Synthesis of polymetallic Group 4 complexes bridged by benzenediolate and triolate ligands. X-ray crystal structure of [{Ti(C5Me5)Cl2}2{μ-1,4-O(2,3-C6H2Me2)O}]

This paper reports the synthesis of polymetallic complexes in which two or three Group 4 metals are linked to a benzene core through oxo groups. Four methods have been evaluated for the synthesis of such derivatives: from the appropriated alcohol with (a) methyl complexes via methane elimination, (b) chloride compounds in the presence of a Lewis base, or (c) a zirconium hydride, and (d) from the lithium salt of the alcohol and chloride complexes. Method a has been used for the synthesis of bimetallic and trimetallic (pentamethylcyclopentadienyl)titanium(IV) complexes [{Ti(C5Me5)Cl2}2{μ-1,4-O(C6H2XY)O}] (X=Y=H (1); X=H, Y=Me (2); X=Y=Me (3)), [{Ti(C5Me5)Me2}2{μ-1,4-O(C6H2Me2)O}] (4), and [{Ti(C5Me5)X2}3(μ3-1,3,5-C6H3O3)] (X=Cl (7), Me (8)) from the corresponding hydroquinones 1,4-HO(2,3-C6H2XY)OH (X=Y=H, Me; X=H, Y=Me) or 1,3,5-trihydroxibenzene and [Ti(C5Me5)Cl2Me] or [Ti(C5Me5)Me3], respectively. Bis(cyclopentadienyl)titanium bimetallic complex [{Ti(C5H5)2Cl}2{μ-1,4-O(C6H2Me2)O}] (5) is better prepared by method d by treatment of the dilithium salt Li2[1,4-O(2,3-C6H2Me2)O] with [Ti(C5H5)2Cl2] whereas the trimetallic compound [{Ti(C5H5)2Cl}3(μ3-1,3,5-C6H3O3)] (9) can be prepared directly from 1,3,5-trihidroxybenzene in the presence of NEt3 (method b). Finally, bis(cyclopentadienyl)zirconium complexes [{Zr(C5H5)2Cl}2{μ-1,4-O(C6H2Me2)O}] (6) and [{Zr(C5H5)2Cl}3(μ3-1,3,5-C6H3O3)] (10) are obtained from [Zr(C5H5)2ClH] (method c). The structure of complex 3 has been determined by X-ray diffraction methods.