FULL PAPER DOI: 10.1002/ejic.201000863 Hydrolytic Decomposition of Tetramethylammonium Bis(trifluoromethyl)- aurate(I), [NMe 4 ][Au(CF 3 ) 2 ]: A Route for the Synthesis of Gold Nanoparticles in Aqueous Medium David Zopes, [a] Silke Kremer, [a] Harald Scherer, [b] Lhoussaine Belkoura, [c] Ingo Pantenburg, [a] Wieland Tyrra, [a] and Sanjay Mathur* [a] Keywords: Gold / Nanoparticles / Hydrolysis / Plasmons Monodisperse gold nanoparticles (AuNPs) were obtained by hydrolytic decomposition of a new molecular precursor, tetra- methylammonium bis(trifluoromethyl)aurate(I), [NMe 4 ][Au- (CF 3 ) 2 ], which has been characterised by spectroscopic and Introduction Gold nanoparticles (AuNPs) attract a fascination in the field of nanotechnology, [1] mainly due to their appealing optical properties and the simplicity of the synthesis pro- cedure, which have already been the focus of historical re- search on metal colloids. [1,2] Furthermore, these nanopar- ticles have already been transformed into commercial goods by incorporating them into glass matrices to obtain a dis- tinct red coloration - caused by the plasmon resonance in nanoscopic gold clusters - seen in the stained glass win- dows of churches (e.g., “Purple of Cassius”, made from gold in the presence of tin [3] ). The tremendous interest in the applications of gold particles in modern nanotechnol- ogy emerges from their fundamentally new properties; for instance, AuNPs can act as carriers for the targeted delivery of drug and biomolecules inside cells. Similarly, their strong interaction with light enables a sensory mechanism in which the optical properties may change upon binding to certain molecules for the detection and quantification of analytes. [4] The most commonly used synthesis of gold nanoparticles involves the aqueous reduction of HAuCl 4 by sodium cit- rate. [5] The quest for a synthetic recipe that enables repro- ducible syntheses of Au nanoparticles with a precise control over size and shape has led to numerous modifications of [a] Department für Chemie, Lehrstuhl für Anorganische und Materialchemie, Universität zu Köln, Greinstrasse 6, 50939 Köln, Germany E-mail: sanjay.mathur@uni-koeln.de [b] Institut für Anorganische und Analytische Chemie, Albert- Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg i. Br, Germany [c] Department für Chemie, Institut für Physikalische Chemie, Universität zu Köln, Luxemburger Strasse 116, 50939 Köln, Germany Eur. J. Inorg. Chem. 2011, 273–280 © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 273 single-crystal X-ray diffraction analyses. On account of the simple and high-yield synthesis, the title compound repre- sents a versatile synthon and an alternative to the commonly used chloroauric acid (HAuCl 4 ). the reduction of the precursor HAuCl 4 . [6–8] Interestingly, a majority of the efforts deal with the modulation of growth parameters (reaction time, nature and concentration of re- ductants and so on) and growth kinetics (addition of cap- ping agents, seed-mediated growth and so on) of AuNPs; [8] however, the development of new precursors for chemically controlled generation of gold nanoparticles has received somewhat less attention. [9] We report herein the synthesis and structural characterisation of (perfluoroalkyl)aurates(I) as potential synthons for the production of gold nanopar- ticles in aqueous media, which can be seen as a viable exten- sion of the well-known HAuCl 4 routes. [5] The efficient use of the reagent combination comprising a fluoride source plus trimethyl(perfluoroalkyl)silane has allowed us in recent years to prepare numerous perfluoro- alkyl-metalate complexes of late transition metals as well as main-group elements that are characterised by their extreme reactivity [10–13] or stability. [14–16] (Trifluoromethyl)gold com- pounds, whereby the predominant numbers of the charac- terised derivatives contain gold in the trivalent oxidation state, have generally been known for more than 30 years. [17] The number of trifluoromethyl gold(I) compounds is lim- ited to the examples of AuCF 3 ·RPF 2 , [18] AuCF 3 ·PR 3 [19] and AuCF 3 ·CNMe; [20] however, no (perfluoroalkyl)aurate(I) has hitherto been described to the best of our know- ledge. The reagent combination Me 3 SiCF 3 /F – efficiently allows access to the synthesis of bis(trifluoromethyl)aurates(I) and avoids the use of alkylzinc or cadmium compounds. [18–22] We report here on the synthesis and structural characterisa- tion of some bis(trifluoromethyl)aurates(I) and their reac- tivity in aqueous solutions, which has led to formations of monodisperse nanoparticles of Au, remarkably as aqueous dispersions.