Synthesis and Reactivity of Boron-, Silicon-, and Tin-Bridged ansa-Cyclopentadienyl–Cycloheptatrienyl Titanium Complexes (Troticenophanes)

摘要

A novel one-pot method was developed for the preparation of [Ti(η5-C₅H₅)(η7-C₇H₇)] (troticene, 1) by reaction of sodium cyclopentadienide (NaCp) with [TiCl₄(thf)₂], followed by reduction of the intermediate [(η5-C₅H₅)₂TiCl₂] with magnesium in the presence of cycloheptatriene (C₇H₈). The [n]troticenophanes 3 (n=1), 4, 8, 10 (n=2), and 11 (n=3) were synthesized by salt elimination reactions between dilithiated troticene, [Ti(η5-C₅H₄Li)(η7-C₇H₆Li)]pmdta (2) (pmdta=N,N′,N′,N′′,N′′-pentamethyldiethylenetriamine), and the appropriate organoelement dichlorides Cl₂Sn(Mes)₂ (Mes=2,4,6-trimethylphenyl), Cl₂Sn₂(tBu)₄, Cl₂B₂(NMe₂)₂, Cl₂Si₂Me₄, and (ClSiMe₂)₂CH₂, respectively. Their structural characterization was carried out by single-crystal X-ray diffraction and multinuclear NMR spectroscopy. The stanna[1]- and stanna[2]troticenophanes 3 and 4 represent the first heteroleptic sandwich complexes bearing Sn atoms in the ansa bridge. The reaction of 3 with [Pt(PEt₃)₃] resulted in regioselective insertion of the [Pt(PEt₃)₂] fragment into the SnC_ipso bond between the tin atom and the seven-membered ring, which afforded the platinastanna[2]troticenophane 5. Oxidative addition was also observed upon treatment of 4 with elemental sulfur or selenium, to produce the [3]troticenophanes [Ti(η5-C₅H₄SntBu₂)(η7-C₇H₆SntBu₂)E] (6: E=S; 7: E=Se). The BB bond of the bora[2]troticenophane 8 was readily cleaved by reaction with [Pt(PEt₃)₃] to form the corresponding oxidative addition product [Ti(η5-C₅H₄BNMe₂)(η7-C₇H₆BNMe₂)Pt(PEt₃)₂] (9). The solid-state structures of compounds 5, 6, and 9 were also determined by single-crystal X-ray diffraction.