Copper(I) Carboxylates of Type [(nBu3P)mCuO2CR] (m = 1, 2, 3) - Synthesis, Properties, and their Use as CVD Precursors
Dedicated to Professor Bernt Krebs on Occasion of his 70th Birthday
Copper(I) carboxylates of type [(nBu3P)mCuO2CR] (m = 1: 3a, R = Me; 3b, R = CF3; 3c, R = Ph; 3d, R = CH=CHPh. m = 2: 4a, R = Me; 4b, R = CF3; 4c, R = Ph; 4d, R = CH=CHPh. m = 3: 8a, R = Me; 8b, R = CF3; 8c, R = CH2Ph; 8d, R = (CH2OCH2)3H; 8e, R = cC4H7O) are accessible by following synthesis methodologies: the reaction of [CuO2CR] (1a, R = Me; 1b, R = CF3; 1c, R = Ph; 1d, R = CH=CHPh) with m equivalents of nBu3P (2) (m = 1, 2, 3), or treatment of [(nBu3P)mCuCl] (5a, m = 1; 5b, m = 2) with [KO2CCF3] (6). A more straightforward synthesis method for 8a - 8e is the electrolysis of copper in presence of HO2CR (7a, R = Me; 7b, R = CF3; 7c, R = CH2Ph; 7d, R = (CH2OCH2)3H; 7e, R = cC4H7O) and 2, respectively. This method allows to prepare the appropriate copper(I) carboxylate complexes in virtually quantitative yield, analytically pure form, and on an industrial scale. IR spectroscopic studies reveal that the carboxylic units in 4, 5, and 8 bind in a unidentate, chelating or ?-bridging fashion to copper(I) depending on m and R. The thermal properties of 4, 6, and 8 were determined by TG and DSC studies. Based on TG-MS experiments a conceivable mechanism for the thermally induced decomposition of these species is presented. Hot-wall Chemical Vapor Deposition experiments (CVD) with precursor 4b showed that copper could be deposited at 480 °C onto a TiN-coated oxidized silicon substrate. The copper films were characterized by SEM and EDX studies. Pure layers were obtained with copper particles of size 200 - 780 nm.