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

The t Bu 2 Sn‐bridged [1]troticenophane [(η 7 ‐C 7 H 6 )Ti(η 5 ‐C 5 H 4 )]Sn t Bu 2 ( 2 ) has been synthesized by low‐temperature salt elimination reaction between stoichiometric amounts of the dilithiated troticene [(η 7 ‐C 7 H 6 Li)Ti(η 5 ‐C 5 H 4 Li)] · pmdta ( 1 ; pmdta = N , N′ , N′ , N″ , N″ ‐pentamethyltriethylenetriamine) and t Bu 2 SnCl 2 . Compound 2 was isolated as a blue‐green crystalline solid in moderate yield and characterized by multinuclear 1 H, 13 C and 119 Sn NMR spectroscopy, UV/Vis spectroscopy and elemental analysis. Compound 2 and the co‐crystal 2· [(pmdta)LiCl] were characterized in the solid state by X‐ray diffraction analyses. The dihedral angles between the planes of the C 5 H 4 and C 7 H 6 rings are 16.3(3) and 17.2(1)°, 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(PEt 3 ) 3 ] afforded the platinastanna[2]troticenophane 3 , in which the Pt 0 fragment was inserted by regioselective cleavage of the ipso ‐C 7 H 6 –Sn bond, as evidenced by 13 C 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 n BuLi 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.