Aggregation of [( t Bu3SiS)MX]:  Structures of {[Br2Fe(μ-SSi t Bu3)2FeBr(THF)]Na(THF)4}∞, cis-[(THF)FeI]2(μ-SSi t Bu3)2, [( t Bu3SiS)Fe]2(μ-SSi t Bu3)2, and Comparative Structure and Magnetism Studies of [( t Bu3SiS)MX] n (M = Fe, Co, X = Cl, n = 12; M = Fe, Ni, X = Br, n = 12; M = Fe, X = I, n = 14)

• Published in: Inorganic chemistry Vol. 45; no. 2; pp. 609 - 626
• Main Authors: Sydora, Orson L, Henry, Thomas P, Wolczanski, Peter T, Lobkovsky, Emil B, Rumberger, Evan, Hendrickson, David N
• Format: Journal Article
• Language: English
• Published: American Chemical Society 23.01.2006
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic051289u

A convenient synthesis of t Bu3SiSH and t Bu3SiSNa(THF) x led to the exploration of “ t Bu3SiSMX” aggregation. The dimer, [( t Bu3SiS)Fe]2(μ-SSi t Bu3)2 (1 2), was formed from [{(Me3Si)2N}Fe]2(μ-N(SiMe3)2)2 and the thiol, and its dissolution in THF generated ( t Bu3SiS)2Fe(THF)2 (1−(THF)2). Metathetical procedures with the thiolate yielded aggregate precursors [X2Fe](μ-SSi t Bu3)2[FeX(THF)]Na(THF)4 (3−X, X = Cl, Br) and cis-[(THF)IFe]2(μ-SSi t Bu3)2 (4). Thermal desolvations of 3−Cl, 3−Br and 4 afforded molecular wheels [Fe(μ-X)(μ-SSi t Bu3)]12(C6H6) n (5−FeX, X = Cl, Br) and the ellipse [Fe(μ-I)(μ-SSi t Bu3)]14(C6H6) n (6−FeI). Related metathesis and desolvation sequences led to wheels [Co(μ-Cl)(μ-SSi t Bu3)]12(C6H6) n (5−CoCl) and [Ni(μ-Br)(μ-SSi t Bu3)]12(C6H6) n (5−NiBr). The nickel wheel disproportionated to give, in part, [( t Bu3SiS)Ni]2(μ-SSi t Bu3)2 (7), which was also synthesized via salt metathesis. X-ray structural studies of 1 2 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-D 6 d wheels of 5−FeCl, 5−CoCl, and 5−FeBr pack in a body-centered arrangement, those of pseudo-C 6 v 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.