Incorporation of [Cp*Rh] and [Cp*Ir] Species into Heterobimetallic Complexes via Protonolysis Reactivity and Dioximato Chelation

The synthesis of multimetallic compounds can enable the placement of two or more metals in close proximity, but efforts in this area are often hindered by reagent incompatibilities and a lack of selectivity. Here, we show that organometallic halfsandwich [Cp*M] (M = Rh, Ir) fragments (where Cp* is eta(5)-pentamethylcyclopentadienyl) can be cleanly installed into metallomacrocyclic structures based on the workhorse diimine-monooxime-monooximato ligand system. Six new heterobimetallic compounds have been prepared to explore this synthetic chemistry, which relies on in situ protonolysis reactivity with precursor Ni(II) or Co(III) monometallic complexes in the presence of suitable [Cp*M] species. Solid-state X-ray diffraction studies confirm installation of the [Cp*M] fragments into the metallomacrocycles via effective chelation of the Rh(III) and Ir(III) centers by the nascent dioximato site. Contrasting with square-planar Ni(II) centers, the Co(III) centers prefer octahedral geometry in the heterobimetallic compounds, promoting bridging ligation of acetate across the two metals. Spectroscopic and electrochemical studies reveal subtle influences of the metals on each other's properties, consistent with the moderate M'center dot center dot center dot M distances of ca. 3.6-3.7 angstrom in the modular compounds. Taken together, our results show that heterobimetallic complexes can be assembled with organometallic [Cp*M] fragments on the diimine-dioximato platform.

Automated summary

The synthesis of heterobimetallic complexes utilizing organometallic [Cp*M] fragments on the diimine-dioximato platform has been successfully demonstrated. The coordination of Rh(III) and Ir(III) centers by the nascent dioximato site allows for the installation of [Cp*M] fragments into metallomacrocycles, resulting in subtle influences on the properties of each metal in close proximity. Spectroscopic and electrochemical studies confirm the moderate M'·M distances in the modular compounds, highlighting the potential for further exploration in this synthetic chemistry.