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

A novel one‐pot method was developed for the preparation of [Ti(η 5 ‐C 5 H 5 )(η 7 ‐C 7 H 7 )] (troticene, 1 ) by reaction of sodium cyclopentadienide (NaCp) with [TiCl 4 (thf) 2 ], followed by reduction of the intermediate [(η 5 ‐C 5 H 5 ) 2 TiCl 2 ] with magnesium in the presence of cycloheptatriene (C 7 H 8 ). 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(η 5 ‐C 5 H 4 Li)(η 7 ‐C 7 H 6 Li)] ⋅ pmdta ( 2 ) (pmdta= N , N′ , N′ , N′′ , N′′ ‐pentamethyldiethylenetriamine), and the appropriate organoelement dichlorides Cl 2 Sn(Mes) 2 (Mes=2,4,6‐trimethylphenyl), Cl 2 Sn 2 ( t Bu) 4 , Cl 2 B 2 (NMe 2 ) 2 , Cl 2 Si 2 Me 4 , and (ClSiMe 2 ) 2 CH 2 , 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(PEt 3 ) 3 ] resulted in regioselective insertion of the [Pt(PEt 3 ) 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(η 5 ‐C 5 H 4 Sn t Bu 2 )(η 7 ‐C 7 H 6 Sn t Bu 2 )E] ( 6 : E=S; 7 : E=Se). The BB bond of the bora[2]troticenophane 8 was readily cleaved by reaction with [Pt(PEt 3 ) 3 ] to form the corresponding oxidative addition product [Ti(η 5 ‐C 5 H 4 BNMe 2 )(η 7 ‐C 7 H 6 BNMe 2 )Pt(PEt 3 ) 2 ] ( 9 ). The solid‐state structures of compounds 5 , 6 , and 9 were also determined by single‐crystal X‐ray diffraction.