Compounds of Nickel, Palladium and Platinum

Table 27.2 Oxidation states and stereochemistries of compounds of nickel, palladium and platinum...

Several groups have screened a variety of transition metal complexes for activity in the double silylation system, but only compounds of nickel, palladium, and platinum appear to be viable catalysts. The key factor appears to be the involvement of a M(0) species, although certain M(II) complexes can also be used, presumably with in situ reduction to M(0). Generalizations regarding the activity of the different transition metal complexes are difficult, as many variables exist in each system. However, the most active complexes seem to combine palladium metal centers with dba, small basic phosphine, or isocyanate ligands. 

For the sake of easy comparison, a few of the more important compounds of nickel, palladium, and platinum are given in the table on page 17. 

Another route to p.-Carbido complexes which we have found is oxidative addition of Lalor s halocarbyne complexes [21] to zero valent triphenylphosphine compounds of nickel, palladium and platinum. In these reactions the heterodimetalla cyclopropenes could be isolated which isomerize at higher temperatures to the dimetalla allene complexes. The first adducts of arylcarbyne complexes to zerovalent platinum complexes (arylcarbyne as analogue of ace-... 

Inner Transition Metal Complexes With Chains of Metal Atoms 103 9.2.12.1. Compounds Containing Nickel, Palladium, and Platinum Chains 9.2.12.1.4. Halogen-Oxidized Complexes Containing 7t-Delocalized Ligands. 

The use of complexes as stationary phases is well developed in gas chromatography. For example, Cartoni et al. [87] studied the properties of nickel, palladium, platinum and copper N-dodecylsalicylaldimines (MSal2) and those of nickel, palladium and platinum methyl-N-octylglyoximes (MGly2). It was shown that the stationary phases studied showed specific retention of amines, alcohols and olefinic compounds. Table 6.3... 

At variance with the easy accessibility of Ni(CO)4, the corresponding tetracarbonyls of palladium (0) and platinum (0), Pd(CO)4 and Pt(CO)4, have been identified only spectroscopically (IR) at low temperature, both being prepared by vaporization of the metal followed by reaction with CO in a solid matrix at about 20 K. These compounds decompose at higher temperature. Table 2 shows the IR spectroscopic properties of the tetracarbonyls of nickel, palladium, and platinum, as obtained by vaporization of the corresponding metal, measured under the same experimental conditions. The compounds show one carbonyl stretching vibration, as expected for the tetrahedral geometry. The values of v>co and the C-0 force constant of Pd(CO)4 are higher than those of both Ni(CO)4 and Pt(CO)4 (see Section Attempts have... 

There are many carbonyl complexes of nickel, palladium, and platinum containing phosphines (L). Nickel compounds of the type [Ni(CO)4 j,Lj,] are readily formed in substitution reactions of [Ni(CO)4]. Palladium and platinum phosphine carbonyls are prepared by reactions of compounds of these metals with carbon monoxide in the presence of phosphines. The following complexes are known [M(CO)L3], [M3(C0)3L3], [M3(C0)3L4], [Pt(CO)2L2] and [M4(CO)5L4] (M = Pd, Pt). Trinuclear platinum compounds resist oxidation. 

Electron transmission spectra of bis-(ri3-allyl) complexes of nickel, palladium and platinum have been reported. Each compound displayed three resonances associated with electron capture into three empty n ligand MO s. The measured electron attachment energies... 

The Chemistry and Solid-State Properties of Nickel, Palladium, and Platinum Bis(maleonitriledithio-late) Compounds. 

P.I. Clemenson, The chemistry and solid state properties of nickel, palladium and platinum bis(maleonitri-ledithiolate) compounds. Coord. Chem. Rev. 106, 171 (1990). 

Substitution of nickel, palladium, and platinum complexes forms part of a recent review on the kinetics of reactions of these compounds. A review up to 1971 on the chemistry of Co cyanides contains references relevant to Sections 2 [Mixed-ligand Carbonyls displacement of CO], 3, and 4 of this chapter. ... 

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)]. 

Many transition metal alkyls react with carbon monoxide to give acyl compounds. In all these cases the acyl derivatives can be detected at least by infrared methods and in most cases isolated. Molybdenum, manganese, rhenium, iron, cobalt, rhodium, nickel, palladium, and platinum alkyls, Grignard reagents, and boranes, all react with carbon monoxide, and one can explain the products from these on the basis of carbon monoxide inserting into the metal alkyl. 

It is convenient to treat each metal, nickel, palladium, and platinum, in turn, because of the large number of compounds involved. 

The chemistry of the zerovalent state in nickel, palladium, and platinum compounds is reviewed. After a historical introduction in which the development of this chemistry is analyzed in terms of the current theory of the stabilization of low valency states, the most interesting classes of zerovalent compounds are described. The stability and properties of these compounds are discussed and related to the nature of the ligands and the coordinated metal. The catalytic properties of these zerovalent derivatives toward olefins, diolefins, and acetylenes are considered in connection with the facility of ligands exchange, the variation of coordination number, and the stereochemistry. A discussion of the % bond is reported. 

There are no results to consider for palladium, osmium, and iridium and few for iron, nickel, and ruthenium. Salient features of the results for the last three metals are compared with those for related compounds of cobalt, rhodium, and platinum in Figure 2. The overall behavior is closely similar for all six metals, although there are variations between them just as there are in their chemical behavior. Thus we shall give a general discussion using the most suitable results from among those for the six metals. 

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