Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

Postigo, Lorena; Sánchez‐Nieves, Javier; Royo, Pascual

doi:10.1016/j.ica.2006.02.026

Cited by 6 publications

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References 34 publications

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“…The imido group is a strong π donor ligand with the widely proven ability to stabilize high-valent metal complexes. , The isolobal relationship of the imido and the cyclopentadienyl ligands is an important feature that allows the half-sandwich imido complexes [MCp(NR)X 2 ] (M = group 5 metal) to be studied as isoelectronic counterparts of dicyclopentadienyl derivatives [MCp 2 X 2 ] (M = group 4 metal). – The reactivities of these two types of complexes are comparable, although the half-sandwich complexes [MCp(NR)X 2 ] (M = group 5 metal) were rather less active olefin polymerization catalysts than the metallocene-type complexes [MCp 2 X 2 ] (M = group 4 metal). – This difference has been attributed to the lower acidity of group 5 metal derivatives, which would consequently be expected to show a greater affinity for polar olefins. Conversely, important differences between these two types of complexes involve the reactivity of the metal−nitrogen multiple bond. ,– …”

Section: Introductionmentioning

confidence: 99%

Isolobal Zwitterionic Niobium and Tantalum Imido and Zirconium Monocyclopentadienyl Complexes: Theoretical and Methyl Methacrylate Polymerization Studies

et al. 2008

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The trichloro derivatives [MCl 3 (NR)(py) 2 ] reacted with LiOAr to give the imido aryloxo complexes [MCl 2 (NR)(OAr)(py) 2 ] (M ) Nb, R ) tBu (1a), Ar (1b); M ) Ta, R ) tBu (2a); Ar ) 2,6-iPr 2 C 6 H 3 ) and were alkylated with [BzMgCl], affording the tribenzyl derivatives [NbBz 3 (NR)] (R ) tBu (3a), Ar (3b)). Similar alkylations of the aryloxo derivatives 1 and 2 gave the dibenzyl complexeswere obtained upon addition of 1 equiv of E(C 6 F 5 ) 3 (E ) B, Al) to the tribenzyl derivatives [MBz 3 (NtBu)] (M ) Nb (3a), Ta (4a)). The aryloxo compound 6a reacted with 2 equiv of the Lewis acids E(C 6 F 5 ) 3 (E ) B, Al) to give the corresponding zwitterionic imido complexes [TaBz(NtBu)(OAr){η 6 -C 6 H 5 CH 2 E(C 6 F 5 ) 3 }] (E ) B (11a-B), Al (11a-Al)) and the adduct (THF) • E(C 6 F 5 ) 3 , through two different intermediates, the ionic [TaBz(NtBu)(OAr)(THF)][BzB(C 6 F 5 ) 3 ] (9a) for E ) B and the neutral [TaBz 2 (NtBu)(OAr)] (10a) for E ) Al. The related monocyclopentadienyl complex [ZrCpBz 2 {η 6 -C 6 H 5 CH 2 Al(C 6 F 5 ) 3 }] (12-Al) was also isolated by reaction of [ZrCpBz 3 ] with Al(C 6 F 5 ) 3 . DFT calculations were carried out to further understand this type of zwitterionic imido derivative in comparison with the isolobal zirconium cyclopentadienyl compound [ZrCpBz 2 {η 6 -C 6 H 5 CH 2 B(C 6 F 5 ) 3 }]. MMA polymerization was investigated for the [MBz 2 X(NtBu)]/E(C 6 F 5 ) 3 (X ) Bz, OAr) and [ZrCpBz 3 ]/E(C 6 F 5 ) 3 (E ) B, Al) systems.

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Section: Introductionmentioning

confidence: 99%

Isolobal Zwitterionic Niobium and Tantalum Imido and Zirconium Monocyclopentadienyl Complexes: Theoretical and Methyl Methacrylate Polymerization Studies

et al. 2008

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“…46 Reactivity at the Si-Cl bond in the complex [Nb(Z 5 -C 5 H 4 SiMeCl 2 )Cl 4 ] provides an entry point into a range of new complexes by in situ modification of the ligand. 47 Silyl-substitution has also recently been utilized in the synthesis of heterobimetallic Ti/Nb and Ti/Ta systems of general formula [TiCl 2 {Z 5 48 In its capacity as a purely spectator ligand, Cp 0 has been used to facilitate study of the insertion of unsaturated molecules into Nb-X s-bonds (X = H, C, P) in compounds containing the ''Cp 0 2 Nb-X'' molecular fragment, such as [Cp 0 2 Nb(H)(CO)], and [Cp 0…”

Section: Niobium and Tantalummentioning

confidence: 99%

Vanadium, niobium and tantalum

Coles

2008

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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This report summarizes the literature from 2007 pertaining to the chemistry of the group 5 elements. Novel coordination and organometallic compounds are included, along with selected applications in the areas of catalysis and bioinorganic/medicinal chemistry. HighlightsHighlights from 2007 include the ingenious use of the vanadium(IV/V) redox couple to sufficiently stabilize a monomeric phosphorus radical to allow its isolation and characterization, 4 the first example of a tantalum complex incorporating both alkyl and aquo ligands at the metal centre, 55 and a new family of Nb-and Ta-based olefin polymerization catalysts supported by bridged calixarene ligands. 79 2 Coordination chemistry Vanadium One of the attractive features of the chemistry of vanadium is the accessibility of the metal in several oxidation states, and whilst this may present a challenge to the synthetic chemist, the variety of ligands available for use in a supporting role ensures that most of the desired complexes can be isolated. Once tamed, the metal can be put to work in number of different roles and clever use of the resonance stabilization of the vanadium(IV/V) redox couple has enabled isolation of a monomeric phosphorus radical for the first time by Cummins and co-workers (1). 4 The redox chemistry of vanadium supported by a s,p,s-tripyrrole ligand set has been exploited in the cleavage of a coordinated dinitrogen molecule, in this case to afford a mixed-valent nitride-bridged complex (2).

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“…Functionalization of cyclopentadienyl rings with chlorosilyl groups − has provided a particularly useful procedure to synthesize dinuclear compounds through hydrolysis of the Si−Cl bonds. ,− Following this procedure, the hydrolysis of the dichlorosilyl-cyclopentadienyl titanium compound [Ti{η 5 -C 5 Me 4 (SiMeCl 2 )}Cl 3 ] allowed us to obtain the dititanium derivative [(TiCl 2 ) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] ( A ) with both Si−O−Si and Si−O−Ti bridges (Figure ) …”

Section: Introductionmentioning

confidence: 99%

Dinuclear Dicyclopentadienyl Titanium Complexes with Bridging Cyclopentadienylsiloxo Ligands

et al. 2010

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Addition of 1 equiv of TlCp to compound [(TiCl 2 ) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (A) at 80 °C gave a mixture with different molar ratios of the two possible isomers of [(TiClCp)(TiCl 2 )(μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (1). Reaction of compound A with 2 equiv of TlCp at 80 °C afforded [(TiClCp) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (2as) as the unique reaction product. Each Cp ligand of 2as is located in different positions anti and syn with respect to the Si-O-Si bridge. However, a mixture of two isomers of [(TiClCp) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})], 2as (>95% by NMR) and 2aa (<5% by NMR), was obtained when the reaction was carried out at 60 °C; the two Cp ligands of 2aa were located at anti positions. Alkylation of isomer 2as with LiMe gave a mixture of the three possible isomers [(TiMeCp) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (3as, 3aa, 3ss). The proportion of each was dependent on the reaction temperature. Isomer 2as reacted with Lewis acids E(C 6 F 5 ) 3 (E=B, Al) and with Li[B(C 6 F 5 ) 4 ] to give the chloro-bridged dititanium compounds [(TiCp) 5aC and 5sC; Q=B(C 6 F 5 ) 4 ), with the remaining methyl ligand located at anti or syn positions depending on the methyl group being abstracted. DFT studies were carried out to determine the stability of the isomers of 2 and 3, to determine which chlorine atom in compound 2as was more easily eliminated, and also to clarify the transformation of isomer 2as into the mixture of isomers 3as, 3aa, and 3ss during the alkylation reaction. Article

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Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

Cited by 6 publications

References 34 publications

Isolobal Zwitterionic Niobium and Tantalum Imido and Zirconium Monocyclopentadienyl Complexes: Theoretical and Methyl Methacrylate Polymerization Studies

Isolobal Zwitterionic Niobium and Tantalum Imido and Zirconium Monocyclopentadienyl Complexes: Theoretical and Methyl Methacrylate Polymerization Studies

Vanadium, niobium and tantalum

Dinuclear Dicyclopentadienyl Titanium Complexes with Bridging Cyclopentadienylsiloxo Ligands

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