15227-72-2Relevant academic research and scientific papers
Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes
Minell, Martin,Maley, Walter J.
, p. 2954 - 2958 (2008/10/08)
M(CO)6-n(CNR)n (n = 0-6) complexes (M = Mo, W; R = 2,6-dimethylphenyl, tert-butyl, cyclohexyl, isopropyl) have been synthesized. Depending on the R group of the isocyanide ligand, four or six carbonyl groups in M(CO)6 can be replaced. The NMR properties of the atoms in these complexes have been studied. The metal centers, observed by 95Mo or 183W NMR, show increased deshielding with the substitution of carbonyl ligands by isocyanide ligands. 95Mo NMR serves as an excellent tool for the identification of mixtures of these compounds and was useful to monitor the reactions. The nitrogen in the isocyanide ligand, observed by 14N NMR spectroscopy, gets more deshielded when the isocyanide is coordinated to the metal center, but with further substitution, the nitrogen becomes more shielded again. The 14N chemical shift of an isocyanide ligand trans to a carbonyl ligand differs slightly from the chemical shift of an isocyanide ligand trans to another isocyanide ligand in the tetrasubstituted complex. The 13C NMR signal of the CNR carbon becomes more deshielded with an increasing number of isocyanides present in the complex. CNR carbons trans to carbonyl groups are more shielded than CNR carbons trans to isocyanides. With the successive substitution of carbonyl groups by isocyanides, the electronic absorption bands in the UV-vis region shift toward longer wavelengths; i.e., the color of the compounds changes from white to orange-red.
Heat of reaction of (norbornadiene)molybdenum tetracarbonyl with monodentate and bidentate ligands. Solution thermochemical study of ligand substitution in the complexes cis-L2Mo(CO)4
Mukerjee, Shakti L.,Nolan, Steven P.,Hoff, Carl D.,Lopez De La Vega, Ramon
, p. 81 - 85 (2008/10/08)
The enthalpy of reaction of (NBD)Mo(CO)4 (NBD = norbornadiene) with a number of monodentate and bidentate ligands forming cis-L2Mo(CO)4 has been measured at 30°C in THF solution. The heats of reaction span a range of 33 kcal/mol. The order of stability for monodentate ligands is PCl3 6H5)3 6H5)3 3 6H5)3 6H5)2(CH3) 6H5)(CH3)2 3)3 3 6H11)NC 3 3. The series of chelating bidentate phosphines R2P-(CH2)nPR2 (n = 1-4, R = C6H5; n = 1, 2, R = CH3) and several related ligands were investigated. The chelating ring systems in the metallacycles show strain energies of about 8 kcal/mol for four-membered rings. The mixed ligand (C6H5)2PCH2CH2-As(C 6H5)2 shows a heat of binding midway between the heats of binding of (C6H5)2PCH2CH2P(C 6H5)2 and (C6H5)2AsCH2C-H2As(C 6H5)2, implying group additivity in this system. The complex (phen)Mo(CO)4 is some 5 kcal/mol more stable than (bpy)Mo(CO)4, presumably due to conformational effects in the free ligand. The ligand 1,5-cyclooctadiene forms a complex 2 kcal/mol less stable than that of norbornadiene. The influences of steric and electronic factors in determining the Mo-L bond strength are discussed.
