A new proposal for the electronic structure of carbon monoxide

Abstract

A new proposal for the electronic structure of carbon monoxide CO is presented. The approach involves the creation of an additional half-filled 2p orbital in the oxygen atom by the transfer of an electron from the filled 2p orbital to one of two half-filled hybridized <mml:math display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> orbitals in the carbon atom. The result is a triple bond comprising one sigma bond and two pi bonds between C and O strengthened by an ionic bond contribution. The proposed structure accounts for many unusual features of the molecule CO including the observed direction of the dipole moment, which is considered anomalous based on the concept of electronegativity of the constituent atoms as well as the increased bond dissociation energy compared with isoelectronic nitrogen <mml:math display="inline"> <mml:mrow> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> . It also provides a basis for the CO molecule being a stable ligand combining with transition metals using the lone electron pair in the filled <mml:math display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> orbital of the carbon atom. The electron transfer mechanism is effectively applied to the isoelectronic compound boron monofluoride BF and predicts properties of the undetected isoelectronic molecule BeNe. Finally, the method proposes new electronic structures for the cyanide ion <mml:math display="inline"> <mml:mrow> <mml:mi>C</mml:mi> <mml:msup> <mml:mi>N</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:mrow> </mml:math> which resolves the long-standing puzzle of “charge reversal” on the molecule and the carbon monofluoride ion <mml:math display="inline"> <mml:mrow> <mml:mi>C</mml:mi> <mml:msup> <mml:mi>F</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:mrow> </mml:math> .