Dipositive oxidation state

Samarium, tris(triphenylphosphine oxide)bis-(diethyldithiophosphato)-structure, 1,78 Samarium complexes dipositive oxidation state hydrated ions, 3, 1109 Samarium(III) complexes salicylic acid crystal structure, 2, 481 Sampsonite, 3, 265... 

Ytterbium, trinitratotris(dimethyl sulfoxide)-structure, 1, 97 Ytterbium, tris(acetylacetone)(4-ammo-3-penten-stereochemistry, 1,81 Ytterbium complexes acetylacetone, 2,373 dipositive oxidation state hydrated ions, 3,1109 polypyrazolylborates, 2,255 Ytterbium(III) complexes ethyl glycinate, diacetate... 

The specified configurations are ground-state configurations except at La (g) and Gd (g) where the ground states are [Xe]5d and [Xe]4F5d respectively. It can be seen that the variations in It, do indeed correspond to the stabihty sequence for the dipositive oxidation state. The correspondence can also be tested quantitatively by using estimated and experimental values of AG (1). These are also plotted in Fig. 1.1. The parallelism between the two is very close. 

Despite the vast number of cobalt(IT) complexes known, the dipositive oxidation state is rare for rhodium. The bulk of the rhodium(ri) complexes known are dimeric, the classic examples being the diamagnetic carboxylato complexes that adopt the classic lantern structure (26). However, even the aqua complex is dimeric so the bridging carboxylato ligands are not essential for the formation of the rhodium-rhodium bond. 

The reverse (N- 6 to N- l) linkage isomerization has also been studied and requires the metal to be in the dipositive oxidation state on the protonated (neutral) ligand. Previous electrochemical work determined the pK of... 

Z10 Electronic Spectra of Lanthanide Complexes 39.Z11 Lanthanides in the Dipositive Oxidation State 39.Z11.1 Hydrated species 39. Z 11.2 Other solvated species 39. Z 11.3 Complexes with nitrogen donors... 

Escherichia coli nitrate reductase structure, 1438 Europium complexes -diketones, 1081 dipositive oxidation state hydrated ions, 1109... 

Keller, Burnett, Carlson, and Nestor [22] have made detailed predictions of the chemical properties of elements 113 and 114. The group IV elements show increasing stability in oxidation state ii relative to the iv state as one goes to higher atomic numbers. Carbon and silicon have very stable tetrapositive oxidation states, and germanium shows a very unstable dipositive oxidation state in addition to a stable tetrapositive state. In tin, both the dipositive and tetrapositive oxidation states are important, and lead is most stable in oxidation state ii. Thus, element 114 should be weakly, if at all, tetrapositive and the most stable oxidation state is expected to be the ii state. The standard electrode potential for the reaction... 

The dipositive oxidation state is unusual among the lanthanides. The more easily available divalent species are europium, ytterbium and samarium, although other divalent lanthanide compounds are known. Several reviews dealing, at least partly, with divalent lanthanides can be found in the literature. The most recent and detailed paper is that of Johnson (1977), which includes preparations and physical properties. Two other reviews are also available (Asprey et al., 1960 Marks, 1978). Thermochemical properties have been reviewed by Morss (1976). 

Thermochemical properties of the lanthanide elements and ions have recently been reviewed by Johnson (1977) and Morss (1976). It is well known that with any particular ligand, the thermodynamic stability of the dipositive oxidation state of the lanthanide varies according to the sequence Eu > Yb > Sm. The ease of preparation of divalent compounds is in the same order. For example, co-condensation of Yb metal vapor with 1-hexyne yields a compound in which Yb is present as 85-92% Yb " in the case of samarium, trivalent products are obtained (W.J. Evans et al., 1981). Eu and Yb cyclooctatetraenyl have been prepared (Hayes et al., 1969), but the samarium compound is as yet unknown. 

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