An iron ketimide single-molecule magnet [Fe₄(NCPh₂)₆] with suppressed through-barrier relaxation

Abstract

The tetrametallic Fe ketimide cluster, [Fe4(NCPh2)6], exhibits a thermally persistent S = 7 ground-state along with single molecule magnet behavior.

Strong Electronic and Magnetic Coupling in M4 (M = Ni, Cu) Clusters via Direct Orbital Interactions between Low-Coordinate Metal Centers

“…The spin energy levels of the truncated model complexes Ni4(NPH3)4 (1′) and [Ni4(NPH3)4] + (2′) were computed using the complete active space self-consistent field (CASSCF) method 31 modulated by second order N-electron valence perturbation theory (NEVPT2), [32][33][34] as implemented in the program ORCA. 35 Calculations on 1′ were carried out by correlating four electrons on four localized 3d molecular orbitals [CAS (4,4)] and extended active spaces, correlating twelve electrons on eight [CAS (12,8)] and twenty eight electrons on sixteen [CAS (28,16)] localized molecular orbitals. All of these calculations yielded a well-isolated S = 2 ground state (Table S5).…”

“…Recently, however, a number of clusters exhibiting strong ferromagnetic direct exchange, mediated by direct metal-metal orbital overlap, have been reported. [6][7][8][9][10][11][12] These complexes have motivated a new design paradigm for accessing single-molecule magnets with thermally isolated large-spin ground states. 11,12 For example, the tetranuclear iron cluster Fe4(N=CPh2)6 was recently shown to exhibit an S = 7 ground state and consequently slow magnetic relaxation with a spin relaxation barrier of Ueff = 29 cm −1 .…”

“…[6][7][8][9][10][11][12] These complexes have motivated a new design paradigm for accessing single-molecule magnets with thermally isolated large-spin ground states. 11,12 For example, the tetranuclear iron cluster Fe4(N=CPh2)6 was recently shown to exhibit an S = 7 ground state and consequently slow magnetic relaxation with a spin relaxation barrier of Ueff = 29 cm −1 . 12 We also recently reported the tetranuclear cluster compound [Co4(NP t Bu3)4][B(C6F5)4], 11 which possesses a well-isolated S = 9 /2 ground state resulting from direct metal-metal orbital overlap.…”

“…Most of these clusters feature metal ions coupled via weak, antiferromagnetic superexchange interactions. Recently, however, a number of clusters exhibiting strong ferromagnetic direct exchange, mediated by direct metal–metal orbital overlap, have been reported. − These complexes have motivated a new design paradigm for accessing single-molecule magnets with thermally isolated large-spin ground states. , For example, the tetranuclear iron cluster Fe 4 (NCPh 2 ) 6 was recently shown to exhibit an S = 7 ground state and consequently slow magnetic relaxation with a spin relaxation barrier of U eff = 29 cm –1 . We also recently reported the tetranuclear cluster compound [Co 4 (NP t Bu 3 ) 4 ]­[B­(C 6 F 5 ) 4 ], which possesses a well-isolated S = 9 / 2 ground state resulting from direct metal–metal orbital overlap.…”

[2+2] Cycloadditions with an Iron Carbene: A Critical Step in Enyne Metathesis

“…We have been studying group 10 metal carbenes supported by [PC­(sp 2 )­P] ((bis­[2-(di-isopropyl­phosphino)­phenyl]­methane)) and discovered new reactivity patterns for late transition metal carbenes. − The rich reactivity observed for these carbenes − prompted us to expand our studies to iron − and probe the reactivity of the corresponding compounds. Herein, we report the synthesis of [{PC­(sp 2 )­P}­Fe­(N 2 )­(PMe 3 )] ( 1-N 2 -PMe 3 ) and its unprecedented [2+2] reactivity with alkynes to produce η 3 -vinyl carbene iron complexes, [{PC­(C Ph C­(sp 2 ) Ph }­Fe­(L)] ( 2-L , L = N 2 , PMe 3 , Figure E).…”