Synthese, Struktur und EPR‐spektroskopische Charakterisierung von Titanocenkomplexen mit Dimethylmalonatoliganden

Abstract

AbstractSynthesis, Structure, and EPR Spectroscopic Characterization of Titanocene Complexes with Dimethylmalonato LigandsThe reaction of [TiCp2(BTMSA)] (1a, Cp = η5‐C5H5, BTMSA = bis(trimethylsilyl)acetylene) with dimethylmalonic acid resulted in the formation of the titanium(III) complex [{TiCp2}2{μ‐(O2C)2CMe2}] (2). Additionally, in an unprecedented case a small amount of the titanium(IV) complex [TiCp2{(O2C)2CMe2‐κO}2] (3) was formed. The identity of complex 2 was confirmed by microanalysis, IR and EPR spectroscopic measurements. Single crystal X‐ray diffraction analysis exhibited a dinuclear structure in which the titanium atoms are distorted tetrahedrally coordinated by two cyclopentadienyl ligands and a κ2O,O′ coordinated dimethylmalonato ligand that acts as bridging ligand, too. Magnetic measurements (μeff = 1.28/Ti, T = 295 K) and EPR investigations both of solutions of 2 in toluene at r.t. and of frozen solutions (T = 130 K) gave proof of a coupling between the two TiIII centres. The fine structure tensor exhibited rhombic symmetry (gx = 1.983, gy = 1.984, gz = 1.979, D = 101·10−4 cm−1, E = 6·10−4 cm−1). Using the equation of Francesconi a Ti···Ti separation of ca 6.3Å was estimated that is in very good agreement with those obtained by X‐ray crystallography (6.685(5) Å). The single‐crystal X‐ray diffraction analysis of [TiCp2{(O2C)2CMe2‐κO}2] (3) exhibited that the Ti centre of 3 is distorted tetrahedrally coordinated by two Cp ligands and two monocoordinated (κO) dimethylmalonato ligands.