Nickel complexes tertiary phosphines

Although trialkyl- and triarylbismuthines are much weaker donors than the corresponding phosphoms, arsenic, and antimony compounds, they have nevertheless been employed to a considerable extent as ligands in transition metal complexes. The metals coordinated to the bismuth in these complexes include chromium (72—77), cobalt (78,79), iridium (80), iron (77,81,82), manganese (83,84), molybdenum (72,75—77,85—89), nickel (75,79,90,91), niobium (92), rhodium (93,94), silver (95—97), tungsten (72,75—77,87,89), uranium (98), and vanadium (99). The coordination compounds formed from tertiary bismuthines are less stable than those formed from tertiary phosphines, arsines, or stibines. 

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

Tertiary phosphines are oxidized catalytically by nickel(O) complexes with formation of phosphine oxides. Also, complexed tert-butylisonitriles can be oxidized to the corresponding isocyanates (examples 1 and 2, Table IX) (225-226). 

I, Table X) requires tertiary phosphine-nickel halide or tertiary phosphine-nickel carbonyl complexes at 140-170°C. This implies oxidative addition of aromatic halides to nickel, replacement of the halide with amines, and reductive elimination. 

Nickel(I) complexes are far less numerous than those of nickel(0). Like nickel(0) complexes, nickel(I) complexes are generally obtained with ligands having -acceptor capability. Most complexes of nickel(I) which have been isolated as solids contain tertiary phosphines (or arsines) as ligands and are sufficiently stable in the absence of air to allow them to be studied with several physicochemical techniques. 

Table 22 Molecular Parameters for some Nickel(I) Complexes with Tertiary Phosphines and Arsines...

The number of nickel(U) complexes with mono-, bi- and poly-dentate ligands containing tertiary phosphines as a donor group is very large and increases day by day while complexes with tertiary arsines are less numerous and those with stibines are rarer still. The number of nickel(II) complexes with mixed donor ligands containing N, O and S donor atoms besides P or As is also very large. 

Following the aforementioned pioneering work, many other organometallic complexes of nickel(II) were prepared using different synthetic procedures. Complexes containing one molecule of tertiary phosphine were prepared using methods similar to that reported in equations (142) and (143) and Scheme 13.1193-11951219-1223 All of these diamagnetic compounds have the square planar structure exemplified by (155).1193... 

A large number of nickel(II) complexes with bidentate tertiary phosphines and arsines have been prepared and characterized since the initial reports on o-phenylenebisdimethylarsine and 1,2-bisdiphenylphosphinoethane (Table 64 XVIII, III) by Chatt and Mann,1267 and Wymore and Bailar126 respectively. The most common diphosphines, diarsines, distibines and mixed donor ligands are collected in Table 64 and selected nickel(II) complexes are reported in Table 65. 

The Ni3S2 fragments in the two complexes (263) and (265) have a trigonal bipyramidal geometry with the two S atoms in the apical positions and the three nickel atoms in the equatorial plane, as found in other organometaUic compounds which contain the same Ni unit.1939 The formation of the enneanuclear complex (264), on the contrary, is exceptional and no other complex of this stoichiometry was isolated with analogous tertiary phosphines, with selenium, or with metals other than nickel. It is not possible to assign any definite oxidation number to nickel in complex (264). The lack of two electrons with respect to the situation of nine nickel(II) ions was reported to be essential for the existence of complex (264) because the oxidation is spontaneous and its reduction invariably leads to the decomposition of the cluster compound.19 ... 

When simple nickel(II) salts are treated with thiols, in most cases stable thiolate-bridged polymers are formed. In a number of cases, treating these polymers with either tertiary phosphines or isocyanides gave mononuclear mixed-ligand complexes (equation 204).1951 These mononuclear complexes, due to the presence of terminal thiolates which possess lone pairs, can further react with nickel(II) and give trinuclear complexes (equation 205).1952... 

Unlike the tertiary phosphine and arsine oxides which form a variety of nickel complexes with peculiar properties, tertiary arsine sulfides and, particularly, tertiary phosphine sulfides... 

The iron compound readily sublimes and yields well-formed, black lustrous crystals. The cobalt complex will also readily sublime, but dependent upon the temperature at which the crystals are formed, they can be either black or brown in color. The crystal structures of both the cobalt and iron complexes have been determined.3 The nickel complex sublimes only in small amounts with difficulty. All three complexes are unstable to air and water, and the nickel complex readily undergoes thermal decomposition above 100°C. All three compounds will also readily form complexes with a variety of donor ligands such as tertiary arsines or phosphines. The nickel compound usually forms 2 1 adducts such as [(C6HS )3P]2Ni(NO)I, while the iron and cobalt complexes often undergo disproportionation.5... 

The synthesis and reactivity of a series of nickelacyclopentane compounds with a range of tertiary phosphine ligands was reported by Grubbs et ol. Compounds of type 69 were prepared by the reaction of 1,4-dilithiobutane with the appropriate dichlorobis(tertiaryphosphine)nickel(II) complex, and isolated as yellow crystals in ca. 40% yield78 (dppe = bis(diphenyl) (phosphinoethane). 

The tertiary phosphine PEt3, in the presence of nickel(II) aquacations and H2S, form diamagnetic tri- and enneanuclear dications having formulae [Nig(p3-S)2(PEt3)g]3+ and [Nig(y3-S)g(y4-S)3]2+. The first complex is formed by a trigonal bipyramidal kernel of two apical sulfur atoms and three equatorial nickel ions. The structure of the second compound consists of nine nickel ions located at the apices of two confacial octahedra. 

Several systematic experimental and computational studies have compared the sigma-donating abilities of NHCs and tertiary phosphines for a variety of transition-metal complexes [8-17]. As illustrative examples, analyses of the nickel-carbonyl complex 1 and iridium carbonyl complex 2 (Fig. 1) re-... 

Both di- and trimerization of butadiene with soluble nickel catalysts are well-established homogeneous catalytic reactions. The precatalyst having nickel in the zero oxidation state may be generated in many ways. Reduction of a Ni2+ salt or a coordination complex such as Ni(acac)2 (acac = acetylacetonate) with alkyl aluminum reagent in the presence of butadiene and a suitable tertiary phosphine is the preferred method. The nature of the phosphine ligand plays an important role in determining both the activity and selectivity of the catalytic... 

In view of the chemical reactivity of the tertiary phosphine and nickel hydride complexes to air, all manipulations should be carried out in a nitrogen or argon atmosphere.6 All solvents should be distilled under a nitrogen or argon atmosphere. 

Scheme 7.4 Preparation of the non-cyclic nickel(II) complex 16 and its reactions with tertiary phosphines to give the nickel(O) compound 17 and with carbon monoxide to yield the cyclic unsaturated ketone 18...

The bis(ij3-allyl)nickel complexes form adducts with tertiary phosphines in which the allyl groups are mutually cis (JO). This arrangement has been confirmed by crystal structure analysis for (V-QHs NiPtCHs (22) and by comparing the, 3C-NMR spectral data with those of the related complex (i73,7)3-C9H12)NiP(CH3)3 (23) formed by reacting allene with bis(l,5-cyclooctadiene)nickel in the presence of the phosphine. The data for this complex are shown in Table XII and those for representative (if-allyl NiPRa complexes in Table XIII. 

The complexes [Ni(acrylonitrile)2] and [Ni(COD)2] catalyze [3 + 2] cycloadditions of (26) with electron deficient l,2 isubstituted alkenes to afford 2,3- or 3,4-disubstituted methylenecyclopentanes such as (32) and (33). Similar reactions have been reported by use of tertiary phosphine complexes of nickel(0) and palladium(0) (equation 13 and Table 1). The reaction proceeds regioselectively to give (32) or (33) depending on both the alkene stmcture and catalytic system. Reactions catalyzed by phos-phine-palladium(0) complexes afford only products of the type (32), via selective cleavage of the C(2)— C(3)bondof(26). 

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