84430-77-3Relevant academic research and scientific papers
Spectroscopic and chemical properties of nitrogen-15-enriched molybdenum dinitrogen complexes trans ,mer-Mo(N2)2(L)(PMePh2)3
Lazarowych, Natalie J.,Morris, Robert H.,Ressner, Joel M.
, p. 3926 - 3932 (2008/10/08)
Grignard Mg reduction of 0.5 equiv of Mo2Cl10 and 4 equiv of PMePh2 in THF at 0°C under 1 atm of N2 gives trans-Mo-(N2)2(PMePh2)4 (1), which is isolated in 82% yield without contamination by Mo(η6-PhPMePh)(PMePh2)3. Substitution of a PMePh2 ligand in 1 by L gives stable complexes trans,mer-Mo(N2)2(L)(PMePh2)3 when L is a phosphorus or nitrogen donor ligand with a Tolman cone angle that falls in the approximate range 100 L 3, PMe3, N-methylimidazole (N-C-H3C3H3N2), pyridine, or 4-Me-, 4-t-Bu-, 3-Me-, 3-C1-, 3-F-, or 3-PPh2-pyridine. The last coordinates only via the nitrogen donor. The substituted pyridine complexes display intense MLCT absorptions. The chelating ligands PPh2(CH2)nSMe (n = 2 or 3) substitute for two PMePh2 ligands to give trans-Mo(N2)2(chelate)(PMePh2)2 complexes. The dinitrogen ligands of these complexes and also of Mo(N2)(η6-PhPPh2)(PPh2(CH 2)2PPh2) exchange with 15N2 gas at 22°C. Force constants kNN are calculated from the IR spectra of the various 14N2/15N2 isotopomers. There is a poor linear correlation (r = 0.85) of kNN with the E1/2ox (Mo(O) ? Mo(I)) values for these and all other N2 complexes of molybdenum(0): kNN = 2.25E1/2ox + 16.75. The kNN value is sensitive to the other ligands in the complex, especially the one trans to N2. Couplings |1J(Nα,Nβ)| as determined by 15N NMR decrease as constants kNN increase for the trans N2 complexes, which implies that this one-bond coupling is negative and that nonbonding s electron density on Nβ is decreasing as the bond strength increases. The 15N NMR spectra show that the N2 ligands in the complexes trans,mer-Mo(N2)2(3-RC5H 4N)(PMePh2)3 (R = Me, F, PPh2) are inequivalent due to hindrance to rotation about the Mo-heterocycle bond as a result of steric crowding and possibly Mo-N(heterocycle) multiple bonding. The A1 mode of ν(N2) is observed in the IR spectra of these complexes because of this reduction in symmetry. Complexes trans,mer-Mo(N2)2(L)-(PMePh2)3, where L = N-CH3C3H3N2, PMePh2, and P(OMe)3, react with H2SO4 in MeOH to give ammonia. The yield of ammonia is highest (0.70 NH3/Mo) for the most reducing complex with L = N-CH3C3H3N2 and lowest for the most electron-poor complex with L = P(OMe)3 (0.22 NH3/Mo) although there is not a linear relationship between the yield of ammonia and kNN or E1/2ox values.
Synthesis and substitution reactions of Mo(η6-PhPMePh)(PMePh2)3. The crystal and molecular structure of Mo(η6-PhPMePh)(CNCMe3)(PMePh2)2
Luck, Rudy L.,Morris, Robert H.,Sawyer, Jeffery F.
, p. 247 - 255 (2008/10/08)
The complex Mo(η6-PhPMePh)(PMePh2)3, 1, is readily prepared in one step by reducing a mixture of Mo2Cl10 and 8 mol of PMePh2 in THF with magnesium under argon. There is evidence for molybdenum complexes in oxidation states IV, II, and 0 as intermediates in the high-yield reduction process. Complex 1 reacts with 1 mol of the strongly coordinating ligands L = P(OMe)3, CNCMe3, and CO at 25°C to give monosubstituted complexes Mo(η6-PhPMePh)(L)(PMePh2)2, 2-4, respectively. Use of excess ligand results in disubstituted products. Only ligands that are sterically smaller than PMePh2 including N2, PMe2Ph, PMe3, and C2H2 react with 1; PPh3 and P(C6H11)3 do not react. Carbon monoxide uptake kinetics indicate that dissociation of a σ-bonded ligand from 1 is the rate-determining step for these reactions; rate = k1[1], k1(303 K) = (1.5 ± 0.1) × 10-3 s-1, ΔH? = 28.8 ± 1.6 kcal mol-1, and ΔS? = 23 ± 5 eu. The σ-bonded PMePh2 ligands in 2-4 are diastereotopic and give ABX or AB 31P NMR spectra. The 31P chemical shift of the η6-PhPMePh ligand is sensitive to the electronic and/or steric properties of the σ-bonded ligands. Compound 3, Mo(η6-PhPMePh)(CNCMe3)(PMePh2)2, has been studied by X-ray crystallography. It crystallizes in the monoclinic space group P21 with cell dimensions a = 9.256 (3) A?, b = 11.497 (3) A?, c = 18.782 (10) A?, β = 103.92 (4)°, V = 1940 A3, and Dcalcd = 1.33 g cm-3 for Z = 2. The structure was solved by the heavy-atom method and refined by least-squares and Fourier methods to final residuals R = 0.0635 (Rw = 0.0785) for 2755 observed (I > 2σ(I)) reflections. The geometry about the molybdenum is distorted octahedral. Principal dimensions are Mo-P = 2.416 (3) and 2.420 (3) A?, Mo-C(isocyanide) = 1.984 (13) A?, and Mo-C(arene) = 2.24 (1)-2.32 (1) A?. Angles in the MoP2(CNCMe3) tripod indicate that the bulky phosphines have moved from ideal octahedral positions toward the CNCMe3 ligand to minimize steric repulsions. The CNCMe3 ligand is nonlinear (C-N-C = 150 (1)°) and is the closest ligand in the tripod to the PMePh group on the η6 ring.
DINITROGEN VERSUS η6-ARENE COORDINATION IN METHYLDIPHENYLPHOSPHINE COMPLEXES OF MOLYBDENUM(0)
Azizian, Hormoz,Luck, Rudy,Morris, Robert H.,Wong, Hector
, p. C24 - C26 (2007/10/02)
High yield syntheses and properties of the new complexes Mo(η6-C6H5PMePh)(PMePh2)2(L), L=PMePh2 and P(OMe)3, are reported along with new direct preparations of Mo(N2)2(PMePh2)4 and Mo(η6-C6H6)(PMePh2)3.
