Iron man or weakling? Ligand‐field strengths are conveniently expressed by the empirical spectrochemical series. Although cyanide has been deeply entrenched as a strong‐field ligand, a couple of recent examples cast doubt toward the position of this ligand, namely the high‐spin (S=2) states of [CrII(CN)5]3? and [FeII(tpp)(CN)]?. tpp=meso‐tetraphenylporphinate.
Conditional cleavage : Photochemical S? N bond cleavage of the Zn2+ complex of N‐dansylcyclen (ZnL2) in aqueous solution was investigated. Moreover, photolysis of ZnL2 (see scheme) facilitated photoreversion of cis,syn‐thymine photodimer (T[c,s]T).
Changing channels : The novel dynamic gas‐separation mechanism is demonstrated by a GC study for a flexible single crystal [Cu2(bza)4(pyz)]n, 1 . The single‐crystal host 1 , because of its flexibility, can separate various gases by adjusting its channel structure according to the features of the guest gaseous molecules.
An sp 2 /sp 3 get‐together : A novel and efficient method can be used to synthesize 3,3‐disubstitued oxindoles by the direct intramolecular oxidative coupling of an aryl C? H and a C? H center (see scheme; DMF=N,N‐dimethylformamide).
All ways lead to Rome? Computer modeling and kinetic measurements identified a distinct residue in Phe/Tyr ammonia lyases (PAL/TAL) which controls whether the Friedel–Crafts or an E1cB reaction mechanism takes place. Hence, Glu484 in pcPAL favors the Friedel–Crafts reaction (see picture, MIO=4‐methylidene imidazol‐5‐one) whereas an Asn in TAL gives an elimination reaction. These mechanistic investigations also reveal activity of a PAL mutant and a TAL towards an amino alcohol.
Not so elusive : [FeII(CN)5(HNO)]3? has been characterized spectroscopically after the two‐electron reduction of nitroprusside (see scheme). The complex is stable at pH 6, slowly decomposing to [Fe(CN)6]4? and N2O. It is deprotonated at increasing pH value with oxidation of bound NO? to [FeII(CN)5(NO)]3?. [FeII(CN)5(HNO)]3? is the first non‐heme iron–nitroxyl complex prepared in aqueous solution that is reversibly redox‐active under biologically relevant conditions.
A powerful fluoride trap : The extremely Lewis acidic silyl cation [Et3Si]+ is an active catalyst for the hydrodefluorination of fluoroalkyl groups at room temperature (see example). The carborane anion [CHB11H5Cl6]? plays an essential role in the catalytic cycle as a weakly coordinating anion that stabilizes cationic intermediates.
Linked to the Pentagon : The addition of molybdate to [HBW11O39]8? ions leads to the formation of mixed pentagonal units {W(Mo5)} and {W(WMo4)} trapped as linkers in the resulting modular assemblies, thus establishing the first link between the conventional Keggin ion derivatives and the giant molybdenum oxide and keplerate ions.
Additional cyclization : Dicyanonitrosomethanide, [C(CN)2(NO)]? undergoes nucleophilic addition and cyclization of 1,2‐diaminoethane and 1,3‐diaminopropane on the nitrile groups to form imidazolinyl and 1,4,5,6‐tetrahydropyrimidinyl groups, respectively. Ethanolamine has lower reactivity and fails to cyclize.
Ring any bells? The differential capacitance curve of Au(100) in neat [BMI]BF4 (BMI=1‐butyl‐3‐methylimidazolium) ionic liquid has a bell‐shaped feature (see picture). The adsorption of BMI+ shows a disorder–order transition and depends on the structure of the surface. Ordered adsorption in a micelle‐like structure stabilizes the underlying Au surface.
Preparation of Cyclophosphates, Cyclophosphatophosphonates, Diphosphonates, and Di-phosphites in Urea Melts Ammonium cyclotriphosphate (NH4)P3O9, ammonium cyclotetraphosphate [PIV? PIV ? O? ]2, ammonium cyclotriphosphatophosphonates Ammonium organyldiphosphonates And ammonium diphosphites are prepared in high yields on heating acidic phosphates, phosphonates, and phosphites in urea or urea/ammonium nitrate melts. The mechanism of the dehydration of phosphorus compounds containing POH groups in molten urea is discussed. 相似文献
Two metal cooperation : A homodinuclear Co2–Schiff base complex Co2(OAc)2– 1 promoted the asymmetric 1,4‐addition of β‐keto esters to alkynones under solvent‐free conditions in air (see scheme). The reactions proceeded without air or moisture sensitivity in high yields and with high enantioselectivities (99–91 % ee) at room temperature under highly concentrated conditions (neat–20 M ) with 0.1–2.5 mol % catalyst loading.
Doped up : The incorporation of Zn2+ dopants in tetrahedral sites leads to the successful magnetism tuning of spinel metal ferrite nanoparticles (see picture). (Zn0.4Mn0.6)Fe2O4 nanoparticles exhibit the highest magnetization value among the metal ferrite nanoparticles. Such high magnetism results in the largest MRI contrast effects (r2=860 mm?1 s?1) reported to date and also huge hyperthermic effects.
Last but not least : A simple molecular redox system is used to split water into hydrogen and oxygen photochemically. Two separate photolyses are combined to a cyclic process (see scheme). Osmocene ([Cp2OsII] with Cp?=C5H5?) serves as photocatalyst.
Always on the move : Molecular dynamics of perylene cores in columnar structures influences the processability and self‐healing of these materials. A combination of X‐ray scattering and advanced solid‐state NMR methods show that these systems have restricted angular mobility of the cores even in the frozen phase, and a cooperative spiral type of motion in the liquid crystalline phase (see picture).
Sensitive functional groups such as COR, CHO, or CH2OH can be present in benzylic indium reagents prepared by the direct insertion of indium in the presence of LiCl. These reagents undergo palladium‐catalyzed cross‐coupling reactions in the presence of a protic cosolvent after activation with iPrMgCl⋅LiCl (see scheme). Remarkable chemoselectivities are achieved by using various electrophiles containing NH or OH groups.
Chalcogen‐transfer reagents? The bonding in the dicationic rings C2N2E2+ (see picture) differs from that in N‐heterocyclic carbenes and their isovalent p‐block analogues in accommodating a lone pair of electrons with π symmetry, as well as σ symmetry, on the chalcogen center. The labile electrophilic chalcogenium dications (E2+) are potentially versatile chalcogen‐transfer reagents in reactions with a variety of inorganic and organic substrates.
Pass the salt, please! State‐of‐the‐art computations indicate that the stacking complex of a guanine quartet and an adenine quartet (G4A4) can function as a potent ditopic receptor for NaCl in aqueous solution (see picture; Na+, Cl? yellow, O red, N blue, C black, H white).
“ Quat's” the story? N‐Aryl amides are effective directing/activating groups for chlorosilane Lewis acids. This aspect has been exploited for the development of the first simple and general method for the highly enantioselective Pictet–Spengler reaction of ketimines derived from α‐ketoamides leading to quaternary α‐amino acid derivatives (see scheme).
