The Reaction of Unactivated Cobalt Powder with Iodophosphoranes. The Synthesis of [Co(PMe 3 ) 2 I 3 ] and the Isolation of the “Frozen Transition‐State” Complex [( n Bu 3 PI) 2 (μ‐I)] [( n Bu 3 PI)(μ‐I)CoI 3 ]

The alkyl substituents at the iodophosphorane determine the nature of the product formed in reactions with cobalt powder. Whereas Co and Me 3 PI 2 react to give the trigonal‐bipyramidal cobalt( III ) complex 1 , the reaction between Co and n Bu 3 PI 2 halts at the very unusual cobalt( II ) compound 2 . The structure of 2 , which corresponds to a possible transition state in the formation of 1 , provides an insight into the mechanistic pathway for the reaction of metal powders with dihalogen phosphoranes.