Coordination-Induced Spin-State Change in Manganese(V) Complexes: The Electronic Structure of Manganese(V) Nitrides

This
work illustrates that manganese­(V) nitrido complexes are able to undergo
a coordination-induced spin-state change by altering the ligand field
from trigonal to tetragonal symmetry. For the reversible coordination
of acetonitrile to trigonal [(TIMENxyl)­Mn­(N)]2+ (1; high-spin S = 1; with
TIMENxyl = tris­[2-(3-xylylimidazol-2-ylidene)­ethyl]-amine),
a temperature-dependent coordination-induced spin-state switch is
established. Starting from the manganese­(V) nitrido complex 1, the synthesis and characterization of a series of octahedral,
low-spin (S = 0) manganese­(V) nitrido complexes of
the type [(TIMENxyl)­Mn­(N)­(L)]n+ (L = MeCN (2), tBuNC (3), CN– (4), NCS– (5), F– (6), μ-{Ag­(CN)2}− (7), with n = 1, 2) is described. These represent
the first examples of d2 transition metal complexes showing
a coordination-induced spin-state change. Spectroscopic, as well as
ligand-field theory and density functional theory studies suggest
a transition from a 2 + 2 + 1 orbital splitting in the trigonal case
to a 1 + 2 + 1 + 1 splitting in tetragonal symmetry as the origin
of the coordination-induced spin-state change.