Bifunctional Chalcogen Linkers for the Stepwise Generation of Multimetallic Assemblies and Functionalized Nanoparticles.

The disulfide ligand (SC6 H4 CO2 H-4)2 acts as a simple but versatile linker for a range of group 8 transition metals through reaction of the oxygen donors. This leads to a range of homobimetallic ruthenium and osmium alkenyl compounds, [{M(CH═CHR)(CO)(PPh3 )2 (O2 CC6 H4 S-4)}2 ] (M = Ru, Os; R = C6 H4 Me-4). Additional metal-based functionality can be added through the use of precursors incorporating rhenium bipyridine units (R = (bpy)ReCl(CO)3 ). The more robust diphosphine ligands in [{Ru(dppm)2 (O2 CC6 H4 S-4)}2 ]2+ (dppm = diphenylphosphinomethane) allow reduction of the disulfide bond with sodium borohydride to yield the thiol complex [Ru(O2 CC6 H4 SH-4)(dppm)2 ]+ . This complex reacts with [AuCl(PPh3 )] to afford the bimetallic compound [Ru(dppm)2 (O2 CC6 H4 S-4)Au(PPh3 )]+ . However, an improved route to the same and related heterobimetallic compounds is provided by the reaction of cis-[RuCl2 (dppm)2 ] with [Au(SC6 H4 CO2 H-4)(L)] (L = PPh3 , PCy3 , PMe3 , IDip) in the presence of base and NH4 PF6 (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). The heterotrimetallic compound [Au(SC6 H4 CO2 Ru(dppm)2 )2 ]+ is accessible through the reaction of the homoleptic gold(I) dithiolate [Au(SC6 H4 CO2 H-4)2 ]PPN (PPN = bis(triphenylphosphine)iminium) with cis-[RuCl2 (dppm)2 ]. Without departure from the same methodology, greater complexity can be incorporated into the system to provide the penta- and heptametallic assemblies [(dppf){AuSC6 H4 CO2 Ru(dppm)2 }2 ]2+ and [(dppf){AuSC6 H4 CO2 Os(CH═CH-bpyReCl(CO)3 )(CO)(PPh3 )2 }2 ]. The same stepwise approach provides the dinuclear organometallic complexes [(L)Au(SC6 H4 CO2 -4)M(CH═CHC6 H4 Me-4)(CO)(PPh3 )2 ] (M = Ru, Os; L = PPh3 , IDip). Complexes containing three metals from different groups of the periodic table [(L)Au(SC6 H4 CO2 -4)M{CH═CH-bpyReCl(CO)3 }(CO)(PPh3 )2 ] (M = Ru, Os) can also be prepared, with one ruthenium example (L = PPh3 ) being structurally characterized. In order to illustrate the versatility of this approach, the synthesis and characterization (IR and NMR spectroscopy, TEM, EDS, and TGA) of the functionalized gold and palladium nanoparticles Au@[SC6 H4 CO2 Ru(dppm)2 ]+ and Pd@[SC6 H4 CO2 Ru(dppm)2 ]+ is reported.