Fused ring systems derived from reactions of half-open titanocenes with diynes: Syntheses, characterization, cage rearrangements, and structural studies

Half-open titanocenes, Ti(C5H5)(pentadienyl)(PR3), react with 1,5-hexadiyne, 1,6-heptadiyne, and several heteroatom-substituted analogues, leading to couplings between the two diyne and two 2,4-C7H11 termini, generating nine-membered rings fused to four- or five-membered rings. The resulting 16 electron complexes can undergo subsequent cage rearrangements, via CC bond activations.