New Heterobinuclear μ-Oxo-Bridged Dimer Complexes: Synthesis, Characterization and Structural Studies of a Macrocyclic Titanyl Complex and its Adducts

Abstract

The titanyl complex, TiO(C22H22N4), a complex of the ligand (I) obtained by the hydrolysis of the corresponding dichloride, has a reactive Ti=O function which readily interacts with other metal species forming μ-oxo heterobinuclear dimers. In these adducts, the Ti=O functions as a base toward oxophilic metal centres such as Fe(lII) and as a π-acid, analogous to the carbonyl group, forming an adduct with a low valent species such as the Mo(CO)5 group, yielding a Ti(IV)-O-Mo linkage. Crystals of the titanyl complex, TiO(C22H22N4).C2O2H6, are monoclinic, P21/C with a = 23.083(3), b = 7.740(7), c = 23.208(5) Å, β = 96.54. (2) and d(calcd) = 1.443 g cm −3 for Z = 4. The Ti=O distance is 1.653(3) Å with a large displacement of 0.754(3) Å for the Ti atom from the N4 macrocyclic coordination plane. The adduct of the titanyl complex with Fe(SALEN)Cl, SALEN = (salicylaldimine)ethylenediamine, in the presence of NaB(C6H5)4 yields a μ-oxo-heterobinuclear complex_of stoichiometry (C22H22N4)Ti-O-Fe- (SALEN)B(C6H5)4. Crystals of the complex are triclinic, P1 with a = 13.122(4), b = 13.883(12), c = 14.539(5) Å, a = 94.21(5), β = 93.08(3), γ = 99.46(3)° with d(calcd) = 1.336gem−3 for Z = 2. In addition to the expected dimeric Ti-O-Fe structure, weak interactions between the SALEN oxygen atoms and the iron atom of the centrosymmetrically related Fe(SALEN) group yields a tetrameric cluster, The Ti-O distance of the Ti-O-Fe linkage is lengthened to 1.706(4) Å and the Fe-O distance is 1.935(6) Å with the Ti-O-Fe angle 160.9(2)°. The Fe-O “intramolecular” interaction distance, 2.178 Å, is indicative of a weak bond.