Synthesis and spectroscopic properties of a novel class of copper particles stabilized by triphenylphosphine

The reaction of (C5H5)Cu(ButNC) with CO (1 or 3 atm) in the presence of sub-stoichiometric amounts of PPh3 leads to phosphine stabilized copper particles of ca., 20 A showing a narrow size distribution; 31P{1H} NMR studies demonstrate both the fluxionality of the phosphine ligands and the absence of the Knight shift on these particles whereas UV–VIS spectroscopy indicates an important modification of the absorption bands of these compounds compared to non complexed copper particles of similar size.