Activation of boryl-, borylene and metalloborylene complexes by isonitriles

The reactions of isonitriles with a variety of metalloboryl and metalloborylene species are shown to yield a range of products, none of which display the typical Lewis acid–base reactivity previously observed between such metal complexes and other Lewis bases. Insertions of one, or several, isonitriles into the metal–boron bond give cyclic and spiro compounds with bonding controlled by the electron count at the metal and in the ring.