How Solid Surfaces Control Stability and Interactions of Supported Cationic Cu^I(dppf) ComplexesA Solid-State NMR Study

Organometallic complexes are frequently deposited on solid surfaces, but little is known about how the resulting complex–solid interactions alter their properties. Here, a series of complexes of the type Cu(dppf)(L_x)⁺ (dppf = 1,1′-bis(diphenylphosphino)ferrocene, L_x = mono- and bidentate ligands) were synthesized, physisorbed, ion-exchanged, or covalently immobilized on solid surfaces and investigated by ³¹P MAS NMR spectroscopy. Complexes adsorbed on silica interacted weakly and were stable, while adsorption on acidic γ-Al₂O₃ resulted in slow complex decomposition. Ion exchange into mesoporous Na-[Al]SBA-15 resulted in magnetic inequivalence of ³¹P nuclei verified by ³¹P-³¹P RFDR and ¹H-³¹P FSLG HETCOR. DFT calculations verified that a MeCN ligand dissociates upon ion exchange. Covalent immobilization via organic linkers as well as ion exchange with bidentate ligands both lead to rigidly bound complexes that cause broad ³¹P CSA tensors. We thus demonstrate how the interactions between complexes and functional surfaces determine and alter the stability of complexes. The applied Cu(dppf)(L_x)⁺ complex family members are identified as suitable solid-state NMR probes for investigating the influence of support surfaces on deposited inorganic complexes.