Reactivity of Transition Metal Gallylene Complexes Toward Substrates with Multiple Carbon–Element Bonds

Reactivity of transition metal complexes containing the
redox-active
gallylene (dpp-bian)Ga ligand (dpp-bian = 1,2-bis­[(2,6-diisopropylphenyl)­imino]­acenaphthene)
toward isocyanide, isocyanate, isothiocyanate, and ketene substrates
is described. The reaction of [(dpp-bian)­GaCr­(CO)5] (1) with tBuNC results in a dative complex [(dpp-bian)­Ga­(CNtBu)­Cr­(CO)5] (2), while compound [(dpp-bian)­GaCr­(CO)5]2[Na­(THF)2]2 (3) reacts with tBuNC to give the coordination polymer [(dpp-bian)­GaCr­(CO)5]­[Na­(CNtBu)­(THF)]n (5). Treatment
of [(dpp-bian)­GaCr­(CO)5]2[Na­(THF)2]2 with an excess of PhNCO results in trimerization of
the latter and formation of complex [(dpp-bian)­GaCr­(CO)5]­[Na­(PhNCO)3(Et2O) (DME)] (4).
[(dpp-bian)­GaFeCp­(CO)2] (7) treated with Ph2CCO or PhNCS results in cycloaddition products [(dpp-bian)­(Ph2CCO)­GaFeCp­(CO)2] (8) and [(dpp-bian)­(PhNCS)­GaFeCp­(CO)2] (9). The formation of 2 and 9 was found to be reversible, which offers a means for facile
regulation of transition metal center reactivity and cooperative substrate
activation. New compounds were characterized by EPR (2), NMR (4, 8, and 9), and
IR spectroscopy (2, 4, 5, 8, and 9). The molecular structures of 2, 4, 5, 8, and 9 were established by single-crystal X-ray diffraction analysis.
Electronic structures of the compounds have been examined by DFT calculations.