Grubbs and Hoveyda-Type Ruthenium Complexes Bearing a Cyclic Bent-Allene.

Stable cyclic bent-allene 1 displaces the chelating ether linkage of the Hoveyda-Grubbs-type ruthenium complex 2 bearing triphenylphosphine. The resulting complex 3 features an unusual cis-arrangement of the phosphine and the cyclic bent-allene, while retaining a distorted square pyramidal geometry around the ruthenium center. Monitoring by (31)P NMR spectroscopy the reaction of cyclic bent-allene 1 with the indenylidene bis(triphenylphosphine)ruthenium dichloride complex 4 allowed for the observation of dissociated triphenylphosphine, and the formation of a ruthenium complex featuring 1 and triphenylphosphine in the desired trans-configuration. However, continued reaction times saw the disappearance of this complex, and after workup complex 5 featuring a cis-arrangement was isolated.