“…Ligands of π type may have open structures like n 3-allyl or n5-(2,4-dimethyl)pentadienyl or cyclic structures like n 5 -cyclopentadienyl (Cp), n6 -arene, n7-cycloheptatrienyl or n 8 -cyclooctatetraenyl (COT). During the latest decades the interest of synthetic chemists, spectroscopists and theorists was mainly focused on f element organometallics with unsubstituted, permethylated and trimethylsilyl substituted Cp and COT ligands [1][2][3][4][5].…”
The crystal field parameters of base-free (Me 3 SiC5 H4 )3 Pr, (C5 H 5 )3 Pr.ΝCCH 3 , (C5 H5 ) 3 La(ΝCCH3 ) 2 :Pr, [Ρr(C8 H8 )]+ and Νd[Ν(SiMe3 ) 2 ]3 as model compound for Νd[CH(SiMe 3 ) 2 ]3 were inserted into the corresponding energy matrices of a model spin-free f1 system. Diagonalizing these matrices the crystal field splitting patterns of the f orbitals were calculated. These experimentally based molecular orbital schemes are compared with the results of previous model calculations.
“…Ligands of π type may have open structures like n 3-allyl or n5-(2,4-dimethyl)pentadienyl or cyclic structures like n 5 -cyclopentadienyl (Cp), n6 -arene, n7-cycloheptatrienyl or n 8 -cyclooctatetraenyl (COT). During the latest decades the interest of synthetic chemists, spectroscopists and theorists was mainly focused on f element organometallics with unsubstituted, permethylated and trimethylsilyl substituted Cp and COT ligands [1][2][3][4][5].…”
The crystal field parameters of base-free (Me 3 SiC5 H4 )3 Pr, (C5 H 5 )3 Pr.ΝCCH 3 , (C5 H5 ) 3 La(ΝCCH3 ) 2 :Pr, [Ρr(C8 H8 )]+ and Νd[Ν(SiMe3 ) 2 ]3 as model compound for Νd[CH(SiMe 3 ) 2 ]3 were inserted into the corresponding energy matrices of a model spin-free f1 system. Diagonalizing these matrices the crystal field splitting patterns of the f orbitals were calculated. These experimentally based molecular orbital schemes are compared with the results of previous model calculations.
“…These contacts are expected to increase with the size of the metal and the need for coordinative saturation. Finally, the possibility of ring methyl metalation to give a so-called tucked-in complex prior to C−H bond activation of the 3-furyl ring proton cannot be excluded at this stage. ,, 4 Eyring plot of furyl ring-opening in complexes 6a , b .…”
Section: Resultsmentioning
confidence: 99%
“…The rare-earth metal centers in half-sandwich complexes are electronically and sterically less saturated than those in metallocene complexes , and show reactivity distinct from that observed for the latter . Intra- and intermolecular C−H bond activation via σ-bond metathesis, particularly well documented for lanthanocene alkyl complexes, has also been reported for half-sandwich complexes. 2a,b For the monocationic complexes, 1j,k the active species proposed for homogeneous olefin polymerization catalysis based on mono(cyclopentadienyl) systems, this reactivity pattern is also pronounced.…”
Section: Introductionmentioning
confidence: 94%
“…The rare-earth metal centers in half-sandwich complexes are electronically and sterically less saturated than those in metallocene complexes , and show reactivity distinct from that observed for the latter . Intra- and intermolecular C−H bond activation via σ-bond metathesis, particularly well documented for lanthanocene alkyl complexes, has also been reported for half-sandwich complexes. 2a,b For the monocationic complexes, 1j,k the active species proposed for homogeneous olefin polymerization catalysis based on mono(cyclopentadienyl) systems, this reactivity pattern is also pronounced. Along with the tendency to undergo ligand redistribution reactions, C−H bond activation is made responsible for the fast catalyst degradation. 2a, We have selected furyl-substituted cyclopentadienyl ligands as typical hemi-labile ligand systems and investigated the stability and reactivity of these complexes.…”
A series of scandium, lutetium, and yttrium complexes containing a tetramethylcyclopentadienyl ligand
with a pendant furyl group, [Ln{η5-C5Me4SiMe2(C4H2RO-2)}(CH2SiMe3)2(THF)] (Ln = Sc, Lu, Y; R =
H, Me), have been synthesized and structurally characterized. Single-crystal X-ray diffraction studies of
the scandium complexes [Sc{η5-C5Me4SiMe2(C4H2RO-2)}(CH2SiMe3)2(THF)] (R = H, Me) revealed a
pseudo-four-coordinate metal center without additional coordination of the furyl group. The previously
elusive lutetium complex [Lu{η5-C5Me4SiMe2(C4H2MeO-2)}(CH2SiMe3)2(THF)] could be isolated and
exhibited structural features analogous to those of the scandium compound. Variable-temperature 1H
NMR spectroscopic studies of the entire series confirmed the labile nature of both the THF ligands and
furyl donor in solution. Rates for the ring-opening reaction, triggered by intramolecular C−H bond
activation, were shown to depend primarily on the metal size. The ring-opening reaction resulted in the
formation of the corresponding dinuclear yne−enolate complexes [Ln{η5:η1-C5Me4SiMe2(C⋮CCHCRO)}(CH2SiMe3)]2 (Ln = Sc, Lu, Y; R = H, Me). Substitution at the 5-furyl position did not markedly influence
the rate of the ring-opening reaction but shifted the position of the monomer−dimer equilibrium toward
the monomer. Only a large excess of THF allowed the observation of monomeric yne−enolate complexes
such as [Y{η5:η1-C5Me4SiMe2(C⋮CCHCHO)}(CH2SiMe3)(THF)2], which was characterized by X-ray
crystallography. Addition of THF increased the stability of the lutetium bis(alkyl) complexes and allowed
the formation of the corresponding cationic compounds by treatment with [NEt3H][BPh4] to yield [Lu{η5:η1-C5Me4SiMe2(C4H2RO-2)}(CH2SiMe3)(THF)
n
][BPh4] (Ln = Lu; R = H, Me), which resisted ring-
opening of the furyl group.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
