Organometallic consequences of a redox reaction: Terminal trimethylsilylmethylidene titanium complexes prepared by a one-electron oxidation step

Basuli, Falguni; Adhikari, Debashis; Huffman, John C.; Mindiola, Daniel J.

doi:10.1016/j.jorganchem.2007.03.033

Cited by 13 publications

(6 citation statements)

References 43 publications

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“…The Ti–F ( 1 ) and Ti–O OTf ( 2 ) bond distances of 1.831(2) and 1.985(4) Å, respectively, are somewhat shorter than the average Ti–F (1.848 Å) and Ti–O OTf (2.036 Å) bond distances reported for similar titanium(IV) terminal fluoride and monotriflate complexes. Likewise, for the new structure 12 presented in this work, the Ti–Cl bond length (2.335(2) Å) in complex 12 is slightly contracted when compared to other Ti–Cl bond distances (2.346–2.379 Å) in similar titanocene chloride complexes .…”

Section: Resultsmentioning

confidence: 70%

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

et al. 2012

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Trifluoromethyltrimethylsilane, (CH 3 ) 3 SiCF 3 , in the presence of CsF serves as an excellent CF 3 group-transfer reagent, and reaction with Cp 2 TiF 2 in THF gives the titanocene trifluoromethyl fluoride complex Cp 2 Ti(CF 3 )(F) (1; Cp = C 5 H 5 ) in 60% isolated yield. Reaction of complex 1 with the trimethylsilyl reagents, (CH 3 ) 3 SiX (X = OTf = OSO 2 CF 3 , Cl, Br, I, N 3 , and OSO 2 Ph), in a tetrahydrofuran or toluene solution affords the corresponding Ti−CF 3 derivatives Cp 2 Ti(CF 3 )(X) (X = OTf (2), Cl (12), Br (13), I (14), N 3 (15), and OSO 2 Ph ( 16)) in good isolated yields of 67−84%. These compounds have been characterized by a combination of reactivity studies, IR and 1 H/ 13 C{ 1 H}/ 19 F NMR spectroscopies, and single-crystal X-ray diffraction. The Ti−CF 3 linkage in these complexes is remarkably robust, and although the α-C−F bonds are elongated, there is no evidence of an α-fluoride (Ti•••F−CF 2 ) between the electrophilic Ti(IV) metal center and any of the C−F bonds in the trifluoromethyl group in the solid-state or in solution. In the solid-state, these complexes are shock-sensitive; energetic decomposition of Cp 2 Ti(CF 3 )(F) (1) produces uniform spherical nanoparticles ranging from ∼70 to 120 nm in size and porous fluorinated oligomers and polymers containing both −(CF 2 −CF 2 )− and −(CF 2 −CFH)− units, as determined by a combination of SEM, XRD, XRF, XPS, and 19 F MAS NMR. Density functional theory results show good agreement with experimental structural data obtained for Cp 2 Ti(CF 3 )(X) (X = F (1), OTf (2), Cl (12), N 3 (15)) and accurately predicts longer Ti−CF 3 distances than for each specific CH 3 analogue, and the trend extends to structurally related Zr and Hf analogues. Simpler model compounds from groups 4 and 8 (M(CH 3 ) 4 , M(CH 3 ) 3 (CF 3 ), M(CH 3 ) 3 (CCl 3 ), and M(CH 3 ) 3 (CF 2 CF 2 CF 2 CF 3 ); M = Ti, Zr, Hf, Fe, Ru, Os)) were also examined and show that, for group 4 complexes, π-bonding is a significant factor in shortening the strongly ionic M−CH 3 relative to M−CF 3 , whereas for the predominantly covalent group 8 analogues, π-back-bonding helps to shorten the predominantly covalent M−CF 3 relative to M−CH 3 . The bonding analysis suggests that the significant elongation of C−F bonds α to metals is mainly a consequence of the electropositivity of the group 4 metal centers, with minor, if any, contributions from π-effects; the bond-lengthening effect is most pronounced at the α-position and decays rapidly on moving away from the metal.

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Section: Resultsmentioning

confidence: 70%

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

et al. 2012

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“…After work-up, the dialkyl product (DMAP)Ti(CH 2 SiMe 3 ) 2 [N(Si i Pr 3 )DIPP] ( 8 ) was isolated in 73% yield as a dark violet powder, and an X-ray diffraction analysis revealed that the structure is generally similar to that of the monoalkyl analogue 7 (Figure ). Related dialkyl complexes of titanium(IV) have been reported, − as well as a few examples of much rarer titanium(III) analogues. , …”

Section: Resultsmentioning

confidence: 99%

Synthesis, Characterization, and Reactivity of Low-Coordinate Titanium(III) Amido Complexes

et al. 2022

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Low-coordinate titanium(III) amido complexes were readily prepared via treatment of β-TiCl 3 with 1 or 2 equiv of Li[N(Si i Pr 3 )DIPP] (DIPP = 2,6-di-iso-propylphenyl) to form dinuclear [{Ti(N(Si i Pr 3 )DIPP)Cl(μ-Cl)} 2 ] (1) or mononuclear Ti[N(Si i Pr 3 )DIPP] 2 Cl (2), respectively. Both complexes were characterized by a variety of methods, including NMR spectroscopy, Evans method magnetic susceptibility, and single-crystal X-ray diffraction studies. Complex 1 was shown to be a versatile precursor for salt metathesis reactions to form heteroleptic complexes bearing alkoxide or silyl ligands. Alternatively, 1 formed adducts with Lewis bases such as 4-dimethylaminopyridine (DMAP) that are paramagnetic, mononuclear species. The base-stabilized complex 5 was alkylated with 1 or 2 equiv of LiCH 2 SiMe 3 to form mono-or dialkyl products, respectively. In contrast, treatment of complex 1 in the absence of DMAP with 2 equiv of LiCH 2 SiMe 3 results in the ultimate formation of a dinuclear cyclometalated complex 9 bearing a [Ti 2 (μ-Cl) 2 (μ:η 1 -CH 2 SiMe 2 CH 2 -)] core. This study demonstrates the convenient synthesis of a family of low-coordinate titanium(III) amido complexes possessing a variety of neutral and monoanionic ligands.

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“…THF binding to precursor ([ArNC(Me)] 2 CH)-TidCH t Bu(OTf) is not unreasonable to propose given that the trimethylsilymethylidene derivative ([ArNC(Me)] 2 CH)-TidCHSiMe 3 (OTf)(THF) readily coordinates THF. 35 We cannot, however, discard the possibility of THF displacing the OTfin a precursor such as 1 or the ionization of the alkyl reagent by THF to generate a more powerful base. Therefore, it is evident that THF blocks other, slower, but competitive processes such as double C-H activation of the isopropyl methines as well as intramolecular cross-metathesis with the β-diketiminate imine group to form the products shown in Scheme to stir in hexane or pentane for 10 days at room temperature and in the absence of donor solvents (Scheme 2).…”

Section: Resultsmentioning

confidence: 99%

“…On the basis of our independent synthetic work, the alkyl complex ([ArNC(Me)] 2 CH)TiCH t Bu(CH 2 SiMe 3 ) does not appear to be an intermediate to formation of 2 . THF binding to precursor ([ArNC(Me)] 2 CH)TiCH t Bu(OTf) is not unreasonable to propose given that the trimethylsilymethylidene derivative ([ArNC(Me)] 2 CH)TiCHSiMe 3 (OTf)(THF) readily coordinates THF . We cannot, however, discard the possibility of THF displacing the OTf − in a precursor such as 1 or the ionization of the alkyl reagent by THF to generate a more powerful base.…”

Section: Resultsmentioning

confidence: 99%

Zwitterionic and Cationic Titanium and Vanadium Complexes Having Terminal M−C Multiple Bonds. The Role of the β-Diketiminate Ligand in Formation of Charge-Separated Species

Adhikari

Basuli²,

Orlando

et al. 2009

Organometallics

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Treatment of the neopentylidene complex ([ArNC(Me)]2CH)TiCHtBu(OTf) (1) with a strong base such as an alkyl reagent (lithium or potassium salt) results in deprotonation of the β-diketiminate β-methyl group to form complex (ArN(Me)CCHC(CH2)NAr)TiCHtBu(THF) (2) along with liberation of the alkane. Likewise, ligand deprotonation of ([ArNC(Me)]2CH)VCtBu(OTf) (3), in THF or Et2O, results in formation of the alkylidyne−solvent adduct (ArNC(Me)CHC(CH2)NAr)VCtBu(L) (L = THF, 4-THF; L = Et2O, 4-OEt 2 ), concomitant with alkane formation. The connectivity in compound 4-Et 2 O has been established by single-crystal X-ray diffraction studies. Compounds 2 and 4-THF react with B(C6F5)3 to produce the first examples of terminal titanium alkylidene and vanadium alkylidyne zwitterions, namely, the borane adducts (ArNC(Me)CHC(CH2B(C6F5)3)NAr)TiCHtBu(THF) (5) and (ArNC(Me)CHC(CH2B(C6F5)3)NAr)VCtBu(THF) (6), respectively. The solid state structure for each zwitterion was also obtained. Compounds 2 and 4-THF react readily with [HNMe2Ph][B(C6F5)4] to produce the discrete salts [([ArNC(Me)]2CH)TiCHtBu(THF)][B(C6F5)4] (7) and [([ArNC(Me)]2CH)VCtBu(THF)][B(C6F5)4] (8), respectively, via protonation of the methylene group in the N,N′-chelating ligand ArNC(Me)CHC(CH2)NAr2− to re-form the β-diketiminate scaffold. The reactivity of 7 allows for spectroscopic elucidation only at low temperatures, while complex 8 has been fully characterized including a single-crystal X-ray structure.

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Organometallic consequences of a redox reaction: Terminal trimethylsilylmethylidene titanium complexes prepared by a one-electron oxidation step

Cited by 13 publications

References 43 publications

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

Synthesis, Characterization, and Reactivity of Low-Coordinate Titanium(III) Amido Complexes

Zwitterionic and Cationic Titanium and Vanadium Complexes Having Terminal M−C Multiple Bonds. The Role of the β-Diketiminate Ligand in Formation of Charge-Separated Species

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