 The most common oxidation states of platinum are + 2 and + 4 . The + 1 and + 3 oxidation states are less common , and are often stabilized by metal bonding in bimetallic ( or polymetallic ) species . As is expected , tetracoordinate platinum ( II ) compounds tend to adopt 16 @-@ electron square planar geometries . Although elemental platinum is generally unreactive , it dissolves in hot aqua regia to give aqueous chloroplatinic acid ( H2PtCl6 ) : 
