Ni II Compounds

Prepare 0.2 M solution of Ni(CH3C02)2.4H20 and add gradually NH2(CH2)2NH2 with shaking, until the maximum change in colour is achieved. Record the visible/u.v. spectrum of the solution in a 1 cm quartz ceil, using water as a blank. 

Prepare 0.2 M solution of NiCl2.6H20 and add gradually, with shaking, ammonia solution until the initial precipitate redissolves and maximum colour change is produced. Measure the spectrum as above. If available, use a spectrophotometer whose wavelength range extends to 1000 nm. 

Comment on the two spectra. What quantitative conclusions can be drawn from the first spectrum  

Prepare concentrated solutions of the two diammino-Ni(II) complexes in dimethyiformamide and in acetonitrile and run their u.v./visible spectra. 

The magnetic susceptibility of Ni(II) compounds and complexes depends on their structure and the ligands strengths. Determine the magnetic susceptibility of the precipitated complex in Sec. 15.3.2 and of the other prepared complexes. 

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In addition, heterodinuclear Fe(III)Ni(II) compounds have been prepared starting from high spin [FeCl(salen)] and NiL with L being the di-anion of the N30 ligand depicted in Fig. 16 [191]. The imidazole-bridged [FeCl (salen)NiL] [191] and also [FeCl(5-OCH3-salen)NiL] both exhibit Fe(III) spin crossover [192]. 

It was shown that room-temperature molten salts derived from the combination of 1,3-dialkylimidazolium chloride and A1C13 can be used as solvents in two-phase catalytic dimerization of propene to give hexenes catalyzed by Ni(II) compounds (125). The effects of phosphane ligands coordinated to nickel and operating variables were also investigated (126). The dimerization products separate as an organic layer above the molten salt. This reaction has been carried out with n-butenes as the reactant and cationic nickel complex catalysts dissolved in organochloroaluminate liquids (127). 

Catalysts capable of 2, co-linkage of a-olefins are obtained from the reaction of Ni(0) or Ni(II) compounds, such as Ni(Cod)2 or Ni(All)2 respectively, with aminobis(imino)phosphorane, such as (Me3Si)2NP(=NSiMe3)2, preferably used in equimolar ratio the catalysts are characterised by the appearance of Ni(II) species as has been shown by scheme (18) [182]. 

The polymers of /i-olefins with 1,2-linked monomeric units have been obtained by polymerisation in the presence of Ziegler Natta catalysts, such as TiCl3—AIR3 (R=Et, z -Bu), used preferably in a combination with Ni(II) compounds, especially NiCb. For instance, monomer isomerisation-polymerisation of m-2-butene with the TiCh/NiCh AIEf (1 1 3) catalyst, carried out in rt-hcptane at 80 °C, produced poly(l-butene) in a yield of ca 72% within 24 h. Polymers obtained under such conditions are characterised by relatively high molecular weight (40 x 103—85 x 103) and contain a significant amount (up to ca 72%) of the isotactic fraction [444], They also contain head-to-head (tail-to-tail) as well as 2,3-linked monomeric units to some extent [193]. 

It should be mentioned that some Ziegler-Natta catalysts containing Ni(II) compounds, which are capable of inducing /i-olefin isomerisation to the corresponding a-olefin, e.g. 2-butene to 1-butene, readily promote the copolymerisation of the a-olefin formed with ethylene [464 166],... 

Square coplanar bonds are formed only in complexes with certain polydentate ligands or combinations of ligands such that steric factors prevent a tetrahedral configuration. They include the phthalocyanine (low-spin), the bis-salicylaldehyde diimine complex (a) (in which the maximum deviation of any atom from the mean plane of the complex is 0 6 A and Co-O(N) is 1-85 A), and the ion (b) in the salt [Co(mnt)2] [N(C4H9)4] 2. The magnetic moment of this salt (3-92 BM) corresponds to 3 unpaired electrons (d" ). The Ni((ii) compound is isostructural. Ions [M(mnt)2] are formed by Ni(m) and Cu(iii). The similar ion formed by... 

Cyclodimerization of 1,3-Diolefins. The nickel-ligand catalysts effective in the cyclodimerization of 1,3-diolefins are composed of preformed complexes such as [Ni(CO) L4 ] or [Ni(cod)2]/L [L = PR3, P(OR)3] or are prepared in situ by reducing a Ni(II) compound such as [Ni(acac)2] in the presence of L and the diolefin . Orga-noaluminum compounds are most commonly used reducing agents, but various other systems have also been investigated . ... 

There is also a direct correlation between Ni 2p binding energy and the estimated charge on Ni for some simple Ni(II) compounds, as shown in Figure 15.8. Similar correlations have been observed recently for a large number of copper compounds [5]. 

The solution preparation of Co(II) coordination compounds containing ligands 1-4 was already reported in the literature [31]. Nevertheless, we have been able to prepare the same compounds using solvent-free mechanochemical synthesis, quantitatively and only in 20 minutes. These complexes were characterized by XRPD and SCXRD, when possible. Interestingly, the Co(II) compound containing ligand 2 was proven to be isostructural with the corresponding Ni(II) compound. 

Earlier work in mammalian systems also tended to use soluble Ni(II) compounds, such as NiCl2. These compounds are, at most, weakly mutagenic at toxic concentrations at the hprt locus of Chinese hamster V79 or mouse FM3A cells (Miyaki et al. 1979 Hartwig and Beyersmann 1989b Morita et al. 1991) and at the TK locus in mouse lymphoma cells (Amacher and Paillet 1980). Nontoxic concentrations of Ni(II) were able to alter the expression of a temperature-sensitive v-mos gene in transformed rat kidney... 

Related dinickel(II) p-N bridging compounds with NHC ligands were reported by Hillhouse et al. in 2009 (Scheme 10.31) [40]. [Ni(I)(p-Cl)(l Pr)]2 underwent one-electron oxidation by MesNj to afford a dinickel(II) bridging imide [ Ni(ll)(l Pr)(Cl) 2(p-NMes)] 66, in which one of the chlorides can be abstracted by NaBAr, to produce the dinickel(ll) ion pair compound 67. The Ni(ll)-Ni(ll) bond lengths in 66 and 67 are 2.5767(15) and 2.2911(8) A, respectively (Entries 5 and 6, Table 10.3). Complex 66 can also undergo one-electron reduction of the [(Ni(ll)Cl 2(p-NMes)] core, to afford a mixed-valent Ni(I)-Ni(II) compound 68, which upon treating with a one-electron oxidant gives 67 as the product. It is noteworthy that 67 and 68 bear similar core structures, but the Ni-Ni bond... 

A Pt(II)-Ni(II) compound 216 was synthesized via straightforward salt metathesis reaction (Scheme 10.88) [151]. The Pt(II)-Ni(II) bond length in 216 is 2.570(1) A (Entry 1, Table 10.16), and a wetik intermolecular Pt-Pt interaction was found to be responsible for the formation of a head-to-tail dimer structure of 216. A magnetism study revealed 216 to be one of the first examples of antrferromagnetic coupling through an unbridged Pt-Pt interaction. 

Ni(n) compounds are used usually in this Ni catalyzed reaction. Kochi disproved already in 1979 (25) the obvious assumption that the catalytic cycle is dominated by a change of Ni(0)/Ni(H). The shortened reaction scheme shows that the oxidative addition involves Ni(I) i(III). In the reductive elimination the product fragments are involved. The halogen is eliminated from the reaction cycle as a Ni(II) compound. Methyl substituted polyphenylenes can be obtained according to tfiis reaction scheme. The GPC of the THF soluble part is shown in figure 2. In Ais GPC the peaks of bi-, quarter-, sexi- and octiphenylene derivatives are included. 

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