Abstract:PCy 3 (2) and P i Pr 3 (3) have been measured by solution calorimetry in THF at 30°C. In order to test the internal consistency of the approach, a thermochemical cycle was constructed involving reactions of Cp*Ru(PR 3 )OR f with tertiary phosphine and phosphite ligands (L) leading to the formation of Cp*Ru(L) 2 OR f complexes. The range of these reaction enthalpies spans some 11 kcal/mol. Furthermore, complex 1 reacts directly with smaller cone angle phosphines to quantitatively yield Cp*Ru(L) 2 OR f complexes… Show more
“…X-ray data are also consistent with a tetramethylfulvene rather than an η 1 :η 5 -CH 2 C 5 Me 4 (σ:η 5 -CH 2 C 5 Me 4 ) description (vide infra). Related methyl C−H activation processes of transition metal coordinated C 5 Me 5 and C 6 Me 6 ligands have been reported previously. , …”
Section: Resultssupporting
confidence: 67%
“…The Ru−C(6) bond distance is comparable (2.298(7) Å) to those of other ruthenium complexes containing the η 6 -C 5 Me 4 CH 2 ligand (cf. 2.301(2), 2.268(4) (2.271(4)), and 2.430(11) Å in Ru(η 6 -C 5 Me 4 CH 2 )(COD),12a [Ru(η 6 -C 5 Me 4 CH 2 )Cl 2 ] 2 , 12b,c and [Ru(η 6 -C 5 Me 4 CH 2 )(Me 2 NCH 2 CH 2 NMe 2 )(OH)]PF 6 ,12e respectively). 4 Structural view of [RuCp(η 4 -CH(C 6 H 9 )CHC(C 6 H 9 )CH−PCy 2 (η 1 -C 6 H 10 ))]PF 6 ( 6a ) showing 20% thermal ellipsoids (PF 6 - omitted for clarity).…”
Ruthenium allyl carbene complexes of the type [RuCp(dC(R)-(η 3 -CHC(R)CHPR′ 3 ))]PF 6 (R, R′ ) aryl, alkyl substituents) are characterized by two reaction modes. (i) They behave as masked coordinatively unsaturated complexes and react readily with the donor ligands PR 3 and P(OR) 3 to give η 3 -butadienyl complexes. This is not a simple nucleophilic addition at the metal center but involves changes in both the bonding mode and the stereochemistry of the allyl carbene C 4 -chain. The incoming nucleophile induces C-H bond activation effecting formally a 1,4 hydrogen shift. (ii) They are capable of activating C-H bonds of aryl and alkyl groups in the bulky tertiary phosphine ligands PPh 3 and PCy 3 to give novel η 4 -butadiene complexes. In these, one R of PR 3 is σ-bonded to the metal center. A divergent rearrangement results if the allyl carbene complex derives from parent acetylene (instead of a terminal alkyne). In this case the C 4 -unit features a η 3 -allyl moiety and the metal center is η 2 -coordinated to an arene ring of the PPh 3 substituent. Finally, RuCp* allyl carbene complexes have been prepared for the first time. They are reactive entities and react slowly with cleavage of one of the ring methyl C-H bonds of the Cp* ligand to give tetramethylfulvene-type complexes.
“…X-ray data are also consistent with a tetramethylfulvene rather than an η 1 :η 5 -CH 2 C 5 Me 4 (σ:η 5 -CH 2 C 5 Me 4 ) description (vide infra). Related methyl C−H activation processes of transition metal coordinated C 5 Me 5 and C 6 Me 6 ligands have been reported previously. , …”
Section: Resultssupporting
confidence: 67%
“…The Ru−C(6) bond distance is comparable (2.298(7) Å) to those of other ruthenium complexes containing the η 6 -C 5 Me 4 CH 2 ligand (cf. 2.301(2), 2.268(4) (2.271(4)), and 2.430(11) Å in Ru(η 6 -C 5 Me 4 CH 2 )(COD),12a [Ru(η 6 -C 5 Me 4 CH 2 )Cl 2 ] 2 , 12b,c and [Ru(η 6 -C 5 Me 4 CH 2 )(Me 2 NCH 2 CH 2 NMe 2 )(OH)]PF 6 ,12e respectively). 4 Structural view of [RuCp(η 4 -CH(C 6 H 9 )CHC(C 6 H 9 )CH−PCy 2 (η 1 -C 6 H 10 ))]PF 6 ( 6a ) showing 20% thermal ellipsoids (PF 6 - omitted for clarity).…”
Ruthenium allyl carbene complexes of the type [RuCp(dC(R)-(η 3 -CHC(R)CHPR′ 3 ))]PF 6 (R, R′ ) aryl, alkyl substituents) are characterized by two reaction modes. (i) They behave as masked coordinatively unsaturated complexes and react readily with the donor ligands PR 3 and P(OR) 3 to give η 3 -butadienyl complexes. This is not a simple nucleophilic addition at the metal center but involves changes in both the bonding mode and the stereochemistry of the allyl carbene C 4 -chain. The incoming nucleophile induces C-H bond activation effecting formally a 1,4 hydrogen shift. (ii) They are capable of activating C-H bonds of aryl and alkyl groups in the bulky tertiary phosphine ligands PPh 3 and PCy 3 to give novel η 4 -butadiene complexes. In these, one R of PR 3 is σ-bonded to the metal center. A divergent rearrangement results if the allyl carbene complex derives from parent acetylene (instead of a terminal alkyne). In this case the C 4 -unit features a η 3 -allyl moiety and the metal center is η 2 -coordinated to an arene ring of the PPh 3 substituent. Finally, RuCp* allyl carbene complexes have been prepared for the first time. They are reactive entities and react slowly with cleavage of one of the ring methyl C-H bonds of the Cp* ligand to give tetramethylfulvene-type complexes.
“…Stable coordinatively unsaturated ruthenium complexes Cp*Ru(L)X, in which L represents a sterically demanding phosphine or an NHC ligand and X represents a halide or an alkoxide ligand, are well-known in the literature . Moreover, the binding of these imidazole- and phosphine-based ligands to the Cp*RuCl moiety was thoroughly investigated by thermochemistry and structural studies . A linear correlation between the experimental bond dissociation energies (BDEs) of this class of complexes and the % V Bur (the percent of a volume occupied by ligand atoms in a sphere centered about a metal) of the corresponding ligands was found, suggesting that the BDEs are significantly affected by the steric requirements of the ligand. 1 NHC ligands used in this work.…”
The performance of 16-electron ruthenium complexes with the general formula Cp*Ru(L)X (in which L = phosphine or N-heterocyclic carbene ligand; X = Cl or OCH 2 CF 3 ) was explored in azide−alkyne cycloaddition reactions that afford the 1,2,3-triazole products. The scope of the Cp*Ru(P
“…A plot of ether binding energies for LDA and LiHMDS determined previously is shown in Figure . In general, there appears to be a modest correlation …”
6Li and 15N NMR spectroscopic
studies of lithium diisopropylamide ([6Li]LDA and
[6Li,15N]LDA) in
toluene/pentane solutions containing a variety of mono- and polydentate
ligands are reported. LDA forms exclusively
dimers in the presence of n-BuOMe, Et2O,
t-BuOMe, THF, 2-methyltetrahydrofuran,
2,2-dimethyltetrahydrofuran,
tetrahydropyran, dimethoxyethane,
N,N,N‘,N‘-tetramethylethylenediamine, and
MeOCH2CH2NR2 (NR2 =
NMe2, NEt2,
pyrrolidino). Addition of 1,2-dipyrrolidinoethane and
(2-pyrrolidinoethyl)dimethylamine provides monomer−dimer
mixtures. Treatment of LDA with
trans-N,N,N‘,N‘-tetramethylcyclohexanediamine (TMCDA) or
trans-1-(dimethylamino)-2-isopropoxycyclohexane in hydrocarbons afford exclusively
monomers. Sparteine binds only reluctantly,
giving a mixture of unsolvated oligomers and monomer. Competitions
of the ethereal ligands vs TMCDA afford
binding constants and associated free energies for dimer solvation
which are correlated with those obtained previously
for lithium hexamethyldisilazide.
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