Terminal rare-earth imido complexes containing metal-nitrogen double bonds have received more attention in recent years due to their importance in group transformation and catalytic reactions.However,due to the large ...Terminal rare-earth imido complexes containing metal-nitrogen double bonds have received more attention in recent years due to their importance in group transformation and catalytic reactions.However,due to the large difference in the orbital energy between rare-earth metals and nitrogen,their synthesis is difficult and the product is easy to polymerize.Here,we use the combination of Cp*and amidinate ligands to inhibit the tetramerization and provide exclusively the first anionic rare-earth(Ⅲ)terminal imido complexes with both electron-donating and electron-withdrawing groups.Chemical bond analysis further confirms the double-bond character,and the strong polarity of the REvN bond,which could be described as three orbital interactions,is primarily derived from the imido nitrogen,while the contribution from the rare-earth metal is limited.The mechanistic study using DFT calculations shows that the formation of the REvN bond involves the activation of two N-H bonds.Furthermore,the anionic rare-earth(Ⅲ)terminal imido complex shows some interesting and unique reactivity towards isocyanates,isonitriles,phenylsilanes,and W(CO)6.The work extends the multiple-bond chemistry between rare-earth metals and main group elements,and is expected to inspire the development of rare-earth organometallic chemistry and related fields.展开更多
The scandium terminal imido complex supported by a monoanionic tetradentate NNNN ligand, [LSc=N(DIPP)](L = [MeC(N(DIPP))CHC(Me)(NCH2CH2N(Me)CH2CH2NMe2]-, DIPP = 2,6-(iPr)2C6H3)(1), undergoes a C–N bond cleavage at el...The scandium terminal imido complex supported by a monoanionic tetradentate NNNN ligand, [LSc=N(DIPP)](L = [MeC(N(DIPP))CHC(Me)(NCH2CH2N(Me)CH2CH2NMe2]-, DIPP = 2,6-(iPr)2C6H3)(1), undergoes a C–N bond cleavage at elevated temperature to give a mononuclear scandium anilido intermediate 2a, which subsequently aggregates into a binuclear scandium anilido complex 2. The mononuclear intermediate 2a reacts with alkyne or imine to provide two scandium anilido complexes 3 and 4, which contain a dianionic tetradentate NNNC ligand or a dianionic tetradentate NNNN ligand. DFT calculations on the reaction mechanism of C–N bond cleavage in 1 were also performed.展开更多
A series of substituted phenyl mono-imido complexes of the type W(NR)Cl_(4)(THF) (R=C_(6)H_(5),2,6-Me-C_(6)H_(3),3,5-Me-C_(6)H_(3),2,4,6-Me-C_(6)H_(2),4-OMe-C_(6)H_(4),2,6-F-C_(6)H_(3) and 3,5-CF_(3)-C_(6)H_(3)) have ...A series of substituted phenyl mono-imido complexes of the type W(NR)Cl_(4)(THF) (R=C_(6)H_(5),2,6-Me-C_(6)H_(3),3,5-Me-C_(6)H_(3),2,4,6-Me-C_(6)H_(2),4-OMe-C_(6)H_(4),2,6-F-C_(6)H_(3) and 3,5-CF_(3)-C_(6)H_(3)) have been synthesised and characterised. Reaction of these complexes with solid polymethylaluminoxane (sMAO) leads to immobilisation and in situ methylation of the chloride positions on the surface of the support. Reaction of W(NR)Cl_(4)(THF) with trimethylaluminium (TMA) yields the trimethyl complexes W(NR)Me3Cl. Immobilisation of the isotopically labelled W{N(2,6-F-C_(6)H_(3))}(^(13)CH_(3))_(3)Cl on sMAO furnished the supported complex with two identifiable methyl resonances in the ^(13)C–{^(1)H} solid state CPMAS spectrum (45 and 56 ppm),with the latter matching the unsupported complex,confirming retention of the structure on the surface. The sMAO-supported complexes (W:Al=1:150) were tested for their propensity to dimerise ethylene (1 bar) in d_(6)-benzene at 100℃ and compared with the previously reported sMAO-W{N(2,6-iPr-C_(6)H_(3))}Cl_(4)(THF) (sMAO-1.a). Complexes with electron deficient imido groups were shown to be the most active,and increased steric bulk in the ortho positions is also an important factor,with sMAO acting as a support,scavenger and activator. sMAO-W{N(3,5-CF_(3)-C_(6)H_(3))}Cl_(4)(THF) was the most active,demonstrating a turnover frequency of 5.65 mol_(C_(2)H_(4)) mol^(−1)_(W) h^(−1) and a selectivity towards 1-butene of 91% after 8 h.展开更多
基金supported by the National Key R&D Program of China(no.2021YFF0701600)the National Natural Science Foundation of China(no.22371006 and 22131001)the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-202401).
文摘Terminal rare-earth imido complexes containing metal-nitrogen double bonds have received more attention in recent years due to their importance in group transformation and catalytic reactions.However,due to the large difference in the orbital energy between rare-earth metals and nitrogen,their synthesis is difficult and the product is easy to polymerize.Here,we use the combination of Cp*and amidinate ligands to inhibit the tetramerization and provide exclusively the first anionic rare-earth(Ⅲ)terminal imido complexes with both electron-donating and electron-withdrawing groups.Chemical bond analysis further confirms the double-bond character,and the strong polarity of the REvN bond,which could be described as three orbital interactions,is primarily derived from the imido nitrogen,while the contribution from the rare-earth metal is limited.The mechanistic study using DFT calculations shows that the formation of the REvN bond involves the activation of two N-H bonds.Furthermore,the anionic rare-earth(Ⅲ)terminal imido complex shows some interesting and unique reactivity towards isocyanates,isonitriles,phenylsilanes,and W(CO)6.The work extends the multiple-bond chemistry between rare-earth metals and main group elements,and is expected to inspire the development of rare-earth organometallic chemistry and related fields.
基金This work was supported by the National Natural Science Foundation of China(21325210,21132002,21121062)the State Key Basic Research&Development Program(2012CB821600)the CAS/SAFEA International Partnership Program for Creative Research Teams.
文摘The scandium terminal imido complex supported by a monoanionic tetradentate NNNN ligand, [LSc=N(DIPP)](L = [MeC(N(DIPP))CHC(Me)(NCH2CH2N(Me)CH2CH2NMe2]-, DIPP = 2,6-(iPr)2C6H3)(1), undergoes a C–N bond cleavage at elevated temperature to give a mononuclear scandium anilido intermediate 2a, which subsequently aggregates into a binuclear scandium anilido complex 2. The mononuclear intermediate 2a reacts with alkyne or imine to provide two scandium anilido complexes 3 and 4, which contain a dianionic tetradentate NNNC ligand or a dianionic tetradentate NNNN ligand. DFT calculations on the reaction mechanism of C–N bond cleavage in 1 were also performed.
文摘A series of substituted phenyl mono-imido complexes of the type W(NR)Cl_(4)(THF) (R=C_(6)H_(5),2,6-Me-C_(6)H_(3),3,5-Me-C_(6)H_(3),2,4,6-Me-C_(6)H_(2),4-OMe-C_(6)H_(4),2,6-F-C_(6)H_(3) and 3,5-CF_(3)-C_(6)H_(3)) have been synthesised and characterised. Reaction of these complexes with solid polymethylaluminoxane (sMAO) leads to immobilisation and in situ methylation of the chloride positions on the surface of the support. Reaction of W(NR)Cl_(4)(THF) with trimethylaluminium (TMA) yields the trimethyl complexes W(NR)Me3Cl. Immobilisation of the isotopically labelled W{N(2,6-F-C_(6)H_(3))}(^(13)CH_(3))_(3)Cl on sMAO furnished the supported complex with two identifiable methyl resonances in the ^(13)C–{^(1)H} solid state CPMAS spectrum (45 and 56 ppm),with the latter matching the unsupported complex,confirming retention of the structure on the surface. The sMAO-supported complexes (W:Al=1:150) were tested for their propensity to dimerise ethylene (1 bar) in d_(6)-benzene at 100℃ and compared with the previously reported sMAO-W{N(2,6-iPr-C_(6)H_(3))}Cl_(4)(THF) (sMAO-1.a). Complexes with electron deficient imido groups were shown to be the most active,and increased steric bulk in the ortho positions is also an important factor,with sMAO acting as a support,scavenger and activator. sMAO-W{N(3,5-CF_(3)-C_(6)H_(3))}Cl_(4)(THF) was the most active,demonstrating a turnover frequency of 5.65 mol_(C_(2)H_(4)) mol^(−1)_(W) h^(−1) and a selectivity towards 1-butene of 91% after 8 h.
