Reactions of methyl-substituted titanocene–bis(trimethylsilyl)acetylene complexes with acetone azine: crystal structures of (η5:η1-C5HMe3CH2CMe2NH)2Ti and (C5Me5)2Ti(NCMe2)

The titanocene–bis(trimethylsilyl)acetylene (BTMSA) complexes Cp′2Ti[η2-C2(SiMe3)2] (Cp′C5H5−nMen; n=0–5) react with acetone azine Me2CNNCMe2 (AA) in two different ways depending on the number of Me substituents at the Cp′ ligands (n). For n=0–2, BTMSA is replaced by AA, which then undergoes an oxidative addition accompanied by a proton transfer, affording titana-2-isopropyl-4-methyl-2,3-diazacyclopent-3-ene complexes A0–A2. For n=3–5, replacement of the acetylene is followed by the splitting of AA to give either (C5Me5)2Ti(III)(NCMe2) (C5) or the Ti(IV) (Cp′A)2Ti complexes B3 and B4 for n=3 and 4, respectively. The intramolecularly bridging Cp′A ligand 1-(η5-2,3,5-trimethylcyclopentadienide)-2-(η1-amide)-2,2′-dimethylethane arises from a formal insertion of the CN bond of isopropylidene amide into a CH bond of one methyl group of the cyclopentadienyl ligands before or after splitting of AA. Crystal structures of C5 and (η5:η1-C5HMe3CH2CMe2NH)2Ti(IV) (B4) were determined.