Malcolm H. Chisholm (1945-2015).

Malcolm H. Chisholm, Distinguished Professor of Mathematical and Physical Sciences at The Ohio State University, passed away on November 20, 2015. He is best known for his pioneering work on the chemistry of metal-metal multiple bonds, the molecular and electronic structure and bonding of transition-metal compounds, and the exploration of excited states of complexes with metal-metal quadruple bonds.

Detection and Electronic Structure of Naked Actinide Complexes: Rhombic-Ring (AnN)2 Molecules Stabilized by Delocalized π-Bonding.

The major products of the reaction of laser ablated and excited U atoms and N2 are the linear N≡U≡N dinitride molecule, isoelectronic with the uranyl dication, and the diatomic nitride U≡N. These molecules form novel cyclic dimers, (UN)2 and (NUN)2, with complex electronic structures, in matrix isolation experiments, which increase on UV photolysis. In addition, (NUN)2 increases at the expense of (UN)2 upon warming the codeposited matrix samples into the 20-40 K range as attested by additional nitrogen and argon matrix infrared spectra recorded after cooling the samples back to 4 or 7 K.

Metathesis of nitrogen atoms within triple bonds involving carbon, tungsten, and molybdenum.

(ButO)3Mo triple bond N and W2(OBut)6(M triple bond M) react in hydrocarbons to form Mo2(OBut)6(M triple bond M) and (ButO)3W triple bond N via the reactive intermediate MoW(OBut)6(M triple bond M). (ButO)3W triple bond N and CH3C triple bond N15 react in tetrahydrofuran (THF) at room temperature to give an equilibrium mixture involving (ButO)3W triple bond N15 and CH3C triple bond N. The (ButO)3W triple bond N compound is similarly shown to act as a catalyst for N15-atom scrambling between MeC13 triple bond N15 and PhC triple bond N to give a mixture of MeC13 triple bond N and PhC triple bond N15.

Infrared spectrum and bonding in uranium methylidene dihydride, CH2=UH2.

Uranium atoms activate methane upon ultraviolet excitation to form the methyl uranium hydride CH3-UH, which undergoes alpha-H transfer to produce uranium methylidene dihydride, CH2=UH2. This rearrangement most likely occurs on an excited-quintet potential-energy surface and is followed by relaxation in the argon matrix. These simple U+CH4 reaction products are identified through isotopic substitution (13CH4, CD4, CH2D2) and density functional theory frequency and structure calculations for the strong U-H stretching modes.

Structure and bonding in SnWO4, PbWO4, and BiVO4: lone pairs vs inert pairs.

Three ternary oxides, SnWO4, PbWO4, and BiVO4, containing p-block cations with ns2np0 electron configurations, so-called lone pair cations, have been studied theoretically using density functional theory and UV-visible diffuse reflectance spectroscopy. The computations reveal significant differences in the underlying electronic structures that are responsible for the varied crystal chemistry of the lone pair cations. The filled 5s orbitals of the Sn2+ ion interact strongly with the 2p orbitals of oxygen, which leads to a significant destabilization of symmetric structures (scheelite and zircon) favored by electrostatic forces.