A novel bonding mode of the diphenylureylene ligand: synthesis, properties, and structures of mono-, bi-, and tri-nuclear diphenylureylene complexes of bis(η-cyclopentadienyl)titanium

Abstract

The reaction of [Ti(cp)₂(CO)₂](1; cp =η-C₅H₅) with PhNCO (2) gives a trinuclear diphenylureylene complex [{Ti(cp)₂}₃{OC(NPh)₂}₂](3), where two Ti(cp)₂{OC(NPh)₂} moieties are symmetrically linked to the central Ti(cp)₂ unit through the ligand oxygen atoms and each ureylene ligand chelates one titanium atom through the nitrogen atoms. The structural data and the i.r. spectrum, showing no band at >1 600 cm^–1, suggest the presence of an electronically delocalised diphenylureylene ligand. These results, together with the magnetic moment corresponding to two unpaired electrons, are in accord with the presence of two titanium(III) atoms and one titanium(IV) atom. Thermal rearrangement of (3) gives a binuclear titanium(III) complex, [{Ti(cp)₂}₂{OC(NPh)₂}](6), together with a mononuclear titanium(IV) complex [Ti(cp)₂{OC(NPh)₂}](5). An X-ray analysis has shown that the ureylene ligand in [{Ti(cp)₂}₂{OC(NPh)₂}]·C₆H₅Me (7) bridges two Ti(cp)₂ units both through the nitrogen and the oxygen atoms. The diphenylureylene moiety in (7) has the same structural features as observed in (3). Furthermore, the X-ray results for (3) and (7) show that the co-ordination geometries around the different titanium atoms are similar to that in many other Ti(cp)₂ complexes. Crystal data: (3), space group C2/c(monoclinic), a= 26.187(7), b= 8.865(3), c= 20.515(5)Å, Z= 4, R 0.095 for 805 reflections; (7), space group Fdd2 (orthorhombic), a= 19.138(2), b= 75.184(10), c= 8.553(2)Å, Z= 16, R 0.059 for 2 891 reflections.