Platinum derivatives, zerovalent

Chemistry of zerovalent nickel, palladium and platinum derivatives... 

Chemistry of Zerovalent Nickel, Palladium, and Platinum Derivatives... 

There are different methods for preparation of the zerovalent nickel, palladium, and platinum derivatives. Generally, these methods are similar to those usually employed in the chemistry of the low oxidation states. The more commonly used are the following ... 

The zerovalent cyanometallates are compounds with strong reducing properties, and they are known to reduce water. The stability of these complex cyanides decreases with increasing atomic number. The nickel compound is stable in vacuo) up to 160° C. the palladium compound decomposes slowly in vacuo) at ordinary temperatures, while the platinum derivative could not be isolated at all. 

In conclusion, the zerovalent nickel, palladium, and platinum derivatives still offer a fertile field for new and extensive researches. 

Molybdenum trioxide, intercalation into, 12, 823 Molybdocenes, as anticancer agents, 1, 892 MOMNs, see Metal-organometallic coordination networks Monisocyanides, with silver(I) complexes, 2, 223 Monitoring methods, kinetic studies, 1, 513 Mono(acetylacetonate) complexes, with Ru and Os halfsandwich rf-arenes, 6, 523 tj2-Monoalkene monodentate ligands, with platinum divalent derivatives, 8, 617 tetravalent derivatives, 8, 625 theoretical studies, 8, 625 zerovalent derivatives, 8, 612... 

Tris- and tetrakis(triphenylphosphine) derivatives of zerovalent platinum can be obtained by reduction of platinum(II) tri-phenylphosphine compounds by alcoholic potassium hydroxide or hydrazine. 1 The tris(triphenylphosphine) derivative is easily obtained from the tetrakis derivative by treatment with hot ethanol, t... 

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. 

The nature of platinum zerovalent derivatives was questioned by Chopoorian et al. (55) who considered them platinum(II) dihydrides. A new careful investigation (47, 133)j however, has confirmed that they are certainly zerovalent compounds. The nickel(0) derivatives with tertiary monophosphines can be obtained as well from NiBr2L2 and sodium tetrahydridoborate or ethanolic potassium hydroxide in the presence of an excess of the ligand 185) j while those with phosphites were prepared using potassium graphite 110) (CsK) as the reducing agent. By reduction with alkylmetals 199), zerovalent tetrasubstituted nickel (0) compounds with tertiary phosphine, arsines, and stibines have been obtained. 

It has been shown that electron-rich cyclopropanes are able to displace ethylene from dichloro(ethylene)platinum to yield four-membered metallocyclic complexes (cf. equation 37). On the other hand 1,1,2,2-tetracyanocyclopropane (171) reacts under mild conditions with zerovalent platinum and palladium complexes of the type Pt(PPh3)2 (C2H4) or ML (n = 3, 4 M = Pd or Pt L = phosphines or triphenylarsines) to give metallocyclobutane derivatives (172) (equation 118) . 

The typical reaction pathways to zerovalent derivatives are included in COMC (1995). These involve (a) preparation via reduction of higher valent platinum or (b) displacements using a zerovalent precursor. 

Allyl Complexes and Complexes Derived from Mono-ol ns Zerovalent Nickle, Platinum, and Palladium.— A series of complexes Ni(ol) (x=l—3, ol=alkyl, chloro, or fluoro olefin) has been detected by matrix condensation of nickel atoms with the olefin the optical spectra show a correlation between the transition energies of the Ni(ol) species and the 7r -orbital energy of... 

The reactions of zerovalent platinum-alkyne complexes with adds have been studied by several groups (Barlex et ai, 1969 Mann et aU 1971 Tripathy and Roundhill, 1970 Kemmitt et al, 1973). When one equivalent of acid is employed, it is possible to isolate the vinyl derivatives. Nmr studies have generally indicated a cis arrangement about the double bond (Mann et ai, 1971), presumably resulting from initial protonation of the metal, followed by cis M—H addition. The yields for this first step were uniformly good. Shaw and co-workers have reported that addition to ter-... 

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