Metal Complexes Co-ordination Numbers Four and Five

Inert Metal Complexes Co-ordination Numbers Four and Five 

Several investigations have demonstrated the possibility or probability of the existence of persistent five- or six-co-ordinate intermediates in the associative pathway for nucleophilic substitution. Examples include the reactions of [AuClJ with thiocyanate and with A-cyclohexylthiobenzamide and of cw-[Pt(N02)2-(NHs)2] with hydrogen bromide. The behaviour of stable five-co-ordinate compounds has been examined with a view to treating them as models for such transient intermediates in associative substitution at four-co-ordinate complexes (see Section 3). A thorough and unusually extensively referenced molecular orbital treatment of 

Reaction Mechanisms in Inorganic Chemistry , ed. M. L. Tobe, M.T.P. International Review of Science, Inorganic Chemistry Series Two, Vol. 9, Butterworths, London, 1974, p. 45. 

Peshchevitskii, A. V. Belyaev, R. L. Shchekochikhina, and G. D. Mal chikov, Kinetika Reaktsii Zameshcheniya Ligandov v Kompleksnykh Soedineniyakh Platinovykh Metallov i Zolota (Spravochnik), Nauka Sib. Otd., Novosibirsk, U.S.S.R., 1974. 

Two groups of authors have suggested that there is a difference between the detailed mechanism of associative nucleophilic substitution at platinum(ii) or palladium(ii) and that at gold(iii). It is claimed that there are indications that bondbreaking and bond-making are asynchronous (A mechanism) at Pt and Pd, but synchronous (/a mechanism) at This distinction is hardly consistent with 

More investigations into the reaction of platinum(ii)-ethene complexes with pyridine have been described. Further details of the attack of pyridine at the co- 

Of two general articles dealing with the trans effect in substitution at square-planar 

This chapter follows broadly the pattern set in earlier Reports. The description inert has been interpreted somewhat liberally in the brief sections on Cu and on the tetrahedral and five-co-ordinate complexes, and is perhaps justified on the grounds that a small amount of overlap is preferable to the existence of gaps. 

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