CONFORMATION OF THE DIMETHYL MALEATE LIGANDS IN A MOLYBDENUM(0) COMPLEX - CRYSTAL-STRUCTURE OF D(6) TRANS-BIS(DIMETHYL ALEATE)-DICARBONYL-O-PHENYLENEDIAMINEMOLYBDENUM(0)

The solid-state structure of Mo(CO)2(DMMA)2(PDA) (DMMA = dimethyl male ate, PDA = o-plienylenediamine) 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) angstrom, gam ma = 120-degrees, and Z = 6. The geometry of this bis(DMMA) complex is distorted octahedral with the two CO groups cis to each other and tra ns 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 liga nds are mutually perpendicular and each DMMA ligand eclipses an N-MoCO vector. The carbon-carbon double bond of DMMA is bonded to molybdenum unsymmetrically with the olefin carbon adjacent to a coordinated amin o group closer to the metal than that adjacent to a carbonyl group. Th e conformation of each DMMA is that the two ester groups attached to D MMA lie in the regions described by N-Mo-C and N-Mo-N. Bond-distance c alculations indicate that each keto oxygen of the ester groups in the region described by N-Mo-C forms a hydrogen bond with an amino hydroge n on the PDA ligand; this hydrogen bonding is responsible for the obse rved conformation of the complex. The conformation of this complex in the solid-state is in agreement with (the results in solution predicte d according to H-1 NMR spectral data.