| Abstract
| - DFT calculations have underscored the importance of the tripodal supporting ligand in tuning the spin-state energeticsof pseudotetrahedral transition metal imido complexes. In particular, we have focused on Co(III)−imido complexes,where our best estimate (OLYP) of the singlet−triplet splitting varies from 0.75 eV for a trisphosphine complex (1)and 0.3 eV for a tris(N-heteroyclic-carbene) complex (2) to essentially 0.0 eV for a hydrotris(pyrazolyl)borate (3)complex. The experimentally studied analogues of 1, 2, and 3 all exhibit S = 0 ground states; however, theexperimental analogue of 3 exhibits spin-crossover behavior due to a low-lying S = 1 state. Interestingly, whereasall the pure functionals examined successfully predict nearly equienergetic singlet end triplet states for 3, thehybrid functionals B3LYP and O3LYP exhibit a clear (and incorrect) preference for the S = 2 state. In addition, wehave also carried out an exploratory survey of Cr(III), Mn(III), and Fe(III) imido complexes with trisphosphine andhydrotris(pyrazolyl)borate (Tp) supporting ligands. Among the more interesting predictions of this study is that anFeIII(Tp)(imido) species should exhibit a high-spin S = 5/2 ground state, which would be unique for an iron−imidocomplex.
- DFT calculations have underscored the enormous influence of the tripodal supporting ligand on the singlet−triplet splitting of pseudotetrahedral Co(III)−imido complexes. In addition, based on experimental calibration, our best estimates (OLYP) suggest that FeIII(TptBu,Me)(NtBu) should be a high-spin complex.
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