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REACTION OF (DIBENZOPHOSPHOLYLLITHIUM)PENTACARBONYLMOLYBDENUM WITH PROPARGYL BROMIDE - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF A TETRACARBONYLMOLYBDENUM COMPLEX OF AN UNSYMMETRICAL CIS-BIS(DIBENZOPHOSPHOLYLETHENE)

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Abstract

Lithium dibenzophospholide (LiDBP) reacts with MO(CO)6 in tetrahydrofuran to produce (DBPLi)Mo(CO)5 (1). Compound 1 reacts with H+, BrCH2C=CH, and BrCH2CH2Br to produce (HDBP)Mo(CO)5, (2), (H-C=C-CH2DBP)Mo(CO)5, (3), and the dimer [(CO)5Mo(DBP)]2, (4), which contains a phosphorus-phosphorus bond, respectively. Compound 2 undergoes a pyridine promoted phosphorus-hydrogen addition to the carbon-carbon triple bond of compound 3 to produce (CO)5Mo[DBP-CH2-C(=CH2)DBP]Mo(CO)5, (5), which undergoes a thermal 1,3-hydrogen migration and Mo(CO)6 elimination to produce cis-[DBPCH=C(CH3)DBP]Mo(CO)4, (6). These compounds have been characterized by elemental analyses, infrared and H-1, C-13 {H-1}, P-31 {H-1} and Mo-95 NMR spectroscopy. The structures of 5 and 6 have been determined from three-dimensional X-ray data collected by counter methods. Compound 5 crystallized in the space group P1BAR with a = 12.010 (4) angstrom, b = 12.557 (3) angstrom, c = 13.174 (3) angstrom, alpha = 104.67 (2)degrees, beta = 101.10 (2)degrees, gamma = 93.54 (2)degrees, U = 1 873.2 (8) angstrom3; and Z = 2. Compound 6 crystallized in the space group P2(1)/n with a = 9.001 (3) angstrom, b = 20.090 (11) angstrom, c = 15.407 (7) angstrom, beta = 94.19 (3)degrees, U = 2 779 (2) angstrom3 , and Z = 4. The structures were refined by least-squares methods with R = 0.038 for 5 and R = 0.064 for 6 for 5 086 and 3 662 unique reflections with I/sigma(I) greater-than-or-equal-to 2.0. The Mo-P distances (2.514 (1), 2.507 (1) angstrom) are slightly different in 5 and both are longer than those (2.463 (4), 2.474 (4) angstrom) in 6. The shorter Mo-P distances in 6 are the combined result of diminished steric interactions, the chelate effect, and the greater pi-acceptor ability of the ligand

Topics: QD
Publisher: EDITIONS SCIENTIFIQUES ELSEVIER
OAI identifier: oai:wrap.warwick.ac.uk:20980
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