Cationic complexes nickel

The nickel cationic complex [Ni(Me)(np)3] reacts with CO giving the corresponding acetyl derivative ... 

ICC1063) and di- 318 (02JCS(D)441) azine-coordinated nickel complexes can be prepared from pyridine-containing aldimines of 2,6-diformyl-4-methylphenol. A nickel cationic complex of a 2,6-bis-azomethine derivative contains two coordinated pyridine N-substituents 319 (M = Ni, R = H, R = Me, = MeOH) (96T3521). Zinc chelate 319 (M = Zn, R = R = Me, no L) has a similar structure (02IC6426). Tetranuclear manganese poly-chelate contains two coordinated pyridine... 

In addition to the neutral nickel/phosphine complexes used in the Shell Higher Olefins Process (SHOP), cationic Ni-complexes such as [(mall)Ni(dppmo)][SbF6] (see Figure 5.2-7) have attracted some attention as highly selective and highly active catalysts for ethylene oligomerization to HAOs [106]. 

NBP reagent la 90, 359 Neatan perservation la 134 Neoamygdalline lb 121 Neo-kestose lb 423 Neomycin la 287,423 Neostigmine lb 290 Nephopam la 45 Nerol la 76,327 -, glucoside la 327 Netilmicin la 105,286,287 Nettle leaf extract lb 217 Neuroleptics lb 352 Nickel-DMSO complex lb 259 Nickel cations la 144,145,311 lb 259-260... 

Triphenylformazan behaves as a bidentate ligand forming 2 1 complexes (217) with divalent copper, nickel, and cobalt.377 Formazan metal complexes can be compared to complexes of azo dyes or beta diketones due to structural similarity.301,302 In general, formazan metal complexes have low stability toward acids. However, when electron-donating substituents are added to the aromatic ring, a considerable enhancement in stability is observed. Cationic complexes of type 218 are also known. The complexation of formazan with metal cation can be accompanied by oxidation to the tetrazolium salt and the formation of a complex... 

Nickel(O) complexes are extremely effective for the dimerization and oligomerization of conjugated dienes [8,9]. Two molecules of 1,3-butadiene readily undergo oxidative cyclization with a Ni(0) metal to form bis-allylnickel species. Palladium(O) complexes also form bis-allylpalladium species of structural similarity (Scheme 2). The bis-allylpalladium complexes show amphiphilic reactivity and serve as an allyl cation equivalent in the presence of appropriate nucleophiles, and also serve as an allyl anion equivalent in the presence of appropriate electrophiles. Characteristically, the bis-allylnickel species is known to date only as a nucleophile toward carbonyl compounds (Eq. 1) [10,11],... 

The formation of cationic nickel hydride complexes by the oxidative addition of Brdnsted acids (HY) to zero-valent nickel phosphine or phosphite complexes (method C,) has already been discussed in Section II. Interesting in this connection is a recent H NMR study of the reaction of bis[tri(o-tolyl)phosphite]nickelethylene and trifluoroacetic acid which leads to the formation of a square-planar bis[tri(o-tolyl)phosphite] hydridonickel trifluoroacetate (30) (see below) having a cis arrangement of the phosphite ligands (82). 

Beyond palladium, it has recently been shown that isoelectronic metal complexes based on nickel and platinum are active catalysts for diyne reductive cyclization. While the stoichiometric reaction of nickel(O) complexes with non-conjugated diynes represents a robust area of research,8 only one example of nickel-catalyzed diyne reductive cyclization, which involves the hydrosilylative cyclization of 1,7-diynes to afford 1,2-dialkylidenecyclohexanes appears in the literature.7 The reductive cyclization of unsubstituted 1,7-diyne 53a illustrates the ability of this catalyst system to deliver cyclic Z-vinylsilanes in good yield with excellent control of alkene geometry. Cationic platinum catalysts, generated in situ from (phen)Pt(Me)2 and B(C6F5)3, are also excellent catalysts for highly Z-selective reductive cyclization of 1,6-diynes, as demonstrated by the cyclization of 1,6-diyne 54a.72 The related platinum bis(imine) complex [PhN=C(Me)C(Me)N=Ph]2Pt(Me)2 also catalyzes diyne hydrosilylation-cyclization (Scheme 35).72a... 

Cationic latexes, 19 855 Cationic metallocene complexes, 16 90 Cationic monomers, of water-soluble polymers, 20 475-482 Cationic nickel ligand complexes,... 

Table 3.2. Cyclopropanation with stoichiometric amounts of cationic iron and nickel carbene complexes.

The compounds in question are classified by oxidation state of the central metal atom. Assignment of oxidation state is normally straightforward when the formula is known, but there are cases where the choice is somewhat arbitrary. Thus bis(cyclopentadienyl)nickel, (CcH Ni, may be considered as the nickel (II) cation complexed by two cyclopentadienyl anions, or as a combination of an uncharged nickel atom with two cyclopentadienyl... 

The organometallic complexes of nickel(II) of general formula [NiX(R)(PR3)2] and [NiR2(PR3)2] are invariably diamagnetic square planar compounds like (156)1196 and (157).1200 The cationic complex [Ni(Me)(PMe3)4]BPh4, on the other hand, is five-coordinate.1199... 

The template condensation of 2,3-butanedione dihydrazone with aldehydes or ketones affords a variety of octaazabis(a-diimine) macrocyclic complexes of nickel(II), according to the Scheme 48.2655 NH deprotonation with py or Et3N of the aforementioned cationic complexes leads to neutral NiL species. 

The isomerization of the internal olefin 3PN to the terminal olefin 4PN is a critical step in the hydrocyanation of 3PN to ADN [Eqs. (9) and (10)]. Unfortunately, there is a loss in yield because the undesirable conjugated isomer 2PN is also produced. Observations discussed below have led us to the belief that cationic nickel-hydride complexes, HNiL4, may be important in the isomerization process. 

Sachtler proposes a "dual site" mechanism where the hydrogen is dissociated on the Ni surface and then migrates to the substrate which is coordinated to the adsorbed nickel-tartrate complex. In this context it is of interest that the well known Sharpless epoxidation probably takes place on a dimeric tartrate complex of Ti. Sachtler suggests that both the anion and the cation have a function which varies according to the conditions used. It is not clear whether the spillover mechanism is also proposed for the reaction in solution [55]. 

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