Treatment of lithium tris(trimethylsilyl)silanide, Li(THF)3Si(SiMe3)3, with heavier alkali metal tert-butoxides yielded the alkali metal silanides MSi(SiMe3)3 (M = K, Rb, or Cs) in a simple, high-yielding, one-step procedure. Separation of the two solid reaction products was achieved by addition of crown ether, which also determines the formation of contact or separated ion pairs in the solid state. Here we report the synthesis and structural characterization of the contact ion K(18-crown-6)Si(SiMe3)3, 2, in addition to the separated [K(12-crown-4)2][Si(SiMe3)3], 1, [Rb(15-crown-5)2][Si(SiMe3)3], 3, and [Cs(18-crown-6)2][Si(SiMe3)3], 5. [Rb(18-crown-6)2][Si(SiMe3)3][Rb(18-crown-6)Si(SiMe3)3]2, 4, is a rare example where both contact and separated ions are observed in the solid state. The investigation of synthetic routes toward the target compounds also examined the previously published metalation of Si(SiMe3)4 with potassium tert-butoxide. This route proved to be temperamental:  depending on reaction conditions and solvent systems, either adducts between product and unreacted starting material, namely, [{K(THF)Si(SiMe3)3}{KO t Bu}3], 6, or the target compound KSi(SiMe3)3 was isolated. All compounds were characterized by X-ray crystallography and NMR spectroscopy.

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An extended family of aryl-substituted alkaline earth metal silylamides M{N(2,4,6-Me3C6H2)(SiMe3)}donor(n) was prepared using alkane elimination (Mg), salt elimination (Ca, Sr, Ba), and direct metalation (Sr, Ba). Three different donors, THF, TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine), and PMDTA (PMDTA = N,N,N',N'',N''-pentamethyldiethylenetriamine) were employed to study their influence on the coordination chemistry of the target compounds, producing monomeric species with the composition M{N(2,4,6-Me3C6H2)(SiMe3)}2(THF)2 (M = Mg, Ca, Sr, Ba), M{N(2,4,6-Me3C6H2)(SiMe3)}2TMEDA (M = Ca, Ba), and M{N(2,4,6-Me3C6H2)(SiMe3)}2PMDTA (M = Sr, Ba). For the heavier metal analogues, varying degrees of agostic interactions are completing the coordination sphere of the metals. Compounds were characterized using IR and NMR spectroscopy in addition to X-ray crystallography.

First successful syntheses and structural characterization of new core modified meso aryl azuliporphyrins by a simple [3 + 1] methodology are reported.

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.

Modified octaphyrins with 34pi electrons have been synthesized and characterized following a simple synthetic methodology. An acid-catalyzed alpha,alpha coupling of tetrapyrranes containing furan, thiophene and selenophene rings resulted in the formation of the respective octaphyrins in relatively good yield. Solution studies by (1)H NMR and 2D NMR methods and single crystal Xray structural characterization reveal an almost flat structure with two heterocyclic rings inverted. Specifically, in 14 two selenophene rings (one on each biselenophene unit) are inverted while in 15 two furan rings (one on each bifuran unit) are inverted when the meso substituent are mesityl groups. On changing the mesityl substituent to m-xylyl group as in 19, the location of ring inversion shifts to pyrrole rings (one on each bipyrrole unit) indicating the dependence of structure on the meso substituents. UV/Vis studies, both in freebase and protonated forms reveal typical porphyrinic character and the aromatic nature of the octaphyrins. The Deltadelta values evaluated by (1)H NMR spectroscopy also support their aromatic nature. The protonated forms of octaphyrins bind TFA anion in a 1:2 ratio. The TFA anions are located one above and below the plane of the octaphyrin macrocycle and they are held by weak electrostatic NH-O interactions similar to that observed for protonated rubyrins. However, in the present case, there is an additional non-electrostatic CH-O interaction involving beta-CH of the inverted heterocyclic ring and the carbonyl oxygen of the TFA. Furthermore, inter molecular interactions between the Cbond;H of the meso-mesityl group and the fluorine of CF(3) group of bound TFA leads to the formation of one-dimensional supramolecular arrays with interplanar distance of 13 A between two octaphyrins.

The combination of equimolar amounts of LiOAr and Mg(OAr)2 (OAr=aryloxide) in polar media afforded several lithium aryloxomagnesiates. Factors influencing the structural chemistry of the compounds, such as the degree of ligand bulk, type of Lewis base donors, and crystallization solvent, are examined. Structural characterization reveals a discrete, solvent-separated species, [Li(thf)4][Mg(BHT)3].THF (1) (BHT=2,6-tBu2-4-MeC6H2O) and a family of molecular compounds with various Li/Mg stoichimetries, including a 1:1 Li/Mg ratio in [LiMg(Odpp)3(thf)2].0.5PhMe (2) (Odpp=2,6-Ph2C6H3O) and [Li(Et2O)Mg(Odpp)3].0.5PhMe (3), a 2:1 Li/Mg ratio as in [{Li(thf)2}2Mg(OMes)4].2THF (4) (OMes=2,4,6-Me3C6H2O) and [{Li(tmeda)}2Mg(m-Odtp)4].0.5Et2O (5) (m-Odtp=3,5-tBu2C6H3O), and a novel 2:3 Li/Mg ratio in [{Li(thf)2}2Mg3(m-Odtp)8(thf)2].3THF (6). Two new homometallic magnesium bis(aryloxides), Mg(Odpp)2(thf)2 (7) and Mg(Odpp)2(Et2O)2 (8), are also included for the sake of comparison. The solution behavior of the heterobimetallic compounds in arene and polar solvent is analyzed by 1H NMR spectroscopy.

Four novel alkaline earth metal tetranuclear aryloxide/pyrazolate hydroxides of the general formula M4(ligand)6(OH)2(donor)n have been prepared by either adding stoichiometric quantities of water to preformed alkaline earth metal aryloxides or in a direct metalation regime combining metal, ligand (alcohol, pyrazole), and donor with stoichiometric amounts of water. The compounds are considered as potential intermediates in the sol-gel process. A nonhydrolyzable magnesium aryloxide has also been obtained using the same reaction scheme. Unexpectedly, a dimeric strontium complex with further association of a second dimer via hydrogen bonding from the solvent of crystallization, ethylenediamine, has been isolated by the treatment of strontium metal with a mixture of alcohol and water. All compounds were characterized using X-ray crystallography, 1H and 13C NMR, and IR spectroscopy.