Synthesis and Structures of the Crystalline Heavier Alkali Metal Alkyls:  X-ray Structures of [K(μ-R){O(Me)Bu^t}]_∞, [(pmdeta)K(μ-R)K(μ-R)₂K(μ-R)K(pmdeta)], and [Cs(μ-R)(tmeda)]_∞ (R = CH(SiMe₃)₂)

Abstract

The crystalline hexane-soluble metal alkyls [Na(µMe 2 NCH 2 CH 2 NMe 2 ) have been prepared from LiR with an equimolar portion of NaOBu t , KOBu t , RbOC 6 H 2 Bu t 2 -2,6-Me-4, or CsOCH 2 CH(Et)Bu n and for 2-6 the appropriate neutral ligand. X-ray crystal structures of the metal alkyls 2, 3, and 6 are presented; 1 and 4 were described in an earlier communication. Treatment of 5 with Bu t CN afforded the cesium 1-azaallyl Cs{N(R)C(Bu t )C(H)R} ( 7).

Adding Rubidium and Cesium to the Homologous Series of Alkali Metal Compounds of (Trimethylsilyl)methanides and 2,2,6,6‐Tetramethylpiperidides

“…The insolubility and high reactivity of 1 and 2 in commonly used solvents prevented the formation of crystalline samples and therefore any possible identification by X‐ray crystallography. Also the introduction of strongly donating solvents such as TMEDA, PMDETA28 ( N , N , N′ , N″ , N″ ‐pentamethyldiethylenetriamine) or tert ‐butyl methyl ether19 led only to rapid decomposition of these heavy alkali metal alkyls. Similar behaviour towards deuterated solvents made their characterisation by 1 H NMR spectroscopy particularly difficult, and thus no informative 13 C NMR spectra could be obtained.…”

“…This is because such compounds are known to undergo various decomposition processes including metalation of the organic solvent,13 β‐elimination14 or self‐metalation 15. Structurally characterised rubidium and cesium alkyl compounds include those with methyl,16 tris(trimethylsilyl)methyl,17 tris(dimethylphenyl)methyl,18 bis(trimethylsilyl)methyl,19,20 diphenylmethyl21 and triphenylmethyl22 groups. (Trimethylsilyl)methylrubidium was produced by a reaction of the corresponding bisalkylmercury with rubidium metal and used in a subsequent benzylic metalation of benzyltrimethylsilane 23.…”

Synthesis and Structures of [(Trimethylsilyl)methyl]sodium and ‐potassium with Bi‐ and Tridentate N‐Donor Ligands

“…Whereas the TMEDA‐solvated potassium compound of the bis(trimethylsilyl)methyl group16b [(PMDETA) 2 {KCH(SiMe 3 ) 2 } 4 ] forms an “open tetramer”31 (with a central K 2 C 2 core, which is extended by two bridging alkyl groups and two terminal PMDETA‐coordinated potassium atoms), the corresponding (trimethylsilyl)methyl compound 2b , which crystallises in the triclinic space group P $\bar {1}$ , forms an asymmetric tetranuclear unit with only three of the four potassium atoms chelated by two TMEDA nitrogen atoms each. The donor‐deficient molecule 2b is best described as a tetrahedron based on four potassium atoms, with each of the four triangular faces capped by the methanide carbon atoms of four (trimethylsilyl)methyl groups, completing a distorted K 4 C 4 heterocubane (Figure 3).…”

“…More structural information is known for alkylsodium and ‐potassium compounds with more stabilising modified/functionalised alkyl groups (see Table 1), such as benzyl,12 diphenylmethyl,12,13 triphenylmethyl,14 bis(trimethylsilyl)methyl,15,16 tris(trimethylsilyl)methyl,17,18 and phenylbis(trimethylsilyl)methyl 19. Structural motifs which can be found in this group of compounds range from solvated monomers,14 solvated dimers,13 separated ion pairs,17 solvated tetramers,12,16b chains,15,18a,19 and solvated chains 16a,16b,18b…”

Alkyl, Silyl, and Phosphane Ligands—Classical Ligands in Nonclassical Bonding Modes

“…Main group elements will not be considered here although many examples are known (for leading references, see ref. 7) especially the definitive example of a type V structure for [Al 2 (CH 3 ) 6 ], recently confirmed through a powder neutron diffraction study of [Al 2 (CD 3 ) 6 ] ( 1 ) at 4.5 K, which also established the staggered conformation of the bridges with respect to each other ( C 2h molecular symmetry) 8. Although this is a common structural type for aluminum,9 [(C 6 F 5 ) 3 Al( μ ‐CH 3 )Al(C 6 F 5 ) 3 ] − has recently been shown to exhibit a type I structure 10…”