Solid-State 31P NMR studies reveal that phosphinine ligands employed for the stabilisation of gold nanoparticles react in part during the synthesis, and that the particles are stabilised by a mixture of intact phosphinine units together with several other surface-bound species. The spectral data of these species are characteristic for phosphine-type donors although unambiguous structure assignment was as yet unfeasible. The spectral data of surface-bound phosphinines were verified by comparison with the spectrum of an authentic complex [(1)AuCl]. The metal-bound phosphinines in both the complex and the nanoparticles prefer η1(P)-coordination to a single metal atom, and the observation of splittings arising from coupling with 197Au (I = 3/2) nuclei indicates that these ligands are not mobile. The fraction of intact phosphinines on the nanoparticles drops with decreasing steric protection although the observed product distribution shows no simple relation with substituent patterns.
