A modified procedure for the preparation and isolation of 6,6'- ( Bl , H, , ), O leads also to the isolation of the new compound 6-Bl,H,,OH,which has been fully characterised by llB and "H n.m.r. and mass spectroscopy. The structures and some chemistry of these two related oxyboranes are compared. The reaction of either 6,6'-( B10H13),0 or 6-B