Metal-metal interactions in bimetallic complexes have been a topic of thorough investigation due to their unique photophysical and structural properties that cannot be attributed to the nature of the coordinated ligands. The initial reaction when one has two filled shells is that no bonding should occur; however, the reality of whether bonding does occur depends on the presence, or absence, of sufficient overlap with low-lying unoccupied orbitals with the filled orbitals. Since bonding is not expected between two closed-shell metal atoms, the existence of these types of interactions has been both supported and refuted at various levels of theory. While there have been many cases of covalent bonding between open-shell metals, fewer examples exist for covalent bonding between closed-shell and pseudo-closed shell metals. This undertaking is a direct continuation of research inspired by a recent discovery in the Omary Group of a new type of chemical bond between closed-shell d10 metal centers in a hexanuclear cluster complex, Au4Cu2 {[Au2(μ-C2,N3-EtIm)2Cu(µ-3,5-(CF3)2Pz)]. The hexanuclear cluster exhibits two monomer-of-trimer units linked by two genuine d10-d10 polar-covalent bonds with Cu(I)-Au(I) distances of 2.875 Å – the shortest intermolecular distance reported between any two d10 centers, regarding it as a metal-metal bond. Where intra- and inter-molecular d10–d10 interactions in hetero- and homometallic structures have been extensively studied, our work is focused on efforts to revisit and expand on metal-metal bonding in heterobimetallic complexes of the form [MM’(MTP)2] (where M/M’= Ag/Au, Au/Cu and MTP=CH2PPh2S). Preliminary DFT computations have shown that, upon careful examination of metal-based Kohn-Sham orbital contours, (n+1)s/p mixing with nd orbitals leads to non-zero bond orders. Whereas the M2(MTP)2, homometallic models exhibited an expected 5 bonding and 5 anti-bonding orbitals giving rise to a zero-bond order. Our research is primarily focused on the design of novel molecular materials that exhibit room temperature phosphorescence utilizing metal-centered phosphorescent states in d10 transition metals. This investigation serves as a comprehensive study of potentially new metal-metal bonds in the complexes discussed above and our future efforts to develop synthetic routes to achieve these [MM’(μ-L)n]m d10-d10 structures.

To be or not to be: Bonding studies in heterobimetallic d10-d10 centers

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.