摘要:

Homogeneous and microheterogeneous transition-metal-based systems that generate dihydrogen and/or reduce carbon dioxide upon irradiation with visible light are considered. Most of the systems involve polypyridine complexes of the d6centers cobalt(III), rhodium(III), iridium(III), ruthenium(II) and rhenium(I). Complexes with diimine ligands serve as photosensitizers and/or catalyst precursors. The corresponding d8metal centers and d6hydrides are important intermediates: bimolecular reactions of the hydrides or their reactions with H2O/H3O+are responsible for formation of dihydrogen. When carbon dioxide is also present, it may insert into the metal-hydride bond to yield formate. Mechanistic schemes for some dual-acting photoconversion systems that generate both dihydrogen and carbon monoxide or formate are considered.

ISSN:0260-3594    

DOI:10.1080/02603599708032729

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A correlation between the direction of the tetrad (double-double) effect in the lanthanide and actinide series and coordination number (CN) is discussed on experimental and theoretical grounds. Some examples of determining the CN values of the f-block elements in solution complexes using the tetrad effect are reviewed. Except for the CN implication, the tetrad effect of the inner transition elements is presented in terms of effective crystal radius, covalent shortening, nephelauxetic and ligand field effects, spin-orbit coupling, hydration, etc.

ISSN:0260-3594    

DOI:10.1080/02603599708032730

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Radii of ions,ri, were compared with radii of their outermost orbitals, ⟨rnl⟩. It has been found that forsandpblock elements in the oxidation state equal to the group number,riis a linear function of ⟨rnl⟩ and, for a constant value of ⟨rnl⟩, decreases with increasing formal charge of the cation. Forpblock elements in the oxidation state two less than the group number, the differenceri—⟨rnl⟩ as well as the difference in orbital energies,np—ns, exhibit sawtooth behavior, i.e., secondary periodicity, similar to that in stability of oxidation states. The sawtooth behavior in the radii suggests that the lone pair acquires somes2character between the third and fourth period, and becomes mainly ans2pair in the sixth period ions, particularly in Tl(+1). The radii of Lr(+1), 104(+4) and 105(+5) have been estimated from linear relationships betweenriandrnl, and those of Al(+1), Ga(+1), In(+1) and Si(+2) from the sawtooth pattern.

ISSN:0260-3594    

DOI:10.1080/02603599708032731

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0260-3594    

DOI:10.1080/02603599708032728

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor