Surprising diversity of non-classical silicon–hydrogen interactions in half-sandwich complexes of Nb and Ta: M–H ⋯ Si–Cl interligand hypervalent interaction (IHI) versus stretched and unstretched β-Si–H⋯M agostic bonding†

Nikonov, Georgii I.; Mountford, Philip; Ignatov, Stanislav K.; Green, Jennifer C.; Leech, Michael A.; Кузьмина, Л. Г.; Разуваев, А. Г.; Rees, Nicholas H.; Blake, Alexander J.; Howard, Judith A. K.; Lemenovskii, D. A.

doi:10.1039/b103362j

Cited by 67 publications

(54 citation statements)

References 77 publications

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“…[18] Surprisingly, the reaction of the niobium congener [Nb(Cp) A C H T U N G T R E N N U N G (=NAr)A C H T U N G T R E N N U N G (PMe 3 ) 2 ] (1) with HSiMe 2 Cl gave the b-agostic silylamido compound [Nb(Cp)A C H T U N G T R E N N U N G {h 3 -N(Ar)SiMe 2 ÀH···}(Cl)A C H T U N G T R E N N U N G (PMe 3 )] (2 b) (Scheme 1), a product of Si À N bond formation. [18,19] In related work, it has been recently found that reactions of the isolobal bisA C H T U N G T R E N N U N G (imido) complex [MoA C H T U N G T R E N N U N G (=NAr') 2 A C H T U N G T R E N N U N G (PMe 3 [20] The latter reactions are rare examples of formal silane addition to a nitrogen based ligand. [10] Intrigued by this diversity, we set out to explore in more detail how different factors (in particular the nature of the phosphine, the substitution(s) at silicon and the R group on nitrogen) influence the course of these reactions, the products formed and the extent of any interligand interactions therein.…”

Section: H T U N G T R E N N U N G (=Nar)a C H T U N G T R E N N U mentioning

confidence: 97%

“…The Nb À Si distance of 2.6794(12) in 15 b is slightly longer than that in the related (1) ), which has a chloride ligand trans to the SiÀH bond. [18] The difference in geometry corresponds well to the difference in the SiÀH coupling constant in 15 b and 2 b; the trans phosphine induces a larger JA C H T U N G T R E N N U N G (HÀSi) (132 Hz in 15 b versus 96 Hz in 2 b) and, presumably, stronger Si À H interaction. It is interesting that in the isomers having chloride trans to hydride the variation of phosphine does not significantly affect the degree of Si À H···M agostic bonding.…”

mentioning

confidence: 89%

“…While 1 reacts with HSiMe 2 Cl to give the agostic complexes 2 b and 2 b' as the only observed thermodynamic products (Scheme 1), the analogous reactions of silanes HSiClR 2 (R 2 = ClMe, Cl 2 , Ph 2 ) with more electron-withdrawing R groups at Si lead exclusively to silyl hydride derivatives 3 d-f (Scheme 2). [23] These compounds were characterized by spectroscopic methods and X-ray structure analyses of 2 b, [18] 3 e, 3 f [22] and 3 g. In particular, agostic species give rise to high-field hydride resonances in the 1 H NMR spectra in the range À2 to À7 ppm and to low frequency Si À H À Nb bands in the range 1620-1670 cm…”

Section: H T U N G T R E N N U N G (=Nar)a C H T U N G T R E N N U mentioning

confidence: 99%

“…The reaction of 6 with HSiMe 2 Cl gives only one isomer of the agostic compound [ 3 )] (7 b, PMe 3 trans to H) within 5-8 min. [18] An analogous reaction with the bulkier silane HSiMePhCl occurred within 35 min to give the b-agostic…”

mentioning

confidence: 98%

“…The reaction of the 2,6-dimethylphenyl imido analogue [18,32] and, as the latter, features the phosphine ligand trans to the agostic Si À H bond. The Nb À Si distance of 2.6794(12) in 15 b is slightly longer than that in the related (1) ), which has a chloride ligand trans to the SiÀH bond.…”

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confidence: 99%

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Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Ignatov¹,

Rees

Merkoulov

et al. 2007

Chemistry A European J

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Reactions of imido complexes [M(Cp)(=NR')(PR''3)2] (M=V, Nb) with silanes afford a plethora of products, depending on the nature of the metal, substitution at silicon and nitrogen and the steric properties of the phosphine. The main products are [M(Cp)(=NR')(PR3)(H)(SiRnCl3-n)] (M=V, Nb; R'=2,6-diisopropylphenyl (Ar), 2,6-dimethylphenyl (Ar')), [Nb(Cp)(=NR')(PR''3)(H)(SiPhR2)] (R2=MeH, H2), [Nb(Cp)(==NR')(PR''3)(Cl)(SiHRnCl2-n)] and [Nb(Cp)(eta 3-N(R)SiR2--H...)(PR''3)(Cl)]. Complexes with the smaller Ar' substituent at nitrogen react faster, as do more acidic silanes. Bulkier groups at silicon and phosphorus slow down the reaction substantially. Kinetic NMR experiments supported by DFT calculations reveal an associative mechanism going via an intermediate N-silane adduct [Nb(Cp){=N(-->SiHClR2)R'}(PR''3)2] bearing a penta-coordinate silicon centre, which then rearranges into the final products through a Si--H or Si--Cl bond activation process. DFT calculations show that this imido-silane adduct is additionally stabilized by a Si--HM agostic interaction. Si--H activation is kinetically preferred even when Si--Cl activation affords thermodynamically more stable products. The niobium complexes [NbCp(=NAr)(PMe3)(H)(SiR2Cl)] (R=Ph, Cl) are classical according to X-ray studies, but DFT calculations suggest the presence of interligand hypervalent interactions (IHI) in the model complex [Nb(Cp) (==NMe)(PMe3)(H)(SiMe2Cl)]. The extent of Si--H activation in the beta-Si--HM agostic complexes [Cp{eta 3-N(R')SiR2--H}M(PR''3)(Cl)] (R''=PMe3, PMe2Ph) primarily depends on the identity of the ligand trans to the Si--H bond. A trans phosphine leads to a stronger Si--H bond, manifested by a larger J(Si--H) coupling constant. The Si--H activation diminishes slightly when a less basic phosphine is employed, consistent with decreased back-donation from the metal.

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Section: H T U N G T R E N N U N G (=Nar)a C H T U N G T R E N N U mentioning

confidence: 97%

mentioning

confidence: 89%

Section: H T U N G T R E N N U N G (=Nar)a C H T U N G T R E N N U mentioning

confidence: 99%

mentioning

confidence: 98%

mentioning

confidence: 99%

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Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Ignatov¹,

Rees

Merkoulov

et al. 2007

Chemistry A European J

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Agostische Wechselwirkungen in d⁰‐Alkylmetallkomplexen

Scherer

McGrady

2004

Angewandte Chemie

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Das Phänomen und die Ursachen der agostischen Wechselwirkung werden hier vorgestellt und neu beschrieben. An einen historischen Rückblick schließt sich eine Übersicht der experimentellen Methoden an, die zur Untersuchung von agostischem Verhalten genutzt werden. Anhand einer Reihe einfacher Alkylmetallkomplexe wird ein neues Modell für die agostische Wechselwirkung in d0‐Systemen vorgestellt. Dabei wird sich eine klare Abgrenzung dieser Systeme von agostischen Komplexen später Übergangsmetalle ergeben. Entgegen den bisherigen Annahmen zeigt sich, dass Faktoren wie die Zahl der Valenzelektronen und die Koordinationszahlen nicht notwendigerweise eine wesentliche Rolle bei der Ausbildung einer agostischen Wechselwirkung in d0‐Systemen spielen. Mit der “Atoms in Molecules”‐Theorie wird die Ladungsdichteverteilung in mehreren Alkylübergangsmetallkomplexen sowohl experimentell als auch theoretisch untersucht. Demnach ist die lokale Ladungskonzentration eine entscheidende Größe bei agostischen Wechselwirkungen. Schließlich werden wir erstmals eine Möglichkeit aufzeigen, wie die Größe und die Verteilung von Ladungskonzentrationen gezielt manipuliert und somit die Stärke der agostischen Wechselwirkung in d0‐Alkylmetallkomplexen verändert werden kann.

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Agostic NSiH⋅⋅⋅Mo Complexes: From Curiosity to Catalysis

et al. 2008

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All manipulations were carried out using conventional inert atmosphere glove-box and Schlenk techniques. Dry ether, toluene and hexanes were obtained, using Grubbs-type purification columns, other solvents were dried by distillation from appropriate drying agents.NMR spectra were obtained with a Bruker DPX-300 and Brucker DPX-600 instruments ( 1 H: 300 and 600 MHz; 13 C: 75.5 and 151 MHz; 29 Si: 59.6 and 119.2 MHz; 31 P: 121.5 and 243 MHz). IR spectra were measured on a Perkin-Elmer 1600 FT-IR spectrometer.(ArN) 2 Mo(PMe 3 ) 3 (Ar = 2,6-( i Pr) 2 C 6 H 3 ) was prepared by a literature procedure. [ was prerared by a literature procedure from SiCl 4 and corresponding Grignard reagent. 2 All catalytic and NMR reactions were done under nitrogen atmosphere using NMR tubes equipped with Teflon valves. The structures and yields of all hydrosilated products were determined using NMR analysis. Preparation of (ArN)(PMe 3 )(PhH 2 Si)Mo(η 3 -NAr-SiHPh-H) (3)PhSiH 3 (0.37 mL, 3.0 mmol) was added to a solution of (ArN) 2 Mo(PMe 3 ) 3 (1.01 g, 1.5 mmol) in 100 mL of hexane at room temperature. After the addition of PhSiH 3 , the colour of reaction mixture immediately turned from dark-green to brown, and the formation of a brown precipitate was observed. The reaction mixture was purged with N 2 under stirring at room temperature for 30 min., concentrated and left in a freezer (-30°C) overnight. More crystalline brown precipitate formed. The cold precipitate was filtered off, washed with cold hexane (10 mL) and dried in vacuum to give a fine brown powder of 3. Yield: 0.7 g, 77 %.

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Surprising diversity of non-classical silicon–hydrogen interactions in half-sandwich complexes of Nb and Ta: M–H ⋯ Si–Cl interligand hypervalent interaction (IHI) versus stretched and unstretched β-Si–H⋯M agostic bonding†

Cited by 67 publications

References 77 publications

Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Agostische Wechselwirkungen in d⁰‐Alkylmetallkomplexen

Agostic NSiH⋅⋅⋅Mo Complexes: From Curiosity to Catalysis

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Surprising diversity of non-classical silicon–hydrogen interactions in half-sandwich complexes of Nb and Ta: M–H ⋯ Si–Cl interligand hypervalent interaction (IHI) versus stretched and unstretched β-Si–H⋯M agostic bonding†

Cited by 67 publications

References 77 publications

Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Agostische Wechselwirkungen in d0‐Alkylmetallkomplexen

Agostic NSiH⋅⋅⋅Mo Complexes: From Curiosity to Catalysis

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Agostische Wechselwirkungen in d⁰‐Alkylmetallkomplexen