Charge Density Analyses of a Mixed-valence tri-Cobalt Complex and a di-Chromium complex with a Cr-Cr Quintuple Bond

In this work, a combined experimental and theoretical study was applied to achieve the bond characterization on a Hofmann-water-type clathrates complex, a mixed-valence tri-cobalt complex and a quintuple bonded di-chromium complex. he first one is [Mn(H2O)2Ni(CN)4](H2O)3 (MnNi) in which the manganese and nickel atom is coordinated in octahedral and square planar environments, respectively. The second one is Co3(u-admtrz)4(u-OH)2(CN)6.2H2O (Co3), admtrz = 3,5-dimethyl-4- amino-1,2,4-triazole) containing three cobalt atoms with CoIII(LS)-CoII(HS)-CoIII(LS) mixed valence and spin state. The third one is a quintuple bonded binuclear Cr complex, Cr2(Dipp)2 (Cr2) (Dipp- = ArdippNC(H)-NArdipp and Ardipp = 2,6-i-Pr2-C6H3). The Cr atoms are coordinated in low covalent and low coordination number situation which were stabilized by two bridging Dipp ligands. This complex has the shortest Cr-Cr distance of 1.75 Å so far.hese three complexes were investigated by high resolution single-crystal X-ray diffraction. Bond characterizations of the three molecules are described in terms of topological properties associated with bond critical points (BCPs), Fermi-hole function, source function, electron localization function (ELF) and natural bonding orbital (NBO) analysis. ccording to topological properties, Ni-C and CoIII-C bonds are characterized as polarized covalent bond and NBO analysis reveals that the effective bond order (eBO) of CoIII-C is closed to 0.9 with mainly interaction. The other metal-ligand bonds; Mn-N, Mn-O, Co-OH and Co-N are characterized as dative bond. The Laplacian density reveals different shape of inner-valence shell charge concentration (i-VSCC) of two distinct cobalt atoms. Different techniques including “near edge X-ray absorption structure” (NEXAS), “X-ray emission spectrum” (XES) and magnetic properties were used to clarify the spin state of Co3. he Cr-Cr quintuple bond is confirmed with one ds, two dp and two dd interactions by Fermi-hole function and NBO analysis with effective bond order of 4.40. The molecular orbitals of these five bonding orbitals indicate that they are predominantly contributed by 3d orbitals of Cr(I) metal ions. The electron density distribution shows significant overlap between two Cr atoms and the electron density at BCP of Cr-Cr bond is 1.7 e/Å, which is a quite high value for a metal-metal bond. The local source function also indicates that the electron density at BCP of Cr-Cr bond is higher than 80% contributed by the quintuple bonded Cr atoms. The topological properties will be discussed with the di-Cr complexes which have Cr-Cr fBO= 4 and 4.5.he detail discussion between experimental and theoretical results of those three compounds will be given.Abstract Iompound list IIIontents IVigure of Contents VIable of Contents Xhapter 1 Introduction 1. 1 Hofmann-like structures 2. 2 Mixed-valence compounds 3. 3 Metal-metal bond 5hapter 2 Experimental section 10. 1 Synthesis and experimental X-ray diffraction data collection 10.1. 1 Synthesis 10.1. 2 Data process 11.1. 3 Absorption correction and strategies of structure refinement 13. 2 Experimental and theoretical electron density distributions 13.2. 1 Experimental multipole model (MM) 13.2. 2 Strategies of multiple model refinement 16.2. 3 Theoretical DFT calculation 17.2. 4 Atoms in molecules: a Quantum Theory (QTAIM) 20.2. 5 Source Function, Fermi-hole Function and Electron Localization Function 26. 3 X-ray absorption and X-ray emission spectrum 30hapter 3 Results and discussion 34. 1 Hofmann-water-type clathrates, [Mn(H2O)2Ni(CN)4](H2O)3 34.1. 1 2-D layer structure of Hofmann-water-type clathrates 37.1. 2 Experimental charge density analysis of Hofmann-water-type clathrates: [Mn(H2O)2Ni(CN)4](H2O)3 39.1. 3 Topological property analyses of intermolecular interactions in Hofmann-water-type clathrates 45. 2 Trinuclear mixed-valence complex Co3(u-admtrz)4(u-OH)2(CN)6.2H2O 48.2. 1 Spin state and atomic charge of Co3(u-admtrz)4(u-OH)2(CN)6.2H2O 49.2. 2 Experimental and theoretical charge density distributions 64.2. 3 Chemical bond characterizations and topological properties 71.2. 4 NBO analysis, atomic basin, atomic charge and d-orbital population 78ummary – Co3 81. 3 Quintuple bond of Cr2(Dipp)2:A combined experimental and theoretical study 82.3. 1 Structure description of dichromium complex, Cr2(Dipp)2 84.3. 2 Experimental and theoretical charge density distributions 88.3. 3 Characterization of Cr-Cr quintuple bond 95. 4 ELF and NBO/MO of metal-metal multiple bonds 112ummary – Cr2 114hapter 4 Conclusion 114eference 12