Syntheses, rearrangements, and structural analyses of unsaturated nitrogen donor ligands derived from diphenyldiazomethane and the chiral rhenium Lewis acid [(η5-C5H5)Re(NO)(PPh3)

Abstract

Diphenyldiazomethane and a labile chlorobenzene complex of [(η5-C5H5)Re(NO)(PPh3)]+ BF4- react to give the η1 adduct [(η5-C5H5)Re(NO)(PPh3)(NNCPh2)]+ BF4- (73%). When this is conducted in the presence of copper powder, a 3-phenyl-1H-indazole complex derived from carbon-hydrogen bond activation, [(η5-C5H5)Re(NO)(PPh3)(NC(Ph)CCHCHCHCHCNH)]+ BF4-, is obtained (65%). Subsequent reaction with NaOCH3 gives indazolyl complex (η5-C5H5)Re(NO)(PPh3)(NCCHCHCHCHCC(Ph)N) (85%), derived from NH deprotonation and a 1,2-rhenium shift. Crystal structures of the three new complexes are determined. DFT calculations are used to probe the mechanism of the 1,2-shift and energetics of alternative Re-N rotamers and linkage isomers, and assign bond orders and dominant resonance formulations.