Density Functional Study of the Primary Photoprocesses of Manganese Pentacarbonyl Chloride (MnCl(CO)₅)

Abstract

Density functional calculations have been performed on the ground and excited states of MnCl(CO) 5 in order to explain the photochemistry of MX(CO) 5 complexes (M ) Mn, Re; X ) Cl, Br, I). As found earlier for Mn 2 -(CO) 10 (Inorg. Chem. 1996, 35, 2886, the e g -type unoccupied 3d orbitals in the pseudooctahedral environment are located rather high in the virtual orbital spectrum, and the corresponding ligand-field (LF) excitations are more than 1 eV above the lowest excitations. Potential energy curves (PECs) nevertheless show that the lowest excited states, which involve transitions to the Mn-Cl σ* orbital at equilibrium geometry, are dissociative for axial and equatorial CO loss. The mechanism is again, as in Mn 2 (CO) 10 , a strongly avoided crossing of the lowest excited state (a 1,3 E) with the higher dissociative LF states (different ones for CO ax and CO eq dissociation) which rapidly descend upon Mn-CO bond lengthening. In spite of the lowest excitation being to the Mn-Cl σ*-orbital, Mn-Cl homolysis cannot occur out of the lowest excited state. The photochemical behavior of Mn 2 -(CO) 10 , MnH(CO) 5 , and MnCl(CO) 5 is compared. The mechanisms of CO loss are found to be very similar, but there is a large difference with respect to the breaking of the σ bond (Mn-Mn, Mn-H, or Mn-Cl). Only in the case of Mn 2 (CO) 10 , the lowest broad absorption band contains the σ f σ* excitation and leads to σ bond breaking.

Manganese pentacarbonyl bromide as candidate for a molecular qubit system operated in the infrared regime

“…18 Its IR spectrum reveals only three peaks in the mid-IR. Its IR spectrum shows two strong absorption bands in the mid-IR regime, for which shaping methods exist.…”

Electronic and Molecular Structure of the Transient Radical Photocatalyst Mn(CO)5 and Its Parent Compound Mn2(CO)10

“…In both Mn 2 (CO) 10 and the Mn(CO) 5 radical, strong metal-to-ligand back-bonding interactions lead to mixing of metal d-and p-orbitals with empty ligand orbitals. 21,24 Hence, the observed spectral features in the pre-edge region represent transitions from metal 1s-core electrons into delocalized MOs that are shared between the metal center and the ligands.…”

“…Bottom: Simplified MO diagrams with dominant metal contributions for Mn 2 (CO) 10 and Mn(CO) 5 are depicted. 21,24,27,55 spectra incorporate bound transitions of 1s electrons to nonand antibonding MOs. Therefore, the details of the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO, respectively) are necessary to understand this spectral region.…”

DFT studies on the mechanism of the conversion of thiols into disulfides and dihydrogen catalyzed by CpMn(CO)3 complex

“…Firstly, one CO dissociates from R1 upon photolysis to give a 16-electron intermediate Int1. This process has been well studied by DFT calculations [32,33], from which, we have known that photolysis of MneCO bond needs to overcome 50 kcal/mol. Secondly, reactant RSH subsequently coordinates to Int1 from the vacant site generated from the CO dissociation, to form an 18-electron intermediate Int2.…”

“…Commonly, it is difficult for such kind of ligand substitution reaction to occur in saturated 18-electon Mn-complex. Considering the inaccessible higher barrier in pathb, patha should be the reasonable pathway for this substitution process and it is the rate-determined step [32,33]. From Int2 to Int3, the H1 and R groups on RS1H1 rotate around the MneS axis to get ready for the following intermolecular hydrogen migration, via a rotation transition state TS1 with a small barrier of 3.9 kcal/mol.…”