Formation and Redox Interconversion of Niobium Methylidene and Methylidyne Complexes

Searles, Keith; Smith, Kyle T.; Kurogi, Takashi; Chen, Chun‐Hsing; Carroll, Patrick J.; Mindiola, Daniel J.

doi:10.1002/anie.201511867

“…The metal–ligand and metal–metal bonding in this class of complexes was discussed previously . In general, structurally characterized dinuclear μ-methylidyne complexes are rare . The Ru–C(methylidyne) bond lengths in [ 9 ] + (1.878(3) and 1.884(3) Å) are shorter than those in [(CpRu) 2 (μ-CO)(μ-CH)(μ-dppm)][BF 4 ] (1.937(7) Å; dppm = Ph 2 PCH 2 PPh 2 ), probably due to the coordinatively unsaturated nature of [ 9 ] + .…”

Section: Resultsmentioning

confidence: 99%

Parent Cyclopentadienyl Ruthenium(II) Chloride Synthon: Derivatization to CpRu Amido, Imido, and Oxo Complexes

Takemoto

¹

,

Ishii

²

,

Yamaguchi

³

et al. 2019

View full text Add to dashboard Cite

The complex salt [CpRu(η6-C10H8)][(CpRu)2(μ-Cl)3] ([1][2]) was synthesized and found to be a useful CpRuCl synthon. The ions [1]+ and [2]− cleanly comproportionate into monomeric CpRuCl(L)2 complexes with liberation of naphthalene upon treatment with donor ligands L such as DMSO, tBuNH2, 1,5-cycloctadiene, and CO. The amine adduct [CpRuCl(NH2 tBu)2] allows access to the coordinatively unsaturated dimeric amido complex [CpRu(NHtBu)]2, which is subsequently transformed into the bridging imido complexes [(CpRu)2(μ-NtBu)(μ-CH2)] and [(CpRu)2(μ-NtBu)(μ-CH)]+. The imido methylidyne complex shows enhanced electrophilicity at the methylidyne carbon compared to its bulkier C5Me5 congener and also allows access to a less hindered parent Cp version of the diruthenocarbene ligand in the form of the Ru2Cu μ3-carbido complex [(CpRu)2(μ-NtBu)(μ3-C)Cu{N(SiMe3)2}]. The salt [1][2] also gives a novel tetranuclear μ4-oxo cluster [(CpRuCl)4(μ4-O)] upon oxidation in air or by N-methylmorpholine N-oxide.

show abstract

“…17 These features suggest, in addition to analytical data and the fact that ∼2 equiv of CH 4 are released in its formation, that the product is the μ-(methylidene) 2 dimer rac-4 (Scheme 2). 18 VT 1 H NMR, 1 H-coupled 13 C, and 1 H− 13 C HSQC NMR experiments (Figure 2 and Figures S15−S18 in the Supporting Information) indicate that the protons within each methylene group in rac-4 are magnetically nonequivalent at low temperature, appearing as two broadened signals at δ 10.01 and 6.10 ppm (Figure 2, −90 °C). Furthermore, the J CH coupling constants (−90 °C, J CH = 124.6 Hz and J CH = 112.7 Hz; 100 °C, J CH = 120.3 Hz) suggest that the methylene hybridization is intermediate 19 between sp 3 and sp 2 .…”

Section: Resultsmentioning

confidence: 99%

Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

Liu

¹

,

Invergo

²

,

McInnis

³

et al. 2017

View full text Add to dashboard Cite

The complex (μ-Me 2 C-3,3′){(η 5 -cyclopentadienyl)[1-Me 2 Si-( t BuN)](TiMe 2 )} 2 (3) was prepared as a new binuclear catalyst motif for homogeneous olefin polymerization. Complex 3 exists as rac-3 and meso-3 diastereomers, which can be separated and characterized by solution NMR spectroscopy and single-crystal X-ray diffraction. While meso-3 has high thermal stability, rac-3 undergoes thermolysis in solution to quantitatively form the dimeric methylidene complex (μ-Me 2 C-3,3′){(η 5 -cyclopentadienyl)[1-Me 2 Si( t BuN)][(μ-CH 2 )Ti]} 2 (rac-4). Activation of rac-3 and meso-3 with 1 equiv of Ph(5; rac-5 and meso-5, respectively). Interestingly, meso-5 is stable in the presence of an additional 1 equiv of Ph] 2 (rac-6) as indicated by multinuclear NMR spectroscopy and DFT computation. meso-3 reacts with 2 equiv of B(C 6 F 5 ) 3 to yield meso-[(μ-CMe 2 -3,3′){(η 5 -cyclopentadienyl)[1-Me 2 Si( t BuN)]} 2 (μ-CH 2 )(μ-CH 3 )Ti 2 ] + MeB(C 6 F 5 ) 3 − (meso-7) containing the same meso-5 cation but with a MeB(C 6 F 5 ) 3 − counteranion. These findings, along with catalytic results, indicate that rac-3 and meso-3 remain structurally intact during polymerization, consistent with the observed diastereoselectivity effects. Under identical ethylene/1octene copolymerization conditions, only activated bimetallic rac-3 produces appreciable polymer, with meso-3 exhibiting low activity, but both yield polymer with a branch density >2× that of the monometallic control [(3-t Bu-C 5 H 3 )SiMe 2 N t Bu]TiMe 2 (Ti 1 ). In ethylene/styrene copolymerizations, rac-3 produces polymers with 3.1× higher M n and 2.1× greater styrene incorporation versus Ti 1 , while meso-3 catalyzes only ethylene-free styrene homopolymerization. In 1-octene homopolymerizations, meso-3 + B(C 6 F 5 ) 3 (i.e., meso-7) produces highly isotactic poly-1-octene (mmmm 91.7%), while rac-3 + Ph 3 C + B(C 6 F 5 ) 4 − (i.e., rac-5), rac-3 + B(C 6 F 5 ) 3 (i.e., rac-7), and meso-3 + Ph 3 C + B(C 6 F 5 ) 4 − (i.e., meso-5) produce only atactic poly-1-octene. These bimetallic polymerization catalysts exhibit distinctive cooperative effects influencing product M n , tacticity, and comonomer selection, demonstrating that binuclear catalyst stereochemical factors are significant.

show abstract

“…32−34,40 Since certain (arylimido)vanadium(V) complexes containing anionic donor ligands (such as phenoxy, ketimide, imidazoline-iminato) exhibit promising characteristics as catalysts or catalyst precursors for olefin metathesis 9,10,13,45 and coordination/insertion polymerization 12,46−49 and also (arylimido)niobium(V)-alkylidene complexes containing fluorinated alkoxo ligand catalyze metathesis polymerization of cyclic olefins and disubstituted acetylene (Scheme 1), 40 synthesis and some reactions of (arylimido)niobium(V) complexes containing ketimide and aryloxo ligands have been a promising subject. 50−52…”

Section: Introductionmentioning

confidence: 99%

“…However, in contrast to a number of reports of ( tert -butyl-imido)niobium complexes especially containing β-diketiminate ligand (Scheme ), − reports concerning the synthesis and reaction chemistry of (arylimido)niobium(V) complexes containing “monodentate” anionic ancillary donor ligands still have been limited so far (Scheme ). − , Since certain (arylimido)vanadium(V) complexes containing anionic donor ligands (such as phenoxy, ketimide, imidazoline-iminato) exhibit promising characteristics as catalysts or catalyst precursors for olefin metathesis ,,, and coordination/insertion polymerization ,− and also (arylimido)niobium(V)-alkylidene complexes containing fluorinated alkoxo ligand catalyze metathesis polymerization of cyclic olefins and disubstituted acetylene (Scheme ), synthesis and some reactions of (arylimido)niobium(V) complexes containing ketimide and aryloxo ligands have been a promising subject. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis of (Arylmido)niobium(V) Complexes Containing Ketimide, Phenoxide Ligands, and Some Reactions with Phenols and Alcohols

Natta

¹

,

Wised

²

,

Tsutsumi

³

et al. 2018

View full text Add to dashboard Cite

Reactions of Nb(NAr)(N=C t Bu 2 ) 3 ( 3a , Ar = 2,6-Me 2 C 6 H 3 ) with 1.0, 2.0, or 3.0 equiv of Ar′OH (Ar′ = 2,6- i Pr 2 C 6 H 3 ) afforded Nb(NAr)(N=C t Bu 2 ) 2 (OAr′), Nb(NAr)(N=C t Bu 2 )(OAr′) 2 , or Nb(NAr)(OAr′) 3 , respectively (at 25 °C), whereas the reaction with 2.0 equiv of 2,6- t Bu 2 C 6 H 3 OH afforded Nb(NAr)(N=C t Bu 2 ) 2 ( O -2,6- t Bu 2 C 6 H 3 ) upon heating (70 °C) without the formation of bis(phenoxide) and the reaction of 3a with 2.0 equiv of 2,4,6-Me 3 C 6 H 2 OH afforded Nb(NAr)(N=C t Bu 2 )( O -2,4,6-Me 3 C 6 H 2 ) 2 (HN=C t Bu 2 ). Similar reactions of 3a with 1.0 equiv of (CF 3 ) 3 COH or 2.0 equiv of (CF 3 ) 2 CHOH afforded Nb(NAr)(N=C t Bu 2 ) 2 [OC(CF 3 ) 3 ](HN=C t Bu 2 ) or Nb(NAr)(N=C t Bu 2 )[OCH(CF 3 ) 2 ] 2 (HN=C t Bu 2 ), respectively. On the basis of their structural analyses and the reaction chemistry, it was suggested that these reactions proceeded via coordination of phenol (alcohol) to Nb and the subsequent proton (hydrogen) transfer to the ketimide (N=C t Bu 2 ) ligand. The reaction of Nb(NAr)(N=C t Bu 2 ) 2 (OAr′) with 1.0 equiv of 2,4,6-Me 3 C 6 H 2 OH gave the disproportionation products Nb(NAr)(N=C t Bu 2 )(OAr′) 2 and Nb(NAr)(N=C t Bu 2 )( O -2,4,6-Me 3 ...

show abstract

Formation and Redox Interconversion of Niobium Methylidene and Methylidyne Complexes

Cited by 14 publications

References 43 publications

Parent Cyclopentadienyl Ruthenium(II) Chloride Synthon: Derivatization to CpRu Amido, Imido, and Oxo Complexes

Parent Cyclopentadienyl Ruthenium(II) Chloride Synthon: Derivatization to CpRu Amido, Imido, and Oxo Complexes

Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

Synthesis of (Arylmido)niobium(V) Complexes Containing Ketimide, Phenoxide Ligands, and Some Reactions with Phenols and Alcohols

Contact Info

Product

Resources

About