Nickel cyclopentadienyl complexes, 898

Sitzmann, H. Saurenz, D. Nickel cyclopentadienyl complexes with 16 valence electrons. Book of Abstracts, 219th ACS National Meeting, San Francisco, CA, USA, March 26-30, 2000, INOR-139. 

CjHjS, Thiophene, tetrahydro-gold complexes, 26 85-87 C4H,NO, 2-Propenamide, 2-methyl-nickel complex, 26 205 C4H1()02, Ethane, 1,2-dimethoxy-solvates of chromium, molybdenum, and tungsten carbonyl cyclopentadienyl complexes, 6 343 tungsten complex, 26 50 ytterbium complex, 26 22 C4H i02.NaC5H5, Ethane, 1,2-dimethoxy-compd. with cyclopentadienylsodium, 26 341... 

With 1,1-difluorocyclopropabenzene and a range of nickel(O) complexes, nickelabicy-clobutanes 118 (84—93%) are formed by loss of olefin or phosphane ligands and addition of the nickel atom across the bridge bond (Scheme 20)256-266. The products appear to be stable at ambient temperatures but are oxygen sensitive the majority revert to cycloproparene in solution even below -20 °C. With (j -allyl)( s-cyclopentadienyl(palladium in the... 

Cycloalkenes, into if-allyl palladium complexes, 8, 363 Cycloalkenyl rings, metal complex conformational interconversions, 1, 414 Cycloalkynes, in nickel complexes, 8, 147 (Cyclobutadiene)cyclopentadienyl complexes, with cobalt, polymercuration, 2, 435 Cyclobutadienes... 

Mixed-sandwich complexes with cyclodextrins, 12, 787 iridium cyclopentadienyl complexes, 7, 368 with nickel, synthesis and reactivity, 8, 160 with vanadium, 5, 47... 

The electrochemical technique has been relatively rarely applied to obtain the metal 7i-complexes [202,506,507], Thus, the electrosyntheses of complexes of copper with cyclo-octadiene and nickel with cyclo-octatetraene were reported [202,506,507]. The electrochemical reactions (3.242) are of especial interest, since they allow us to produce fe-cyclopentadienyl complexes [563-565] ... 

Scheme 1.2 Preparation of ( y5-cyclopentadienyl)(jy3-cyclopentenyl)nickel(II) from nickel tetracarbonyl via the nickel(0) complex Ni(C5H6)2 as the supposed intermediate...

Elements of the first transition series from vanadium to nickel form stable bis(7j-cyclopentadienyl) complexes having the normal ir-sandwich structure typical of ferrocene. In contrast, bis(Tj-cyclopentadienyl)ti-tanium, (i7-CsH5)2Ti (1), is not even known as a discrete compound. 

A second group of complexes that have received detailed attention are the (i73-allyl)nickel(i75-cyclopentadienyl) complexes, which may be prepared by reacting nickelocene with an allyl-Grignard reagent (69). Data for typical examples are shown in Table IX. In this particular case, a sufficiently large number of complexes have been studied that a series of chemical shift increments can be extracted from the data (shown in Table X) and have been used with considerable success in assigning structures to ij3-allyl nickel complexes of unknown structure. 

Other rate processes studied include isopropyl group rotation, (529) restricted rotations in phosphine derivatives of cyclopentadienyl complexes of iron and nickel, (530) and ring and nitrogen inversion in (en) complexes of praseodymium. (531) Molecular geometries of molecules in solution can be accurately determined from NMR spectra of the molecules oriented in a nematic phase of a liquid crystalline solvent. The effect of Eu(dpm), on the nematic phase spectrum of pyridine has been examined. The pyridine geometry is unaffected by the LSR. The observed LIS values can be separated into isotropic and anisotropic components. (532)... 

The transformation of P4 in the coordination sphere of 15 VE fragments has been studied by allowing group-6 carbonyls, [M(CO)6] (M=Cr, Mo, W), and nickel cyclopentadienyl carbonyl complexes to react using Scheer s one-pot/three-components practice under thermal or photochemical conditions. Remarkably, the combination of P4, [Cr(CO)6], and the nickel dimer [ Cp Ni (CO) 2] under UV irradiation yields complexes incorporating Pj, P2, and P3 lig-... 

Difluorobenzocyclopropene (9) can be coordinated to palladium(O) and to nickel(O) in a tj -tnanner at the most strained double bond by reaction of the ligand with nickel(O) complexes (see following table) or with (> -allyl)(> -cyclopentadienyl)palladium(II). ... 

For the metal—alkyne fragmait, nonlinearity also increases upon increasing valence electron count [14 valence electron (triphenylphosphine) gold alkynyl compounds <18 valence electron (cyclopentadienyl) (triphenylphosphine)nickel, and (cyclopentadienyl) bis(triphenylphosphine) ruthenium alkynyl compounds] and increasing ease of oxidation (less easily oxidizable (cyclopentadienyl)(tri-phenylphosphine)nickel alkynyl complexes < more easily oxidizable (cyclopen-tadienyl)bis(triphenylphosphine)ruthenium alkynyl complexes). 

Bis(cyclopentadienyl)complexes have been isolated for the elements of the First Transition Series from vanadium to nickel inclusive and also for ruthenium and osmium. The most general method of preparation is to treat an anhydrous halide of the metal with sodium cyclopentadienide in tetrahydrofuran under an atmosphere of nitrogen or argon. 

The Group VIII cyclopentadienyl complexes of formula CpM(NO) (M = Ni, Pd, Pt) have all been synthesized. The nickel complex is best prepared from nickelocene and nitric oxide, and a method for the preparation of the nickelocene m situ without its isolation has been described (56). The palladium complex can be prepared from [Pd(NO)Cl] and sodium cyclopentadienide (23) and the platinum complex from Pt2(CO)2Cl4 and sodium cyclopentadienide and nitric oxide (22). The microwave (13) and infrared spectra (18) of CpNi(NO) have received detailed study, and the electronic structure of the complex is discussed in an early paper (77). 

The nickel cyclopentadienyl carbonyl dimer [NiCp (CO)]2, where Cp is iV,7V-(dimethylamino)ethylcyclopenta-dienyl, was reacted with Ga2Cl4 to give a heterodinuclear complex (Equation (20)). 

A bidentate cyclopentadienyl-functionalized NHC complex of nickel(II) catalyses hydrosilylation of aldehydes, allowing quantitative reduction in 5 min at 25 A transient nickel hydride complex, ( Cp-NHC)NiH, is implicated as the active species. 

Many 7i-cyclopentadienyl complexes may be prepared from the reaction of alkali metal cyclopentadienides with ammonia-soluble transition metal salts such as nitrates and thiocyanates in liquid ammonia (2-30). The amine complexes, [M(NH3) ] (C5H5)2, lose ammonia when heated in vacuo, and the uncharged dicyclopentadienyl complexes of iron, cobalt, nickel, chromium, and manganese are obtained. 

Books have been published on cyclic polyolefin complexes and metal vapour synthesis, while a review on metal vapour cryochemistry also contains information relevant to the latter. Reviews have also been published on organometallic derivatives of alkenes and ketenes, cationic Rh diolefin complexes, and nucleophilic addition to cationic hydrocarbon complexes. More personalized reviews have appeared by Maitlis on Pd -acetylene chemistry, by Jonas and Kruger on alkali-metal-transition-metal w-complexes, and by Werner on bridged allyl and cyclopentadienyl complexes. Articles by Wilke on homogeneous catalysis, by Vollhardt on metal-mediated approaches to steroid synthesis, by Schrock > on organotantalum chemistry, and by Grubbs on nickel metallocycles also contain material of relevance to r-complexes. 

Nickel(n) cyclopentadienyl complexes [(ri -C5Ph5)Ni(S2CNMe2)] (1464) and [(T] -C5Me5)Ni(S2CNEt2)] (1547) have been prepared, the latter from an unusual reaction between [(T] -C5Me5)Ni(CO)] and Te(S2CNEt2)2 (Eq. 146) (1547). 

TC-Cyclopentadienyl Nickel Complexes. Nickel bromide dimethoxyethane [29823-39-9] forms bis(cydopentadienyl)nickel [1271 -28-9] upon reaction with sodium cyclopentadienide (63). This complex, known as nickelocene, 7T-(C3H3)2Ni, is an emerald-green crystalline sandwich compound, mp 173°C, density 1.47 g/cm. It is paramagnetic and slowly oxidi2es in air. A number of derivatives of nickelocene are known, eg, methylnickelocene [1292-95-4], which is green and has mp 37°C, and bis( 7t-indenyl)nickel [52409-46-8], which is red, mp 150°C (87,88). 

Substituted derivatives of nickelocene, where one ring has been replaced, include the complex cyclopentadienyl nitrosyl nickel [12071 -73-7], (7T-C3H3)NiNO, a red Hquid, mp -41°C. A review of nitrosyl complexes with nickel is available (89). The dimer complex... 

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