Kinetics and mechanism of the racemic addition of trimethylsilyl cyanide to aldehydes catalysed by Lewis bases

Quest for a Desolvated Structure Unveils Breathing Phenomena in a MOF Leading to Greener Catalysis in a Solventless Setup: Insights from Combined Experimental and Computational Studies

The crystal structure of the metal-organic framework (MOF), {Mn2(1,4-bdc)2(DMF)2}n (1) (1,4-bdcH2, 1,4-benzenedicarboxylic acid; DMF, N,N-dimethylformamide), is known for a long time; however, its desolvated structure, {Mn2(1,4-bdc)2}n (1'), is not yet known. The first-principles-based computational simulation was used to unveil the structure of 1' that shows the expansion in the framework, leading to pore opening after the removal of coordinated DMF molecules. We have used 1' that contains open metal sites (OMSs) in the structure in cyanosilylation and CO2 cycloaddition reactions and recorded complete conversions in a solventless setup. The pore opening in 1' allows the facile diffusion of small aldehyde molecules into the channels, leading to complete conversion. The reactions with larger aldehydes, 2-naphthaldehyde and 9-anthracenecarboxaldehyde, also show 99.9% conversions, which are the highest reported until date in solventless conditions. The in silico simulations illustrate that larger aldehydes interact with Mn(II) OMSs on the surfaces, enabling a closer interaction and facilitating complete conversions. The catalyst shows high recyclability, exhibiting 99.9% conversions in the successive reaction cycles with negligible change in the structure. Our investigations illustrate that the catalyst 1' is economical, efficient, and robust and allows reactions in a solventless greener setup, and therefore the catalysis with 1' can be regarded as "green catalysis".

Construction of defected MOF-74 with preserved crystallinity for efficient catalytic cyanosilylation of benzaldehyde

Numerous open metal sites and well-developed micropores are the two most significant characteristics that should be imparted to design metal-organic frameworks (MOFs) as effective catalysts. However, the construction of the best MOF catalyst with both these characteristics is challenging because the creation of numerous open metal sites generally triggers some structural collapse of the MOF. Herein, we report the construction of well-structured but defected MOFs through the growth of defected MOFs, where some of the original organic linkers were replaced with analog organic linkers, on the surface of a crystalline MOF template (MOF-on-MOF growth). Additional open metal sites within the MOF-74 structure were generated by replacing some of the 2,5-dihydroxy-1,4-bezenedicarboxylic acid presenting in MOF-74 with 1,4-benzenedicarboxylic acid due to the missing hydroxyl groups. And the resulting additional open metal sites within the MOF-74 structure resulted in enhanced catalytic activity for the cyanosilylation of aldehydes. However, the collapse of some of the well-developed MOF-74 structure was also followed by structural defects. Whereas, the growth of defected MOF-74 (D-MOF-74) on the well-crystallized MOF-74 template led to the production of relatively well-crystallized D-MOF-74. Core-shell type MOF-74@D-MOF-74 having abundant open metal sites with a preserved crystallinity exhibited the efficient catalytic cyanosilylation of several aldehydes. Additionally, MOF-74@D-MOF-74 displayed excellent recyclability during the consecutive catalytic cycles.

Main group cyanides: from hydrogen cyanide to cyanido-complexes

Homoleptic cyanide compounds exist of almost all main group elements. While the alkali metals and alkaline earth metals form cyanide salts, the cyanides of the lighter main group elements occur mainly as covalent compounds. This review gives an overview of the status quo of main group element cyanides and cyanido complexes. Information about syntheses are included as well as applications, special substance properties, bond lengths, spectroscopic characteristics and computations. Cyanide chemistry is presented mainly from the field of inorganic chemistry, but aspects of chemical biology and astrophysics are also discussed in relation to cyano compounds.

Isolation of a Nitromethane Anion in the Calix-Shaped Inorganic Cage

A calix-shaped polyoxometalate, [V₁₂O₃₂]⁴⁻ (V12), stabilizes an anion moiety in its central cavity. This molecule-sized container has the potential to control the reactivity of an anion. The highly-reactive cyanate is smoothly trapped by V12 to form [V₁₂O₃₂(CN)]⁵⁻. In the CH₃NO₂ solution, cyanate abstracts protons from CH₃NO₂, and the resultant CH₂NO₂⁻ is stabilized in V12 to form [V₁₂O₃₂(CH₂NO₂)]⁵⁻ (V12(CH₂NO₂)). A crystallographic analysis revealed the double-bond characteristic short bond distance of 1.248 Å between the carbon and nitrogen atoms in the nitromethane anion in V12. ¹H and ¹³C NMR studies showed that the nitromethane anion in V12 must not be exchanged with the nitromethane solvent. Thus, the V12 container restrains the reactivity of anionic species.

Cyanosilylation of Aldehydes Catalyzed by Ag(I)- and Cu(II)-Arylhydrazone Coordination Polymers in Conventional and in Ionic Liquid Media

The novel Ag(I) and Cu(II) coordination polymers [Ag(μ3-1κO;2:3κO′;4κN-HL)]n∙n/2H2O (1) and [Cu(en)2(μ-1κO;2κN-L)]n∙nH2O (2) [HL− = 2-(2-(1-cyano-2-oxopropylidene)hydrazinyl)benzene sulfonate] were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and single crystal X-ray diffraction analyses. Compounds 1 and 2 as well as the already known complex salt [Cu(H2O)2(en)2](HL)2 (3) have been tested as homogenous catalysts for the cyanosilylation reaction of different aldehydes with trimethylsilyl cyanide, to provide cyanohydrin trimethylsilyl ethers. Coordination polymer 2 was found to be the most efficient one, with yields ranging from 76 to 88% in methanol, which increases up to 99% by addition of the ionic liquid [DHTMG][L-Lactate].

Two metal–organic frameworks based on pyridyl–tricarboxylate ligands as size-selective catalysts for solvent-free cyanosilylation reaction

Two novel 3D metal–organic frameworks based on multifunctional pyridyl–tricarboxylate ligands as size-selective heterogeneous catalysts for the cyanosilylation of acetaldehydes.

1-Ethyl-3-methylimidazolium acetate as a highly efficient organocatalyst for cyanosilylation of carbonyl compounds with trimethylsilyl cyanide

1-Ethyl-3-methylimidazolium acetate is introduced as a robust organocatalyst for solvent-free cyanosilylation of carbonyl compounds with trimethylsilyl cyanide (TMSCN). The catalyst loading can be reduced to as low as 0.1–0.0001 mol % under mild reaction conditions, giving considerably high TOF values from 10,843 h⁻¹ to 10,602,410 h⁻¹ in the field of organocatalyzed transformations. The present protocol not only tolerates with extensive carbonyl compounds but also provides somewhat insight into the mechanism of ionic liquids (ILs)-catalyzed reactions.