Some New Developments in Aryl-Gold and Aryl-Platinum Chemistry

The enhanced stability of the metal-to-carbon bond M-R (M= Au, Pt) when R is a polyhalophenyl group (R= C F , C F H , C Cl ) allows the isolation of neutral, cationic or anionic §rl drvtivs f both metals, which are excellent precursors for the synthesis of polynuclear compounds or mixed clusters with unusual structures and properties. On the other hand, stable solutions of the neutral complexes MR2L2 (M= Pd, Pt; R= C6F5, CCl; L= OC4HQ) are a suitable source for the preparation of otherwise iHacdessible c3mpounds. INTRODUCTION Following arguments (ref. 1) advanced by Chatt and Shaw (1959-60) many stable complexes of the types MR2L2 and MRXL2 (L= 'i-acid ligand) were prepared. From 1969 to 1976 we synthesized several hundreds of stable gold, palladium and platinum derivatives, both neutral and cationic with R= C6X (X= F, Cl), and began to wonder whether (1) the 'i-acid ligands were at all necessary t achieve the observed stability and if (2) the presence of these neutral ligands effectively hindered further arylation of the metal centres. We also began to use starting materials containinci either weaker coordinating ligands (such as tetrahydrothiophen, SC4H8) or ligand-free compounds (PdC12, PtC12) which react with RLi or RMgX to give anionic homoleptic or Scheme 1 * more arylated complexes (Scheme 1). Types of anionic complexes (1976-1982) Some of these novel anionic complexes provided the startingpoint of a new Au derivatives Pd and Pt derivatives chemistry, where the presence of the AURX MR (SC H ) polyhalophenyl groups is a critical 428 factor, as may be seen from the AuR2I MR2C12I following selected examples. AuRX3I JMR3C1 2 JAuR2X2I MR4I2 AuR3XJ JM(p-X)R222 AuR *Isolated as salts of bulky cations (NBu4,PPN,etc) POLYNUCLEARGOLD-SILVER COMPLEXES There is much evidence that metal centres M can act as Lewis bases towards other metal centres N, thus forming M —-M' donor bonds. The stability of such compounds is dependent upon the respective M and N' , the most important stabilizing factor being a large electron density on M. (ref. 2). We have therefore chosen the anions AuR2I as metal centre M and have tried to form a M —M' metal bond, Ag being selected as N' centre. (Equation 1) (ref. 3) Et 0 or (NBu )IAuR2 + AgClO4 2 (N8u4)Cl04 + AuAgR2J (yellow solutions) CHC1 2 2 L= 0-, N-, 5-, P-donor R= C6F3H2, C6F5, C6C15 alkene, alkyne, (1) arene AuArR2L n 647