(η8‐Cyclooctatetraene)(η4‐1,2‐ and ‐1,3‐diphosphacyclobutadiene)titanium: Preparation, Structure, and Reactivity

The synthesis of the (η8‐cyclooctatetraene)(η4‐1,3‐ and ‐1,2‐diphosphacyclobutadiene)titanium complexes 3a‐c and 4a, b by cyclodimerization of the phosphaalkynes 2a‐c [a: R = tBu, b: R = adamantyl (ad), and c: R = (iPr)(Me3Si)N] in the coordination sphere of the (η8‐cyclooctatetraene)titanium complex 1 is described. The molecular structures of 3a‐c and 4a, b were determined by spectroscopic methods (31P, 1H, and 13C NMR). In the case of 3a and 4a, X‐ray analyses were carried out. The increased reactivity of 4a compared to 3a was utilized to separate 3a from 4a. Displacement of the 1,2‐diphosphete (isolated as its cyclodimer 5) from 3b was achieved by reaction with hexachlorethane.