Polynuclear complex

Reaction with vatious nucleophilic reagents provides several types of dyes. Those with simple chromophores include the hernicyanine iodide [16384-23-9] (20) in which one of the terminal nitrogens is nonheterocyclic enamine triearbocyanine iodide [16384-24-0] (21) useful as a laser dye and the merocyanine [32634-47-2] (22). More complex polynuclear dyes from reagents with more than one reactive site include the trinuclear BAB (Basic-Acidic-Basic) dye [66037-42-1] (23) containing basic-acidic-basic heterocycles. Indolizinium quaternary salts (24), derived from reaction of diphenylcyclopropenone [886-38-4] and 4-picoline [108-89-4] provide trimethine dyes such as (25), which absorb near 950 nm in the infrared (23). 

During the cracking process, fragmentation of complex polynuclear cyclic compounds may occur, leading to formation of simple cycloparaffins. These compounds can he a source of Ce, C7, and Cg aromatics through isomerization and hydrogen transfer reactions. 

A higher steam/hydrocarhon ratio favors olefin formation. Steam reduces the partial pressure of the hydrocarbon mixture and increases the yield of olefins. Heavier hydrocarbon feeds require more steam than gaseous feeds to additionally reduce coke deposition in the furnace tubes. Liquid feeds such as gas oils and petroleum residues have complex polynuclear aromatic compounds, which are coke precursors. Steam to hydrocarbon weight ratios range between 0.2-1 for ethane and approximately 1-1.2 for liquid feeds. 

Increasing the throughput of the unit may involve recycling of the unconverted bottoms, its analysis has shown accumulation of complex polynuclear aromatics, such as coronene (seven-rings PAH). However, they could have been produced on reaction or were originally present and could not be converted under reaction conditions. 

Many of the mononuclear metal carbonyls have been the object of detailed and precise calorimetric measurement by Wilkinson10 and Skinner6 and their respective groups. Measurements on the more complex, polynuclear carbonyls have been made almost exclusively by microcalorimetry4 9, with the notable exception of Good s work12 on Mn2(CO)10. The results of these measurements are collected in Table 1. 

When naphtha or gas oil is cracked, imagine the limitless combinations possible. Naphthas are made up of molecules in the C5 to Cio range gas oils from Cio to perhaps C30 or C40. The structures include everything from simple paraffins (aliphacics) to complex polynuclear aromatics, so a-much wider range of possible molecules can form. Ethylene yields.froin..cracking naphtha or gas oil are much smaller than those from ethane or propane, as you can see from Table 5-1- But to compensate the plant operator, a full range of other hydrocarbons is produced as by-products also. 

There are still some complex polynuclear cobalt-ammines to which satisfactory constitutional formulas have not yet been assigned. These are, for example, the Fusko salts described by Fremy 1 a class of compounds containing sulphur prepared by Hofmann 2 by the action... 

Eliminations from Os(CO)4RR occur by dinuclear mechanisms only if either R or R is H. A hydride on one metal is necessary to interact with a vacant coordination site on the other in the dinuclear transition state. With Os(CO)4H2, the vacant site is created by dissociation of CO. With Os(CO)4-(H)CH the vacant site is created by a facile rate-determining isomerization which we suggest is to an acetyl hydride. The unique instability of hydridoalkyl carbonyls thus is explained. The synthesis and properties of Os(CO)4(H)C2H and various polynuclear ethyl osmium derivatives show that (3-hydrogens have no significant effect on these elimination mechanisms. Dinuclear hydridoalkyls are excellent starting points for the synthesis of more complex polynuclear alkyls. 

The apparent reactivity of the hydride end of the dinuclear hydridomethyl species is in line with the considerable substitutional lability noted above for H2Os2(CO)8. This reactivity contrasts with the comparative inertness (mentioned above) of the mononuclear hydride Os(CO)4H2 and of Os3(CO)i2. Its origin is unclear, but it makes the dinuclear hydrides and hydridoalkyls excellent starting points for the synthesis of more complex polynuclear alkyls. For example,... 

Recently the stability of silver(I) complexes of iV-methyl-substituted 4-methyldiethylenetriamines has been investigated by potentiometric pH and pAg measurements. Besides mononuclear complexes, polynuclear and protonated complexes were formed. Evidence of hydroxo complexes was also presented.48... 

Structural nomenclature for more complex polynuclear compounds is based on the description of the fundamental structural unit, and a logical procedure for numbering the atoms of the fundamental or central structural unit. For nonlinear clusters, descriptors such as tetrahedro, dodecahedro, etc. have traditionally been used to describe a central structural unit (CSU). However, synthetic chemistry has now advanced far beyond the utility of the limited CSU set associated... 

The number of similar cyclizations, including tandem and cascade sequences where an SnH reaction is a key step, has been considerably increased. As a rule, they are easily performed allowing at times the synthesis of complex polynuclear heterocycles in one step. The present paper, which summarizes about 130 articles on this topic, shows SnH cyclizations to be a very promising strategy for heterocyclic ring annulations. 

Cluster Compounds Inorganometalhc Compounds Containing Transition Metal Main Group Elements Copper Inorganic Coordination Chemistry DinuclearOrganometal-lic Cluster Complexes Polynuclear Organometalhc Cluster Complexes Silver Inorganic Coordination Chemistry. 

There are a number of computer programs available for the determination of stability constants from pH titration data. The most general of these perform a least-squares fit of the data to a calculated titration curve. The programs are able to handle protonated complexes, polynuclear systems, etc. In this example least-squares curve fitting is applied to a somewhat simpler case, a polyprotic acid in which the equilibria overlap extensively. The method is that used in the... 

Much of the interest in complex polynuclear hydrocarbons has arisen because a considerable number of them have cancer-producing properties. Some of the most powerful carcinogens are derivatives of 1,2-benzanthracene ... 

Organotin carboxylates and sulfonates form an important class among the family of organotin compounds.These compounds possess rich structural diversity. A range of structures from simple mononuclear compounds to complex polynuclear cages and clusters are formed." The structural diversity of these compounds emanates from several features. These include ... 

Sorbed trace element species may range from simple cations to complex polynuclear hydroxides formed by hydrolysis and condensation in solution or... 

The importance of metal clusters stems from our efforts to understand the clusters-to-bulk problem, i.e. the correlation between properties of molecular and solid states of matter (mononuclear complex => polynuclear complex (cluster) => bulk metal). A considerable research effort (theoretical and PES)26 has been expended on trying to obtain the following information about gold clusters ... 

The treatment of many of the metal carbonyls with bases affords complex polynuclear carbonylates (see (140) for a recent review). As is the case for the mononuclear carbonylate anions, hydrolysis of the anions, often with dilute acids, affords diamagnetic metal carbonyl hydride complexes (see Table VI). The majority of these complexes which are described below have not been studied by infrared and proton magnetic resonance spectroscopy their formulations are based primarily on analysis and mode of decomposition, and thus remain tentative. 

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