Phospholes, and

Phospholes and analogs offer a wide variety of coordination modes and reactivity patterns, from the ti E) (E = P, As, Sb, Bi) through ri -dienic to ri -donor function, including numerous and different mixed coordination modes. Electrophilic substitution at the carbon atoms and nucleophilic properties of the phosphorus atom are well documented. In the ri -coordinated species, group V heteroles nearly acquire planarity and features of the ir-delocalized moieties (heterocymantrenes and -ferrocenes). 

The phosphacyclopentadienes with phosphine function are called 1//-phospholes and they form an important part of contemporary P-heterocyclic chemistry. Phosphole chemistry has undergone an intensive development, which is well demonstrated by the fact that while in the first edition of Comprehensive Heterocyclic Chemistry (1984), only several pages were devoted to phospholes [1], the second edition (1996) discusses this topic in a lengthy chapter [2], Besides these, exhaustive monographs have been published in P-heterocyclic chemistry also incorporating the new developments of phosphole chemistry [3, 4], The first review in the subject was written by Mathey [5],... 

Nyulaszi summarized the theoretical background of the aromaticity of phospholes and the possibilities of establishing aromatic phospholes [34],... 

Further examples of deoxygenation of epoxides by phosphine sulphides or selenides have appeared,41 as shown in Scheme 6 for simple epoxides (50). Incorporation of phosphorus into a five-membered ring appears to be responsible for the relatively rapid deoxygenations by the phosphole and A3-phospholen derivatives.41... 

For the complete set of aza-. diaza-. and triaza-phospholes and also for 3. ring fragmentation energies (HF/4-31G(d)) were also investigated to study the... 

Hughes, A. N. Phospholes and Related Compounds. In Handbook of Organophosphorus Chemistry Engel, R., Ed. Marcel Dek-ker New York, 1992. 

Irradiation of 2,3-diphenyl-2//-azitine in the presence of Cgo fullerene leads to the formation of mono- and ohgo adducts (98,99). A monoadduct, l,9-(3,4-dihydro-2,5-diphenyl-2//-pytTolo)fullerene-60 was isolated and characterized. Mechanistic studies showed that under conditions of direct irradiation it was formed by a classic nitrile yhde cycloaddition but in the presence of 1,4-napthalenedicarbonitrile (DCA) it resulted from reaction of the radical cation intermediate 108. Cycloaddition reactions have also been carried out with diaza-phospholes and diazaarsoles (100) to give adducts of the type 189 (A=As,P) and with cyanogen to give 190 and with atyldiazocyanides where addition to both the azo moiety and the cyano group were observed (101). 

A rich and diverse chemistry has developed based on the phosphorus ring system complexed to transition metals analogous to the metallocenes. Phospholes and phosphametallocenes have recent-... 

MO calculations at the MP4SDTP/6-311G //MP2/6-311G level on the Diels-Alder reaction of ethylene with l-phosphabut-3-en-l-yne show that the reaction is endothermic compared with the all-carbon case, which is exothermic.249 Ab initio studies have been presented for hetero-Diels-Alder reactions between phosphorus-containing dienes and dienophiles.250 Ab initio calculations on the Diels-Alder reaction between 21 /-phosphole and phosphaethene indicate that the reaction is concerted and synchronous.251 The Diels-Alder reaction between 1,3,5-triphosphabenzene and phosphaacetylene to form tetraphosphabarrelene was studied at the MP4SDQ/6-... 

Compared with organic molecules, metal complexes offer a larger variety of molecular structures and a diversity of electronic properties [13]. Since it is well known that phospholes and pyridines behave as classical two-electron donors toward transition metals [13, 14], we have explored the coordination behavior of 2-pyridyl-substituted phospholes with the aim of obtaining complexes exhibiting interesting physical properties. Moreover, original structures can be expected since these heteroditopic P,N-ligands possess two coordination centers with different stereo-electronic properties. The performances of such complexes have been evaluated as catalysts as well as new materials for optoelectronics. 

An X-ray diffraction study of complex 52 showed that this mixed oligomer is not planar. The thiophene-thiophene, thiophene-phosphole and phosphole-phosp-hole twist angles are 6.35, 24.24 and 66.26°, respectively [43a]. Compound 51 un-... 

Of special interest with respect to the stereochemical questions was the yellow spirophosphorane 31 since according to the new synthetic procedure it could formally be obtained by two ways, either from the tosylimine of 5-phenyldibenzo-phosphole and 4,4 -bis(dimethylamino)-2,2 -dilithiobiphenyl or, the other way round, from 3,7-bis(dimethylamino)-5-phenyldibenzophosphole tosylimine and 2,2 -dilithio-biphenyl. 

Phospholes and Their Transition Metal Complexes as Therapeutic Agents... 

Table 1 Calculated aromatic Indexes for parent phosphole and pyrrole (Scheme 1, R = H)...

CN 4 1//-phospholes make up the largest class of structurally characterized phospholes and encompasses their metal complexes, and (r ,A -derivatives (Table 11). The metric parameters associated with these ring systems... 

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