A Terminal and Four-Coordinate Titanium Alkylidene Prepared by Oxidatively Induced α-Hydrogen Abstraction

Basuli, Falguni; Bailey, Brad C.; Tomaszewski, John; Huffman, John C.; Mindiola, Daniel J.

doi:10.1021/ja034786n

Cited by 99 publications

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“…Similar transformations have been reported by our group for four-coordinate [(Nacnac)Ti IV ] complexes with reactive alkylidene or phosphinidene functionalities. [7,15] Concentration-dependent experiments on the titanium-alkylidene system (by 1 H NMR spectroscopy) determined the cross-metathesis reaction to be first-order in titanium, hence we suspect the same to be valid for the thermolytic transformation of 4 to 6.…”

Section: )]mentioning

confidence: 70%

“…Owing to the instability of the previously reported fourcoordinate alkylidene complex [(Nacnac)Ti=CHtBu(OTf)], [7] it was presaged that complexes 2 and 4 would also be prone to "Wittig-like" reactivity involving the metal-alkylidene functionality. Accordingly, when complex 2 is heated at 60 8C for 6 h in THF, extrusion of neopentane is observed (by 1 H NMR spectroscopy and GC MS analysis) concomitant with the formation of the zwitterion vanadium(ii) product [(Nacnac)V(h 6 -C 6 H 5 BPh 3 )] (5) (77 % yield, Scheme 2).…”

Section: )]mentioning

confidence: 99%

“…[4] Since there are only a handful of vanadium-alkylidene complexes known, [3][4][5][6] we report the synthesis of the first cationic and neutral four-coordinate vanadium(iv)-neopentylidene complexes [(Nacnac)V=CH-tBu(thf)](BPh 4 ) and [(Nacnac)V = CHtBu(I)] (Nacnac À = [Ar]NC(Me)CHC(Me)N[Ar], Ar = 2,6-(CHMe 2 ) 2 C 6 H 3 ), and subsequent thermolysis of each system. These d 1 paramagnetic species reported herein are kinetically stable, and contain the shortest V=C bonds reported so far.Our recent strategy to prepare the first four-coordinate titanium-neopentylidene complex by an oxidatively induced a-hydrogen abstraction reaction [7] motivated us to pursue other 3d transition metals containing this reactive motif.Unlike titanium, vanadium displays more diverse redox chemistry, hence oxidation states ranging from + 2 to + 5 can occur. Using the precursor [(Nacnac)VCl 2 ]…”

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Cationic and Neutral Four‐Coordinate Alkylidene Complexes of Vanadium(IV) Containing Short VC Bonds

Basuli

Kilgore

et al. 2004

Angew Chem Int Ed

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High-oxidation state transition-metal alkylidenes have received considerable attention in the past few years since these systems are capable of catalyzing important processes such as olefin metathesis, alkyne polymerization, and Wittigtype reactions. [1,2] Although transition-metal alkylidene complexes of the nucleophilic "Schrock-type" have been extensively studied for the 4d and 5d metals of Group 5, the chemistry for 3d vanadium systems has been far less explored. The first example of a vanadium(iii)-alkylidene complex, [CpV(CHtBu)(dmpe)](dmpe = bis(dimethylphosphanyl)-ethane), was reported by Hessen, Teuben, and co-workers and involved a-hydrogen abstraction of the bis(alkyl) precursor.[3] In contrast to the heavier d 0 alkylidene congeners, which are prepared by a-hydrogen abstraction, the synthesis of the first(Ar = 2,6-(CHMe 2 ) 2 C 6 H 3 ) involved a two-electron oxidation of the precursor [CpV(NAr)(PMe 3 ) 2 ] with the Wittig reagent Ph 3 P = CHPh by alkylidene transfer. [4] Since there are only a handful of vanadium-alkylidene complexes known, [3][4][5][6] we report the synthesis of the first cationic and neutral four-coordinate vanadium(iv)-neopentylidene complexes [(Nacnac)V=CH-tBu(thf)](BPh 4 ) and [(Nacnac)V = CHtBu(I)] (Nacnac À = [Ar]NC(Me)CHC(Me)N[Ar], Ar = 2,6-(CHMe 2 ) 2 C 6 H 3 ), and subsequent thermolysis of each system. These d 1 paramagnetic species reported herein are kinetically stable, and contain the shortest V=C bonds reported so far.Our recent strategy to prepare the first four-coordinate titanium-neopentylidene complex by an oxidatively induced a-hydrogen abstraction reaction [7] motivated us to pursue other 3d transition metals containing this reactive motif.Unlike titanium, vanadium displays more diverse redox chemistry, hence oxidation states ranging from + 2 to + 5 can occur. Using the precursor [(Nacnac)VCl 2 ][8] developed by Budzelaar and co-workers and two equivalents of LiCH 2 -tBu, [1g] we prepared the corresponding bis(neopentyl) complex [(Nacnac)V(CH 2 tBu) 2 ] (1) in 80 % yield as dark brown needles (Scheme 1). Attempts to obtain crystals suitable for a single-crystal X-ray structure determination were unsuccessful, but elemental analysis, magnetic susceptibility measurements (m eff = 2.96 m B ), and reactivity (vide infra) are in agreement with the formation of 1.[9] Complex 1 is a close analogue of the nBu derivative prepared by Budzelaar and co-workers, differing only by the lack of b-hydrogen atoms. (2) in 74 % yield (Scheme 1). Complex 2 is stable in the solid state, but its solutions (Et 2 O, C 6 H 6 , THF) gradually decompose over several hours at room temperature.Dark brown single crystals of 2 were grown from THF solutions of the complex layered with Et 2 O at À35 8C. The structure of 2 (Figure 1) reveals a cationic and four-coordinate vanadium center with pseudotetrahedral geometry, a very short V = C bond length (V(1)ÀC(33) 1.795(3) ), and an obtuse V(1)-C(33)-C(34) angle of 159.8(4)8. [9,10] The highly distorted neopentylidene ligand suggests that there is ...

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Cationic and Neutral Four‐Coordinate Alkylidene Complexes of Vanadium(IV) Containing Short VC Bonds

Basuli

Kilgore

et al. 2004

Angew Chem Int Ed

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“…[53,54] Representative substituents on terminal phosphinidene ligands include Mes* (2,4,6-tBu 3 C 6 H 2 ), [55][56][57][58][59] 2,6-dimesitylphenyl (dmp), [60] cyclohexyl, [61] phenyl, [62] and trimethylsilyl. [63] An intriguing possibility was that the availability of a terminal phosphide anion, for example, [PNb(NNpAr) 3 ]…”

Section: Diorganophosphanylphosphinidenes: Phosphinidenes With a Pr 2mentioning

confidence: 99%

Terminal, Anionic Carbide, Nitride, and Phosphide Transition‐Metal Complexes as Synthetic Entries to Low‐Coordinate Phosphorus Derivatives

Cummins

2006

Angew Chem Int Ed

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Anionic terminal one‐atom nitride, phosphide, and carbide complexes are excellent starting materials for the synthesis of ligands containing low‐coordinate phosphorus centers in the protecting coordination sphere of the metal complex. Salt‐elimination reactions with chlorophosphanes lead to phosphaisocyanide, iminophosphinimide, and diorganophosphanylphosphinidene complexes in which the unusual phosphorus ligands are stabilized by coordination. X‐ray structure analyses and density‐functional calculations illuminate the bonding in these compounds.

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“…For example, the archetypical Schrock carbene (Cp) 2 33 , whereas X 2 Ti ¼ CH 2 (X ¼ H, F, Cl) species were isolated in low-temperature inert gas matrices 34,35 . At the same time, Ti alkylidenes with a higher coordination number, when Ti-based LUMO is further coordinated, can form stable molecules 22,23,[36][37][38][39] .…”

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Endohedral fullerene with μ3-carbido ligand and titanium-carbon double bond stabilized inside a carbon cage

et al. 2014

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In all metallofullerenes known before this work, metal atoms form single highly polar bonds with non-metal atoms in endohedral cluster. This is rather surprising for titanium taking into account the diversity of organotitanium compounds. Here we show that the arc-discharge synthesis of mixed titanium-lutetium metallofullerenes in the presence of ammonia, melamine or methane unexpectedly results in the formation of TiLu 2 C@I h -C 80 with an icosahedral I h (7) carbon cage. Single-crystal X-ray diffraction and spectroscopic studies of the compound reveal an unprecedented endohedral cluster with a m 3 -carbido ligand and Ti-C double bond. The Ti(IV) in TiLu 2 C@I h -C 80 can be reversibly reduced to the Ti(III) state. The Ti ¼ C bonding and Ti-localized lowest unoccupied molecular orbital in TiLu 2 C@I h -C 80 bear a certain resemblance to titanium alkylidenes. TiLu 2 C@I h -C 80 is the first metallofullerene with a multiple bond between a metal and the central, non-metal atom of the endohedral cluster.

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A Terminal and Four-Coordinate Titanium Alkylidene Prepared by Oxidatively Induced α-Hydrogen Abstraction

Cited by 99 publications

References 23 publications

Cationic and Neutral Four‐Coordinate Alkylidene Complexes of Vanadium(IV) Containing Short VC Bonds

Cationic and Neutral Four‐Coordinate Alkylidene Complexes of Vanadium(IV) Containing Short VC Bonds

Terminal, Anionic Carbide, Nitride, and Phosphide Transition‐Metal Complexes as Synthetic Entries to Low‐Coordinate Phosphorus Derivatives

Endohedral fullerene with μ3-carbido ligand and titanium-carbon double bond stabilized inside a carbon cage

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