Synthesis of a cobalt(iv) ketimide with a squashed tetrahedral geometry

Lewis, Richard A.; George, Stephen P.; Chapovetsky, Alon; Figueroa, Joshua S.; Hayton, Trevor W.

doi:10.1039/c3cc40461g

Cited by 43 publications

(90 citation statements)

References 23 publications

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“…17,18 In addition, the average Ta-N-C angle (172.7°) is indicative of sp hybridization at nitrogen, and is suggestive of significant π-donation from the ketimide to the metal, consistent with our ligand field analysis (see below). 3,4,6,19 Finally, the Ta-Cl bond lengths (2.498(1), 2.496(1) Å) are similar to those observed for other structurally characterized Ta(V) chlorides. 14,15,20–22 …”

Section: Resultssupporting

confidence: 76%

“…These calculations demonstrated that the partially occupied orbitals ( d xz , d yz , d z 2 ) all possess considerable π* Co-N character. 6 Several Group 5 tetra(amido) complexes (e.g., M(NR 2 ) 4 ) have also been structurally characterized, and a comparison of their metrical parameters with those of 1, 2 , and 7 is similarly informative. Most interestingly, this class of materials does not exhibit the squashed tetrahedral geometry observed in M(N=C t Bu 2 ) 4 , and instead exhibit only slightly distorted tetrahedral geometries.…”

Section: Resultsmentioning

confidence: 99%

“…This symmetry and coordinate system is identical to that used by some of us in our previous study of [Co(N=C t Bu 2 ) 4 ]. 6 To achieve this description, we define the x and y axes as lying between the M-L bonds (bisecting the L-M-L angles) (Figure 11), which is in any case more appropriate for an axial ( x = y ) system. If the x and y axes were defined along the M-L bonds, as done by Soriaga et al, 9 then the representation of d x 2 − y 2 and d xy would be reversed.…”

Section: Resultsmentioning

confidence: 99%

“…6 Soriaga et al . identified the ketimide MOs having π-interactions with an electron poor metal ion.…”

Section: Resultsmentioning

confidence: 99%

“…The d xz , d yz , AOs are moderately affected by these π-bonding interactions using the AOM (see Table S2 in Supporting Information), but in V(IV) (and Cr(IV)), these empty AOs are relatively unimportant compared to their role in Co(IV). 6 …”

Section: Resultsmentioning

confidence: 99%

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Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

et al. 2015

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Addition of 4 equiv of Li(N=CtBu2) to VCl3 in THF, followed by addition of 0.5 equiv I2, generates the homoleptic V(IV) ketimide complex, V(N=CtBu2)4 (1), in 42% yield. Similarly, reaction of 4 equiv of Li(N=CtBu2) with NbCl4(THF)2 in THF affords the homoleptic Nb(IV) ketimide complex, Nb(N=CtBu2)4 (2), in 55% yield. Seeking to extend the series to the tantalum congener, a new Ta(IV) starting material, TaCl4(TMEDA) (3), was prepared via reduction of TaCl5 with Et3SiH, followed by addition of TMEDA. Reaction of 3 with 4 equiv of Li(N=CtBu2) in THF results in a isolation of a Ta(V) ketimide complex, Ta(Cl)(N=CtBu2)4 (5), which can be isolated in 32% yield. Reaction of 5 with Tl(OTf) yields Ta(OTf)(N=CtBu2)4 (6) in 44% yield. Subsequent reduction of 6 with Cp*2Co in toluene generates the homoleptic Ta(IV) congener Ta(N=CtBu2)4 (7), although the yields are poor. All three homoleptic Group 5 ketimide complexes exhibit squashed tetrahedral geometries in the solid state, as determined by X-ray crystallography. This geometry leads to a dx2−y21 (2B1 in D2d) ground state, as supported by DFT calculations. EPR spectroscopic analysis of 1 and 2, performed at X- and Q-band frequencies (~9 and 35 GHz, respectively), further supports the 2B1 ground state assignment, while comparison of 1, 2, and 7 with related Group 5 tetra(aryl), tetra(amido) and tetra(alkoxo) complexes shows a higher M-L covalency in the ketimide-metal interaction. In addition, a ligand field analysis of 1 and 2 demonstrates that the ketimide ligand is both a strong π-donor and strong π-acceptor, an unusual combination found in very few organometallic ligands.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…6 Soriaga et al . identified the ketimide MOs having π-interactions with an electron poor metal ion.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

et al. 2015

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The Ketimide Ligand is Not Just an Inert Spectator: Heteroallene Insertion Reactivity of an Actinide–Ketimide Linkage in a Thorium Carbene Amide Ketimide Complex

Lu¹,

Lewis²,

Blake³

et al. 2014

Angewandte Chemie

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The ketimide anion R2CN− is an important class of chemically robust ligand that binds strongly to metal ions and is considered ideal for supporting reactive metal fragments due to its inert spectator nature; this contrasts with R2N− amides that exhibit a wide range of reactivities. Here, we report the synthesis and characterization of a rare example of an actinide ketimide complex [Th(BIPMTMS){N(SiMe3)2}(NCPh2)] [2, BIPMTMS=C(PPh2NSiMe3)2]. Complex 2 contains ThCcarbene, ThNamide and ThNketimide linkages, thereby presenting the opportunity to probe the preferential reactivity of these linkages. Importantly, reactivity studies of 2 with unsaturated substrates shows that insertion reactions occur preferentially at the ThNketimide bond rather than at the ThCcarbene or ThNamide bonds. This overturns the established view that metal‐ketimide linkages are purely inert spectators.

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Dispersion Forces, Disproportionation, and Stable High‐Valent Late Transition Metal Alkyls

et al. 2016

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The transition metal tetra‐ and trinorbornyl bromide complexes, M(nor)4 (M=Fe, Co, Ni) and Ni(nor)3Br (nor=1‐bicyclo[2.2.1]hept‐1‐yl) and their homolytic fragmentations were studied computationally using hybrid density functional theory (DFT) at the B3PW91 and B3PW91‐D3 dispersion‐corrected levels. Experimental structures were well replicated; the dispersion correction resulted in shortened M−C bond lengths for the stable complexes, and it was found that Fe(nor)4 receives a remarkable 45.9 kcal mol−1 stabilization from the dispersion effects whereas the tetragonalized Co(nor)4 shows stabilization of 38.3 kcal mol−1. Ni(nor)4 was calculated to be highly tetragonalized with long Ni−C bonds, providing a rationale for its current synthetic inaccessibility. Isodesmic exchange evaluation for Fe(nor)4 confirmed that dispersion force attraction between norbornyl substituents is fundamental to the stability of these species.

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Synthesis of a cobalt(iv) ketimide with a squashed tetrahedral geometry

Cited by 43 publications

References 23 publications

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

The Ketimide Ligand is Not Just an Inert Spectator: Heteroallene Insertion Reactivity of an Actinide–Ketimide Linkage in a Thorium Carbene Amide Ketimide Complex

Dispersion Forces, Disproportionation, and Stable High‐Valent Late Transition Metal Alkyls

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Synthesis of a cobalt(iv) ketimide with a squashed tetrahedral geometry

Cited by 43 publications

References 23 publications

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═CtBu2)4 (M = V, Nb, Ta)

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═CtBu2)4 (M = V, Nb, Ta)

The Ketimide Ligand is Not Just an Inert Spectator: Heteroallene Insertion Reactivity of an Actinide–Ketimide Linkage in a Thorium Carbene Amide Ketimide Complex

Dispersion Forces, Disproportionation, and Stable High‐Valent Late Transition Metal Alkyls

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Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)