Ring complexes

Alternatively, using a polyethylene glycol stationary phase, aromatic hydrocarbons can also be retained and separated primarily by dipole-induced dipole interactions combined with some dispersive interactions. Molecules can exhibit multiple interactive properties. For example, phenyl ethanol possesses both a dipole as a result of the hydroxyl group and is polarizable due to the aromatic ring. Complex molecules such as biopolymers can contain many different interactive groups. 

The amino group may be secondary or tertiarj, or be associated -with simple or bridged ring complexes. 

Interest in the synthesis and reactivity of coordinatively unsaturated low-valent metal complexes has led to the use of an o-carboranedithiolato ligand in the formation of metalladithiolene ring complexes. Recently, we69 70 and Wrackmeyer et al.1 72 have reported on the synthesis of the 16e cobalt, rhodium, and iridium... 

In an extension of this study, the dissociation rates for the copper complexes of the corresponding 16- and 17-membered N5-macrocycles have been studied (Hay, Bembi, McLaren Moodie, 1984). Similar rate laws to that just given for the 15-membered ring complex also apply in these cases. It was found that there is an increase in rate as the ring size increases the respective kH constants being 0.049 dm6 mol-2 s 1 (15-membered), 4.85 dm6 mol 2 s 1 (16-membered) and 1.18 x 103 dm6... 

In another study, Co(m) has been shown to be favoured over Co(n) as the ligand strain energy decreases in the complexes of the N4-donor aliphatic macrocycles (278 X = NH). Thus, for the 13- to 16-membered ring complexes of type /ra s-[CoCl2L]2+, it is the complex of cyclam (14-membered) which most promotes the Co(n)/Co(m) transformation (Hung et al., 1977). 

Synthesis and characterization Mononuclear C4B ring complexes (double-decker sandwiches) Lithium ... 

Multinuclear C4B Ring Complexes, Clusters, and Extended Systems... 

The reaction is thermodynamically controlled and was postulated to involve an achiral, delocalized anion 15, which cyclizes to a somewhat strained 7-membered ring complex 16 capable of existing in isomeric forms. The more stable form could be hydrolyzed to the predominant ( + )-(S)-allenic alcohol 17 (Scheme 1)... 

The ring complex shown would account for the low A factor, and further explains the formation of only cis-diene. This 1,5-hydrogen shift mechanism has also been postulated to account for the thermal isomerization of a number of 1,3-dienes (Wolinsky et al. 1962). This type of isomerization has been studied in detail as applied to the reversible interconversion of cis-2-methylpenta-l,3-diene and 4-methylpenta-l,3-diene,... 

The dissociation rate constant measures directly the value of k 2 in (4.52). The strain resident in multi-ring complexes is clearly demonstrated by some hydrolysis rate studies of nickel(II) complexes. The AFT values for the first bond rupture for Ni(II)-polyamine complexes fall neatly into groups. They are highest for en, containing the most strain-free ring (84 kJ mol ), about 75 kJ mol for complexes with terdentate ligands and only —63 kJ mol for complexes of quadridentate and quinquedentate amines and with NH3 itself. See also Ref. 109. 

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