text: By metal vapor synthesis, metal atoms co-condensed with arenes react to give complexes of the type M(arene).  Cr(CH) can be produced by this method.
  Cr(CO) reacts directly with benzene and other arenes to give the piano stool complexes Cr(CR)(CO). The carbonyls of Mo and W behave comparably. The method works particularly well with electron-rich arenes (e.g., anisole, mesitylene). The reaction has been extended to the synthesis of [Mn(CR)(CO)]:
  :BrMn(CO)  +  Ag  +  CR  →   [Mn(CR)(CO)]  +  AgBr  +  2 CO