Synthesis and Substituent Interactions of Tricarbonylchromium‐complexed Arylalkynylbenzenes — Novel Organometallic Push‐pull Chromophores

Abstract

Abstract The tricarbonylchromium complexes chlorobenzene 1 reacts with terminal alkynes 2 through a palladium‐copper‐catalyzed coupling to give a variety of Cr(CO) 3 ‐complexed phenylethynyl arenes, heteroarenes and ferrocene 3 in good to excellent yield. Due to the electron‐withdrawing nature 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 analysis of the singly Cr(CO) 3 ‐complexed tolane 3e reveals a strong deviation from coplanarity of both phenyl rings by an angle of 50.9(2)° presumably due to crystal packing. Correlations are established between selected substituent parameters (σ P , σ I , σ R , σ P+ and Δ π ) and the carbonyl carbon resonances in the 13 C‐NMR spectra for the complexes 3 . The overall electronic substituent effect is transmitted to the carbonyl groups by both mesomeric and inductive mechanisms. The push‐pull complexes 3 display relatively small negative solvochromicities of longest wavelength absorption band (MLCT band).