Magnetostructural correlation in isolated trinuclear iron(iii) oxo acetate complexes.

We elucidate the correlation between geometric structures and magnetic couplings in trinuclear iron(iii) oxo acetate complexes [Fe3O(OAc)6(Py)n]+ (n = 0, 1, 2, 3) when isolated and trapped as gaseous ions. Structural information arises from Infra Red-Multiple Photon Dissociation (IR-MPD) and Collision Induced Dissociation (CID) experiments in conjuction with Density Functional Theory (DFT) based calculations. We simulate the antiferromagnetic couplings between the FeIII (d5) centers by employing a Broken Symmetry approach within our DFT calculations, and we extract the associated antiferromagnetic coupling constants. Coordination of one, two or three axial pyridine ligands to the [Fe3O(OAc)6]+ subunit distorts the geometry of the triangular Fe3O core. The Fe-Ocentral bond lengths are enlarged or shortened depending on number of coordinated pyridine ligands. This significantly affects the antiferromagnetic coupling constants between the FeIII centers ranging from -62 cm-1 to -28 cm-1 in [Fe3O(OAc)6(Py)n]+ (n = 0, 1, 2, 3). A detailed analysis of the associated exchange couplings indicates a switching of magnetic ground states by pyridine coordination. The total spin ST in the ground states of [Fe3O(OAc)6(Py)n]+ raises from ST = 1/2 (n = 0) to 3/2 (n = 1) and 5/2 (n = 2). Coordination of the third pyridine ligand (n = 3) re-establishes a spin ground state of ST = 1/2. We thus identify a coordination controlled switching of magnetic ground states.

Infrared spectroscopy of N2 adsorption on size selected cobalt cluster cations in isolation.

We report IR active N2 stretching frequencies in isolated and size selected cobalt cluster nitrogen adsorbate complexes, [Con(N2)1](+) as recorded by virtue of InfraRed Photon Dissociation (IRPD) spectroscopy. The observed frequencies of the [Con(N2)1](+) complexes (n = 8-17) are significantly redshifted (2180 to 2290 cm(-1)) with respect to the IR inactive vibrations of free N2 (2359 cm(-1)). These bands are assigned to a µ1 head-on type of coordination of the N2 to the cobalt cluster surface, revealing remarkable cluster size dependent features to interpret.

Doubly Regioselective C-H Hydroarylation of Unsymmetrical Alkynes Using Carboxylates as Deciduous Directing Groups.

A catalyst system composed of [(C6Me6)RuCl2]2, potassium carbonate/guanidine carbonate, and mesitoic acid efficiently promotes the doubly regioselective C-H hydroarylation of unsymmetrical alkynes. The process involves carboxylate-directed ortho-C-H bond activation followed by regioselective addition to the alkyne C-C triple bond with concerted decarboxylation. This action of the carboxylate as a deciduous directing group ensures exclusive monovinylation with high selectivity for the (E)-1,2-diarylalkene.

Vibrational blue shift of coordinated N2 in [Fe3O(OAc)6(N2)n]+: "non-classical" dinitrogen complexes.

We present "non-classical" dinitrogen Fe(iii) oxo acetate complexes in vacuo utilizing Infrared Photodissociation (IR-PD) at cryo temperatures. The IR-PD spectra reveal a blue shift of the N2 stretching vibration frequencies in the complexes. Density Functional Theory (DFT) calculations confirm the experiments and indicate strengthened N-N bonds due to pronounced σ bonding and a lack of π back donation.