Synthesis, Reactivity and Ring-Opening Polymerization of a Tin-Bridged ansa-Cycloheptatrienyl-Cyclopentadienyl Titanium Sandwich Complex

The tBu2Sn-bridged [1]troticenophane [(eta 7-C7H6)Ti(?5-C5H4)]SntBu2 (2) has been synthesized by low-temperature salt elimination reaction between stoichiometric amounts of the dilithiated troticene [(eta 7-C7H6Li)Ti(eta 5-C5H4Li)]center dot pmdta (1; pmdta = N,N',N',N?,N?-pentamethyltriethylenetriamine) and tBu2SnCl2. Compound 2 was isolated as a blue-green crystalline solid in moderate yield and characterized by multinuclear 1H, 13C and 119Sn NMR spectroscopy, UV/Vis spectroscopy and elemental analysis. Compound 2 and the co-crystal 2 center dot[(pmdta)LiCl] were characterized in the solid state by X-ray diffraction analyses. The dihedral angles between the planes of the C5H4 and C7H6 rings are 16.3(3) and 17.2(1)degrees, respectively, for 2 and its co-crystal. Compound 2 is the first monocrystalline structurally characterized heteroleptic stanna[1]troticenophane. The reaction of 2 with [Pt(PEt3)3] afforded the platinastanna[2]troticenophane 3, in which the Pt0 fragment was inserted by regioselective cleavage of the ipso-C7H6Sn bond, as evidenced by 13C NMR spectroscopy and X-ray diffraction analysis. Compound 2 underwent thermal ring-opening polymerization in the solid state to form poly(troticenylstannane) 4. In solution and in the presence of nBuLi as initiator, 2 opens and reassembles to form the metallopolymer 5. The polymeric nature of both 4 and 5 was determined by gel permeation chromatography.