Tris-chelate dianions

For a given M and z, the ease of oxidation of [MfS R ]2 decreases in the order R = H, alkyl > Ph > CF3 > CN and R = Ph > CF3 > CN for the analogous tris-chelated complexes. The series parallels the election-donating tendency of the. substituent R. For the dianion, another stability trend was noted the oxidative stability increases across the first row transition metals Fe Co < Ni < Cu. 

A statistical analysis, carried out on the crystal structure data for the tris-chelates 488a-d and 489a988, indicated that the most critical factors in controlling the overall shape of the dianion were the distances of the Sn atom from the dithiolate ligand planes. 

The dodecaiodide dianion in [Ag2([15]aneS5)2](li2) is described as a charge-transfer complex [(l )2-(l2)5] bound to the cation by Ag-I bonds with weak 1- -S interactions combining to build up an extended three-dimensional, spiral superstructure. In marked contrast, the same anion in bis[potassium(dibenzo-18-crown-6)] dodecaiodide nearly a discrete entity (I2 I3 1213 12). In [Cu(Dafone)3](Ii2), iodine-iodine interactions assemble novel, planar, [I ] anions into a network around the strained tris-chelate complex ofCu(II). ... 

The structure of the dianion SiF was first confirmed106 by X-ray diffraction in 1935, and has since been re-examined with a variety of counteranions that of Si(-OC6H46)3 was determined107 in 1969. The tris-chelate cations Si(acac)3 108 Si(tropolonato)3 109 and 511,0 have been resolved for use in mechanistic studies. 

Fig.4 Generation of chirality upon metal ligand coordination from a orientation of individual chelating ligands (8/k) ([Ni(en)(OH2)4]2+) b tris-bidentate octahedral coordination (A/A) ([Fe(cat2 )3]3" [88]) c coordination of chiral ligands (R/S) ([Co(NH3)4(sarcosinato)]2+) d loss of improper symmetry axes of individual ligands upon coordination ([Pt(iso-butylenediamine)(meso-stilbenediamine)]2+ [89]) en = 1,2-ethylenediamine cat2- = 1,2-catecholate dianion...

Neutral bis-chelate complexes of the type [ /ac-(OC)3Re(MeCO)3 2Zr] and [ fac-(OC)3Re(MeCO)2(RCO) 2Hf] (R = Me, CHMe2 or PhCH2) have been prepared by reaction of [RC(0)Re(C0)s] with MeLi in THF, followed by addition of a THF solution of ZrCU or FIfCl4. The [/flc-(OC)3Re(MeCO)3] dianion is the formal, metalla analogue of the tri-acetylmethanate anion. The Zr and Hf complexes were obtained in rather poor yields as pale yellow air-sensitive solids. IR and HNMR spectra are consistent vrith tridentate coordination (22) of the triacetylmetallate ligands. ... 

In order to obtain insight into the stability of the anion radical of borane chelates, Okada and co-workers examined the reduction of the 2,4,6-tribenzoyl-l,3,5-tris(diphenylboryloxy)benzene 105 <1998TL6483>. Treatment of 105 with an Na-K alloy in THE produced the dianionic species 106 whose ground state was shown to be a triplet. 

Complexes prepared from [Rh(CO)2Cl]2 include (a) five-coordinate [Rh(CO)2L2CI] (L = many imidazoles), (b) [Rh(CO)2(bid)), [Rh(CO) P(OPh)(bid)] and [Rh(CO)(PPh )(bid)] (bid = the anionic chelate ligands, 2-carboxyquinolinato, 1,1,1-trifluoro - 5,5,5-tri-methylpentanedionato, N-hydroxy-N-nitrosobenzenaminato, oxinate derivatives, and the Schiff bases derived from condensations of 3-diketones with N-methyl-S-methyldithiocarbazates),(c) [ Rh(CO)2)2 -L4] (L4 = tetradentate azine dianions e.g. 0CgH4CH=NN=CHCgH40 ),... 

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