Crystal structure of a heavier alkali metal diisopropylamide complex: a discrete (KN)2 ring dimer with TMEDA chelation and short intramolecular K⋯H(C) contacts

Syntheses and Structures of the First Heavy‐Alkali‐Metal Tris(trimethylsilyl)germanides

“…The potassium-nitrogen distances in compounds 6 and 7 are essentially identical, ranging from 2.807(2) to 2.933(2) for 6 and 2.808(3) to 2.935(3) for 7. These values agree well with previously reported potassium-nitrogen (TMEDA) distances in compounds [K(tmeda){N(iPr) 2 } 2 ] (iPr = isopropyl) (2.878 and 2.894 ) [41] and [K(tmeda) 2 (h 5 -fluorenide)] (2.824 and 3.057 ).…”

Solvent‐Free and TMEDA‐Solvated Mixed Alkali Metal‐Magnesium Tris‐diisopropylamides

“…[18] More relevant to the solution phase, the solvated derivative [(LDA·THF) 2 ] (B) exhibits a planar (LiN) 2 dimeric ring, the Li corners of which carry monodentate THF ligands. [19] A similar discrete four-membered ring structure (B) is observed in both the aforementioned [(NaDA·TMEDA) 2 ] [11] and [(KDA·TMEDA) 2 ], [12] though the wider exocyclic coordination arcs offered by the larger alkali metals allows for the chelation of didentate TMEDA ligands. Combining LDA with the same diamine molecule in [{(LDA·TMEDA) 2 } ϱ ] [20] again generates a (LiN) 2 dimeric ring, but the reduced space about the Li centres forces the TMEDA ligands into bridging (non-chelating) roles to create an infinite chain of linked dimers (C).…”

“…This is because the crystals of both 2 and 3 readily dissolve in hexane/ heptane solution at ambient temperature, hence the isolation procedure is best carried out at subambient temperature (even then, a large proportion of the crystalline material is visibly lost). Such exceptionally good solubility in hydrocarbon media pointed to a synergic effect with both metal atoms intimately involved in the crystalline structures (as confirmed later by the X-ray crystallographic studies, vide infra), as on their own NaDA/KDA exhibit little or [12] only limited solubility. The solubilising effect of mixing alkali metal and magnesium compounds in certain systems has also been noted in alkoxide chemistry.…”

“…This is because TMEDA fulfils the donor responsibility in 2, and effectively at that going on the lengths of the dative KϪN bonds (mean, 2.8759 Å ) which, unusually, are of the same magnitude (mean, 2.8899 Å ) as their anion-containing K-(µ-N) comrades. In the aforementioned homometallic relative [(KDA·TMEDA) 2 ], [12] the KϪN ''anionic'' bonds are significantly shorter than their this emphasises the profound proximal effect that the introduction of a Mg atom can exert on the dimensions of an identical K coordinative environment (here involving four N atoms, two from DA and two from TMEDA). The presence of TMEDA in 2 also lessens the need for reinforcement K···C agostic bonding.…”

Synthesis, Structure and Theoretical Studies of the Hydrido Inverse Crown [K2Mg2(NiPr2)4(μ‐H)2·(toluene)2]: a Rare Example of a Molecular Magnesium Hydride with a Mg‐(μ‐H)2‐Mg Double Bridge

“…Complex 1 is only the second example of a crystallographically characterised potassium diisopropylamide, the first example being the simple dimeric, TMEDA solvate [(KNiPr 2 ·TMEDA) 2 ] (3). [6] Recent work in our laboratory has focused on the synergistic chemistry of combining an alkali metal amide with its magnesium (or zinc) bis(amide) analogue. The major consequence of these studies thus far has been the development of a series of heterobimetallic macrocyclic amide complexes that have become known collectively as ''inverse crowns.''…”