Square Planar Ni II Complexes

When two diamine chelating ligands replace four water molecules in [Ni(H20)6] a square planar complex is formed. The following two preparations are based on the precipitation of large cations by large anions and on the chelate effect. 

Weigh your product to the nearest centigram and calculate the percentage yield based on the mass of Cul. 

The compound can be characterised by elemental analysis. Heating with nitric acid oxidises the anion to copper (II) nitrate with the removal of some I2 leaving Cul. Cu(Il) is then determined by reaction with excess iodide librating I2 which is titrated with thiosulphate. 

Calculate from each result the percentage of Cu in your preparation and hence its percentage purity. The titration may be carried out potentiometrically (Sec.2.5.1). 

Compare the appearance of the three prepared complexes and comment on their structure. 

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Nitroethane also has been utilized in place of primary amine or amide as a locking fragment in the template condensation reaction of amines and formaldehyde for the synthesis of macrocyclic complexes. For example, the square-planar Ni(II) complex of Lj was prepared by the reaction of Ni(en) +, formaldehyde, and nitroethane (17). 

The square-planar Ni(II) complex of an anionic macrocyclic ligand, 21, was prepared from the template reaction of 3,3 -(ethylenebis(imino-methylidene)bis(2,4-pentanedionato)nickel(II) with 1,3-diamino-2-pro-panol [Eq. (10)]. The uncoordinated -OH group reacted smoothly with acylating agents, resulting in -COPh and -COCH3 (28). 

Spectrophotometric data on some Ni(II) macrocyclic complexes are summarized in Table I. The maximum absorption of the square-planar Ni(II) complex with neutral azamacrocyclic ligand shifts to a longer... 

The structural parameters of various Ni(II) macrocyclic complexes are summarized in Table III. Square-planar Ni(II) complexes with saturated macrocyclic ligands have Ni—N bond distances ranging from 1.90 to 1.95 A, depending on the type of ligand. The Ni—N bond distances increase when square-planar Ni(II) complexes bind axial ligands to form octahedral species. For example, the square-planar Ni(II) complex... 

The square-planar Ni(II) complexes of Lie and L17 catalyze the cathodic reduction of several alkyl halides in aprotic solvents (76). In the presence of activated olefins such as CH2=CHCN or CH2=CH COOC2H5, the reduction of alkyl bromide leads to mixtures of products that are compatible with those formed by radical addition to the double... 

The reduction of various square-planar Ni(II) complexes of saturated macrocyclic ligands in acetonitrile leads to the formation of square-planar Ni(I) complexes (57, 135). In the case of Ni(II) complexes that... 

Why does the incorporation of a rigid, diphospine ligand with (3n of about 110° cause destabilization of square planar Ni(II) complexes ... 

It has been known that square-planar Ni(II) complexes are most stable with the 14-membered macrocyclic ligands. The t3q)ical 14-membered macrocycle is [14]aneN4, which is called cyclam. Therefore, many Ni(II) complexes synthesized are those with 14-membered macro-cyclic ligands that form 6-5-6-5-membered chelate rings with the metal... 

In the previous review examples of 7 couplings whose transmission is mediated by an intermediate moiety were quoted. During the period of this review an interesting example was presented by Jirman et al. in which the transmission of 7 is assumed to be mediated by the Ni orbitals in square-planar Ni(II) complexes of the Schiff base of (s)-2-(AT-benzylprolyl)aminobenzophenone and glycine. 

Comment on the observations that octahedral Ni(II) complexes have magnetic moments in the range 2.9-3.4 /ib, tetrahedral Ni(II) complexes have moments up to 4.1 /iB, and square planar Ni(II) complexes are diamagnetic. 

The basic reaction catalyzed by CODH is related to the water gas shift reaction employed industrially to generate H2 by the reaction of CO and H2O. Industrially the process is iron-catalyzed, and numerous organometallic complexes effect the same reaction [133]. Additionally, square-planar Ni(II) complexes electrocatalyze the reduction of CO2 to CO, including [Ni (cyclam)] (cyclam = 1,4,8,11-tetraazacyclotetradecane), nickel-porphyrins and phthalocyanines. The cluster [Fe4S4(SR)4] and certain Fe-porphyrins also catalyze this reaction [124]. 

The kinetics of substitution of a series of square-planar Ni(II) complexes by dithiocarbamate ion in acetone are generally second order. The variations... 

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