Linearly Bridging N2 versus CO: Chemical Bonding and Spin‐Controlled Reactivity.

Abstract

AbstractThe synthesis of the linearly N2 bridged, dichromium complex [(μ‐N2){Cr(PNP)}2] (PNP=N(CHCHPtBu2)2) is reported. Experimental and computational data favor a three‐spin electronic structure model with high‐spin CrII ions that are antiferromagnetically coupled to an N22− bridge due to spin‐polarized backbonding. Reaction with CO gave isocarbonyl complex [(PNP)(CO)2Cr(μ‐CO)Cr(PNP)] and [(PNP)(CO)2Cr(μ‐N2)Cr(PNP)] could be trapped as intermediate. The latter is best described by a (ls‐CrI)(N2−)(hs‐CrII) ground state model, while more covalent bonding with the CO bridge is reflected by a (ls‐Cr0)(CO0)(hs‐CrII) electronic structure description. The selectivity of the carbonylation reaction is attributed to a spin transition after binding of the first CO ligand to [(μ‐N2){Cr(PNP)}2].