Limits...
Structural Diversity in Alkali Metal and Alkali Metal Magnesiate Chemistry of the Bulky 2,6 ‐ Diisopropyl ‐ N ‐ (trimethylsilyl)anilino Ligand

View Article: PubMed Central - PubMed

ABSTRACT

Bulky amido ligands are precious in s‐block chemistry, since they can implant complementary strong basic and weak nucleophilic properties within compounds. Recent work has shown the pivotal importance of the base structure with enhancement of basicity and extraordinary regioselectivities possible for cyclic alkali metal magnesiates containing mixed n‐butyl/amido ligand sets. This work advances alkali metal and alkali metal magnesiate chemistry of the bulky arylsilyl amido ligand [N(SiMe3)(Dipp)]− (Dipp=2,6‐iPr2‐C6H3). Infinite chain structures of the parent sodium and potassium amides are disclosed, adding to the few known crystallographically characterised unsolvated s‐block metal amides. Solvation by N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) or N,N,N′,N′‐tetramethylethylenediamine (TMEDA) gives molecular variants of the lithium and sodium amides; whereas for potassium, PMDETA gives a molecular structure, TMEDA affords a novel, hemi‐solvated infinite chain. Crystal structures of the first magnesiate examples of this amide in [MMg{N(SiMe3)(Dipp)}2(μ‐nBu)]∞ (M=Na or K) are also revealed, though these breakdown to their homometallic components in donor solvents as revealed through NMR and DOSY studies.

No MeSH data available.


Low‐coordinate Ni and Fe complexes showing interaction of potassium with π‐system as reported by Tilley.14
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5096043&req=5

chem201602683-fig-0001: Low‐coordinate Ni and Fe complexes showing interaction of potassium with π‐system as reported by Tilley.14

Mentions: Casting the net wider for other bulky amides that might possess interesting cooperativity in magnesiate modifications our attention was drawn to the arylsilyl amido ligand [N(SiMe3)(Dipp)]− (where Dipp=2,6‐diisopropylphenyl=2,6‐iPr2‐C6H3). Its metallo chemistry is well developed, with Power10 recently reporting the extraordinary finding that C−H⋅⋅⋅H−C dispersion forces between two such eclipsed amido ligands helped stabilise linear, two‐coordinate Fe, Co and Ni bis(amides), while Tilley11 demonstrated the catalytic capability of the Ni bis(amide) in carbon–carbon cross‐coupling reactions. Though [(Li{N(SiMe3)(Dipp)})2] commonly acts as a transfer agent to generate such transition‐metal amides, surprisingly the alkali metal chemistry of this amide has many gaps. While Roesky12 has determined the dimeric structure of [(Li{N(SiMe3)(Dipp)})2] and solvated structures such as Anwander's [Li{N(SiMe3)(Dipp)}(THF)3]13 are known, the sodium and potassium congeners have not been crystallographically characterised. However, potassium has been observed in interesting transition‐metal bimetallic systems reported by Tilley14 that demonstrate the large, soft alkali metal's propensity for engaging with arene‐π systems (Figure 1).15 While Ruhlandt‐Senge16 has described two‐coordinate [Mg{N(SiMe3)(Dipp)}2] and the THF solvate [(THF)2Mg{N(SiMe3)(Dipp)}(nBu)], and [Mg{N(SiMe3)(Dipp)}2(OEt2)]17 was described by our group, to the best of our knowledge no alkali metal magnesiate has hitherto been reported. Therefore this study sets out to fill in important gaps in the alkali metal chemistry of [N(SiMe3)(Dipp)]− and to synthesise and characterise the first magnesiate examples as a prerequisite to determining whether this amide also possesses synergistic template base potential.1


Structural Diversity in Alkali Metal and Alkali Metal Magnesiate Chemistry of the Bulky 2,6 ‐ Diisopropyl ‐ N ‐ (trimethylsilyl)anilino Ligand
Low‐coordinate Ni and Fe complexes showing interaction of potassium with π‐system as reported by Tilley.14
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5096043&req=5

chem201602683-fig-0001: Low‐coordinate Ni and Fe complexes showing interaction of potassium with π‐system as reported by Tilley.14
Mentions: Casting the net wider for other bulky amides that might possess interesting cooperativity in magnesiate modifications our attention was drawn to the arylsilyl amido ligand [N(SiMe3)(Dipp)]− (where Dipp=2,6‐diisopropylphenyl=2,6‐iPr2‐C6H3). Its metallo chemistry is well developed, with Power10 recently reporting the extraordinary finding that C−H⋅⋅⋅H−C dispersion forces between two such eclipsed amido ligands helped stabilise linear, two‐coordinate Fe, Co and Ni bis(amides), while Tilley11 demonstrated the catalytic capability of the Ni bis(amide) in carbon–carbon cross‐coupling reactions. Though [(Li{N(SiMe3)(Dipp)})2] commonly acts as a transfer agent to generate such transition‐metal amides, surprisingly the alkali metal chemistry of this amide has many gaps. While Roesky12 has determined the dimeric structure of [(Li{N(SiMe3)(Dipp)})2] and solvated structures such as Anwander's [Li{N(SiMe3)(Dipp)}(THF)3]13 are known, the sodium and potassium congeners have not been crystallographically characterised. However, potassium has been observed in interesting transition‐metal bimetallic systems reported by Tilley14 that demonstrate the large, soft alkali metal's propensity for engaging with arene‐π systems (Figure 1).15 While Ruhlandt‐Senge16 has described two‐coordinate [Mg{N(SiMe3)(Dipp)}2] and the THF solvate [(THF)2Mg{N(SiMe3)(Dipp)}(nBu)], and [Mg{N(SiMe3)(Dipp)}2(OEt2)]17 was described by our group, to the best of our knowledge no alkali metal magnesiate has hitherto been reported. Therefore this study sets out to fill in important gaps in the alkali metal chemistry of [N(SiMe3)(Dipp)]− and to synthesise and characterise the first magnesiate examples as a prerequisite to determining whether this amide also possesses synergistic template base potential.1

View Article: PubMed Central - PubMed

ABSTRACT

Bulky amido ligands are precious in s‐block chemistry, since they can implant complementary strong basic and weak nucleophilic properties within compounds. Recent work has shown the pivotal importance of the base structure with enhancement of basicity and extraordinary regioselectivities possible for cyclic alkali metal magnesiates containing mixed n‐butyl/amido ligand sets. This work advances alkali metal and alkali metal magnesiate chemistry of the bulky arylsilyl amido ligand [N(SiMe3)(Dipp)]− (Dipp=2,6‐iPr2‐C6H3). Infinite chain structures of the parent sodium and potassium amides are disclosed, adding to the few known crystallographically characterised unsolvated s‐block metal amides. Solvation by N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) or N,N,N′,N′‐tetramethylethylenediamine (TMEDA) gives molecular variants of the lithium and sodium amides; whereas for potassium, PMDETA gives a molecular structure, TMEDA affords a novel, hemi‐solvated infinite chain. Crystal structures of the first magnesiate examples of this amide in [MMg{N(SiMe3)(Dipp)}2(μ‐nBu)]∞ (M=Na or K) are also revealed, though these breakdown to their homometallic components in donor solvents as revealed through NMR and DOSY studies.

No MeSH data available.