SYNTHESIS, STRUCTURE, AND REACTIVITY OF ZEROVALENT GROUP-6 METAL PENTACARBONYL ARYL OXIDE COMPLEXES - REACTIONS WITH CARBON-DIOXIDE
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The synthesis of [Et4N] [M(CO)5OR] (M = Cr, Mo, W; R = Ph, C6H4CH,-m) from the reaction of M(CO)5THF and [Et4N] [OR] in tetrahydrofuran is reported. In the absence of a carbon monoxide atmosphere these mononuclear species readily aggregate via a CO dissociation pathway to the tetranuclear species [Et4N]4[M(CO)3OR]4. It was possible to isolate pure crystalline samples of the [Et4N] [W(CO)5OR] derivatives by precipitation from solutions under a carbon monoxide atmosphere. The [Et4N][W(CO)5OPh] complex was characterized in the solid-state by X-ray crystallography. [Et4N][W-(CO)jOPh] crystallizes in the space group PI with cell dimensions a = 9.416 (3) , b = 12.665 (2) , c = 18.371 (3) , = 92.38 (1), = 94.50 (2), = 95.85 (2), V = 2168.3 3, Z = 4, and Rf = 7.71%. An additional salt of the tungsten phenoxide complex has been crystallized that contains 0.5 equiv of water, i.e., [Et4N][W(CO)5OPh*0.5H2O]. This species has as well been characterized by X-ray crystallography. [Et4N] [W(CO)5OPh.0.5H2O] crystallizes in the space group P21/c with cell dimensions a = 17.545 (5), b = 25.322 (8), c = 10.337 (3), = 102.52 (3), V= 4483 (2) 3, Z = 8, and RF = 5.60%. The water molecule is shown to be hydrogen bonded between ligated-OPh ligands of adjacent W(CO)5OPh-anions. This intermolecular hydrogen-bonding interaction is observed in tetrahydrofuran solution as well between alcohols and W(CO)5OPh-. The M(CO)5OR-(M = Cr, W) derivatives were demonstrated to undergo facile insertion reactions with CO2, COS, and CS2 to afford the corresponding metal pentacarbonyl phenyl carbonate, phenyl thiocarbonate, and phenyl dithiocarbonate complexes. This carbon dioxide insertion reaction is reversible, and the rate of insertion is unaffected by carbon monoxide pressures up to 10 atm. The relative rates of insertion of CO2, COS, and CS2 into the M(CO)5OPhanions are Cr > W and CS2 > COS > CO2. On the other hand, in the presence of ligands at the metal center that are sterically more demanding than CO, i.e., cis-M(CO)4(L)OPh-derivatives, the relative rates of carbon dioxide insertion are W > Cr and L = P(OMe)3 > PMe3 > PPh3. The W(CO)5XC(X)OPh-(X = O or S) derivatives underwent hydrolysis in the presence of small quantities of water to provide the corresponding W(CO)4(CX2O)2-products. One of these products, namely, [Et4N]2[W(CO)4CO3], was subjected to an X-ray crystallographic investigation. The salt crystallizes in the Pi space group with cell dimensions a = 10.513 (5) , b = 15.881 (10) , c = 8.130 (6) , = 101.69 (6), = 92.12 (5), = 83.25 (5), V= 1319.8 3, Z = 2, and RF = 3.01%. The W-O bond distances (2.204 ) are quite similar to those observed (2.203 ) in the W-OPh-complexes. The carbonate ligand is bidentate with a very acute O-W-O angles of 59.4. 1989, American Chemical Society. All rights reserved.