Formation of cyanates in low-valent uranium chemistry: a synergistic experimental/theoretical study

Computational studies on the reductive activation of a mixture of CO and NO by the U(III) complex [U(?-C8H6{SiiPr3-1,4}2)(?-Cp*)], which affords a mixture of [U(?-C8H6{SiiPr3-1,4}2)(?-Cp*)]2(µ-OCN)21 and [U(?-C8H6{SiiPr3-1,4}2)(?-Cp*)]2(µ-O) 2, show that the reaction proceeds via an initial attack of CO on a µ–?2:?2 coordinated NO, side-on bridged between two uranium centres. This leads to the formation of the bridging oxo complex 2 and the cyanate radical; coordination of the latter to the starting complex and dimerisation affords 1. The DFT studies also predict the existence of the monocyanate-bridged, mixed valence species [U(?-C8H6{SiiPr3-1,4}2)(?-Cp*)]2(µ-OCN) 3, which has now been experimentally observed.