A Dinucleating β-Thio-δ-Diiminate Ligand Enables Metal-Dependent CO2 Reactivity in Homo- and Heterobimetallic Zn and Cu Complexes
Year: 2026
Type: preprint
Abstract: Herein, we investigate the β-thio-δ-diimine (BTDDI) ligand, recently reported as a sulfur containing analogue of the established BODDI framework, as a platform for mono- and bimetallic Cu(I) and Zn(II) chemistry. Sequential metalation enables selective access to homo- and heterobimetallic complexes, including the first structurally characterised Cu/Zn derivative of this ligand class. Replacement of the central oxygen donor by sulfur expands the dinuclear framework, resulting in significantly increased metal–metal separations. The reactivity of these complexes towards CO 2 is strongly dependent on both metal identity and nuclearity: monometallic Cu(I) and Zn(II) complexes and the homobimetallic Cu(I) analogue are unreactive, whereas the Cu/Zn and di-Zn complexes undergo CO 2 activation. The di-Zn complex undergoes selective C–C bond formation at the γ-position of the ligand backbone to give a reversibly formed carboxylate-containing product featuring an unusual tripodal [N,S,O] donor motif. Isotopic labelling, spectroscopic and structural studies establish incorporation of CO 2 into the ligand framework, while DFT calculations reveal substantially lower barriers to γ-C insertion for the bimetallic complexes and identify Zn(II) as a key contributor to stabilisation of the resulting carboxylate through Zn–O interactions and subsequent dimerisation. These results establish a mode of CO 2 activation in which ligand-centred reactivity is coupled to metal-centred substrate stabilisation, with metal identity and nuclearity determining the outcome of the reaction.
Source: ChemRxiv
Institutions: University of Leicester, Trinity College Dublin
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214072526