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

Synthesis, Structure, and EPR Spectroscopic Characterization of Titanocene Complexes with Dimethylmalonato Ligands The reaction of [TiCp 2 (BTMSA)] ( 1a , Cp = η 5 ‐C 5 H 5 , BTMSA = bis(trimethylsilyl)acetylene) with dimethylmalonic acid resulted in the formation of the titanium(III) complex [{TiCp 2 } 2 {μ‐(O 2 C) 2 CMe 2 }] ( 2 ). Additionally, in an unprecedented case a small amount of the titanium(IV) complex [TiCp 2 {(O 2 C) 2 CMe 2 ‐κ O } 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 κ 2 O,O′ coordinated dimethylmalonato ligand that acts as bridging ligand, too. Magnetic measurements (μ eff = 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 Ti III centres. The fine structure tensor exhibited rhombic symmetry ( g x = 1.983, g y = 1.984, g z = 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 [TiCp 2 {(O 2 C) 2 CMe 2 ‐κ O } 2 ] ( 3 ) exhibited that the Ti centre of 3 is distorted tetrahedrally coordinated by two Cp ligands and two monocoordinated (κ O ) dimethylmalonato ligands.