Coordination Chemistry of the Redox Non‐Innocent Ligand Bis(2‐amino‐3,5‐di‐tert‐butylphenyl)amine with Group 10 Metal Ions (Ni, Pd, Pt)
Nicolas Leconte; Jules Moutet; Thibaut Constantin; Florian Molton; Christian Philouze; Fabrice Thomas
Index: 10.1002/ejic.201701448
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Abstract
The pincer ligand H3L3N, bis(2‐amino‐3,5‐di‐tert‐butylphenyl)amine}, was chelated to NiII, PdII, and PtII. Square‐planar complexes of stoichiometry 2:1 (ligand/metal) formed, wherein the ligand coordinates in a bidentate fashion. By X‐ray diffraction we established that each ligand molecule coordinates in its diiminosemiquinone radical form in the neutral NiII, PdII, and PtII complexes (1, 2, and 3, respectively). The resulting systems are singlet diradical species, with a predicted J value in the range –1062 to –1764 cm–1. These diradicals display an intense LLCT transition involving the diiminosemiquinone moieties: 860, 852, and 760 nm for 1, 2, and 3, respectively. Complex 1, 2, and 3 exhibit reversible oxidation waves in their CV curves. Cations 1+, 2+, and 3+ are (S = 1/2) systems with g values close to 2. The increase in the intensity of the resonance in the order 1+ < 2+, 3+ is consistent with the easy comproportionation of 1+. X‐ray diffraction analysis discloses that 3+ is a mixed‐valent radical mononuclear complex. An intense IVCT is observed at low energy (1536, 1656, and 1256 nm for 1+, 2+, and 3+, respectively), confirming that this classification applies to all the cations. Dications 12+, 22+, and 32+ are closed‐shell bis(diiminobenzoquinone) species. The crystal structure of 32+ shows that this complex exhibits the shortest mean C–N bond lengths within the series.