Nickel hydrido

Hydrides. The hydrides have the trans-structure, and the cis-species appear not to exist.28 Most of the studies have been on platinum compounds since the comparable palladium (and also nickel) hydrido complexes are usually less stable thermally some compounds such as ra w-PdClH(PR3)2 with R = cyclohexyl or Ph have been made.29... 

While investigating the oligomerization of ethene by aluminium alkyls (p. 80), Ziegler and coworkers noticed that in the presence of traces of nickel dimerization to 1-butene occurs instead. Very active catalysts can be generated by adding an alkylaluminium halide to [(f/ -CjHJNiCl]. The phosphine complexes NiL are also effective in the presence of acids. A nickel hydrido complex is first formed which adds to ethene to give an ethyl intermediate which can either eliminate 1-... 

Oxidative addition reactions of imidazolium salts to electron-rich, coordinatively unsaturated Ni (NHC)2 complexes have been used to synthesize Ni(ii) tris(carbene)-nickel-hydrido complexes (Equation (15))." ... 

Several hydrido(phenoxo) complexes of nickel, trans-[NiH(OPh)L2] (6) (a L= P Prs b L = PCys c L = PBnj), have been prepared by the metathesis reaction of NaOPh with trans-[NiHClL2] (Eq. 6.6). The complex 6c was obtained as the phenol-solvated complex whose structure was determined by X-ray analysis [9]. An analogous platinum complex trans-[PtH(OPh)(PEt3)2] (7) was prepared by the reaction of trans-[PtH(N03)(PEt3)2] with NaOPh (Eq. 6.7). The complex 7 is air-stable but thermally sensitive and decomposes at room temperature. The structure was elucidated by X-ray analysis [10]. 

B,) Treatment of an organo- or a hydrido-nickel(II) compound with a Lewis acid. Organometallic compounds, such as alkylaluminum halides, which have Lewis acid properties, can also be used. 

The nature and distribution of the products of the dimerization or oligomerization of unsymmetrical olefins, such as propene, will depend, among others, on the direction of addition of the hydrido- and alkylnickel species to the olefin, i.e., on the regioselectivity of the catalyst (see Section 1 V,E). In order to define the direction of addition of hydrido- or alkylnickel species to terminal olefins, we shall adopt the convention nickel-to-C, addition [Eq. (12)] (Ni —> Cj) ... 

The reaction of [Ni(ethene)3] with a hydride donor such as trialkyl(hydrido)-aluminate results in the formation of the dinuclear anionic complex [ Ni(eth-ene)2[2l 11 [22]. The nickel(O) centers in this complex are in a trigonal planar environment of two ethene molecules and a bridging hydride ion, with the ethene carbons in the plane of coordination. The two planes of coordination within the dinuclear complex are almost perpendicular to each other, and the Ni-H-Ni unit is significantly bent, with an angle of 125° and a Ni-Ni distance of 2.6 A [22],... 

The anion [Fe3Co(CO)12] has recently been reported to be prepared by Chini from the redox reaction of Fe3(CO)12 with Co(CO)infrared spectra indicate a Co4(CO)i2 structure with nickel in the basal plane (234). 

While the reductive elimination is a major pathway for the deactivation of catalytically active NHC complexes [127, 128], it can also be utilized for selective transformations. Cavell et al. [135] described an interesting combination of oxidative addition and reductive elimination for the preparation of C2-alkylated imida-zohum salts. The in situ generated nickel catalyst [Ni(PPh3)2] oxidatively added the C2-H bond of an imidazolium salt to form a Ni hydrido complex. This complex reacts under alkene insertion into the Ni-H bond followed by reductive elimination of the 2-alkylimidazolium salt 39 (Fig. 14). Treatment of N-alkenyl functionalized azolium salts with [NiL2] (L = carbene or phosphine) resulted in the formation of five- and six-membered ring-fused azolium (type 40) and thiazolium salts [136, 137]. 

C22H46ClCrNi6Ni2, Chromate(III), trans-bis(tetraethylenepentamine nickel(II))-hexacyano-, chloride, 34 147 C24H4Na20240sio, Osmate(2-), tetra-cosacarbonyltetra(/4-hydrido)deca-, sodium, 34 223... 

Ni0s,C 4H , Osmium, nonacarbonyl(T -cyclopentadienyl)tri-p-hydrido-nickel-tri-, 26 362... 

Because of its low acidity, hydrogen cyanide seldom adds to nonactivated multiple bonds. Catalytic processes, however, may be applied to achieve such additions. Metal catalysts, mainly nickel and palladium complexes, and [Co(CO)4]2 are used to catalyze the addition of HCN to alkenes known as hydrocyanation.l67 l74 Most studies usually apply nickel triarylphosphites with a Lewis acid promoter. The mechanism involves the insertion of the alkene into the Ni—H bond of a hydrido nickel cyanide complex to form a cr-alkylnickel complex173-176 (Scheme 6.3). The addition of DCN to deuterium-labeled compound 17 was shown to take place... 

The borohydride reduction of nickel(II) compounds in protic solvents may result either in the formation of nickel(O) complexes66,71 or in the formation of hydrido complexes of nickel(II). Two easily interconvertible isomers, Ni(triphos)2, have been obtained in the reduction of Ni(N03)2 in the presence of the ligand triphos, but their structures are not known with certainty. 

By reducing hydrated nickel(II) nitrate with NaBHt, in the presence of the tetradentate tripodal ligand np3 (equation 80), the complex [Ni(np3)j (66) has been obtained.263 Complex (66) undergoes oxidative reaction with HC104 or HBF4 to afford the nickel(II) hydrido complex [NiH ps)]-1".264 It also reacts with CO to give the carbonyl derivative263 and with white... 

Some complexes of nickel(0) with phosphines have been found to react with several Bronsted acids in non-aqueous solvents and under an inert atmosphere to give hydrido complexes of nickel(I) and nickel(II) (equations 85-87).264,268,269... 

When nickel(II) salts containing a coordinating anion (halide and pseudohalide) are reacted with NaBH4 in the presence of np3, trigonal bipyramidal nickel(I) complexes of the type [NiXnp3], in which the coordinating anion occupies die axial position, 39,340 are obtained. When nickel(II) salts with poorly coordinating anions are used, non-stoichiometric hydrido complexes of nickel(II) are obtained (equations 108 and 109). 

A few representative examples of simple organometallic compounds of nickel(II) including carbonyl and hydrido compounds are reported here. A more complete listing of such types of compound is given in Comprehensive Organometallic Chemistry (vol. 6, p. 37) and references therein. Selected structural data for organometallic nickel(II) complexes with monodentate phosphines are reported in Table 61. 

The hydrido complexes are diamagnetic, and are square planar or five-coordinate. Their stability, in general, increases with the number of coordinated phosphines. In the complex [Ni(BH4)(H)(PCy3)2] (153) the nickel atom is coordinated in the equatorial positions by two hydrogens of the borohydride and by one hydride anion. 

Sodium borohydride-Palladium chloride. Sodium borohydride-Rhodium(lII) chloride. Sodium borohydride-Tin(II) chloride. Sodium cyanoborohydride. Sodium 9-cyano-9-hydrido-9-borabicyclo[3.3.1]nonane. Sodium dithionite. Sodium hydride-Sodium t-amyl oxide-Zinc chloride. Sodium trimethoxyborohydride. Tetra-/i-butylammonium borohydride. Tetra-n-butylammonium cyanoborohydride. Tetra-n-butylammonium octahydrotriborate. Tri-n-butyltin hydride. Triethoxy silane. Triisobutylaluminum-Bis(N-methyl-salicyclaldimine)nickel. Zinc borohydride. REDUCTIVE CYCLIZATION Cobaloximc(I). 

As well as finessing the use of p and r in "inorganic" nomenclature, the proposed nomenclature discards the entire kappa convention [48]+. The molecule illustrated in Figure 25, which has the IUPAC name [2(-diphenylphosphino-Kp)-phenyl-KC1]hydrido (triphenylphosphine-Kp)nickel(II), using the phenyl abbreviation described in the footnote on page 55, would be named ... 

The thermally stable nickel and palladium hydride complexes, trans-[MHX(PR3)2], where M = Ni or Pd, R = cyclohexyl or isopropyl, and X = halogen, have been prepared by various methods.1-5 Hydrido[tetra-hydroborato( 1 - )] complexes can be prepared from them by metathet-ical reactions.3 The hydrido[tetrahydroborato( 1 — )]bis(tricyclohexylphos-... 

A. fra s-[HYDRIDO[TETRAHYDROBORATO(l -)]BIS-(TRICY CLOHEX YLPHOSPHINE)NICKEL]... 

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