation of "tuck-in" intermediates are those directed toward the side of the metallocene wedge in the ligand array (eq 5). The remarkably exacting orientations for metalation of a methylsubstituted cyclopentadienyl ligand is perhaps most evident in the H/D exchange reactions for Cp*{η 5 -C 5 H 3 -1,3-(CMe 3 ) 2 }ZrH 2 (9). Treatment of 9 with D 2 at 23 °C results in slow exchange with the C-H positions of the CMe 3 groups over a period of several hours.…”

“…More recently, ansa -zirconocene dihydride complexes have been synthesized. Buchwald has reported the synthesis of [ rac -(EBTHI)MH 2 ] 2 (EBTHI = ethylene-1,2-bis(η 5 -tetrahydroindenyl); M = Zr, Hf) via reduction of the corresponding dichloride complexes with NaBEt 3 H. Royo has used similar methodology to prepare dimeric, doubly SiMe 2 -bridged [(Me 2 Si) 2 (η 5 -C 5 H 3 ) 2 MH 2 ] 2 (M = Zr, Hf). Parkin has prepared [OpZrH 2 ] 2 (Op = Me 2 Si(η 5 -C 5 Me 4 ) 2 ) via hydrogenation of the dimethyl complex at elevated temperatures in cyclohexane solution .…”

β-Hydrogen-Containing Zirconium Alkyls with the Doubly-Bridged Bis(dimethylsilanediyl)dicyclopentadienyl Ligand. X-ray Molecular Structures of [Zr{(SiMe2)2(η5-C5H3)2}ClEt] and [Zr{(SiMe2)2(η5-C5H3)2}Et]2(μ-CH2CH2)

“…Previously, we reported , some group 4 ansa -metallocene complexes with the di- ansa -bis(dimethylsilandiyl)dicyclopentadienyl dianion, [(η 5 -C 5 H 3 ) 2 (Me 2 Si) 2 ] 2- . This ligand increases the stereorigidity of the complex and usually leads to rather close bending angles, θ, between the cyclopentadienyl rings when compared with typical values of 123−134° …”

Unusual stability of the coordinated triethylborohydride anion in an alkaline-earth metal complex: crystallographic characterization of [Ca(HBEt3){1,2,4-C5(SiMe3)3H2}(thf)2]

“…Parallels between the structure and reactions of the heavier Group 2 and divalent lanthanide elements 9 suggest that an alkaline-earth mono(cyclopentadienyl) halide might serve as a precursor to an organometallic hydride by metathetical reaction with an appropriate hydride source. 10,11 To examine this possibility, the iodide-bridged dimer {Ca(m-I)[1,2,4-C 5 (Si-Me 3 ) 3 H 2 ](thf)} 2 12 was allowed to react in toluene with Na[HBEt 3 ]; removal of the NaI precipitate and evaporation of the filtrate left an air-and moisture-sensitive white solid that could be recrystallized from thf and was characterized as the triethylborohydride complex [Ca(HBEt 3 ){1,2,4-C 5 (Si-Me 3 ) 3 H 2 }(thf) 2 ] 1. † Spectroscopic evidence indicates that the [HBEt 3 ]anion in 1, which has transferred intact from Na + , is involved in a bridging Ca•••H•••BEt 3 interaction.…”