Complex divalent

Low-spin square pyramidal divalent complexes of the form [Co(hmd)(X)]n+ (X = OH2 (75) and 0C1C)3 ) have been structurally characterized.331 The rate of outer-sphere ([Co(OH2)6]3+) and... 

In contrast with the Schiff base salen, salicylaldehyde oxime (79) (salox) complexes of Co have received comparatively little attention, but a series of bis-bidentate divalent complexes of the form iraiis-Co(sa 1 ox)2( D M SO)2 have been reported.343 The heterocyclic bidentate oxime violurate (lH,3H-pyrimidine-2,4,5,6-tetrone 5-oximate, Hvi) (80) and its /V-methyl (mvi) and /V,/V -dimethyl (dmvi) derivatives form high-spin divalent [Co(vi)]+ and Co(vi)2 complexes, whereas [Co(vi)3] is low spin.344 The mixed-ligand Co(dmvi)2(phen) complex is also low spin. The crystal structure of m-Co(pxo)2Br2 (pxo = 2-acetylpyridine-l-oxide oxime) is isostructural with the Ni11 relative.345 The dichloro complex also adopts a cis configuration. The tridentate dioximes 2,6-diformyl-4-methylphenol dioxime and 2,6-diacetyl-4-methylphenol dioxime (Hdampo) form binuclear complexes of the type (81a) and (81b) respectively.346 Cobalt oxide nanoparticles were prepared by... 

Figure 7 Tripodal triamide complexes of (left) (82) with hydroxocobalt(III) (divalent complex is similar) (reproduced with permission of the American Chemical Society from Inorg. Chem., 2001, 40, 4733-4741) and (right) (83) with Co11 (reproduced with permission of the American Chemical Society from Inorg. Chem.,...

Chromatography cyclophosphazenes, 21 46, 59 technetium, 11 48-49 Chromites, as spinel structures, 2 30 Chromium, see Tetranuclear d-block metal complexes, chromium acetylene complexes of, 4 104 alkoxides, 26 276-283 bimetallics, 26 328 dimeric cyclopentdienyl, 26 282-283 divalent complexes, 26 282 nitrosyls, 26 280-281 trivalent complexes, 26 276-280 adamantoxides, 26 320 di(/ >rt-butyl)methoxides, 26 321-325 electronic spectra, 26 277-279 isocyanate insertion, 26 280 substitution reactions, 26 278-279 [9]aneS, complexes, 35 11 atom... 

Figure 14.4 The three forms of the copper-complexed catenane, each species being either a monovalent or a divalent complex, (a) Four-coordinate complex, (b) five-coordinate complex, and (c) six-coordinate complex.

Condensation can occur, however, with divalent complex ions besides the normal sulphates, pyrosulphates can be formed,... 

X-Ray diffraction shows that the [Pt(CN)6]2 ion is regular octahedral with linear Pt—C—N bonds.3"2 The IR and Raman spectra of K2[Pt(CN)6] have C—N stretching vibrations at higher frequencies and C—N force constants which are larger than the corresponding divalent complexes.303,304 This correlates with less n back-donation from the metal to the empty n orbitals of the cyanide ligand in the PtIV complexes. 

Platinum porphyrin complexes can be prepared by reaction with PtCl2(PhCN)2. Purification of the final complex is by medium pressure liquid chromatography on alumina. The strongly phosphorescent platinum(II) porphyrin complexes are efficient sensitizers for stilbene isomerization. The quantum yields for the cis to trans process are greater than unity because of a quantum chain process in which the metalloporphyrin serves both as an energy donor and an acceptor.1110 Picosecond laser spectroscopy has been used to obtain time-resolved excited-state spectra of platinum octaethylporphyrin complexes, and to probe the excited-state energy levels.1111 Tetrabenzoporphyrin complexes have been prepared for platinum in both the divalent and tetravalent oxidation states. The divalent complex shows strong phosphorescence at 745 nm.1112... 

Divalent Synthetic Equivalents. These species display a fascinating ambiguity by showing a formal appearance of divalent complexes, but having in reality electronic structures of higher valent species. Yet, the chemical reactivity is what one could predict for genuine divalent species. 

Fig. 21 The 4-, 5-, and 6-coordinate copper complexes involved. The corresponding Cu(i i)/Cu(i) redox potentials are also indicated. They clearly show the sequence of preferred stabilities for copper(i i) versus copper(i), the hexacoordinate complex producing the most stable divalent complex.

An interesting part of chemistry comprises the divalent complexes of the Group 14 elements, germanium, tin and lead, supported by tetradentate nitrogen and oxygen donor ligands. The [Salen ] ligand system, obtained by condensation of a salicylaldehyde... 

Tml2(DME)3, Dyl2 (DME)3, and Ndl2(THF)5 have similar structures to those of the classical divalent lanthanide iodides. However, metathesis reaction with these iodides usually affords not a divalent complex but a trivalent lanthanide complex instead, because of their strong reductive ability [102], To date, only one structurally characterized divalent organothulium complex has been synthesized by metathesis reaction (Equation 8.34) [104]. 

Evans, W.J. (2002) The expansion of divalent organolanthanide reduction chemistry via new molecular divalent complexes and sterically induced reduction reactivity of trivalent complexes. Journal of Organometallic Chemistry, 647, 2. 

In CH3CN or CH2CI2, all copper]I) [2]catenates are reversibly oxidized to the divalent complexes (Figure 3). The oxidation potentials are high ( 0.6 V versus SCE), making the Cu species relatively strong oxidants. 

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