Room Temperature Ring-Opening Metathesis of Pyridines by a Transient Ti⋮C Linkage

The transient titanium alkylidyne complex (PNP)Ti⋮CtBu (PNP = N[2-P(CHMe2)2-4-methylphenyl]2-), prepared from α-hydrogen abstraction of the corresponding alkylidene−alkyl species (PNP)TiCHtBu(CH2tBu), can readily cleave the CN bond of N-heterocycles such as pyridine and 4-picoline at room temperature to afford azametallabicyclic systems. Experimental and theoretical studies strongly favor a ring-opening metathesis pathway where [2 + 2] cycloaddition of pyridine across the Ti⋮C linkage ultimately leads to CN bond rupture.