Tri ligands

The mixed thiazole-pyrazole system 25 (Dq(Ni2+)=1110 cm-1) yields a tris(ligand) iron(II) complex in which one of the ligand molecules is depro-tonated. For the complex perchlorate a complete and fairly abrupt transition occurs below room temperature but no associated hysteresis was observed [27]. 

Structures of l-hydroxy-2-pyridinonate and 3-hydroxy-2-p5rridino-nate complexes may be compared with those of the more extensively studied 3-hydroxy-4-pyridinonates through the published crystal structures of their tris-ligand iron(III) complexes. The iron(III) tris-ligand complex of l-n-butyl-3-hydroxy-2-pyridinone has fac geometry it crystallizes as a trihydrate 135). 

Bis(2 -methoxyphenyl)-l,10-phenanthroline, bmpphen (2), forms a high-spin bis- but not a low-spin tris-ligand iron(II) complex due to interligand repulsion. ... 

Pyrrole units form part of the coordinating entities of Schiff base ligands derived from pyrrole 2-carboxaldehyde, for example in the iron(II) complex of the ligand derived from pyrrole 2-carboxaldehyde and trien, which is low-spin despite the feeble coordinating properties of the pyrrole—CH=N— units. The synthesis, structure, and spectroscopic and electrochemical properties of tris-ligand iron(III) complexes of phenyldipyrromethenate (dipyrrin, (129)), and its... 

A-Hydroxypyrimidinones, e.g., (249), and A-hydroxypyrazinones, e.g., (250), form stable tris-ligand iron(III) complexes, but these are of much lower stability than iron(III) complexes of hydroxypyridinones. Stability can, as one would expect, be increased greatly by going to analogous hexadentate ligands containing three A-hydroxypyrimidinone or A-hydroxypyrazinone units. 

Partition coefficients have been measured for tris-maltolatoiron(III) and tris-ligand complexes derived from a range of A-substituted 3-hydroxy-4-pyridinones, particularly (251) with R and R variously Me, Et, pj 1325,1326 j- nge of complexes with alkyl (up to A-butyl) or... 

Diastereomeric distributions (A A) in several tris-ligand Fe + complexes of chiral catecholamide and terephthalamide ligands have been established in solution by CD and NMR spectroscopies. The complex of (253), whose structure in the solid state was determined, exists wholly in the A conformation in aqueous solution. Weak polar interactions determine conformational preferences here. ... 

Tris(ligand) complexes involving ligand (41), or derivatives thereof, have been synthesized and characterized. Appending electron-releasing Ph or cyclic alkyl groups to the ligand leads to a blue... 

The tris-ligand cation of bipy-A-oxide (120),613 and the bis-ligand cation of terpy-A-oxide314 can be prepared by electrochemical oxidation of the Mnu species in CH3CN, and the robust dark-red crystalline perchlorates have been isolated. 

A few interesting Mn111 compounds of O—S bidentates have been prepared. The interaction of Mn111 acetate with (183) (R = Ph) leads to ligand oxidation, but when R = Bu the tris-ligand Mn111 compound was obtained.665... 

Treatment of the tris(dialkyldithiocarbamato)iron(III) complexes in benzene with a controlled amount of concentrated hydrohalic acid affords the black bis(ligand) complexes [FeX(S2CNR2)2] (X = Cl, Br or I).306 For X = Cl the complexes may also be prepared by irradiation of the tris-(ligand) complex in a halogenated solvent. This free radical reaction is believed to proceed via excited-state labilization of one ligand followed by attack of solvent.307 Analogous complexes of pseudohalide ions (X = NCO, NCS- or NCSe ) have been obtained from reaction of the parent tris complex with the appropriate Ag+ salt.380 Representative complexes of this class have been shown by X-ray diffraction methods to have square pyramidal structures (71) in which the sulfur atoms of the two bidentate ligands comprise the basal plane (Fe—S 2.228 2.30 A) with the halide ion in the apical position (Fe—Cl 2.26-2.28 A).309 310 In the cases examined the metal atom sits 0.6 A out of the mean S4 plane in the direction of the apical halide ion. 

Over recent years there have been a number of publications concerned with formation constants of [Fe(a,a -diimine)3]2+ complexes at various temperatures. Consequently additional AH° and AS° values are now available (Table 13),425428 and some data concerning mixed solvents have also been reported.424 459 4,1 Most of the substitution reactions of the tris ligand, low-spin, intensely coloured complexes proceed at rates conveniently monitored by conventional spectrophotometric techniques, and a considerable body of literature dealing with these kinetic and mechanistic aspects has been published. The most important a,a -diimine ligands are 2,2 -bipyridine and 1,10-phenanthroline, and their iron(II) complexes are dealt with first before considering complexes of other a,a -diimines. 

Recent developments include synthesis of optically active trispyrazolylborates118 and both bis and tris ligands with CF3 groups,119 e.g., [HB(3,5(CF3)2)pz3] . It may be noted that main group elements such as tin can form pyrazolylborates.120... 

Complexes with other Bidentate 1,4-Diimines. The thermodynamic stability of the five-membered iron(II) 1,4-diimine chelate ring in low-spin complexes is illustrated by the facile autoxidation of saturated amine complexes to the corresponding colored 1,4-diimine complexes. The first example of this oxidative dehydrogenation is shown in equation (14), and the more recently studied " reaction (15) is known to involve iron(III) species and radical intermediates. Interestingly, the complex [Fe(CN)4(HN=CHCH=NH)] can be obtained by oxidizing [Fe(CN)4(en)] , whereas the tris-ligand complex of this smallest diimine ligand has yet to be prepared. 

Solution NMR spectroscopic data of these tris(ligand) adducts point to the existence of /solid state for In(pyS)3, In(3-CF3pyS)3, In(3-Me3SipyS)3, and In(pymS)3. However, the compound In(5-Et-4,6-Me2pymS)3 adopts a mer conformation in the solid state. The indium(III) complexes of... 

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