In addition to the traditional metals and semimetals, elements such as boron, silicon, arsenic and selenium are considered to form organometallic compounds, e.g. organomagnesium compounds MeMgI iodo(methyl)magnesium, Et2Mg diethylmagnesium; an organolithium compound BuLi butyllithium; an organozinc compound ClZnCH2C(=O)OEt