Heterobimetallic complexes stabilized by the P2N2 macrocyclic ligand system: synthesis and reactivity of a rhodium-copper system that activates molecular hydrogen.
Siyuan L XieCorey A SanzMichael D FryzukPublished in: Dalton transactions (Cambridge, England : 2003) (2021)
The synthesis and reactivity of the bimetallic rhodium-copper complex, Rh(COE)[P2N2]Cu, which is stabilized by the P2N2 macrocycle, is reported. In the solid state, the rhodium and copper centers are on opposite sides of the macrocyclic ring with the Cu(I) in a linear environment and the Rh(I) in a square planar array. However, in solution a very symmetrical structure is suggested on the basis of the 1H NMR data, which is consistent with at least two separate fluxional processes, rotation of the cyclooctene unit and movement of the Rh(I) unit between the two amido donors. Addition of H2 to Rh(COE)[P2N2]Cu results in the formation of ([P2N2H]RhH(μ-H)2Cu)2via hydrogenation of the coordinated cyclooctene unit, oxidative addition of H2 to the rhodium center and hydrogenolysis of the copper amido unit. Monitoring the reaction of H2 by NMR spectroscopy indicated the formation of a number of intermediates which suggests hydrogenolysis of the copper amido linkage occurs to generate CuH in some form, along with Rh(COE)[P2N2H], which is converted to Rh(H)2[P2N2H] by hydrogenation of the cyclooctene, which then recombines with the CuH present to generate the final product. Deuteration studies indicate that there is considerable H/D scrambling in the cyclooctane produced that we attribute to reversible beta-elimination, migratory insertion steps.