Main group monocarbonyls

Non-local density functional calculations are used to investigate the prope rties and bonding of the monocarbonyl complexes of the s- and p-block main group elements of the first five periods. There is good agreement between t he calculated properties and those of experimentally observed monocarbonyls . Predictions of the vibrational frequencies and stabilities of, as yet, un known complexes are given. A bonding model involving synergistic M <-- CO s igma -donation and M CO pi -backbonding analogous to that used for transiti on metal carbonyls is described. It is used to describe the variations in t he properties of these systems within the groups and periods of the main gr oup elements. The limitations of this description when applied to electron- poor and electron-rich main group MCO molecules are outlined. The bonding i n the s-block monocarbonyls is dominated by the repulsive a-interaction bet ween the metal s-electrons and the CO lone pair. In the monocarbonyls of el ectronegative elements, there is significant involvement of the filled pi - level on CO. (C) 2001 Elsevier Science B.V. All rights reserved.