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 MOSSBAUER-SPECTROSCOPY OF [FEIICL2(DAPBH2)].H2O AND [FEIIICL(DAP-ME-B)(H2O)]

Reaction of [ReCl3(MeCN)(PPh3)2], with the planar pentadentate diacety lpyridinebis(benzoylhydrazone) ligands DAPBH2 and DAP-Me-BH2 and triet hylamine in isopropanol under reflux gave the dark brown seven-coordin ate complexes [ReCl(L)PPh3], containing the doubly deprotonated pentad entate ligand [L = DAPB(2-) (1); L = DAP-Me-B(2-) (2)]. Complex 1 has been characterized by crystallography. The central rhenium atom in 1 i s seven-coordinate, with pentagonal bipyramidal geometry with the axia l positions being occupied by the chloride ion and the triphenylphosph ine ligand. The DAPB coordinates in a pentadentate manner in the equat orial plane of the complex and the five donor atoms of the doubly depr otonated DAPB(2-) ligand form an approximately planar pentagon. The rh enium atom is slightly displaced out of the ligand plane towards the p hosphorus atom. Reaction of 2 with Ag[BF4] in CH2Cl2 at room temperatu re 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 und er reflux gave deep green [MoCl2(DAP-MeB2)] (4), formulated as a seven -coordinate molybdenum(II) complex containing the doubly deprotonated pentadentate DAP-MeBH2 ligand in the equatorial plane of the complex. The Mossbauer spectra of the complexes [FeCl2(DAPBH2)].H2O (5) and [Fe C](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.