Coordinating Tectons 4: Coordination Chemistry of the 4,5-Diazafluoren-9-yl Moiety as a Metallo-Ligand for Allenylidene Complexes

We describe how the 4,5-diazafluoren-9-yl moiety has been utilized in the construction of multinuclear complexes incorporating a ruthenium­(II) allenylidene functionality. The coordination chemistry of diazafluorenyl-terminated allenylidene complexes is limited by the sensitivity (instability) of the allenylidene moiety under a variety of synthetic conditions. In contrast the κ2-N,N′-coordination of the diazafluorenyl propargylic alcohol (alkynol) to a metal center prior to allenylidene formation provides a facile route toward the synthesis of multinuclear allenylidene coordination complexes. Our synthetic attempts and successes are discussed in combination with spectroscopic and electronic characterization of the latter cases.