Bis complexes and

DR. MARGERUM Yes, it does turn up in a number of instances. The example you are talking about was an EDTA reaction with a copper triglycine in which the released triglycine catalyzed the substitution of the EDTA. This resulted from the fact that the bis-triglycine complex is faster to undergo substitution than is the mono complex. The released triglycine formed a bis complex and the EDTA then attacked that. 

Solution studies on the compounds [BU4N] [M(R2NCS2)3] (M = Zn or Cd R = Me or Et) show the zinc complex (unlike the cadmium complex) to be some 90% dissociated into the neutral bis complex and the free ligand anion. This is in accord with the structure of the solid complex,907 which shows that only one dithiocarbamato group is bidentate, the other two being formally unidentate. 

In the past, ESR studies on isoxazole(s) revealed the formation and structure of radical as well as the stereochemical information of metallic complexes. It has been reported that the metal appears to be 4-coordinate square planar in bis complexes and hexacoordinate in tetrakis complexes... 

The kinetics of the formation and dissociation of the thiocyanate complexes of Ni + in the solvents HjO, DMSO, DMF, methanol, and acetonitrile have been investigated by various relaxation techniques. In all solvents except water, two temperature- and concentration-dependent relaxation times were observed they were attributed to the mono- and bis-complexes and the corresponding rate constants and activation parameters were evaluated. It is suggested that the rate and equilibrium constants can be correlated with the donicity scale for the solvents introduced by Gutmann (see below). The normal dissociative-interchange (/d) mechanism is invoked for the formation of nickel monothiocyanate in DMSO and of nickel nitrate, toluene-4-sulphonate, and trifluoroacetate in acetonitrile, ... 

A two-step mechanism is proposed for the binding of imidazole (Im) to tetra-phenylporphinatoiron(iii) in DMSO. Overall rate constants of (3.8 0.4)x 10 1 mol s and 17 2s, respectively, have been obtained for the formation and dissociation of the bis-complex, and it is suggested that the rate-determining step is the second ... 

Figure 5.22 NHC2E2 (E = P, As) complexes 189 and 190, CAAC2Sb2 complex 191, [(NHC)Bi] complexes and IPr-stabilized diphosphorus tetroxide 194.

Classic A/-heterocychc ligands, eg, bipyridyl (bipy), terpyridyl, imidazole, pyrazine, phenanthroline, piperazine (including alkyl- and aryl-substituted derivatives), and polypyrazol-l-yl-borates (bis, tris, and tetra), have all been found to coordinate Th(IV) chlorides, perchlorates, and nitrates. The tripodal hydrotris(pyrazolyl)borates, HBPz, have been used to stabilize organometaHic complexes (31). Bis-porphyrin Th(IV) "sandwich" complexes have been... 

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

Bismuth trioxide forms numerous, complex, mixed oxides of varying composition when fused with CaO, SrO, BaO, and PbO. If high purity bismuth, lead, and copper oxides and strontium and calcium carbonates are mixed together with metal ratios Bi Pb Sn Ca Cu = 1.9 0.4 2 2 3 or 1.95 0.6 2 2 3 and calcined at 800—835°C, the resulting materials have the nominal composition Bi PbQ4Sr2Ca2Cu20 and Bi 25PbQgSr2Ca2Cu20 and become superconducting at about 110 K (25). 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Potassium 2,3-dimethylphosphindolide and Sml2(THF)2 give the complex 262 [94JOM(464)149]. Bis(dibenzophospholyl) and metallic samarium activated by HgCb lead to the ri -coordinated species 263. 

It exists as optical isomers and was first resolved by Alfred Werner. The route to the bis complexes generates the ammine in situ and is applicable to other ammines (tren, trien, etc.) yielding principally the trans-isomer... 

The synthesis, structures, and reactivity of neutral and cationic mono- and bis(guanidinato)zirconium(rV) complexes have been studied in detail. Either salt-metathesis using preformed lithium guanidinates or carbodiimide insertion of zirconium amides can be employed. Typical examples for these two main synthetic routes are illustrated in Schemes 73 and 74. Various cr-alkyl complexes and cationic species derived from these precursors have been prepared and structurally characterized. 

Bis complexes of pyrrole-A -carbodithiolate (L) with Pt(II), Pd(II), and Co(II), as well as Cu(II), have been reported. A mixed chlorine-ligand complex of Pt(IV), [PtCl2L2], was also prepared. Infrared spectra of these complexes indicated an exocyclic single C-N bond, as opposed to similar complexes containing other dithiocarbamate ligands (407). 

Borylated Bis(dioxime)metal Complexes and Related Compounds... 

Significant advance in the field of asymmetric catalysis was also achieved with the preparation of l,2-bis(phospholano)benzene (DuPHOS 4) and its confor-mationally flexible derivative (l,2-bis(phospholano)ethane, known as BPE) by Burk et al. [59]. Two main distinctive features embodied by these Hgands, as compared to other known chiral diphosphine ligands, are the electron-rich character of the phosphorus atoms on the one hand and the pseudo-chirality at phosphorus atoms, on the other. These properties are responsible for both the high activity of the corresponding metal complex and an enantioselection indepen-... 

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