Title full: Synthesis and characterization of some novel pentagonal bipyramidal 2,6-diacetylpyridine bis(benzoylhydrazone) (DAPBH2) complexes of Rhenium(III) and molybdenum crystal and molecular structure of [ReCl(DAPB)(PPh3)]. An investigation of the Mössbauer spectroscopy of [FeIICl2(DAPBH2)]·H2O and [FeIIICl(DAP-Me-B)(H2O)]. Reaction of [ReCl3(MeCN)(PPh3)2] with the planar pentadentate diacetylpyridinebis(benzoylhydrazone) ligands DAPBH2 and DAP-Me-BH2 and triethylamine in isopropanol under reflux gave the dark brown seven-coordinate complexes [ReCl(L)PPh3], containing the doubly deprotonated pentadentate ligand [L = DAPB(2-)(1); L = DAP-Me-B(2-) (2)]. Complex 1 has been characterized by crystallography. The central rhenium atom in 1 is seven-coordinate, with pentagonal bipyramidal geometry with the axial positions being occupied by the chloride ion and the triphenylphosphine ligand. The DAPB coordinates in a pentadentate manner in the equatorial plane of the complex and the five donor atoms of the doubly deprotonated DAPB(2-) ligand form an approximately planar pentagon. The rhenium atom is slightly displaced out of the ligand plane towards the phosphorus atom. Reaction of 2 with Ag[BF4] in CH2Cl2 at room temperature gave a black complex of stoichiometry [Re(DAP-Me-B)(PPh3)][BF4] (3). Reaction of [MoCl4(MeCN)2] with DAP-Me-BH2 and Et3N in dry CH2Cl2 under reflux gave deep green [MoCl2(DAP-MeB2)] (4), formulated as a seven-coordinate molybdenum(II) complex containing the doubly deprotonated pentadenate DAP-MeBH2 ligand in the equatorial plane of the complex. The Mössbauer spectra of the complexes [FeCl2(DAPBH2)]·H2O (5) and [FeCl(DAPMe-B)(H2O)] (6) were investigated as a function of temperature. The spectrum of 5 was consistent with high-spin seven-coordinate iron(II) and 6 was shown to contain two distinct iron(III) sites; possible structures are discussed. © 1993.
