The civilian, commercial, and defense sectors of most advanced industrialized nations are faced with a tremendous set of environmental problems related to the remediation of hazardous wastes, contaminated groundwaters, and the control of toxic air contaminants. For example, the slow pace of hazardous waste remediation at military installations around the world is causing a serious delay in conversion of many of these facilities to civilian uses. Over the last 10 years problems related to hazardous waste remediation have emerged as a high national and international priority.

Environmental Applications of Semiconductor Photocatalysis

The Cationminus signpi Interaction.

C–H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C–H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C–H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C–H activation until summer 2018.

3d Transition Metals for C-H Activation.

Free Radical Lipid Peroxidation: Mechanisms and Analysis

Catalytic activities of Schiff base transition metal complexes

First Examples of Complexes Containing η1-Bonded Phosphaalkynes Synthesis and Crystal and Molecular Structure of trans-(Mo(Ad-CP)2(Et2P-(CH2)2-PEt2)2) (Ad: Adamantyl).

One the π-allylmetal hydride mechanism for the isomerisation of olefins catalysed by transition metal complexes

Cycloaddition Reactions of a 1,2,4-Triphosphacyclopenta-1,3-diene. Synthesis, Crystal, and Molecular Structure of the Novel Hexaphosphorus Cage Compound P6C4But3H2 Containing Five Directly Bonded Phosphorus Atoms.

The potential energy surfaces of both neutral and dianionic SnC(2)P(2)R(2) (R=H, tBu) ring systems have been explored at the B3PW91/LANL2DZ (Sn) and 6-311 + G* (other atoms) level. In the neutral isomers the global minimum is a nido structure in which a 1,2-diphosphocyclobutadiene ring (1,2-DPCB) is capped by the Sn. Interestingly, the structure established by Xray diffraction analysis, for R=tBu, is a 1,3-DPCB ring capped by Sn and it is 2.4 kcal mol(-1) higher in energy than the 1,2-DPCB ring isomer. This is possibly related to the kinetic stability of the 1,3-DPCB ring, which might originate from the synthetic precursor ZrCp(2)tBu(2)C(2)P(2). In the case of the dianionic isomers we observe only a 6 pi-electron aromatic structure as the global minimum, similarly to the cases of our previously reported results with other types of heterodiphospholes.([1,4,19]) The existence of large numbers of cluster-type isomers in neutral and 6 pi-planar structures in the dianions SnC(2)P(2)R(2)(2-) (R=H, tBu) is due to 3D aromaticity in neutral clusters and to 2D pi aromaticity of the dianionic rings. Relative energies of positional isomers mainly depend on: 1) the valency and coordination number of the Sn centre, 2) individual bond strengths, and 3) the steric effect of tBu groups. A comparison of neutral stannadiphospholes with other structurally related C(5)H(5)(+) analogues indicates that Sn might be a better isolobal analogue to P(+) than to BH or CH(+). The variation in global minima in these C(5)H(5)(+) analogues is due to characteristic features such as 1) the different valencies of C, B, P and Sn, 2) the electron deficiency of B, 3) weaker p pi-p pi bonding by P and Sn atoms, and 4) the tendency of electropositive elements to donate electrons to nido clusters. Unlike the C5H5+ systems, all C(5)H(5)(-) analogues have 6 pi-planar aromatic structures as global minima. The differences in the relative ordering of the positional isomers and ligating properties are significant and depend on 1) the nature of the pi orbitals involved, and 2) effective overlap of orbitals.

Structure and Bonding in Stannadiphospholes and their Dianions SnC2P2R2m (R=H, tBu m=0, −2): A Comparative Study with C5H5+ and C5H5− Analogues

Treatment of CoCl2 with Li(C2R2P3)(R = But) in 1,2-dimethoxyethane yields the complex [Co(η5-C2R2P3)(η4-C2R2HP3)] containing a ligated 1,2,4-triphosphacyclopenta-1,3-diene ring system.

John F. Nixon

Papers

First Examples of Complexes Containing η1-Bonded Phosphaalkynes Synthesis and Crystal and Molecular Structure of trans-(Mo(Ad-CP)2(Et2P-(CH2)2-PEt2)2) (Ad: Adamantyl).

One the π-allylmetal hydride mechanism for the isomerisation of olefins catalysed by transition metal complexes

Cycloaddition Reactions of a 1,2,4-Triphosphacyclopenta-1,3-diene. Synthesis, Crystal, and Molecular Structure of the Novel Hexaphosphorus Cage Compound P6C4But3H2 Containing Five Directly Bonded Phosphorus Atoms.

Structure and Bonding in Stannadiphospholes and their Dianions SnC2P2R2m (R=H, tBu m=0, −2): A Comparative Study with C5H5+ and C5H5− Analogues

First Example of a 1,2,4-Triphosphabuta-1,3-diene Complex: Synthesis and Crystal and Molecular Structure of (Co(η5-C2R2P3)(η4-C2R2HP3)) (R = But).