Selective Reaction of Aminorhenium Complexes and the Formation of Cp‐N‐P Tridentate Complexes

Rhenium complexes containing cyclopentadienyl‐amino‐phosphanyl tridentate ligands have been prepared starting from a cyclopentadienyl‐amino bidentate complex in a controlled manner. Dehydrobromination of [η 5 :η 1 ‐C 5 H 4 CH 2 CH 2 NH(CH 3 )Re(CO) 2 Br] + ( 2 ) was carried out selectively at low temperature to give an exocyclic iminorhenium complex [η 5 :η 1 ‐C 5 H 4 CH 2 CH 2 N(=CH 2 )Re(CO) 2 ] ( 5 ). Selective N ‐methylation provided a cationic heterocyclopropane complex 8 which reacted with various nucleophiles ( t BuNH 2 , NaOCH 3 , KPPh 2 ) to give precursors for tridentate complexes. A formal oxidation of the carbonyl ligand to a labile carbon dioxide ligand was accomplished by oxidation with peroxy acid. Intramolecular N ligand displacement furnished the Cp‐N‐P tridentate complex. The relative stability of the N, P and CO ligands was revealed when an η 3 ‐allyl ligand was formed. The N ligand became detached from the metal rather than the P or CO ligands as the η 1 ‐allyl was transformed to the corresponding η 3 ‐allyl coordination mode. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)