SYNTHESIS AND SUBSTITUENT INTERACTIONS OF TRICARBONYLCHROMIUM-COMPLEXED ARYLALKYNYLBENZENES - NOVEL ORGANOMETALLIC PUSH-PULL CHROMOPHORES

The tricarbonylchromium complexes chlorobenzene 1 reacts with terminal alkynes 2 through a palladium-copper-catalyzed coupling to give a var iety of Cr(CO)(3)-complexed phenylethynyl arenes, heteroarenes and fer rocene 3 in good to excellent yield. Due to the electron-withdrawing n ature of the Cr(CO)(3) group these novel complexes can be regarded as organometallic push-pull chromophores. Analogously, the corresponding free ligands 4 (phenylethynyl arenes, heteroarenes and ferrocene) were synthesized by coupling iodobenzene and 2. The crystal structure anal ysis of the singly Cr(CO)(3)-complexed tolane 3e reveals a strong devi ation from coplanarity of both phenyl rings by an angle of 50.9(2)degr ees presumably due to crystal packing. Correlations are established be tween selected substituent parameters (sigma(P), sigma(I), sigma(R), s igma(P+) and Delta(x)) and the carbonyl carbon resonances in the C-13- NMR spectra for the complexes 3. The overall electronic substituent ef fect is transmitted to the carbonyl groups by both mesomeric and induc tive mechanisms. The push-pull complexes 3 display relatively small ne gative solvochromicities of longest wavelength absorption band (MLCT b and).