Dinuclear Palladium Complexes with Two Ligand‐Centered Radicals and a Single Bridging Ligand: Subtle Tuning of Magnetic Properties |
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Authors: | M?Sc Daniël L J Broere Dr Serhiy Demeshko Prof?Dr Bas de?Bruin Dr Evgeny A Pidko Prof?Dr Joost N H Reek Dr Maxime A Siegler Dr Martin Lutz Dr Jarl Ivar van?der?Vlugt |
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Institution: | 1. Homogeneous, Bioinspired & Supramolecular Catalysis van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (The Netherlands);2. Institut für Anorganische Chemie, Georg‐August‐Universit?t G?ttingen, Tammanstrasse 4, 37077 G?ttingen (Germany);3. Inorganic Materials Chemistry Group, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (The Netherlands);4. Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (USA);5. Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht (The Netherlands) |
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Abstract: | The facile and tunable preparation of unique dinuclear (L?)Pd?X?Pd(L?)] complexes (X=Cl or N3), bearing a ligand radical on each Pd, is disclosed, as well as their magnetochemistry in solution and solid state is reported. Chloride abstraction from PdCl( NNOISQ )] ( NNOISQ =iminosemiquinonato) with TlPF6 results in an unusual monochlorido‐bridged dinuclear open‐shell diradical species, {Pd( NNO ISQ)}2(μ‐Cl)]+, with an unusually small Pd‐Cl‐Pd angle (ca. 93°, determined by X‐ray). This suggests an intramolecular d8–d8 interaction, which is supported by DFT calculations. SQUID measurements indicate moderate antiferromagnetic spin exchange between the two ligand radicals and an overall singlet ground state in the solid state. VT EPR spectroscopy shows a transient signal corresponding to a triplet state between 20 and 60 K. Complex 2 reacts with PPh3 to generate Pd(NNOISQ)(PPh3)]+ and one equivalent of PdCl( NNOISQ )]. Reacting an 1:1 mixture of PdCl( NNOISQ )] and Pd(N3)( NNOI SQ)] furnishes the 1,1‐azido‐bridged dinuclear diradical {Pd( NNO ISQ)}2(κ1‐N;μ‐N3]+, with a Pd‐N‐Pd angle close to 127° (X‐ray). Magnetic and EPR measurements indicate two independent S=1/2 spin carriers and no magnetic interaction in the solid state. The two diradical species both show no spin exchange in solution, likely because of unhindered rotation around the Pd?X?Pd core. This work demonstrates that a single bridging atom can induce subtle and tunable changes in structural and magnetic properties of novel dinuclear Pd complexes featuring two ligand‐based radicals. |
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Keywords: | ligand effects magnetism open‐shell systems palladium radicals |
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