Five-Membered Titanacyclocumulenes that Contain Linked Amido−Cyclopentadienyl Ligands

The first non-metallocene five-membered titanacyclocumulene complexes (titanacyclo-2,3,4-trienes, η4-1,2,3,4-butadiyne complexes) that contain linked amido−cyclopentadienyl ligands (η5:η1-C5Me4SiMe2NtBu)Ti(η4-RC4R) (1, R = tBu; 2, R = SiMe3) were prepared by reaction of the dichloride (η5:η1-C5Me4SiMe2NtBu)TiCl2 with magnesium in the presence of the corresponding disubstituted 1,3-butadiynes. The insertion of carbon dioxide into complexes 1 and 2 was achieved, forming the dinuclear complexes {(η5:η1-C5Me4SiMe2NtBu)Ti[−OC(O)C(C⋮CR)C(R)−]}2 (3, R = tBu; 4, R = SiMe3). The structures of complexes 1, 3, and 4 were determined by X-ray diffraction.