Synthesis of heterobimetallic metal derivatives: A carbene complex as chelate ligand

Article abstract of DOI:10.1002/zaac.200300078

The carbene complex (4-hydroxybenzoxazol-2-ylidene)-pentacarbonyl tungsten (2b) has been synthesized from [(CO)₅W-C≡N-C₆H ₃(OSiMe₃)₂-2,6] by Si-O bond cleavage and subsequent intramolecular cyclization. Compared to 2-aminophenol the acidity of the NH/OH protons is inverted in 2b. Consequently, the stepwise monodeprotonation/methylation of 2b yields exclusively the N-alkylated complex 3. A second deprotonation/methylation gives the N- and O-alkylated complex 4. Complex 4 can be obtained directly from 2b by treatment of with two equivalents of base and two equivalents of MeI. In the presents of one equivalent of base 2b reacts with [Cp₂MoCl₂] under formation of the heterobimetallic chelate complex μ ²-N,O-molybdocene-4-oxobenzoxazol-2-ylidene)-pentacarbonyl tungsten 5. Complexes 2b, 3, 4 and 5 were characterized by X-ray crystallography.