Abstract
The ESR and UV/VIS spectra have been studied for solutions of [N,N′-bis(pyridine-2-carbonyl)-o-phenylenediamido]nitridochromium(V) having a square-pyramidal (CrN5) chromophore. The g and 53Cr hyperfine coupling tensors (A) are axially symmetric. An analysis of the A tensor indicated a 3dxy ground-state Kramers doublet. Fairly high dπ–pπ interaction in the CrN formally triple bond was also revealed. The striking stability of this complex can be attributed to the remarkable dπ–pπ covalency of the CrN bond. None of the d–d* transitions has been observed in the region of λ 600 nm at room temperature. Bands at 25 000 and 29 000 cm–1 have been tentatively assigned to charge-transfer transitions. The considerable difference between the A⊥(53Cr), a(53Cr), g⊥ and giso values of nitrido-and those of oxo-chromium(V) complexes have been explained in terms of the different extents of covalency in the CrN and CrO multiple bonds.
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