Groups 5 and 6 Terminal Hydrazido(2−) Complexes: N_β Substituent Effects on Ligand-to-Metal Charge-Transfer Energies and Oxidation States

Brightly colored terminal hydrazido(2−) (dme)MCl_3(NNR_2) (dme = 1,2-dimethoxyethane; M = Nb, Ta; R = alkyl, aryl) or (MeCN)WCl_4(NNR_2) complexes have been synthesized and characterized. Perturbing the electronic environment of the β (NR_2) nitrogen affects the energy of the lowest-energy charge-transfer (CT) transition in these complexes. For group 5 complexes, increasing the energy of the N_β lone pair decreases the ligand-to-metal CT (LMCT) energy, except for electron-rich niobium dialkylhydrazides, which pyramidalize N_β in order to reduce the overlap between the Nb═Nα π bond and the Nβ lone pair. For W complexes, increasing the energy of N_β eventually leads to reduction from formally [W^(VI)≡N–NR_2] with a hydrazido(2−) ligand to [W^(IV)═N═NR_2] with a neutral 1,1-diazene ligand. The photophysical properties of these complexes highlight the potential redox noninnocence of hydrazido ligands, which could lead to ligand- and/or metal-based redox chemistry in early transition metal derivatives

The comparative resistance of varieties of oats to crown and stem rusts

Numerous instances of the production of disease-resistant crops may be noted in this and other countries, but comparatively little work has been done on the problem of resistance of oats to stem rust (Puccinia grarninis Pel\u27s.) and crown rust (P. coronata Corda.) Many of the published records on the rust resistance of oats are observations covering but a single season and too often with no determination of the species of rust present. The use of resistant varieties, however, appears . to be the most hopeful method of combating these rusts. This paper is chiefly an account of studies conducted to determine which of the existing varieties are resistant to either or both of the rusts mentioned above

Reviews

The following publications have been reviewed by the mentioned authors;GCSE Design and Technology - Resistant Materials - reviewed by Alison HardyGCSE Design and Technology - Textiles Technology - reviewed by Julie BoydIssues in Design and Technology Teaching - reviewed by John DurrellAgriculture in the Food Supply Chain: an overview - reviewed by Anne ConstableFood Chemical Composition: dietary significance in food manufacturing - reviewed by Anne ConstableFood The Chemistry of its Components - reviewed by Brenda Greatwoo