High-Spin [Fe I 3 ] Cluster Capable of Pnictogen Atom Capture.

Using a new hexanucleating anildophosphine ligand t Bu LH 3 (1,3,5-C 6 H 9 (NHC 6 H 3 -5-F-2-P( t Bu) 2 ) 3 ), the all-monovalent [Fe I 3 ] compound ( t Bu L)Fe 3 ( 1 ) was isolated and characterized by X-ray diffraction analysis, SQUID magnetometry, 57 Fe Mössbauer spectroscopy, and cyclic voltammetry. The molecular structure of 1 reveals very close Fe-Fe distances of 2.3825(7), 2.4146(8), and 2.3913(8) Å which results in significant Fe-Fe interactions and a maximum high-spin S = 9 / 2 spin state as determined by SQUID magnetometry and further supported by quantum chemical calculations. Compound 1 mediates the multielectron, oxidative atom transfer from inorganic azide ([Bu 4 N][N 3 ]), cyanate (Na[NCO]), and phosphonate (Na(dioxane) 2.5 [PCO]) to afford the [Fe 3 ]-nitrido (N 3- ) and [Fe 3 ]-phosphido (P 3- ) pnictides, ( t Bu L)Fe 3 (μ 3 -N) ( 2 ) and [( t Bu L)Fe 3 (μ 3 -P)(CO)] - ( 3 ), respectively. Compounds 1 - 3 exhibit rich electrochemical behavior with three (for 1 ), four (for 2 ) and five (for 3 ) distinct redox events being observed in the cyclic voltammograms of these compounds. Finally, the all-monovalent 1 and the formally Fe II /Fe II /Fe I compound 3 , were investigated by alternating current (ac) SQUID magnetometry, revealing slow magnetic relaxation in both compounds, with 3 being found to be a unique example of a [Fe 3 ]-phosphido single-molecule magnet having an energy barrier relaxation reversal of U = 30.7(6) cm -1 in the absence of an external magnetic field. This study demonstrates the utility of an all low-valent polynuclear cluster to perform multielectron redox chemistry and exemplifies the redox flexibility and unique physical properties that are present in the corresponding midvalent oxidation products.