Linear species group 14 compounds

The silylene species may be coordinated to a metal center rather than being free (see Section V,C). When two Si-H groups are separated by —(CH2)2— links, either a cyclic (entry 8) or a linear (entry 26) compound may result the latter is somewhat unstable thermally. Correspondingly, cyclic (entry 10) or linear (entry 27) species are formed from the dihydrido derivatives (HSiMe X (X = 0,CH2) the linear compound with two Co(CO)4 groups is again thermally unstable. 

Counting NO as a three-electron donor, [IrCl(NO)(PPh3)2]+ is, therefore, a 16-electron species isoelectronic with Vaska s compound, isolable as a red crystalline hexafluorophosphate (m.p. 211°C, i/(N-0) 1870 cm-1) or similar perchlorate and tetrafluoroborate a trans-structure is indicated by spectroscopic data, and it is presumed to have a linear Ir-N-0 grouping. 

The 2 1 species are known as cuprates and are the most common synthetic reagents. Disubstituted Cu(I) species have the 3c 10 electronic configuration and would be expected to have linear geometry. The Cu is a center of high electron density and nucleophilicity, and in solution, lithium dimethylcuprate exists as a dimer [LiCu(CH3)2]2.3 The compound is often represented as four methyl groups attached to a tetrahedral cluster of lithium and copper atoms. However, in the presence of Lil, the compound seems to be a monomer of composition (CH3)2CuLi.4... 

GC is coupled with many detectors for the analysis of pesticides in wastewater. At the present time the most popular is GC-MS, which will be discussed in more detail later in this section. The flame ionization detector (FID) is another nonselective detector that identifies compounds containing carbon but does not give specific information on chemical structure (but is often used for quantification because of the linear response and sensitivity). Other detectors are specific and only detect certain species or groups of pesticides. They include electron capture,nitrogen-phosphorus, thermionic specific, and flame photometric detectors. The electron capture detector (ECD) is very sensitive to chlorinated organic pesticides, such as the organochlorine compounds (OCs, DDT, dieldrin, etc.). It has a long history of use in many environmental methods,... 

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