Hofmann-type inclusion compounds

Hofmann reaction, 76 320. See also Hoffman reaction Hofmann rearrangement, 77 741 Hofmann-type inclusion compounds, 74 171-172... 

The structure of a Hofmann type inclusion compounds is shown in scheme (C). The reaction of (HI) and (IV) with oxidants such as Fe + in water results in a color change from pale violet to black. When single crystals are used as starting materials, the resulting products, retain the original crystal shape (pseudomorphs), but they lose their single crystal nature and under SEM microscopic examination show small cracks and other defects. The proper formulation of the oxidation products would be [Ni(CN)2NH3] (polymer)(A)x y where polymer=polypyrrole, polyaniline ... 

Hofmann- and Werner-Type Inclusion Compounds. There is a wide range of clathrates having as the host component inorganic coordination compounds represented by the general formulae M(NH2)2 (CN) and X2Y4. The first formula is typical of Hofmaim-type clathrates... 

The Hofmann-dabn-type inclusion compounds were prepared by the method described in the previous communication [6] in Table I the results of elemental analyses and the basal spacings estimated from the powder X-ray diffraction patterns are listed. They are not stable under ambient condition but the rates of decomposition are slow enough to be subjected to the elemental analyses if the specimens are kept in tightly capped vials some of them, marked with an asterisk in the Table I, are rather unstabe, however. 

Table I. Hofmann-dabn-type inclusion compounds Cd(CifHi2N2)Ni(CN) i. nG. Elemental analyses are given as Found/Calcd in % d refers to the basal...

Investigations of cyanides and cyano complexes of Cd and Hg have augmented tremendously since about 1990, after detection of inclusion compounds of Cd(CN)2. A thorough review on transition-metal cyanides especially emphasizes the chemistry of inclusion compounds of both the Hofmann type (frameworks dominated by planar Ni(CN)4 building blocks) and the cyanocad-mate type (frameworks with tetrahedral Cd(CN)4 units).87 The structures of these inclusion compounds, but also of cyanides themselves, often topologically resemble the structures of minerals this aspect ( mineralomimetic chemistry ) is dealt with in a simultaneous survey.88 A more generic review of framework structures, with a section on cyanide inclusion compounds, is also to be mentioned.90... 

The chemistry of inclusion compounds also looks back on a lively history There are many events of significance in the area of inclusion chemistry till the middle of the twentieth century including the discovery of new inclusion compounds and hosts (Fig. 1), among them the graphite intercalates, the P-quinol and cyclodextrin inclusion compounds, the Hofmann-type clathrates as well as the inclusion compounds of tri-o-thymotide, Dianin s compound, the choleic acids, of phenols, of urea and others specified in comprehensive monographs... 

So-called Werner clathrates are another prominent series of clathrate compounds formed between a metal complex host and an aromatic guest molecule. The name Werner originates from A. Werner, who established the coordination theory of metal complex compounds. The host of the series has a general formula [M(NCS)2(4-Mepy)4], and in fact, the series is obtained conceptually by replacement of C N and NH3 in the Hofmann-type host by SCN and 4-Mepy (4-methylpyridine), respectively. This was done in order to increase the inclusion capability for bulkier substituted aromatic molecules, in particular, those related to the petroleum industry. 

A number of compounds with chemical compositions that are similar to that of the original Hofmann-type clathrates were reported. However, as usual for other inclusion compounds, similarity in composition does not necessarily co relate with similarity of structure. For example, in the [Cd(pn)Ni(CN)4] G series with aliphatic guests, the host structure is entirely different from the Hofmann-pn-type pyrrole clathrate [Cd(pn)Ni(CN)4]. (3/ 2)C4H5N. Two subseries of structures were observed for the channel cavities, one being a snake-like extension similar to chat observed for the urea-host inclusion... 

Almost all important contributions to the chemistry of Hofmann-type and related inclusion compounds and host cyanometal complexes were reviewed in the lit-erature." - ... 

Iw amoto, T. The Hofmann-Type and Related Inclusion Compounds. In Inclusion Compounds, I Atwood. J.L., Davies. J.E.D., MacNicol. D.D., Eds. Academic Press London, 1984 29-57. 

Hofmann-type clathrates Werner clathrates clathrate hydrates inclusion compounds of urea, thiourea, and selenourea cyclodextrins calixarenes gossypol hexa-hosts hydroquinone phenol and Dianin s compounds graphite intercalates natural and pillared clays and others. Such studies contributed to the birth of supramolecular chemistry, with relevance to a new understanding of the world of materials that was emphasized with a Nobel Prize. 

Channel Inclusion Compounds, p. 223 Chiral Guest Recognition, p. 236 Clathrate Hydrates, p. 274 Crown Ethers, p. 326 Crystalline Microporous Silicas, p. 380 Cyclodextrins, p. 398 Hofmann-Type Clathrates, p. 645 Hydrogen Bonding, p. 658 Hydroquinone, p. 679... 

T.Iwamoto The Hofmann-type and Related Inclusion Compounds (Inclusion Compounds v. 1, Ed. J.L.Atwood, J.E.D.Davies, and D.D.MacNicol) pp. 29-57. Academic Press (1984). 

One of the problems to be solved for the formation trend of Hofmann-(long-carbon-chain a,oo-diaminoalkane)-type series of inclusion compounds is to interpret the reason why Hofmann-dahxn-type host cannot accommodate xylidines as guest, which Hofmann-dabn-type host can do even with the shorter carbon chain in the full length than dahxn. In order to solve the problem we need more information about the crystal structures of the series. The structure analyses of Hofmann-dahxn-type m-and p-toluidine inclusion compounds are in progress. 

While Wemer complexes are based on discrete coordination complexes, another type of coordination compound with a distinctive extension into 2D layers through utilization of ditopic bidentate ligands was developed and first reported by K. A. Hofmann in 1897, Ni(NH3)2Ni(CN)4 2(C6H6). Hofmann-type compounds also exhibit inclusion properties of suitably sized guest molecules. Iwamoto and coworkers prepared a number of derivatives of Hofmann clathrates (Figure 2). 

T. Iwamoto, The Hofmann-type and Related Inclusion Compounds, ... 

Over the past four years there has been considerable interest in the NMR of Hofmann-type and related metal-cyanide inclusion compounds, with regard to local order or disorder and the dynamics of both guest and host molecules. 

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