We have obtained a new molecular metal containing a rare-earth complex anion, g "-(BO) 2 [YbCl 4 (H 2 O) 2 ]. This salt retains metallic conductivity down to 4 K. This crystal is metastable at room temperature; it gradually tranforms into another phase, f -(BO) 2 [YbCl 4 (H 2 O) x ], which becomes insulating below 210 K. The g "-phase crystal have a chain structure of the anions, formed by OHCl hydrogen bonding. This is the first example of a ~ molecular conductor based on an assembled rare-earth complex. Preparation, structure and resistivity of (BO) 2 [YbCl 4 (H 2 O) x ] system is reported. Rare-earth molecular conductors structure f -electrons