Hexacarbonyls, electronic structure studies

Brown made a theoretical study of the electronic structure of rr-complexes of heteroaromatic systems, and predicted rr-complexes of borazoles to be less stable than the corresponding complexes of benzene (95). Although many attempts to synthesize a 7r-borazole complex were unsuccessful, Et3B3N3Me3 and Me3B3N3Et3 derivatives were later prepared from the hexacarbonyl by irradiation. [Cr(CO)3(MeftB3N3)] (LV) was eventually... 

A. Jost, B. Rees, and W. B. Yelon, Acta Crystallogr., Sect. B, 31, 2649 (1975). Electronic Structure of Chromium Hexacarbonyl at 78 K. 1. Neutron Diffraction Study. 

A mixture of molybdenum hexacarbonyl and 4-chlorophenol is effective in performing al-kyne metathesis of dipropynylated dialkylbenzenes. Alkyne metathesis of these precursors leads to the clean formation of dialkyl poly( paraphenyleneethynylene)s (PPEs) in high yield and with high molecular weights. This facile yet effective access to the PPEs has allowed study of their spectroscopic, structural, and thermal properties. While PPEs have been made before, the dialkyl-PPEs turned out to have particularly interesting optical and liquid-crystalline properties that can be explained in terms of the conformation of the main chains. The PPEs have also been utilized to construct light-emitting diodes and other semiconductor devices. This chapter discusses the interplay of structure, chromicity, and electronic properties of the dialkyl-PPEs. 

The interpretation of the structures of the simpler carbonyls was also aided by infrared spectroscopy. Chromium, molybdenum, and tungsten form hexacarbonyls of the type M(CO)6. Electron-diffraction and x-ray studies have indicated a regular octahedral structure Infrared measurements have confirmed this. 

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