Encapsulating amine ligands

The octahedral Ni(II) complex 16 of encapsulating macrocyclic ligand also shows short C—N bond distances, 1.41(2) and 1.44(2) A, and large C—N—C bond angles, 117(1)° and 118(1)°, involving tertiary amines at the apices of the caps, which indicates sp2 hybridization (4). 

The remarkable physical properties exhibited by the divalent macrobicyclic cage complex [Co(sep)]2+ (29) are unparalleled in Co chemistry.219 The complex, characterized structurally, is inert to ligand substitution in its optically pure form and resists racemization in stark contrast to its [Co(en)3]2+ parent. The encapsulating nature of the sep ligand ensures outer sphere electron transfer in all redox reactions. For example, unlike most divalent Co amines, the aerial oxidation of (29) does not involve a peroxo-bound intermediate. 

Hexadentate ligands l,12-bis(2-pyridyl)-5,8-dioxa-2,ll-diazadodecane and l,12-bis(2-pyridyl)-5,8-dithia-2,ll-diazadodecane have pyridine, amine, and ether or thioether donors offering an N402 or N4S2 donor set. The X-ray structures of the zinc complexes are distorted octahedral with the zinc center encapsulated by the ligand.898... 

In both the chloride and bromide structures, the halide was also found to be encapsulated, but was positioned more centrally within the cavity, as explained by a better size match between the ligand and halide (Figure 7B) [48], In both cases the cryptand is hexaprotonated and all six of the protonated amines exhibit hydrogen bonding with the internal halide, with average NH—X distances of 3.30 A for chloride and 3.39 A for bromide. The distance between the bridgehead amines is 7.40 A and 7.50 A for the chloride and bromide complexes, respectively. 

Since 1980, the applications zeolites and molecular sieves in the speciality and fine chemicals increased enormously. Zeolites are being used in the various types of reactions like cyclization, amination, rearrangement, alkylation, acylations, ammoxidation, vapour and liquid phase oxidation reactions. Zeolites and molecular sieves have also been used to encapsulate catalytically active co-ordination complexes like ship-in-bottle and as a support for photocatalytic materials and chiral ligands. Redox molecular sieves have been developed as an important class of liquid and vapour phase oxidation and ammoxidation reactions. We have discussed few typical recent examples of various types of reactions. 

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