Nickel, Platinum, and Palladium

Irradiation of -allylpalladium complexes results in the formation of 1,5-dienes [e.g. (25) from (26)], products presumably of the coupling of allyl radicals. The 

The dissociation of Ni(CO)4 by multiphoton i.r. laser excitation or sensitized by excited argon atoms has been described. 

Alcock, T. J. Kemp, F. L. Wimmer, and O. Traverse, Inorg. Chim. Acta, 1980, 44, L245. 

Costanzo, S. Giuffrida, G. Condorelli, A. GiuSrida, and G. Guglielmo, Congr. Naz. Chim. Inorg., [Atti], 13th, 1980, 206 (Chem. Abstr., 1981, 94, 217457). 

Photolysis of Kr matrices containing HI and NiCCO) at 4 K leads to a new product vdilch on the basis of its ESR spectrum is thought to be the radical HNl(CO),. This has a trigonal geometry and a A, ground state of C,y symmetry.The first exaunples of d ° metal phosphine and phosphite complexes of Ml, Pd, auid Pt which possess long-lived emissive excited states in fluid solution at room temperature have been described these con lexes are photochemically reactive towards orgwlc substrates. 

The primary photoprocess in the homo- and heteronuclear palladlum(I) and platlnum(I) hexedcls(methyl isocyanlde) dimers [IM (CNMe)(M-M -Pd, Pt M-Pd, M -Pt), is metal-metal bond homolysls to give the 15-valence electron radicals [M(CMMe) 

These radicals are reactive towards halogen atom abstraction from CX4. (X-Cl, Br) to give mononuclear pseudo-square planar [MX(CNMe),] (M-Pd, Pt). 25 photolysis of irans-(Pd(PPrS) (NCS) ] 

Ft(IV), whereas (36) is formed by p-hydrogen elimination from [EtPtClsl Kinetics auid mechanisms of thermal, 

The catalytic reactivites of [Ni2(cod)2(jM-RC=CR)] and [Ni2Cp2CM-RC CR)] and the Ni surface have been examined by MO theory. RC CC CR reacts with [Pt3(CNBu )8] to give [Pt2(CNBu )4(RC4R)] in which only one of the acetylenic bonds bridges the two Pt(CNBu )2 groups.  

Z-Ray structural studies have shown that [ NiMe(7 -l,3-dimethylallyl) 2] contains two methyl groups bridging the metal-metal bond the slightly un-symmetrical Ni2C2 ring is folded. The results of MO calculations explain the 

Nickel, Palladium, and Platinum.— The crystal structure and molecular geometry of the complex [(ir-Cp)Ni(PPh3)CFal has been reported. In the two discrete molecular units, the two independent Ni—CFg bond lengths are 1-949 0-029 and 1-947 0-034 A.  

Oxidative addition of perfluoroalkyl iodides to low-valent complexes of nickel, palladium, and platinum provides a convenient route to perfluoroalkyl derivatives. (Ethylene)bistriphenylphosphine nickel and perfluoroalkyl iodides produce the nickel(m) complexes [(Ph3P)3Ni(Rp)Ia] (Rp = CFa or n-CsF,), whereas the complex (Bu 3P)3Ni( ydo-octa-l,5-diene) reacts with CF,I to give (Bu 3P)aNi(CF3)I, a reaction related to the previously reported reaction of [(diphos)Ni(CO)2] to give (diphos)Ni(RF) (Rf = CaF or n-CgF,). The CO in the complexes (7r-Cp)Ni(RFXCO), formed from (w-Cp)Ni(CO)a and RfI (Rf = CF, CjFa, or n-CgF,), is displaced by PhsP. The complexes (PhaPMe)4M (M = Pd or Pt) afford rra 5-((Ph2PMe)Pt(RF)I] (Rf = CFg or n-CgF,) with perfluoroalkyl iodides. - With the add diloride n-CaF,-COCl, the acyl complexes rra j-[(Ph8PMe)3M(CO-C3F,)a] (M = Pd or Pt) are formed. -  

Certain platinum(n) complexes will also undergo oxidative addition reactions with perfiuoroalkyl halides. The complexes m-fLaPtMca] (L = PhAsMe, or PhPMej) react at room temperature with the halides CFJ, CjFsI, n-CjFyBr, n-CsF, , or n-C,FijI to give platinum(iv) complexes of configuration (153). 

Bis(benzonitrile)palladium dichloride reacts with the diazo-compoimd (CFaljCN, in methylene chloride to give complexes (156) and (157) in which insertion into the Pd—Cl bond has occurred. Insertion into the Pt—H bond occurs in the complex ra j-[(Et3P)2Pt(H)Cl] under more vigorous conditions, yielding cis- and tra -(Et3P)aPt[CH(CF3)2]Cl.  

Fluoro-olefins may react in three ways with complexes of nickel, palladium, and platinum (i) halogen (or pseudo-halogen) transfer to the metal may occur with formation of a vinyl derivative (ii) the olefin monoadduct may be stable [these are probably best regarded as metal(n) complexes] or (iii) insertion of a further mole of olefin may occur, a metallo-cyclopentane being formed. The possible reaction pathway is affected by quite subtle changes in the olefin and in the metal ligands. 

A most interesting study was published in 1993 by Aubke and co-workers dealing with the cations [Pd(CO)4]2+ and 

The metal cluster chemistry of this group is expanding quite rapidly and a number of papers have come to light in this category. New colloidal platinum complexes have been prepared a platinum dimer, Pt2(p-C0)(CO)2(p-dppm)2 has 

7 Nickel, Palladium and Platinum.- An alternative Cp transfer reagent that is being extensively exploited is Cp 2Zn. Products 

7 Nickel, Palladium and Platinum. This group has provided very few papers in recent years but 2000 was something of an exception with reports involving mononuclear species and much larger high-nuclearity clusters. 

Using Ni(CO)4 as a catalyst (or, perhaps more correctly, as a promoter) the carbonylative cycloaddition of allyl halides and alkynes has been investigated with a thorough expose of the reaction mechanism. 

In a paper reminiscent of an earlier entry for iron, Schaefer has described the (theoretical) structures of binuclear homoleptic nickel carbonyls, examining the possible Ni-Ni single, double, and triple bonds in Ni2(CO)x(x = 5,6,7) species. 

Finally in this section. Boys reports the synthesis, spectroscopic characterisation, and crystal structure of the bimetallic complex [Ni2( a-CO)(CO)2(NH(PPh2)2)2]. 

For these nickel aryl complexes, the marked stability of the ortho-substituted aryls compared with the meta- and /urrci-substituted analogues is believed to result from a combination of steric and electronic factors in the following manner. 

Those aryl ligands which do not contain ortAo-substituents would be expected to rotate about the Ni-Ar bond and thus interact at various times with the metal d , dy and orbitals. This interaction (7r-bonding) 

Ortho-effect. The ortho-methyl groups of the mesial ligands are hdd in the xz plane by the tertiary phosphine ligands. Thus the metal d,y orbital must interact with the 

To summarize, the or/Ao-substituted aryl complexes (R 3P)2NiAr2 are stabilized with respect to a dissociative mechanism by virtue of the increased A and enforcement of a planar configuration and they are also stabilized against a bimolecular mechanism of decomposition involving attack along the octahedral axis. 

Fie 54 The preparations and some reactions of the palladium complexes (EtjPlzPdRz and (EtjPlzPdRX [43,44] 

Earlier reference has been made to vibrational studies on the following [Ni(dien)2][Mo202S6] Ni(acac)3 [Mo i203( i2-OH)ioH2 NP(H20)3 4] and Ni-W-oxide thin films.  

The complexes Ni(PIpip), where H2PIpip = pyridylbis[N(4)-(piperidyl)] thiosemi-carbazones, show vNiN at 461 cm and vNiS at 335 cm Metal-isotope and deuteriation experiments were used to assign skeletal modes for the nickel-histamine complexes Ni(hm)Cl2 (vNiNH2 401 cm ) and [Ni(hm)3] + (380 

The tetramer [Ni(03SCF3)(NPMe3)]4 has vNiN of the Ni4N4 fragment (of approximately Td symmetry) at 522 cm with vNiO modes at 364 and 291 cm These latter are at unusually low wavenumbers for such modes. The IR and Raman spectra of [Ni Xdiars)2X]X, where X = Cl, Br or I, gave the following assignments vNi-As 274 cm- (X = Cl), 274 cm- (Br), 269 cm- (I) vNiX 223 

IR assignments have been proposed for the skeletal modes of Pd(H2) and Pd(H2)2 - matrix-isolated from the Pd atom -h H2 reaction. The Raman spectrum of an amorphous alloy catalyst Pd-B/Si02 included features in the range 300-500 cm and near 800 cm which were ascribed to Pd-B vibra-tions.  

The Raman and IR spectra of M(CO)4, where M = Pd or Pt, gave detailed assignments to vMC, 8MCO and 8CMC modes. Table 10.  

The preparation of a wide range of trifluoromethylplatinum compounds [frans-Pt(CF3)Q2L]+ and /rans-Pt(CF3)ZQ2 (where Q = PMcjPh, L is a neutral ligand such as acrylonitrile, CO, an imine, isocyanide, phosphine, etc., and Z is an anionic ligand such as halide, isocyanate, nitrite, etc.) by the routes  

Bis(trifluoromethyl)platinum complexes may conveniently be prepared by the reaction of dimethyl(cyclo-octa-l,5-diene)platinum with trifluoro-iodomethane in methylene chloride, followed by displacement of the cydo-octadiene with the required ligand L (L = AsMcs, PMeaPh, pyridine, RNC, etc.) Oxidative addition of iodine thence gives the platinum(iv) compounds  

Trifluoroiodomethane also displaces trimethyl phosphite from tetrakis-(trimethyl phosphite)palladium to give the bistrifluoromethyl compound cis-Pd(CF3)2 P(OMe), 2.  

Protonation of tetrafluoroethylene complexes LjPKCjF,) with trifluoro-acetic acid leads, as previously noted in a preliminary communication (cf, Vol. 1, p. 185), to the formation of the tetrailuoroethyl complexes LjPtX(CF3-CHF,) (L = PPh AsPh PEtgPh, PMePh, or PBu or L, = 2,2 -bipyridyl X = 0 C-CFa), but under the conditions used only the complex (2,2 -bipyridyl)PtCl(CF CHFa) was formed with hydrogen chloride. nie complexes LaPt(olefin) (L = PPh, AsPh, or PEtjPh olehn = CFjrCFCl or CF, CF CFj) all reacted readily with trifluoroacetic acid, but the solid products L8Pt(OjC CFs)(X) (X = CjHFaCl or CsHF ) could be isolated only when L = PPhj or AsPh and these were too insoluble to allow the position of protonation to be determined by n.m.r. spectroscopy. 

Unlike the hexafluorobut-2-yne complex (see below), (Ph3P)2Pt(CsFJ fails to give a mercurated derivative when treated with mercuric chloride, and the same product, a mixture of cis and rrans-PtClaOPPh ), is also obtained from attempted reactions with t-butyl chloride. This complex also fails to react with tetrachioro-o-benzoquinone, but the olefin is displaced from (Ph3P)2Pt(CF CHs).  

This triad attracted little attention in 1994. Of the few papers that are relevant in this section, special mendon must be made of the preparation, by Aubke and co-wotkers, of ds- P6(CO)j(SO. It should be ranembered that the same group prepared [Pd(CO)4]2 and [Pt(CO)4] in 1993. The si ene ligand 

Earlier reference has been made to vibrational studies on LaNio.sFeo.sOs NiCl2 ° Ni(LH)2X2, where LH = 3-hydroxyimino-l-iV-phenylaminobutan-l-one, X = halide and NiO.  

MN2 isolated in argon matrices has skeletal modes at 563.5/557.7 cm and 357 Resonance Raman spectroscopy was used to determine the vibronic 

The complexes [NiBr(NPR3)]4, where R = Me or Et, and [NiI(NPEt3)]4 all show vNi4N4 in the range 525-530 cm and vNiX near 280 cm (Br) or 197 cm The resonance Raman spectrum of the Ni(II)-substituted 

Bands due to vPtH were used to characterise H2 adsorption on platinum-supported Al-Mg hydrotalcite. The complex ran5 -PtH(Cl)[P(CH2CH2CN)3]2 has vPtH at 2245 cm and vPtCl at 285 cm h  

The complex cw-[PtCl2(Me2Ppz)], where Me2ppz = A,A -dimethylpiperazine, has an IR band due to vPtN at 260 cm with vPtCl at 327 and 287 cm C The IR and Raman spectra of dicarboxylatoplatinum(II) complexes contained bands in the range 470-600 cm due to vPtN and vPtO modes.vPtN (490-500 cm ) and vPtS (380-400 cm ) modes were assigned from the IR spectra of [Pt(L)2]Cl2, where L = [ -substituted 4-phenylthiosemicarbazides, ArNHCSNHNH2, where Ar = -XC6H4, X = H, Me, Br, F or N02.  

Norbomadieneplatinum(n) chloride reacts with octafluoro-2,2 -dilithiobiphenyl to give a low yield of the metallofluorene complex (237) (c/. pp. 426 and 431), and the imino-ether complex (238) is formed when cyclo-octa-l,5-dienyl(melhyl)- 

PtCFClCF2(PPha)2 is treated with pentafluorophenylsilver is believed to involve ionic intermediates and yields PtfCF CF2)(C6F8)(PPh3)a. The reaction of tiispen- 

Fornies, Rev. Acad. Cienc. Exactas, Fis-Quim. Natur. Zaragoza, 1973, 28, 349 (Chem. Abs., 1974, 81, 37 636k). 

Fornies, Syn. Reactiv. Inorg. Metal-Org. Chem., 1974, 4, 157. 

Actinide Eluents.—The chemistry of organic complexes of the actinides, including Cp complexes, has been reviewed. New complexes of the types [( -C5Me4Et)M(L)2a3] and [( -indenyl)M(L)2Cl3]i (M=U and Th L=THF, PhaPO, MeCONMCa, etc.) have been prepared. 

Carbaborane Complexes.—rewiew has appeared dealing with carbaborane-metal complexes, including those incorporating a CpCo residue.  

In the main, the work reviewed in this Section deals with chemistry in which the metallocene residue is specifically involved. Papers dealing with the elaboration of substituent groups attached to the cyclopentadienyl rings, particularly in the case of ferrocene derivatives, have been omitted except for work of particular interest. 

Calculations to find the transition state for the oxidative addition of H2 to Pt(PH3)2 to give cfs-[Pt(H)2(PH3)2] indicate a C2, geometry with a P-Pt-P bond angle equal to 148 and an H-H bond length only 4% larger than in free H2. The activation energy to reach this transition state is only about 8 kcal mol . The pathway which would result in tran addition is symmetry forbidden. 

Three groups have collaborated on a theoretical treatment of reductive elimination from d complexes as in equation (116). In four-coordinate 

Theoretical studies have also been made on nickelacyclopentane. In practice the product of decomposition of such a compound, [L Ni], depends on its coordination number, being, respectively, butene, cyclobutane, and ethene for (n + 2) = 3, 4, and 5. The theoretical studies show that for planar four- and three-coordinate systems viz. cis-[L2Ni] and [LNi]), the reductive elimination of cyclobutane is symmetry allowed, while the production of ethene is not. The reverse is true for tetrahedral [L2Ni]. Five-coordinate species, [LsNi], can give either cyclobutane or cyclobutane and ethene depending on their shape. 

Oxidation addition to Ni(0) can lead to both Ni(II) and Ni(I) complexes, as in equations (117) and (118), respectively. Morvillo and Turco have 

Morvillo and Turco also looked at the oxidative addition of methyl and ethyl halides to nickel(I) complexes, [NiX(PEt3)3], which is about ten times faster than the first step of the same process for nickel(O) systems, [Ni(PEt3)4] (X = Br or I). As some nickel(I) is formed in the second case, an overall reaction scheme can be constructed which includes both oxidation states, (120)-(124). Reactions (122) and (123) are slow and (124) is very slow. 

9 Nickd, Palladium and Platinum A series of [Cp Ni(alkene)L], L = alkyl, compounds has been prepared, Cp = Cp, Cp, CsPhs. The reaction of substituted cyclo-pentadienes and nickelocene with nickel and iron vapour, to give new cluster conqwunds, have 

The main current interest in the metals of this group (as far as carbonyls are concerned) lies in the preparation of mixed metal carbonyls (see below). The number of papers 

The self-exchange rate constants for several Ni(I)/Ni(II) couples, [NiCMe CHlaneNJ]- / - (kn = 1.0 x 10 s ), [NiCMe CMldieneNj]- / -  

A self-exchange rate constant of 48 s was determined for nickel 

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Table 27.1 Some properties of the elements nickel, palladium and platinum...

The mechanism by which this low oxidation state is stabilized for this triad has been the subject of some debate. That it is not straightforward is clear from the fact that, in contrast to nickel, palladium and platinum require the presence of phosphines for the formation of stable carbonyls. For most transition metals the TT-acceptor properties of the ligand are thought to be of considerable importance and there is... 

The last vertical column of the eighth group of the Periodic Table of the Elements comprises the three metals nickel, palladium, and platinum, which are the catalysts most often used in various reactions of hydrogen, e.g. hydrogenation, hydrogenolysis, and hydroisomerization. The considerations which are of particular relevance to the catalytic activity of these metals are their surface interactions with hydrogen, the various states of its adatoms, and admolecules, eventually further influenced by the coadsorbed other reactant species. 

Recent advances in the stereochemistry of nickel, palladium and platinum. J. R. Miller, Adv. Inorg. Chem. Radiochem., 1962,4,133-195 (270). 

Kinetics of nickel, palladium and platinum complexes. A. Peloso, Coord. Chem. Rev., 1973, 10, 123-181 (305). 

Recent Advances in the Stereochemistry of Nickel. Palladium, and Platinum J R. Miller... 

Substantially more work has been done on reactions of square-planar nickel, palladium, and platinum alkyl and aryl complexes with isocyanides. A communication by Otsuka et al. (108) described the initial work in this area. These workers carried out oxidative addition reactions with Ni(CNBu )4 and with [Pd(CNBu )2] (. In a reaction of the latter compound with methyl iodide the complex, Pd(CNBu )2(CH3)I, stable as a solid but unstable in solution, was obtained. This complex when dissolved in toluene proceeds through an intermediate believed to be dimeric, which then reacts with an additional ligand L (CNBu or PPh3) to give PdL(CNBu )- C(CH3)=NBu I [Eq. (7)]. 

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