Syntheses and Structures of the First Heavy Alkaline Earth Metal Bis(tris(trimethylsilyl))silanides

Abstract

The first heavy alkaline earth metal bis(tris(trimethylsilyl))silanides were obtained in high yield and purity by a straightforward metathesis reaction involving the treatment of potassium tris(trimethylsilyl)silanide, K(THF) n Si(SiMe3)3, with calcium, strontium, and barium iodides. The addition of specific donors provided either contact or separated species in the solid state, whereas in aromatic solvents the compounds dissociate into separated ions, as shown by 29Si NMR spectroscopic studies. We here report on the syntheses and characterization of compounds displaying M−Si bonds in the solid state with the general formula of M(THF) n (Si(SiMe3)3)2 (M = Ca, n = 3, 1; Sr, n = 3, 2; and Ba, n = 4, 3) and Sr(TMEDA)(THF)(Si(SiMe3)3)2, 4 (TMEDA = N,N,N‘,N‘-tetramethylethylenediamine). Compound 5, [Ba(HMPA)6][(Si(SiMe3)3)2], displays separated ions, while 6, [Ba(18-crown-6)(Si(SiMe3)3)2][Ba(HMPA)6][(Si(SiMe3)3)2], is a rare example containing both contact and separated ions in the asymmetric unit. All compounds were characterized using X-ray crystallography, 1H, 13C, and 29Si NMR, and IR spectroscopy.

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

“…Difficulties mounting the highly reactive 3 on the diffractometer and problems with disorder prevented a satisfactory structure refinement, but pertinent structure parameters are clearly visible. However, the identity of compound 3 has also been confirmed by 1 H, 13 C, and 29 Si NMR and IR spectroscopic data.…”

“…[25] The similarity of chemical shifts for the germanides and silanides suggests a close chemical relationship, an assumption also supported by the closely related values for atomic size and electronegativity. [35,36] The high reactivity of compound 8 did not allow its characterization by 13 C and 29 Si NMR spectroscopy, since the sample decomposed rapidly even when handled in the freshly regenerated glove box. However, Structural aspects: Crystallographic information and data collection parameters for compounds 1, 2, 4-7 are summarized in Table 1, while a summary of structural parameters is given in Table 2.…”

“…The purity of all germanides with the exception of 8 was confirmed by 1 H and 13 C NMR, and IR spectroscopy, while compounds 1, 2, and 4-7 were also characterized by singlecrystal X-ray crystallography. Extensive 29 Si NMR studies were conducted on compounds 1-5 to investigate the ion association of the target compounds in solution.…”

“…The chemistry of alkaline-earth-metal derivatives bearing heavy Group 14 ligands has attracted attention [1][2][3][4][5][6][7][8][9][10][11][12][13] due to applications in synthetic and polymer chemistry. [9,14] While alkali-and alkaline-earth-metal silanides have been studied in some detail, [1,2,4,7,9,[15][16][17][18][19][20][21][22][23][24][25] little is known for the closely related, but more reactive germanides.…”

Molekulares Calciumhydrid: Dicalciumtrihydrid‐Kation, stabilisiert durch einen neutralen makrocyclischen NNNN‐Liganden

“…[5] Während Bis(triphenylsilyl)calcium [Ca(SiPh 3 ) 2 (THF) 4 ]( 1) mit Wasserstoff anscheinend kolloidales Calciumdihydrid bildet, [6] sollte sich Me 4 TACD-gebundenes Bis(triphenylsilyl)calcium als Vorstufe für das molekulare Calciumdihydrid [CaH 2 (Me 4 TACD)] (Me 4 TACD = 1,4,7,4,7, (SiMe 3 ) 3 } 2 (THF) 3 ]. [8] Der kleine Si1-Ca1-Si1'-Winkel von 85.68 (5) [4] (Ca···Ca = 3.3551(10) ) und vergleichbar zu denen in zweikernigen Lanthanoidtrihydriden [Ln 2 H 3 ]( Ln = Yu nd Lu; Ln···Ln = 2.93-3.75 ), [9,11] obwohl der Radius des Ca 2+ -Ions (1.06 b ei KZ = 7) grçßer als der des Y 3+ -Ions (0.96 b ei KZ = 7) und des Lu 3+ -Ions (0.86 b ei KZ = 6) ist. [12] Die Stabilität des kationischen Calciumhydrids 3 wurde anhand einer NBO-Analyse über DFT-Rechnungen auf dem gleichen Niveau wie für 2 bewertet.…”