The reaction of bromo- and iodo-phosphoranes with unactivated coarse grain manganese metal powder to yield [MnI2(phosphine)2] and [{MnX2(phosphine)}n](X = Br or I) by insertion of Mn into the P–X bond. The crystal structure of [MnI2(PPh3)2]

Abstract

The novel reaction of crude manganese metal powder with dibromo- and diiodo-phosphoranes, R₃PX₂, has been studied. Reaction of the phosphoranes R₃PI₂(R = phenyl or substituted aryl) with manganese allows insertion of the metal into P–X bonds and gives the monomeric tetrahedral complexes [MnI₂(PR₃)₂] and MnI₂. However, reaction of R₃PX₂(R₃= mixed aryl/alkyl, trialkyl; X = Br or I) with manganese, whilst once again proceeding via insertion into P–X bonds, now leads to the quantitative isolation of the polymeric complexes [{MnX₂(PR₃)}_n], thus illustrating the subtle nature of these reactions. Examples of both types of complex have been crystallographically characterised and represent rare examples of such. There is some evidence that where R₃= Ph₂Me an equilibrium exists and both types of complex, [MnI₂(PPh₂Me)₂] and [{MnI₂(PPh₂Me)}_n] can be detected from the same reaction.