Zinc complexes Zn

Bis-phosphaallyl complexes of zinc have been prepared and characterized from cyclic amino-phosphazanes and aminoiminophosphanes. The structure of the bis(l,3-diaza-2-phosphaallyl)zinc complex [Zn(RNPNR )2] (R = R = C6H3Pr2i-2,6) was determined.311... 

Fig. 2.136. Molecular structures of (a) naturally occurring magnesium chlorin, bacteriochlorophylls-d (Bchls-d), (b) their synthetic analogues, methyl bacteriopheophorbides-d (MBPhes-d, and (c) 3 -epimeric zinc complexes (Zn-MBPhes-d). Reprinted with permission from S. Sasaki et al. [307],...

N3CI plane (207). The other halids and the cadmium complexes are isomor-phous with the appropriate forms, and undoubtedly possess related five-coordinate structures. A number of studies of the vibrational spectra of the [M(terpy)X2] species have been described, all of which support the formulation as isomorphous five-coordinate complexes (124, 171, 225, 371). The copper(II) complexes [Cu(terpy)Cl2] are isostructural, and a number of studies of the paramagnetic species doped into a host matrix of [Zn(terpy)Cl2] have been reported (23, 213). The zinc complex [Zn(terpy)Cl2] exhibits absorption maxima at 22,650 and 18,000 cm (23, 348). The mercury(II) halide adducts are not so well characterized, but may be prepared by the direct reaction or HgX2 with terpy (171) or by trans-metallation of [Ph2Sn(terpy)Cl2] with HgCl2 (471). They are thought to possess similar, five-coordinate structures. The structures of the 1 1 adducts of the nitrates M(N03)2 terpy are not known with any certainty (171,328). A Cd NMR study of Cd(N03)2 terpy has been reported (430). 

The monomeric zinc complex [Zn(2-C6H4PPh2NSiMe3)2], which was recently obtained by reaction of the ortho-metaUated species [Li(2-C6El4PPh2NSiMe3)]2 Et20 with ZnCE in THF, represents a good example of side-arm intramolecular coordination. Its molecular structure determined by X-ray crystallography shows a tetrahedrally... 

If an extra anion binds to form a five-coordinate complex, it should become more difficult to dissociate a proton from bound water, so raising the p/Co and decreasing the catalytic efficiency. This theory has been tested using the pendant arm ligand L3 (Fig. 6), which forms a five-coordinate zinc complex [Zn(L3)(H20)]C104. An X-ray structure of the... 

The introduction of all l groups at the porphyrin meso positions induces ruffled deformation [9,10,27,28]. A typical example is meso-tetra(te/t-butyl)porphyrin prepared by Smith and coworkers [27,51]. The meso carbon atoms deviate from the mean porphyrin plane upward and downward alternately. The average deviation of the meso carbons in the zinc complex Zn(T BuP) reaches as much as 0.899 A [28], Thus, the iron complexes of this porphyrin such as Fe(T BuP)X and [Fe(T BuP)L2] should be the best model to elucidate the effect of ruffled porphyrin ring on the electronic structure of the iron(lll) complexes. However, the synthesis of Fe(T BuP)X has been unsuccessful until now. For this reason, meso-tetraisopropylporphyrin complexes Fe(T PrP)X, where the meso te/t-butyl groups are replaced by the less bullqr isopropyl groups, have been examined [52,53]. 

X-ray diffraction studies on alkoxy-dithio-benzoato zinc complexes [Zn(n-odtb)2] showed that in the solid state the material is a dimer containing an eight-membered Zn-S-C-S-Zn-S-C-S ring the dimer held together in the nematic phase and disappeared in solution where is found a monomeric structure [85]. This work is confirmed by EXAFS studies [90]. 

The first crystallographic study of a dithiocarbamate complex was carried out by Simonsen and Ho in 1953 (382), whereby they reported the space group and unit-cell parameters of the zinc complex [Zn(S2CNEt2)2]- In the proceeding 50 years, a massive amount of structural data has been amassed for dithiocarbamate... 

Derive a solubility diagram (solubility versus pH) for Zn(OH)2 that takes into account the following soluble zinc hydroxide complexes Zn(OH)+, Zn(OH)3, Zn(OH)4 . 

Simultaneous detenuination of Cu and Zn in the form of coloured PAR complexes is performed at pH 10 in the presence of pyrophosphate which binds the admixtures of Al, Fe and Mn into the inactive complexes. The measurements of the change in the optical density are made at 520 and 550 nm before and after the destmction of the complexes by EDTA, or at 530 nm before and after the destruction of the copper complexes by the thioglycolic acid and the destmction of the zinc complexes by EDTA. The detection limit for Cu is 2-5, for Zn - 3 p.g/diW. The application of these methodics at pH 8 enables one to determine simultaneously Cu and Zn at high excess of the latter. 

Mixtures of manganese, magnesium, and zinc can be similarly analysed. The first EDTA end point gives the sum of the three ions. Fluoride ion is added and the EDTA liberated from the magnesium-EDTA complex is titrated with manganese ion as detailed above. Following the second end point cyanide ion is added to displace zinc from its EDTA chelate and to form the stable cyanozincate complex [Zn(CN)4]2- the liberated EDTA (equivalent to the zinc) is titrated with standard manganese-ion solution. 

It is interesting to note that the magnesium or zinc complexes of methyl pheophorbide a (11, M = Mg, Zn R = C02Me) or methyl pyropheophorbide a (11, M = Mg, Zn R = H) are cleaved between positions 20 and 1 by singlet oxygen, whereas in contrast nature cleaves the chlorin at the 4,5-C —C double bond.44-45a h46 The ring fission at the 4.5-C —C double bond can be achieved with the cadmium(II) complex of methyl pheophorbide (11, M = Cd R = C02Me) to produce 12.43i... 

It has been reported that the zinc hexasulfido complex, Zn(S6)(TMEDA) (TMEDA=] r,] T,N, N -tetramethylethylenediamine) acts as a sulfur transfer reagent in an analogous manner as the above-mentioned titanium polysulfido complexes. The sulfur transfer reaction between Zn(S6)(TMEDA) and TiCp2Cl2 cleanly proceeds at room temperature to afford ZnCl2(TMEDA) and TiCp2S5 together with Ss (Scheme 51) [132]. This result suggests that... 

H NMR data has been reported for the ethylzinc complex, Zn(TPP—NMe)Et, formed from the reaction of free-base N-methyl porphyrin H(TPP—NMe) with ZnEti. The ethyl proton chemical shifts are observed upheld, evidence that the ethyl group is coordinated to zinc near the center of the porphyrin. The complex is stable under N2 in the dark, but decomposed by a radical mechanism in visible light.The complex reacted with hindered phenols (HOAr) when irradiated with visible light to give ethane and the aryloxo complexes Zn(TPP—NMe)OAr. The reaction of Zn(TPP—NMe)Et, a secondary amine (HNEt2) and CO2 gave zinc carbamate complexes, for example Zn(TPP—NMclOiCNEti."" ... 

C18-0033. Zinc oxalate, Zn(C2 O4), is sparingly soluble in water (Zjp = 1.4 X 10 ). The Zn ion forms a tetrahedral-shaped complex with ammonia. The formation constant for the complex is 4.1 X 10. How many moles of zinc oxalate will dissolve in 1.0Lof0.200M aqueous ammonia ... 

Single-phase ZnS films of a fine grain size (no XRD shown) and a band gap of 3.7 eV were electrodeposited from aqueous alkaline (pH 8-10) solutions of zinc complexed with EDTA, and thiosulfate as a sulfur source [101]. The voltammet-ric data implied that deposition occurred either by S-induced UPD of Zn or by a pathway involving both Zn " and thiosulfate concurrently. 

The zinc tris(ferf-butoxy)siloxide complex Zn[0Si(0 Bu)3]2 2 was prepared from the reaction of ZnMe2 with HOSi(O Bu)3 [107]. This complex was structurally characterized as an asymmetric dimer with four - OSi(O Bu)3 ligands, each exhibiting a unique coordination mode ( fi - , r] ... 

CH3 -Zn with superstoichiometric (defect) zinc atoms (Zn -impurity centres of conductivity). The larger is the electric positivity of the metal in these complexes, the larger is the ionicity of the carbon-metal bond, carbon being at the negative end of the dipole. Thus, in the case of C - K bond, ionicity amounts to 51%, whereas for C - Mg and C - Zn bonds ionicity amounts to 35% and 18%, respectively [55]. Consequently, metalloorganic compounds are characterized by only partially covalent metal-carbon bonds (except for mercury compounds). 

Diethylenetriamineacetic acid has been used in the formation of homodinuclear zinc complexes with the bridging imidazole. The crystal structure of [LZn(imidazolate)ZnL]C104 was obtained. The magnetics of the heterodinuclear Cu-Zn complex were studied and single crystal EPR of the Zn2 dimer doped with the CuZn dimer.139... 

The pyrazole phosphazine ligand, hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene (16) forms a dizinc complex, that has been structurally characterized, and the analogous copper zinc complex.158 Two ZnCl2 units are coordinated, one distorted tetrahedral and one distorted trigonal-bipyramidal, separated by 7.51 A. Cu1 and ZnCl2 can also be coordinated giving a heteronuclear compound with a Zn Cu separation of 6.798 A. 

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