Ferrous tris(trimethylsilyl) silanolates: synthesis, structure, reactivity and thermal decomposition

Abstract Reaction of FeBr 2 with 3 equiv. of sodium tris(trimethylsilyl)silanolate ( 1 ) in DME affords the ate-complex {(Me 3 Si) 3 SiOFe[μ-OSi(SiMe 3 )] 2 Na(DME)} ( 2 ). X-ray studies have shown the Fe atom in 2 is bonded to three O atoms of OSi(SiMe 3 ) 3 groups, two O atoms are connecting as a μ-bridge the Fe[OSi(SiMe 3 ) 3 ] 3 ] unit with the Na(DME) group. The FeO 3 core is slightly non-planar: the deviation of the Fe atom from the O 3 plane is 0.08A. The four-member Fe(μ-O) 2 Na cycle is also non-planar: the dihedral angle between the Fe(μ-O) 2 and the (μ-O) 2 Na planes is 31.0°. The bridging and terminal FeO distances are 1.840(2) and 1.894(2), 1.910(2) A, respectively. The average SiSi and SiC distances are 2.358(8) A and 1.873(8) A. Interaction of FeBr 2 with two equiv. of 1 in THF followed by treatment with pyridine yields the adduct, [(Me 3 Si) 3 SiO] 2 Fe(Py) 2 ( 3 ). The Mossbauer spectrum of complex 2 at 295 K consists of a single doublet with isomer shift 0.60(1) mm/s and quadrupole splitting 0.90(3) mm/s. The corresponding parameters of 3 are as follows: isomer shift, 1.08(1) mm/s, and quadrupole splitting, 2.12(2) mm/s. Molecular oxygen 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, [(Me 3 Si) 3 SiO] 3 Fe ( 4 ) and the anion-radical salt, Na + TCNE − . Slow thermolysis of 2 and 3 yields (Me 3 Si) 2 SiOSiMe 3 and (Me 3 Si) 4 Si as well as polyferrsiloxane with MW ∼ 3500. Fast thermolysis results in formation of α-Fe and a complicated mixture of oligosiloxanes.