Bridging η2 -BO in B2(BO)3(-) and B3(BO)3(-) clusters: boronyl analogs of boranes

Anion photoelectron spectroscopy and theoretical calculations are combined to probe the structures and chemical bonding of two boron-rich oxide clusters, B(5)O(3)(-) and B(6)O(3)(-), which are shown to be appropriately formulated as B(2)(BO)(3)(-) and B(3)(BO)(3)(-), respectively. The anion clusters are found to each possess a bridging η(2)-BO group, as well as two terminal BO groups and are analogs of B(2)H(3)(-) and B(3)H(3)(-). This finding advances the boronyl chemistry and helps establish the isolobal analogy between boron-rich oxide clusters and boranes.