Synthesis and Reactivity of Silicon- and Germanium-Bridged<i>ansa</i>-Cycloheptatrienyl−Cyclopentadienyl Titanium Complexes

Abstract

A new type of ansa -cycloheptatrienyl−cyclopentadienyl complex with germanium as a bridging atom has been synthesized. Using the established route for the formation of [(η-C 5 H 4 )Me 2 Si(η-C 7 H 6 )Ti], [1]silatroticenophane 1, the analogous germylene-bridged derivative [(η-C 5 H 4 )Me 2 Ge(η-C 7 H 6 )Ti] ( 2 ) has been isolated from the reaction of [(η-C 7 H 7 )Ti(η-C 5 H 5 )] (troticene) with n -butyllithium/ N,N,N ‘,N ‘-tetramethylethylenediamine (tmeda) in hexane and subsequent treatment of the intermediate dilithio complex with dimethyl(dichloro)germane. [1]Germatroticenophane 2 has been isolated in yields up to 15−20% and was characterized by means of 1 H, 13 C NMR spectroscopy, elemental analysis, and mass spectrometry. In addition, an X-ray diffraction study on a single crystal of 2 has been performed, and the structural characteristics are discussed in comparison to related ansa -compounds. The differential scanning calorimetry trace of 2 shows a strong exotherm at about 130 °C, which is the result of a thermally induced ring-opening polymerization reaction, and a strain energy of about 45 kJ mol -1 has been determined. The reaction of 2 with equivalent amounts of tris(triethylphosphine)platinum(0) involves a regioselective insertion of a [Pt(PEt 3 ) 2 ] moiety into the germanium−carbon bond at the C 7 H 6 site, yielding the [2]platinasilagermatroticenophane [(η-C 5 H 4 )Me 2 GePt(PEt 3 ) 2 (η-C 7 H 6 )Ti] ( 10 ), which was characterized by 1 H, 13 C, 31 P, and 195 Pt NMR spectroscopy. In addition, the reactivity of 1 toward protic acids such as HCl and HBF 4 has been investigated, yielding complexes of the type [(η-C 7 H 7 )Ti(η-C 5 H 4 SiMe 2 X)] (X = Cl, F) by exclusive cleavage of the Si−C 7 H 6 silicon−carbon bond and protonation of the cycloheptatrienyl ipso -carbon atom.