W(CO)5–Pyridine-π-acceptor complexes: synthesis, structure and electronic absorption spectra

W(CO)5-complexes of 3-(4-pyridyl)propenal (1b), 5-(4-pyridyl)penta-2,4-dienal (1c), dimethyl (4-pyridylmethylene)malonate (2a), methyl 2-cyano-3-(4-pyridyl)acrylate (2b) and (4-pyridylmethylene)malononitrile (2c) have been synthesised. The molecular structures of 2b and 2c have been determined by X-ray diffraction. Significant distortions from the coplanarity of the WN bond and the pyridine rings planes were observed in both structures. Electronic absorption spectra of 1b–c and 2a–c display red-shifted MLCT bands and a strong solvatochromism.