Sandmeyer and related reactions

A new method for monitoring dediazoniation reactions: Simultaneous monitoring of concentration and rates of product formation and loss of starting material for the dediazoniation ofp-methylbenzenediazonium tetrafluoroborate

“…complexes in the medium constant [17,18,20]. The k obs values are not affected by changing Cu(II) concentration from and they are…”

Radical reactions of arenediazonium ions: An easy entry into the chemistry of the aryl radical

“…If we go back to the Sandmeyer reaction, the formation of a precipitate on addition of cuprous halide to the solution of diazonium salt had been observed since the very first experiments. 39 This was ascribed to the formation of a complex featuring a covalent bond between Cu and nitrogen, and that species was considered to be an essential intermediate in all the Sandmeyer-like reactions induced by copper salts. 40,41 The formation of aryl radicals in the dediazoniation reactions was clearly proposed for the first time by Grieve and Hey37 in 1934.…”

“…Another contradictory way of looking at the dediazoniation processes was that of Cowdrey and Davies. 39 In a kinetic study on a chloro-dediazoniation of to imply the presence of a cuprous species in solution, even though the Cu+ ion is not stable but forms complexes such as CuX2'.] However, they maintained that the cuprous salt was required not for its being a reductant, but "...for its ability to form complexes so that both the reagents ArN2+ and Cl" are activated and brought together more often".39 Even a transient Cu-(III) state was invoked by the same authors,39 as leading to an intermediate where "...there would be little difficulty in the occurrence of an internal nucleophilic displacement by halogen".…”

Sandmeyer reactions. Part 7.1 An investigation into the reduction steps of Sandmeyer hydroxylation and chlorination reactions

“…It is the rate determining step 4 and the rate has been shown to depend on substituents in the aryl ring and on the nature and number of ligands in the copper complex, 1,5,6 but its precise nature is uncertain. The precipitates often formed during synthetic procedure when solutions of diazonium salts and cuprous halides are mixed were widely believed to be copper()-diazonium complexes 7 but an X-ray crystallographic investigation demonstrated that, in the case of benzenediazonium bromide and CuBr at least, the precipitate is a simple salt, PhN 2 ϩ Cu 2 Br 3 Ϫ , which shows no evidence of bonding contact between the metal and the diazonium group. 8 Although complexes involving ligation of many transition metals by diazonium ions are known, none has been reported involving copper.…”