Synthesis and antibody-labeling studies with the p-isothiocyanatobenzene derivatives of 1,2-dicarba-closo-dodecarborane(12) and the dodecahydro-7,8-dicarbanido-undecaborate(-1) ion for neutron-capture therapy of human cancer. Crystal and molecular structure of Cs+[nido-7-(p-C6H4NCS)-9-I-7,8-C2B9H11]