The complex hydrides formed by o-styryldiphenylphosphine (sp), HM(CO)4(sp)(M = Mn or Re), rapidly undergo intramolecular hydride addition to the free vinyl group of the ligand giving stable chelate M–C σ-bonded complexes, the direction of addition being predominantly Markownikoff in the case of manganese and anti-Markownikoff in the case of rhenium.
