A series of bis- and tris(oxobenzimidazolyl)hydroborato compounds, namely, [Bo(RBenz)]Na and [Bo(RBenz)]Na (R = Me, Bu-t, Ad), which feature uncommon sterioally demanding LX [O-2] and L2X [O-3] donor ligands, have been obtained, via the reactions of NaBH4 with 1-R-1,3-dihydro-2H-benzimidazol-2-ones. Evidence that the alkyl substituents are suitably located to have a significant impact on the coordination environment is provided "by the observation that the methyl derivative [To(MeBenz)]Na(kappa(3)-diglyme) exhibits kappa(3)-coordination of the diglyme, whereas the t-butyl and adamantyl derivatives, [To(Bu'Benz)]Na(kappa(2)-diglyme) and [To(AdBenz)]Na(kappa(2)-diglyme), exhibit K2-coordination. The [Bo(RBenz)] and [To(RBenz)] ligands also allow for isolation of discrete mononuclear thallium compound's, [Bo(RBenz)]Tl and [Bo(RBenz)]Tl, for which "the steric demands of the ligands'have been quantified in terms of both cone angle and buried volume concepts.