Synthesis and Reactivity of Silicon- and Germanium-Bridgedansa-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.

Photoinduced iron–cyclopentadienyl (Fe–Cp) bond cleavage reactions and photocontrolled polymerizations of strained [1]ferrocenophanes

“…In contrast, use of terpyridines led to polyferrocenylsilane formation or the cleavage of both Fe-Cp bonds [38]. Clearly subtle substituent effects play a key role in determining the products that arise from the photoinduced reactivity of the Fe-Cp bonds in ferrocenophanes and fascinating results are also likely for related species [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…Since the discovery of the first example, sila [1]ferrocenophane in 1975 by Osborne and co-workers [1], strained [1]ferrocenophanes have attracted considerable attention and have inspired growing interest in a range of related species containing various d-and f-block metals, bridging elements, and even different p-hydrocarbon ligands [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The angle created by the planes of the two cyclopentadienyl (Cp) rings in a ferrocenophane, generally denoted as a, represents a convenient qualitative measure of the degree of strain present [2].…”

Ansa‐Bridged Bis(benzene) Titanium Complexes

“…The TiC bond lengths, which extend over the wide range 221.8(3) to 229.4(3) pm (TiX Bz =174.3 pm) further illustrate the distorted geometry and significant strain in the molecule. The geometrical parameters of compound 7 are very similar to those of the isoelectronic complex [Ti(η 5 ‐C 5 H 4 )(η 7 ‐C 7 H 6 )GeMe 2 ] ( α =22.9, β Cp =28.5, β Cht =28.5, δ =161.0, θ =92.8°) 15d. On the other hand, the ring strain is much more pronounced in compound 7 than the analogous chromium complex [Cr(η 6 ‐C 6 H 5 ) 2 GeMe 2 ] ( α =14.4(2)°) 7e…”

Syntheses of Group 4 ansa‐Trovacene Complexes and Conversion of [1]Silatrovacenophanes into Paramagnetic Metallopolymers by Ring‐Opening Polymerization

“…Due to the larger interannular distance in trovacene (338 pm; trochrocene: 326 pm), 6 and 7 are slightly more strained than the related chromium species [Cr(η 5 ‐C 5 H 4 )(η 7 ‐C 7 H 6 )SiMe 2 ] ( α =15.6(1)°, δ =167.5°) and [Cr(η 5 ‐C 5 H 4 )(η 7 ‐C 7 H 6 )GeMe 2 ] ( α =15.1(2)°, δ =168.3°) 21b,c. By contrast, the larger interannular distance in troticene (347 pm) results in an opposite behavior, as illustrated by the corresponding angles for [Ti(η 5 ‐C 5 H 4 )(η 7 ‐C 7 H 6 )SiMe 2 ] ( α =24.1°, δ =160.5°) and [Ti(η 5 ‐C 5 H 4 )(η 7 ‐C 7 H 6 )GeMe 2 ] ( α =22.9°, δ =161.0°) 20a,e…”