Aggregation of [(<i><sup>t</sup></i><sup></sup>Bu<sub>3</sub>SiS)MX]: Structures of {[Br<sub>2</sub>Fe(μ-SSi<i><sup>t</sup></i><sup></sup>Bu<sub>3</sub>)<sub>2</sub>FeBr(THF)]Na(THF)<sub>4</sub>}<sub>∞</sub>, <i>cis</i>-[(THF)FeI]<sub>2</sub>(μ-SSi<i><sup>t</sup></i><sup></sup>Bu<sub>3</sub>)<sub>2</sub>, [(<i><sup>t</sup></i><sup></sup>Bu<sub>3</sub>SiS)Fe]<sub>2</sub>(μ-SSi<i><sup>t</sup></i><sup></sup>Bu<sub>3</sub>)<sub>2</sub>, and Comparative Structure and Magnetism Studies of [(<i><sup>t</sup></i><sup></sup>Bu<sub>3</sub>SiS)MX]<i><sub>n</sub></i> (M = Fe, Co, X = Cl, <i>n</i> = 12; M = Fe, Ni, X = Br, <i>n</i> = 12; M = Fe, X = I, <i>n</i> = 14)
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A convenient synthesis of tBu3SiSH and tBu3SiSNa(THF)x led to the exploration of “tBu3SiSMX” aggregation. The dimer, [(tBu3SiS)Fe]2(μ-SSitBu3)2 (12), was formed from [{(Me3Si)2N}Fe]2(μ-N(SiMe3)2)2 and the thiol, and its dissolution in THF generated (tBu3SiS)2Fe(THF)2 (1−(THF)2). Metathetical procedures with the thiolate yielded aggregate precursors [X2Fe](μ-SSitBu3)2[FeX(THF)]Na(THF)4 (3−X, X = Cl, Br) and cis-[(THF)IFe]2(μ-SSitBu3)2 (4). Thermal desolvations of 3−Cl, 3−Br and 4 afforded molecular wheels [Fe(μ-X)(μ-SSitBu3)]12(C6H6)n (5−FeX, X = Cl, Br) and the ellipse [Fe(μ-I)(μ-SSitBu3)]14(C6H6)n (6−FeI). Related metathesis and desolvation sequences led to wheels [Co(μ-Cl)(μ-SSitBu3)]12(C6H6)n (5−CoCl) and [Ni(μ-Br)(μ-SSitBu3)]12(C6H6)n (5−NiBr). The nickel wheel disproportionated to give, in part, [(tBu3SiS)Ni]2(μ-SSitBu3)2 (7), which was also synthesized via salt metathesis. X-ray structural studies of 12 revealed a roughly planar Fe2S4 core, while 1−(THF)2, 3−Br, and 4 possessed simple distorted tetrahedral and edge-shared tetrahedral structures. X-ray structural studies revealed 5−MX (MX = FeCl, FeBr, CoCl, NiBr) to be wheels based on edge-shared tetrahedra, but while the pseudo-D6d wheels of 5−FeCl, 5−CoCl, and 5−FeBr pack in a body-centered arrangement, those of pseudo-C6v 5−NiBr exhibit hexagonal packing and two distinct trans-annular d(Br···Br). Variable-temperature magnetic susceptibility measurements were conducted on 5−FeCl, 5−CoCl, 5−FeBr, and 6−FeI, and the latter three are best construed as weakly antiferromagnetic, while 5−FeCl exhibited modest ferromagnetic coupling. Features suggesting molecular magnetism are most likely affiliated with phase changes at low temperatures.
