Conformation of the Dimethyl Maleate Ligands in a Molybdenum(0) Complex. Crystal Structure of d6trans‐Bis(Dimethyl Maleate)‐Dicarbonyl‐O‐Phenylenediaminemolybdenum(O)

Abstract

AbstractThe solid‐state structure of Mo(CO)2(DMMA)2(PDA) (DMMA = dimethyl maleate, PDA = o‐phenylenediamine) was determined by X‐ray diffraction of single crystal. The complex crystallizes in the hexagonal space group P6122 with a = 11.085(5), b = 11.085(5), c = 33.653(21) Å, γ = 120°, and Z = 6. The geometry of this bis(DMMA) complex is distorted octahedral with the two CO groups cis to each other and trans to the PDA ligand and the two DMMA ligands trans to each other and cis to the two CO ligands. The orientations of the two trans DMMA ligands are mutually perpendicular and each DMMA ligand eclipses an N‐Mo‐CO vector. The carbon‐carbon double bond of DMMA is bonded to molybdenum unsymmetrically with the olefin carbon adjacent to a coordinated amino group closer to the metal than that adjacent to a carbonyl group. The conformation of each DMMA is that the two ester groups attached to DMMA lie in the regions described by N‐Mo‐C and N‐Mo‐N. Bond‐distance calculations indicate that each keto oxygen of the ester groups in the region described by N‐Mo‐C forms a hydrogen bond with an amino hydrogen on the PDA ligand; this hydrogen bonding is responsible for the observed conformation of the complex. The conformalion of this complex in the solid‐state is in agreement with the results in solution predicted according to 1H NMR spectral data.