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

Abstract

The reaction between {CeCp*2H}2 with CO2 in thf resulted in a new cerium­(III) carbonate species, {Ce­(Cp*)2(thf)}2(μ-η2:η1-CO3). Investigations into the mechanism suggest the intermediacy of a bridging oxo-complex, {CeCp*2(thf) x }2(μ-O), which could either be formed from the ring opening and oxygen abstraction from an oxygenated solvent such as thf or via insertion of CO2 and elimination of formaldehyde from the resulting methylenediolate intermediate.

Pentamethylcyclopentadienyl Complexes of Cerium(IV): Synthesis, Reactivity, and Electrochemistry

“…Unsurprisingly, the Ce–O bond in 4 Ph is elongated compared to those in 2 Et and 2 t Bu , while the Ce–Cp* distances are in the same range as the Cp*–Ce–Cp* angles. The overall structural motif of these first cerium­(IV)–Cp* derivatives is similar to those of 1* and 1 tet discussed above and of the cerium­(III) ate complexes [Na­(18-crown-6)­(THF) 2 ] + [Cp* 2 Ce­(S i Pr) 2 ] − as well as the dimeric cerous [Cp* 2 CeH] 2 , [Cp*Ce­(O t Bu) 2 ] 2 , and [Cp* 2 Ce­(SPh)] 2 . ,, Most relevant, isostructural complexes were also found in the presence of other bulky cyclopentadienyls such as in complexes [C 5 H 3 (SiMe 3 ) 2 ] 2 Ce­(O t Bu) 2 and [C 5 H 4 (SiMe 3 )] 2 Ce­(O t Bu) 2 derived from ceric ammonium nitrate (CAN) as the precursor . The terminal Ce–O distance of [Cp*Ce­(O t Bu) 2 ] 2 is slightly elongated [2.116(6) Å] compared to that of 2 t Bu [2.1024(14) and 2.0868(14) Å], which is expected for the contraction of the metal ion with an increasing nuclear charge.…”

“…The latter ate complex did not form a stable cerium­(IV) oxidation product . In 2017, carbonato derivative [Cp* 2 Ce] 2 (μ-CO 3 ) was obtained by treatment of both [Cp* 2 Ce­(μ-H)] 2 and [Cp* 2 Ce] 2 (μ-O) with CO 2 , reiterating the stability of the “Cp* 2 Ce” fragment . Mixed cerous cyclopentadienyl/alkoxy complexes of the type Cp R 2 Ce­(OR′) 2 include [(C 5 H 3 t Bu 2 ) 2 Ce­(OMe)] 2 and [(C 5 H 4 t Bu) 2 Ce­(O i Pr)] 2 . , Related bis­(cyclopentadienyl) cerium­(IV) complexes comprise trimeric oxy derivative [(C 5 H 4 SiMe 3 ) 2 Ce­(O)] 3 , as well as tert -butoxides [C 5 H 3 (SiMe 3 ) 2 ] 2 Ce­(O t Bu) 2 , [C 5 H 4 (SiMe 3 )] 2 Ce­(O t Bu) 2 , and Cp 2 Ce­(O t Bu) 2 , resulting from reactions with ceric ammonium nitrate as the key precursor. − …”

“…The higher steric demand of the tBu substituents in 2 tBu involves slightly larger Ce−O and Ce− Cp* distances than in 2 Et (Table 6). 18,26,43 Most relevant, isostructural complexes were also found in the presence of other bulky cyclopentadienyls such as in complexes [C 5 H 3 (SiMe 3 ) 2 ] 2 Ce-(OtBu) 2 and [C 5 H 4 (SiMe 3 )] 2 Ce(OtBu) 2 derived from ceric ammonium nitrate (CAN) as the precursor. 30 The terminal Ce−O distance of [Cp*Ce(OtBu) 2 ] 2 is slightly elongated [2.116( 6) Å] compared to that of 2 tBu [2.1024( 14) and 2.0868( 14) Å], which is expected for the contraction of the metal ion with an increasing nuclear charge.…”

About the Reaction of C(PPh3)2 with [M(CO)6] (M = Cr, Mo): Unusual Formation of μ‐Carbonato Complexes of Mo under Participation of THF

“…In recent times, oxygen abstraction from THF and formation of a carbonate via CO 2 was described with a Ce complex in THF solution by Sutton. [27]…”