Nickel tetraphenyl

Reduction of both nickel porphyrins and thiaporphyrins to Ni1 species has been studied by EPR and 2H NMR spectroscopy.179, 2 58 The Ni1 complex of 5,10,15,20-tetraphenyl-21-thiaporphyrin has been isolated and characterized. Reaction of this complex with sulfur dioxide produced a paramagnetic five-coordinated Ni1 S02 adduct, while reaction with nitrogenous base ligands (amines, pyridines, imidazoles) yielded five- and six-coordinate complexes. In addition, the crystal structure of Ni1 diphenyldi-p-tolyl-21-thiaporphyrin has been determined. The coordination geometry about the nickel center is essentially square planar with extremely short Ni—N and Ni—S bonds (Ni—N = 2.015(2) A, 2.014(12) A, and 1.910(14) A and Ni—S = 2.143(6) A).2359... 

Both iron- and nickel-mediated cyclooligomerization processes have been used in direct routes to pyrrole derivatives. Preformed ferracyclopentadiene complexes can be converted in moderate yields into 2,3,4,5-tetraphenyl-... 

Fig. 10 Electrochemical energy level model for orbital mediated tunneling. Ap and Ac are the gas-and crystalline-phase electron affinities, 1/2(SCE) is the electrochemical potential referenced to the saturated calomel electrode, and provides the solution-phase electron affinity. Ev, is the Fermi level of the substrate (Au here). The corresponding positions in the OMT spectrum are shown by Ar and A0 and correspond to the electron affinity and ionization potential of the adsorbate film modified by interaction with the supporting metal, At. The spectrum is that of nickel(II) tetraphenyl-porphyrin on Au (111). (Reprinted with permission from [26])...

Tetramethyl- or tetraphenyl- (cyclobutadiene)nickel dihalides undergo reductive ligand substitution with nitrogen donor ligands such as 2,2 -bipyridine or 1,4-diaza-1,3-dienes with the addition of sodium metal237. The 2,2/-bipyridyl ligand is readily displaced and reaction of this complex with a variety of olefins and alkynes leads to cycloaddition reactions with the cyclobutadiene ligand. 

Bromoarenes are converted into the corresponding chloroarenes on treatment with sodium hypochlorite in the presence of a catalytic amount of nickel(II) tetraphenyl-porphin (NiTPP) and benzyltributylammonium bromide [8]. Fluoro and iodo substituents are not replaced. The reaction involves chlorine radical attack via the initial formation of a Ni(II)-OCl complex. Although high conversions are recorded, the procedure has not been extended for synthetic purposes. 

Through the presence of aromatic or pseudoaromatic groups in the molecule (tetraphenylborate and related derivatives, the tetraphenyl-arsonium ion, cationic triphenylmethane dyes, complexes of o-phenanthroline with divalent nickel or ion, where the hydrophobicity is increased by further substitution by a hydrophobic group on the pseudoaromatic nucleus). 

Charged to a one liter Hastelloy-C autoclave (Autoclave Engineer), provided with a magnet-drive stirrer, a mixture of methanol (5.4 mole), methylacetate (3.5mole), methyliodide (350 mmole), nickel iodide (40 mmole), lithium iodide ( 380 mmole) and tetraphenyl tin (130 mmole). 

Bis(dithiobenzil)nickel decomposes on being heated at 292° to give (exclusively) 2-phenylbenzo[ ]thiophene(95%).263a,263b Related metal complexes (e.g., those of Pd and Pt) behave similarly. In some cases (e.g., Pd) a mixture of 2-phenylbenzo[6]thiophene and tetraphenyl-thiophene is obtained. 

The photochemical couplings of 4,5-diphenyl- and 4-phenyl-l,3-diselenole-2-thione to give tetraphenyl- and diphenyl-tetraselenafulvalene, respectively, and elemental sulfur have been reported (79ZC192). In this same report the irradiation of 4,5-diphenyl-l,3-thiaselenol-2-one (52) in the presence of nickel tetracarbonyl gave the nickel thiaselenane (53). 

The Reppe hydrocarboxylation of acetylenes was initially carried out in the presence of an acid, but little was known about the function of the acid or the nature of the carbon monoxide transfer agent. Sternberg et al. found that diphenylacetylene can be hydrocarboxylated in alkaline solution and that in this case a nickel carbonyl anion is the source of carbon monoxide. When the hydrocarbon was shaken with a saturated solution of sodium hydroxide in methanol in the presence of excess nickel carbonyl under helium the reaction mixture turned dark red. After 80 hrs., acidification and workup aiforded a-phenyl-rru/is-cinnamic acid and 1,2,3,4-tetraphenyl-butadiene in the yields indicated. Note that the ciimamic acid results from cis addition of the elements of formic acid. 

Equimolar amounts of 2,3-diphenylcyclopropenone, phenyl isothiocyanate, and tetracarbonyl-nickel(O) were reacted in dimethylformamide at 65-70 C to give a mixture containing 2,3,6,8,9-pentaphenyl-l-thia-6-azaspiro[4.4]nona-2,8-diene-4,7-dione (30%). Similarly, the reaction of 2,3-diphenylcyclopropenone with carbon disulfide produced 2,3,8,9-tetraphenyl-l,6-dithia-spiro[4.4]nona-2,8-diene-4,7-dione (41 %). ... 

REACTION PRODUCTS AND ORGANOMETALLIC INTERMEDIATES WITH NICKEL(0) COMPLEXES. Nickel(O) complexes such as (Cod)2Ni, show a striking parallel with lithium(0) complexes in their reactions with diphenylacetylene a sequence of monomolecular reduction bimolecular, stereospecific reduction and cyclotrimerization (Scheme IX). Consonant with the suggestion that nickel(0) forms nickelirene (26) and nickelole (27) intermediates in the course of cyclotrimerization of diphenylacetylene is the isolation of (Z)-l,2-di-phenylethene (28) and (E,E)-1,2,3,4-tetraphenyl-l,3-butadiene (29) upon hydrolysis. Furthermore, when DC1 was used in the workup, both 28 and 29... 

Recent studies on the allylation of alkynes with bis (7r-allyl) nickel have revealed that the Ni(0) generated in this process causes the trimeri-zation and, more importantly, the reductive dimerization of a portion of the alkyne (8). A deuterolytic work-up led to the terminally di-deuter-ated diene (5), supporting the presence of a nickelole precursor (4) (Scheme 1). The further interaction of 4 with 1, either in a Diels-Alder fashion (6) or by alkyne insertion in a C-Ni bond (7), could lead to the cyclic trimer 8 after extrusion of Ni(0), thereby accounting for the trimerizing action of Ni(0) on alkynes. This detection of dimer 5 then provided impetus for the synthesis of the unknown nickelole system to learn if its properties would accord with this proposed reaction scheme. Therefore, E,E-l,4-dilithio-l,2,3,4-tetraphenyl-l,3-butadiene (9) was treated with bis (triphenylphosphine) nickel (II) chloride or l,2-bis(di-phenylphosphino ethane)nickel(II) chloride to form the nickelole 10 (9) (Scheme 2). The nickelole reacted with dimethyl acetylenedicarboxylate to yield 11 and with CO to produce 12. Finally, in keeping with the hypothesis offered in Scheme 1, 10a did act as a trimerizing catalyst toward diphenylacetylene (13) to yield 14. 

The name dithiolenes was chosen to describe these compounds without prejudice towards one of the limiting structures. The equally descriptive name dithienes has been coined for the same reason, but it is now rarely used. The less fortunate description of dithiolenes as dithiolato complexes is found occasionally, but it does have a much more restricted meaning (see Section 16.5.2.4) and should be avoided for the neutral species. Nevertheless, Chemical Abstracts refers to dithiolenes as bis[l,2-ethenedithiolato(2—)] complexes of the respective central metal, for example the parent nickel complex (4) is listed as nickel, bis[l,2-ethenedithiolato(2—)-5,S ]- however, depending on the date of the CA issue, its tetraphenyl derivative will be found either under bis[a,a -stilbenedithiolato(2 — )]-nickel or as bis[ 1,2-diphenyl-1,2-ethenedithiolato(2 -)-S,S"]-nick-el. Even less appropriate are the CA names for the radical anions and dianions of the dithiolenes, which are referred to as metallates(—) and metallates(2 —) of the respective ligands the dianion of the parent nickel dithiolene thus is found as bis[l,2-ethenedithiolato(2—)]-nickelate(2—), a name which has little to do with the electronic structure of the compound. 

Epoxidation of cholesterol. This reaction can be effected with O2 and isobutyraldehyde as reductant in quantitative yield in CH2CI2 at room temperature. This reaction provides the a- and /3-oxides as a 1 1 mixture. Addition of a (tetraphenyl-porphrinato)nickel(ll) catalyst does not affect the rate, but enhances 8-stereoselectivity (74 26). 

Nickelocene undergoes reductive substitution with tetracyclene to furnish bis(tetracyclene)nickel(0), >y -l,2,3,4-tetraphenyl-5-ketocyclopentenylcyclopentadienyl-nickel, and ra 5-2,3,4,5-tetraphenyl-2-cyclopenten-1 -one ... 

A classical example of the subtleties of the stereospinomeric choice in Ni(II) chemistry is offered by the family of salicylenealdiminato (salen. Scheme 37) complexes, which are diamagnetic and square planar for R = H, OH, CH3, Ft, n-Pr, or n-Bu, but paramagnetic and tetrahedral for R = r-Pr or f-Bu. The structures of two well-characterized stereospinomers of bis(tetraphenyl-dithioimidodiphosphinato-S, SO-nickel(II), high-spin tetrahedral and low-spin square planar, are shown in Figure 33. 

Figure 33 Two stereospinomers of bis(tetraphenyl-dithioimidodiphosphinato-5, 5 )-nickel(II) high-spin tetrahedral and low-spin square planar.

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