Stabilization of η3-indenyl compounds by sterically demanding N,N-chelating ligands in the molybdenum coordination sphere

Abstract

A series of η³-indenyl molybdenum compounds [(η³-4,7-Me₂C₉H₅)Mo(CO)₂(^N,NL)Cl] (^N,NL = bpy, phen, pyma), isostructural with well-known η³-allyl compounds, was synthesized from the recently established halide synthon [{(η⁵-4,7-Me₂C₉H₅)Mo(CO)₂(μ-Cl)}₂]. The low stability of the hexacoordinated η³-indenyl molybdenum species in solution has been overcome by a modification of the chelating ligand. Hence, the dissociation of the compounds bearing ligands with methyl groups beside nitrogen donor atoms (e.g. 6,6′-Me₂-bpy, 2,9-Me₂-phen; 2,9-Me₂-4,7-Ph₂-phen) is strongly disfavored due to the steric requirements of the substituents. The considerable discrimination of the pentacoordinated species enables the use of [(η⁵-4,7-Me₂C₉H₅)Mo(CO)₂(2,9-Me₂-phen)][BF₄] for the assembly of derivatives bearing other halides and pseudohalides in the coordination sphere of molybdenum. The current study further describes some other new indenyl complexes accessible from [{(η⁵-4,7-Me₂C₉H₅)Mo(CO)₂(μ-Cl)}₂]. All structural types presented in this experimental study were supported by X-ray crystallographic data.