Based on ab initio quantum-chemical and density functional methods we determined the geometry, electronic and structural properties of three cluster-families: boron spheres, double-rings and quasi-planars up to a cluster size of 122 atoms. The most stable structure is the B100 sphere showing similar shape but more stability than the B80 cage recently proposed by Yakobson et al [PRL 98, 166804 (2007)]. In addition we compared the stability of the three cluster families to each other, and reported the structural transition from 2D quasiplanar clusters to 3D double-rings. This transition occurs between the B16 and B19 clusters.