Automated test systems for distribution transformers – Part II

Distribution transformers are used worldwide and in very large quantities as a link between regional medium-voltage networks and local low-voltage distribution systems. To ensure quality, the required electrical characteristics must be demonstrated through extensive testing procedures on each distribution transformer in the production. This paper gives an overview of the equipment for automated testing of distribution transformers. There are also various options presented for a significant reduction of the required test time which can be achieved by optimizing the interaction of automatic switching devices, intelligent system control and largely intuitively designed test sequences

Preparation of Metal-Imidazolidin-2-ylidene Complexes by Oxidative Addition

An entry into (chiral) palladium complexes bearing N-heterocyclic carbene (NHC) ligands is outlined on the basis of the oxidative addition of Pd(PPh3)4 to easily accessible (enantiopure) 2-chloro-1,3-disubstituted imidazolinium salts. This procedure is complementary to existing methodology that relies on metathetic ligand exchange reactions without changing the oxidation state of the involved metal center

Diaminocarbene- and Fischer-carbene complexes of palladium and nickel by oxidative insertion: Preparation, structure, and catalytic activity

Oxidative insertion of [Pd(PPh₃)₄] or [Ni(cod)₂]/PPh₃ into the C–Cl bond of various 2-chloroimidazolinium- and other -amidinium salts affords metal–diaminocarbene complexes in good to excellent yields. This procedure is complementary to existing methodology in which the central metal does not change its oxidation state, and therefore allows to incorporate carbene fragments that are difficult to access otherwise. The preparation of a variety of achiral as well as enantiomerically pure, chiral metal–NHC complexes (NHC = N-heterocyclic carbene) and metal complexes with acyclic diaminocarbene ligands illustrates this aspect. Furthermore it is shown that oxidative insertion also paves a way to prototype Fischer carbenes of Pd^II. Since the required starting materials are readily available from urea- or thiourea derivatives, this novel approach allows for substantial structural variations of the ligand backbone. The catalytic performance of the resulting library of nickel- and palladium–carbene complexes has been evaluated by applications to prototype Suzuki-, Heck-, and Kumada–Corriu cross-coupling reactions as well as Buchwald–Hartwig aminations. It was found that even Fischer carbenes show appreciable catalytic activity. Moreover, representative examples of all types of neutral and cationic metal–carbene complexes formed in this study have been characterized by X-ray crystallography

Synthesis and study of the first n-aryl acyclic diaminocarbene and its transition-metal complexes

The first acyclic diaminocarbene (ADC) featuring N-aryl groups, as well as two complexes containing this ligand, (ADC)RhCl(1,5-cis,cis-cyclooctadiene) and (ADC)RhCl(CO)(2), were synthesized and characterized. Insight into controlling conformational diversity in acyclic diaminocarbenes with N-aryl groups through judicious N substitution was also explored

Palladium(II) pyrazolin-4-ylidenes: Substituent effects on the formation and catalytic activity of pyrazole-based remote NHC complexes

10.1021/om8010849Organometallics2892778-2786ORGN