Interaction of carbon dioxide with zirconocene and hafnocene dihydrides

Molecular Understanding of the Formation of Surface Zirconium Hydrides upon Thermal Treatment under Hydrogen of [(⋮SiO)Zr(CH2tBu)3] by Using Advanced Solid-State NMR Techniques

“…The chemical shifts of these new signals are consistent with the formation of formate zirconium complexes and can be assigned to the bis(formate) and monoformate species, respectively. [50][51][52][53] Besides, there is a shoulder peak next to the (SiH x ) signals at 3.6 ppm, which could be associated with the formation of downfield C sp3 -H protons, that of a methoxy fragment (vide infra), and which is consistent with what has been observed by IR spectroscopy. The DQ 1 H MAS NMR spectrum (Figure 4b) shows autocorrelation peaks for high field signals at 1.0 ppm (2.0 ppm in the ω 1 dimension, residual alkyl fragments), 3.6 ppm (7.2 ppm in the ω 1 dimension, ZrOCH 3 ), and 4.4 ppm (8.8 ppm in the ω 1 dimension, SiH 2 ).…”

“…Reactivity of [Zr − H] with CO 2 . Metal hydrides are known to react with CO 2 to give metal formates. − Upon addition of CO 2 (300 equiv) onto [Zr−H], the ν(Zr−H) bands disappear immediately to give new bands at 1590/1386 and 1544/1370 cm -1 (Figure ), assigned to the antisymmetric/symmetric stretching modes of the two different formate surface complexes. Moreover, two other weak bands also appear: one at 2960 cm -1 , which is consistent with the formation of new C sp3 −H containing fragments, along with a very weak one at 2223 cm -1 .…”

Cerium(III) Carbonate Formation from {CeCp*2H}2 and Carbon Dioxide: Structure and Mechanistic Insights

“…27 Although reports of Ce−H/CO 2 reactivity are scant, zirconocene hydride derivatives such as Schwartz's reagent (Cp 2 Zr(H)Cl) have been shown to react with CO 2 to form formaldehyde, methanol and methyl formate along with Zr oxides. [23][24][25]28 Dimeric titanium hydride complex {CpTi} 2 (μ−H) 2 (μ−C 10 H 8 ) reacts to form an insertion formate product; furthermore, at low CO 2 concentration, methanol is formed. 29,30 Hafnocene hydride Cp* 2 Hf(H)(PR 2 ) reacts with CO 2 to form a double insertion product Cp* 2 Hf(HCO 2 )-(Ph 2 PCO 2 ).…”

“…Although the small-molecule reactivity of the cerium hydride moiety has been previously investigated with {CeCp* 2 H} 2 and other complexes, there have not been any reports to our knowledge using CO 2 . Although reports of Ce–H/CO 2 reactivity are scant, zirconocene hydride derivatives such as Schwartz’s reagent (Cp 2 Zr­(H)­Cl) have been shown to react with CO 2 to form formaldehyde, methanol and methyl formate along with Zr oxides. − , Dimeric titanium hydride complex {CpTi} 2 (μ−H) 2 (μ−C 10 H 8 ) reacts to form an insertion formate product; furthermore, at low CO 2 concentration, methanol is formed. , Hafnocene hydride Cp* 2 Hf­(H)­(PR 2 ) reacts with CO 2 to form a double insertion product Cp* 2 Hf­(HCO 2 )­(Ph 2 PCO 2 ) . Given the predominance of the insertion reaction motif for these types of complexes and the precedence for the formation of a lanthanide carbonate species via a methylene diolate intermediate, it seems most likely that this pathway is also followed for the formation of 1 .…”

Dinuclear Cationic Zirconium Hydrides Stabilized by the N,N-Dibenzylcyclam Ancillary Ligand

“…Not only are zirconium hydride complexes important reagents in organic synthesis − but they have also been used in the reduction of small molecules such as CO 2 and CO; − in addition, certain zirconium hydride species have been found useful in the preparation of dinitrogen complexes via dihydrogen elimination. , For the vast majority of structurally characterized zirconium hydride complexes, cyclopentadienyl-type ligands are typically found to stabilize these derivatives; in fact, the bis(cyclopentadienyl) motif dominates this chemistry. ,− For some time we have been interested in alternative ligand environments − in an attempt to expand early-transition-metal chemistry and, in particular, to explore the use of group 4 and 5 hydride complexes that can serve as entry points into N 2 activation . For this reason, we investigated the formation of zirconium hydride derivatives stabilized by the N,N -dibenzylcyclam (Bn 2 Cyclam) ancillary ligand, in an effort to build on the alkyl and amido chemistry already reported for complexes of this type. − Herein we report the synthesis and characterization of a unique dinuclear zirconium hydride species that is unexpectedly cationic.…”