Ortho-nitrophenyl Complexes of Gold(III)

Abstract

Many organogold complexes have been prepared using Grignard or organolithium reagents [l] , as well as organothallium [2] or organotin [3] complexes. We have recently shown that organomercury compounds can also be used for the synthesis of organogold(II1) complexes which are inaccessible through other routes [4]. Many authors have used organomercurials in order to prepare organometallic compounds of other elements [S] and also of gold(I) [6]. We therefore thought it of interest to know how useful could organomercurials be m the synthesis of gold(II1) complexes. To test the method we chose a group such as ortho-nitrophenyl, which is difficult to bond to a metallic atom due to the unstability of the corresponding organolithium derivative [7] that has only scarcely been used [8]. The interest of preparing nitrophenyl organometallics is well documented, and the methods used are good examples of how the difficulties m the synthesis of organometallics can be overcome by choosing the proper intermediates [9-221. In any case, this is the first report of the use of organomercurials in the synthesis of nitrophenyl complexes. On the other hand it is known that ortho substituents exert a profound influence on the stability of arylmetal complexes [23-311 and this fact explains the great number of such complexes and the advances in the organometallic chemistry of many elements promoted by such special stability. Our continuing mterest in the synthesis of metallacycle complexes [3, 4, 321 relates to the possibility of the orfho-nitrophenyl group acting as a new type of chelate ligand to give a fivemembered ring metallacycle. Although there is no evidence of such type of coordination in the complexes reported here, we have prepared some palladium( I1) complexes where the metallacycle is present [33]. In the light of these results we continue in our attempts to obtain similar findings in the chemistry of gold(II1).

Many organogold complexes have been prepared using Grignard or organolithium reagents [l] , as well as organothallium [2] or organotin [3] complexes. We have recently shown that organomercury compounds can also be used for the synthesis of organogold(II1) complexes which are inaccessible through other routes [4]. Many authors have used organomercurials in order to prepare organometallic compounds of other elements [S] and also of gold(I) [6]. We therefore thought it of interest to know how useful could organomercurials be m the synthesis of gold(II1) complexes. To test the method we chose a group such as ortho-nitrophenyl, which is difficult to bond to a metallic atom due to the unstability of the corresponding organolithium derivative [7] that has only scarcely been used [8]. The interest of preparing nitrophenyl organometallics is well documented, and the methods used are good examples of how the difficulties m the synthesis of organometallics can be overcome by choosing the proper intermediates [9-221. In any case, this is the first report of the use of organomercurials in the synthesis of nitrophenyl complexes. On the other hand it is known that ortho substituents exert a profound influence on the stability of arylmetal complexes [23-311 and this fact explains the great number of such complexes and the advances in the organometallic chemistry of many elements promoted by such special stability. Our continuing mterest in the synthesis of metallacycle complexes [3, 4, 321 relates to the possibility of the orfho-nitrophenyl group acting as a new type of chelate ligand to give a fivemembered ring metallacycle. Although there is no evidence of such type of coordination in the complexes reported here, we have prepared some palladium( I1) complexes where the metallacycle is present [33]. In the light of these results we continue in our attempts to obtain similar findings in the chemistry of gold(III).