Tetrakis transition metals

These rod-shaped ligands share a sterically efficient terminal N-donor and their divalent Co chemistry is well established. They will be discussed here only with selected examples. [Co (NCMe)6](TFPB)2 (TFPB- = tetrakis(3,5-bis(trifhioromethyl)phenyl)borate)) has been synthesized and characterized in the solid state along with a number of other divalent transition metal analogs.357 As a result of the extremely poor coordinating ability of the anion and facile loss of MeCN ligands from the cation, the salt is an excellent source of naked Co2+ ions. Thermolysis up to 100 °C leads to the loss of one MeCN and formation of a r -bound nitrile, whereas above 130 °C decomposition occurs with loss of MeCN and abstraction of fluoride from the anion to form CoF2. 

Bis[(tris(isopropyl)cyclopentadienyl)]zinc (Zn C5(Pr1)3H2 2, 21) and bis[(tetrakis(isopropyl)cyclopentadienyl)]zinc (Zn C5(Pr1)4H 2, 22) were synthesized from the respective potassium cyclopentadienides and zinc iodide as shown in Scheme 18.50 The same slipped sandwich compounds were also isolated from zinc-reduced VC13 solutions when they were treated with these alkali metal cyclopentadienides at room temperature.51 The outcomes of these reactions suggest that zincocenes are likely intermediates in the syntheses of transition metal metallocenes, in which the metal halides have been pre-reduced with zinc. The solid-state structure of Zn G5(Pr1)4H 2 is shown in Figure 10. The sole... 

Biuret (bu) co-ordinates transition metals in both neutral and anionic forms. Compounds containing neutral bu include both bis- and tetrakis-complexes. The latter are limited to the larger cations of the group II [e.g., [Sr(bu)4]2+ [9] and lanthanide groups e.g., [Sm(bu)4]2+ [ 10,11]. Only the former are considered in detail in this review, together with bis-complexes containing anionic bu as they have the greater potential for formation of 1-D chains and 2-D sheets. 

N,N, N, iV -Tetrakis(2-benzimidazolylmethyl)-l,3-diaminopropan-2-ol, hydrogen peroxide determination, 637 A,A,A, iV -Tetrakis[2 (l -ethylbenzimidazol-yl)-l, 3-diamino-2-hydroxypropane], transition metal peroxides, 1066 meiO-Tetrakis(4-sulfonatophenyl)porphine, luminol oxidation, 646... 

At the time of our investigation the only known coordination compounds of chlorophosphines (aside from phosphorus trichloride complexes) were the nickel-(0) compounds, tetrakis(methyldichlorophosphine)nickel-(0) (20) and tetrakis-phenyldichlorophosphine) nickel- (0) (17). Tetrakis (methyldichlorophosphine) -nickel-(0) is noteworthy in that it represents a still rare example of the direct reaction of a ligand with an elemental transition metal to give a complex, while tetrakis (phenyldichlorophosphine) nickel- (0), like tetrakis (trichlorophosphine) -nickel-(0), was obtained readily via the carbonyl. AD chlorophosphine-nickel-(O) complexes, including the phosphorus trichloride complex, Ni(PCl3)4, are compounds relatively stable in the atmosphere, but show poor stability in almost any organic solvent, even under strictly anaerobic conditions. 

The problem of terminal addition (anti-Markovnikov) of HCN to isolated unactivated double bonds was not solved until carbon monoxide-free, low-valent transition metal complexes became available. During the mid 1960s, W. C. Drinkard allowed 1-hexene to react with HCN in the presence of tetrakis(triethylphosphite)nickel(0) and the resulting product mixture contained a small amount of the terminal addition product n-heptanenitrile, and Drinkard and Lindsey found that the reaction with 3-pentenenitrile produced ADN (7). 

A recent report 121) on the reactions of tetrakis(trimethylphosphine) iron, Fe(PMe3)4, with carbon dioxide reveals a rich and varied chemistry, illustrating many of the reaction modes of C02 with low-valent transition metal complexes. Two primary reactions of C02 with Fe(PMe3)4 are noted, as a consequence of the two isomers in equilibrium (49). 

For the transition-metal catalyzed decomposition of silyl-substituted diazoacetates 205 [silyl = SiMe3, SiEt3, SiMeiBu-i, SitPr-i SiPtnBiW, SiMe2SiMe3], copper triflate and dirhodium tetrakis(perfluorobutyrate) proved to be the best catalysts114. While these two catalysts induce the elimination of N2 at 20 °C even with bulky silyl substituents, dirhodium-tetraacetate even at 100 °C decomposes only the trimethylsilyl-and triethylsilyl-diazoacetates. When the decomposition reactions are carried out in... 

The third order optical susceptibility was measured for a series of transition metal tetrakis(cumylphenoxy)phthalocyanines at 1.064 pm. Metal substitution caused a dramatic variation in the third order susceptibility. The largest s were found in the Co, Ni, and Pt complexes. Metal substitution introduces low lying electronic states which can enhance the susceptibility in these phthalocyanines. A strategy for enhancing the figure of merit, x(3)/a> of centrosymmetric nonlinear optical materials is suggested. 

This paper is a more extensive survey of the influence of the metal on the hyperpolarizability of a series of the transition metal tetrakis(cumylphenoxy)-phthalocyanines (MPcCP4). The compounds chosen were those most closely related to PtPcCP4, the compound which showed the largest hyperpolarizibility in the previous study. Specifically, phthalocyanines substituted with the last four members of the first row transition metal series (Co, Ni, Cu, and Zn) and also with the Ni, Pd, Pt triad were prepared and studied. The near IR spectra of these tetrakis(cumylphenoxy)-phthalocyanines are briefly discussed. Speculation on how metal substitution can influence the third order susceptibility of a near centrosymmetric structure, like that of the phthalocyanines, is presented. 

ECL from inorganic chromophores has been observed from a variety of transition metal complexes of ruthenium, osmium, palladium, platinum, and a few other transition metal chromophores, some of which are listed in Tables 2 and 3. For example, ECL has been observed from tetrakis(pyrophosphito)diplatinate(II),... 

F. BIS[TETRAKIS(l-PYRAZOLYL)BORATO]MANGANESE(II)— TRANSITION-METAL POLY(l-PYRAZOLYL)BORATES... 

Enynes can also be synthesized in excellent yields with high regio- and stereoselectivity by transition metal catalyzed cross-coupling reaction. Thus, ( >l-alkenyl-disiamylboranes react with 1-halo-1-alkynes in the presence of catalytic amount of tetrakis(tripheny]phosphine)palladium to afford conjugated trans enynes (Eq. 100)145). 

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