The tetratolylporphyrinato complex, (TTP)TiCl2, oxidatively couples lithium acetylide reagents (LiC⋮CR; R = Ph, SiMe3) to 1,3-butadiyne products. The reduced Ti(II) fragment scavenges the diyne to form an η2-complex involving π-bonding to only one of the alkyne units, (TTP)Ti(1,2-η2-RC⋮C−C⋮CR). Independent syntheses of the diyne complex starting from (TTP)TiCl and (TTP)Ti(η2-EtC⋮CEt) confirm the composition of the π-adduct. The lability of the butadiyne ligand in these Ti porphyrin complexes is readily demonstrated by displacement with pyridine.
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