Structure and Dynamic Behavior of (η3-Allyl)bromodicarbonylmolybdenum(II) Complexes Containing Polydentate 2-Pyridylphosphanes or Their Oxides as Chelating Ligands: Occurrence of Three Fluxional Processes

Abstract

The pseudo-octahedral complexes [Mo(η 3 -allyl)Br(CO) 2 (PPy n Ph 3-n -P,N)] (Py = 2-pyridyl; n = 2, 3) and [Mo(η 3 -allyl)Br(CO) 2 (OPPy m Ph 3-m -O,N)] (m = 1, 2, 3) undergo three different dynamic processes in solution, depending on the chelating ligand. The complexes containing PPhPy 2 and PPy 3 as chelating P,N-donors undergo a novel ''pivoted double switch'' mechanism which scrambles two equatorial coordination sites with racemization, while maintaining the identity of the phosphorus atom trans to the allyl ligand. The com-

Syntheses, Reactivity, and Stereochemistry of η3-Allyl Dithio-Molybdenum Complexes: Crystal Structures of endo-[Mo(η3-C3H5)(η2-S2CNC4H8)(CO)(η2-dppe)], endo-[Mo(η3-C3H5){η2-S2P(OEt)2}(CO)(η2-dppe)], exo-, endo-[Mo(η3-C3H5)(η2-S

“…The values for the Mo−CO angles are similar to those found for other terminal carbonyls contained in Mo systems. The Mo−CO (1.895(6)−1.925(2) Å) and C−O distances are both within the range of values reported for other molybdenum carbonyl complexes. ,,,, …”

Fluxional Processes in Diamagnetic and Paramagnetic Allyl Dicarbonyl and 2-Methylallyl Dicarbonyl Molybdenum Histidinato Complexes as Revealed by Spectroscopic Data and Density Functional Calculations

“…The stereochemical implications of fluxional processes in [M(h-allyl)(CO) 2 L 2 X] have been discussed, but all complexes investigated so far were either achiral or racemic mixtures. [35] In the chiral complex 1, which is easily obtained enantiomerically pure, three different orientations of the His ligand with respect to the (allyl)(CO) 2 plane are possible. Furthermore, very little is known about the presence of rotational isomers (either allyl rotation or trigonal twist) in related one-electron-oxidized species, [36,37] let alone about the parameters that might cause such fluxionality in paramagnetic compounds [Mo-(h-allyl)(CO) 2 L 2 X] .…”

Synthesis and Structure of Dicarbonyldichloro{2-(Diphenylphosphineoxide)pyridine}ruthenium(ii)

“…Similar spectroscopic behaviour is found in related octahedral molybdenum complexes containing the 2-(diphenylphosphineoxid e)pyridine ligand. 8 The 1 H NMR spectrum of the complex shows a broad multiplet centred at δ: 7.8 ppm, assigned to the phenyl and 4,5,6-pyridine protons, and a doublet resonance at δ: 9.23 ppm (J = 5.3 Hz) assigned to H 3 proton of the pyridine moiety. These resonances were assigned of the basis of reported data.…”

“…These resonances were assigned of the basis of reported data. 8 The In order to determine the molecular structure in the solid state of the complex, an X-ray diffraction study was undertaken. Suitable crystals for structural determination were obtained from a slow diffusion of n-pentane into a chloroform solution of the complex.…”