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Dinuclear Palladium Complexes with Two Ligand‐Centered Radicals and a Single Bridging Ligand: Subtle Tuning of Magnetic Properties
Author(s) -
Broere Daniël L. J.,
Demeshko Serhiy,
de Bruin Bas,
Pidko Evgeny A.,
Reek Joost N. H.,
Siegler Maxime A.,
Lutz Martin,
van der Vlugt Jarl Ivar
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201500084
Subject(s) - diradical , chemistry , electron paramagnetic resonance , bridging ligand , magnetochemistry , palladium , crystallography , intramolecular force , ligand (biochemistry) , radical , antiferromagnetism , singlet state , photochemistry , stereochemistry , nuclear magnetic resonance , excited state , crystal structure , catalysis , organic chemistry , atomic physics , biochemistry , physics , receptor , condensed matter physics
The facile and tunable preparation of unique dinuclear [(L ⋅ )PdXPd(L ⋅ )] complexes (X=Cl or N 3 ), 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( NNO ISQ )] ( NNO ISQ =iminosemiquinonato) with TlPF 6 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 d 8 –d 8 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 PPh 3 to generate [Pd(NNO ISQ )(PPh 3 )] + and one equivalent of [PdCl( NNO ISQ )]. Reacting an 1:1 mixture of [PdCl( NNO ISQ )] and [Pd(N 3 )( NNO I SQ )] furnishes the 1,1‐azido‐bridged dinuclear diradical [{Pd( NNO ISQ )} 2 (κ 1 ‐N;μ‐N 3 ] + , 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 PdXPd 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.