Synthesis, structure, electronic properties and thermal behavior of butadiynyl substituted phenylCr(CO)3-complexes

Butadiynyl-substituted η⁶-benzeneCr(CO)₃ complexes 3 are very efficiently prepared by a copper catalyzed coupling of the phenylacetylene complex 1 and bromo alkynes 2. The transmission of electronic effects through the butadiynyl bridge operates by resonance mechanisms as established by correlations between Hammett's σ_p, σ_R and σ_P⁺ parameters. Most interestingly, however, is an unusual thermal behavior that leads to intractable paramagnetic polymers of unknown structure. According to thermal analyses (thermal gravimetrical analysis, differential scanning calorimetry) the complexes 3 react in a thermal solid-state reaction under CO extrusion to give amorphous cross-linked polymers.