Titanyl complexes with 1,10-phenanthroline-based diols

The reaction of the O,N,N,O-type ligands, namely, 4,7-bis(4-tert-butylphenoxy)2-2,9-(HOCRR’CH)2-1,10-phenanthrolines, LH2 (R = R′ = Ph (1), RR′ = −(CH2)5− (2), 2,2-adamantylene (3)), with an equimolar amount of Ti(OPri)4 in toluene under mild conditions afforded the mixtures of the corresponding titanium LTi(OPri)2(4–6) and titanyl complexes LTi=O (7–9). Subsequent reflux of these mixtures in toluene gave pure derivatives 7–9, which were characterized by 1H and 13C NMR spectroscopy and elemental analysis. The presence of the Ti=O fragment in molecules 7–9 was unambiguously confirmed by IR spectroscopy data and was found to be consistent with the data of quantum chemical calculations. The new ligand 3 was obtained by sequential treatment of 4,7-di(4-tert-butylphenoxy)-2,9-dimethyl-1,10-phenanthroline with an excess of lithium diisopropylamide and adamantan-2-one. The titanyl complex 7 was found to be moderately active as an initiator of ε-caprolactone polymerization.