FERROUS TRIS(TRIMETHYLSILYL)SILANOLATES - SYNTHESIS, STRUCTURE, REACTIVITY AND THERMAL-DECOMPOSITION

Reaction of FeBr2 with 3 equiv. of sodium tris(trimethylsilyl)silanola te (1) in DME affords the ate-complex ((Me3Si)(3)SiOFe[mu-OSi(SiMe3)(3 )](2) Na(DME)) (2). X-ray studies have shown the Fe atom in 2 is bonde d to three O atoms of OSi(SiMe3)(3) groups, two O atoms are connecting as a mu-bridge the Fe[OSi(SiMe3)(3)](3) unit with the Na(DME) group. The FeO3 core is slightly non-planar: the deviation of the Fe atom fro m the O-3 plane is 0.08 Angstrom. The four-member Fe(mu-O)(2)Na cycle is also non-planar: the dihedral angle between the Fe(mu-O)(2) and the (mu-O)(2)Na planes is 31.0 degrees. The bridging and terminal Fe-O di stances are 1.840(2) and 1.894(2), 1.910(2) Angstrom, respectively. Th e average Si-Si and Si-C distances are 2.358(8) Angstrom and 1.873(8) Angstrom. Interaction of FeBr2 with two equiv. of 1 in THF followed by treatment with pyridine yields the adduct, [(Me3Si)(3)SiO](2)Fe(Py)(2 ) (3). The Mossbauer spectrum of complex 2 at 295 K consists of a sing le doubler with isomer shift 0.60(1) mm/s and quadrupole splitting 0.9 0(3) mm/s. The corresponding parameters of 3 are as follows: isomer sh ift, 1.08(1) mm/s, and quadrupole splitting, 2.12(2) mm/s. Molecular o xygen is easily incorporated into the Si-Si bonds of compounds 2 and 3 by activation at the iron (II) center. Reaction of 2 with 1 equiv. of tetracyanoethylene leads to iron (III) silanolate, [(Me3Si)(3)SiO](3) Fe (4) and the anion-radical salt, Na+TCNE-. Slow thermolysis of 2 and 3 yields (Me3Si)(3)SiOSiMe3 and (Me3Si)(4)Si as well as polyferrisilo xane with MW similar to 3500. Fast thermolysis results in formation of alpha-Fe and a complicated mixture of oligosiloxanes. (C) 1997 Elsevi er Science S.A.