Multimetallic Arrays: Bi-, Tri-, Tetra-, and Hexametallic Complexes Based on Gold(I) and Gold(III) and the Surface Functionalization of Gold Nanoparticles with Transition Metals

Reaction of [AuCl(PPh3)] with the zwitterion S2CNC4H8NH2 yields [(Ph3P)Au(S2CNC4H8NH2)]BF4. Treatment of this species with NEt3 and CS2 followed by [AuCl(PPh3)] leads to [{(Ph3P)Au}2(S2CNC4H8NCS2)], which can also be obtained directly from [AuCl(PPh3)] and KS2CNC4H8NCS2K. A heterobimetallic variant, [(dppm)2Ru(S2CNC4H8NCS2)Au(PPh3)]+, can be prepared by the sequential reaction of [(dppm)2Ru(S2CNC4H8NH2)]2+ with NEt3 and CS2 followed by [AuCl(PPh3)]. Reaction of the same ruthenium precursor with [(dppm)(AuCl)2] under similar conditions yields the trimetallic complex [(dppm)2Ru(S2CNC4H8NCS2)Au2(dppm)]2+. Attempts to prepare the compound [(dppm)Au2(S2CNC4H8NH2)]2+ from [(dppm)(AuCl)2] led to isolation of the known complex [{(dppm)Au2}2(S2CNC4H8NCS2)]2+ via a symmetrization pathway. [{(dppf)Au2}2(S2CNC4H8NCS2)]2+ was successfully prepared from [(dppf)(AuCl)2] and crystallographically characterized. In addition, a gold(III) trimetallic compound, [{(dppm)2Ru(S2CNC4H8NCS2)}2Au]3+, and a tetrametallic gold(I) species, [{(dppm)2Ru(S2CNC4H8NCS2)Au}2]2+, were also synthesized. This methodology was further exploited to attach the zwitterionic (dppm)2Ru(S2CNC4H8NCS2) unit to the surface of gold nanoparticles, which were generated in situ and found to be 3.4 (±0.3) and 14.4 (±2.5) nm in diameter depending on the method employed. Nanoparticles with a mixed surface topography were also explored.