Igor O. Koshevoy

Self-Assembly of Supramolecular Luminescent AuI–CuI Complexes: “Wrapping” an Au6Cu6 Cluster in a [Au3(diphosphine)3]3+ “Belt”†

Growing attention to alkynyl complexes of coinage metals, stimulated by their intriguing photophysical properties, has substantially focused on polynuclear homoand heterometallic compounds. The versatile bonding mode of alkynes and metallophilic interactions resulted in the synthesis of numerous cluster complexes which display different structural motifs and emission properties. 9,11] However, in most cases assembly of the complexes occurs in an uncontrolled way 11] and therefore it is a challenge to find a synthetic approach which would allow directed modification of the structural and electronic properties of these compounds. One of the most attractive features of supramolecular construction is the possible tuning of the luminescent behavior through changes in the electron richness of the alkyne ligands by p coordination to different metal ions. This method has been successfully used to synthesize heterometallic complexes by coordination of phosphine–gold(I)– alkyne p-donor metalloligands to d metal centers. These examples of alkynyl p coordination do not lead to ligand rearrangement, and the products formed obey the simple stoichiometry of the reaction. Composition and structure of the metal frameworks of these complexes are mainly determined by the steric properties of the phosphine ligands coordinated to the gold(I) center. This inspired our interest in probing rigid diphosphine ligands for the preparation of Au–alkynyl complexes containing spatially separated Au centers and studying their reactivity towards Cu ions. Herein we report the stepwise synthesis, structural characterization, and luminescence properties of Au–Cu supramolecular complexes self-assembled from simple Au and Cu precursors. Complex [Au2(C CPh)2(m-4,4’-Ph2PC6H4C6H4PPh2)] (1) was obtained by treating polymeric gold phenylacetylide [AuC CPh]n with the diphosphine. X-ray diffraction on 1 revealed a dimeric structure (Figure 1), similar to that found for analogous gold complexes based on the 1,2bis(diphenylphosphanyl)ethane ligand. However, the spectroscopic data (see the Supporting Information) indicate dissociation of the Au Au bonds in solution.

Synthesis and structural characterization of two novel heterometallic clusters: [Rh4Pt2(CO)11(dppm)2] and [Ru2Rh2Pt2(CO)12(dppm)2]

Two novel heterometallic octahedral clusters [Rh(4)Pt(2)(CO)(11)(dppm)(2)](1) and [Ru(2)Rh(2)Pt(2)(CO)(12)(dppm)(2)](2) were synthesized by the reaction of [Rh(2)Pt(2)(CO)(6)(dppm)(2)] with [Rh(6)(CO)(14)(NCMe)(2)] and Ru(3)(CO)(12), respectively. Solid state structures of 1 and 2 have been established by a single crystal X-ray diffraction study. Two dppm ligands in 1 are bonded to one platinum and three rhodium atoms, which form an equatorial plane of the Rh(4)Pt(2) octahedron. Two rhodium and two platinum atoms bound to the diphosphine ligands in 2 are nonplanar to give an octahedral C2 symmetric Ru(2)Rh(2)Pt(2)(dppm)2 framework. The (31)P NMR investigation of and (1D, (31)P COSY, (31)P-[(103)Rh] HMQC) and simulation of 1D spectral patterns showed that in both clusters the structures of the M(6)(PP)(2) fragments found in the solid state are maintained in solution.

Synthesis and structural characterization of mixed-metal Pt–Rh clusters. Assembly of tetra- and tetra-hexanuclear clusters from smaller metal fragments

The tetranuclear cluster [Rh2Pt2(CO)6(dppm)2] (1) has been obtained in good yield by redox condensation of [Rh(CO)4]− with [PtCl(dppm)]2 and also by substitution of two rhodium atoms in [Rh4(CO)12] for the binuclear [Pt2(CO)3(dppm)2] fragment. The cluster 1 crystallizes in two isomeric forms, 1a and 1b, the former prevails both in solution and in the solid state. The molecular structures of both isomers have been established by X-ray analysis, which showed the presence of a tetranuclear butterfly framework with platinum atoms at the wingtip positions in the both clusters. The isomers differ from each other in the mode of dppm coordination on the cluster core. Reaction of the labile cluster [Rh6(CO)15(NCMe)] with 1 results in formation of [{Rh6(μ3-CO)4(CO)10}(μ2-CO)2{Pt2Rh2(μ2-CO)3(CO)2(dppm)2}] (2), containing two cluster frameworks linked by a dative metal–metal bond. This cluster can also be obtained in slightly lower yield by reaction of [PtCl(dppm)]2 with either [Rh7(CO)16]3− or [Rh6(CO)15]2−. Treatment of [Rh6(CO)15(NCMe)] with two equivalents of [Pt2(CO)3(dppm)2] affords [{Rh6(μ3-CO)4(CO)10}(μ2-CO)2{Pt4(dppm)3}] (3), which displays another structural pattern containing the hexa- and tetranuclear cluster frameworks linked by a dative interaction. 31P spectroscopic studies of 1a and 2, and simulation of the corresponding spectroscopic patterns showed that the structures of the “Pt2Rh2(dppm)2” fragments found in the solid state remain unchanged in solution.

Linkage of heteronuclear rhodium–platinum clusters

Two coupled clusters [Rh8Pt2(CO)21(dppm)2] (1) and [Rh6Pt4(CO)16(dppm)3] (2) have been synthesised and characterised; the mixed metal Rh2Pt2 cluster in 1 and the tetranuclear Pt4 cluster in 2 are bonded to the Rh6 metal core via Rh–Rh and Pt–Rh bonds.