Synthesis of Heterobimetallic Metal Derivatives: a Carbene Complex as Chelate Ligand

The carbene complex (4‐hydroxybenzoxazol‐2‐ylidene)pentacarbonyl tungsten ( 2b ) has been synthesized from [(CO) 5 W‐C≡N‐C 6 H 3 (OSiMe 3 ) 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 [Cp 2 MoCl 2 ] 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.