Complex zerovalent

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

J. Chatt and H. R. Watson, Complexe.s of zerovalent transition metals with the ditertiary phosphine, Me2PCH2CH2PMe2, J. Chem. Soc. 2545-9 (1962). 

The tertiary phosphine complexes are the most important zerovalent compounds. They are frequently prepared by reductive methods, often using the phosphine as the reducing agent [43], e.g. 

Zerovalent complexes are also obtained with polydentate phosphines [53] Pd2Cl2(dppm)2 NaBH > Pd2(dppm)3... 

The coordination sphere of transition-metal complexes can furthermore be utilized for the fixation of silicon ligands in their lowest oxidation states. Even examples of compounds containing a formally zerovalent silicon (E) are now known [41]. 

Molecular compounds of silicon in a formally zerovalent oxidation state can be stabilized by appropriate transition-metal fragments. An entry to such polyme-tallated complexes of silicon is given by the chlorosilylene compounds 7, 11 as a starting-point. 

Reactions of zerovalent platinum and palladium complexes with organometallic compounds of nontransition metals. V. I. Sokolov and O. A. Reutov, Coord. Chem. Rev., 1978, 27, 89-107 (80). 

The transition-metal catalyzed decomposition of thiirene dioxides has been also investigated primarily via kinetic studies103. Zerovalent platinum and palladium complexes and monovalent iridium and rhodium complexes were found to affect this process, whereas divalent platinum and palladium had no effect. The kinetic data suggested the mechanism in equation 7. 

Scheme 6 Synthesis of platinum disulfido complexes from zerovalent platinum complexes...

Hidai et al. have reported the reaction of a diruthenium complex, (RuCp )2(yU-Si-Pr)2(//-S2), with zerovalent complexes of group 10 metals, [M(PPh3)4] (M=Pd, Pt) (Scheme 65) [146]. The reaction with the Pt complex... 

Scheme 65 Reaction of (RuCp )2( t-Si-Pr)2( U-S2) with zerovalent platinum and palladium complexes...

The first ruthenium porphyrin alkyls to be reported were prepared from the zerovalent dianion, [Ru(Por)] with iodomethane or iodocthane, giving the ruthe-nium(lV) dialkyl complexes Ru(Por)Me2 or Ru(Por)Et2 (Por = OEP, TTP). Alternatively, the Ru(lV) precursors Ru(Por)X2 react with MeLi or ArLi to produce Ru(Por)Mc2 or Ru(Por)Ar2 (Ar = / -C(,H4X where X = H, Me, OMe, F or Cl) 147-149 The osmium analogues can be prepared by both methods, and Os(Por)R2 where R = Me, Ph and CH2SiMe2 have been reported.Some representative structures are shown in Fig. 5, and the preparation and interconversion of ruthenium porphyrin alkyl and aryl complexes are shown in Scheme 10. 

Tindall D,PawlowJH,Wagener KB (1998) RecentAdvancesin ADMET Chemistry. 1 183-198 Tobisch S (2005) Co-Oligomerization of 1,3-Butadiene and Ethylene Promoted by Zerovalent Bare Nickel Complexes. 12 187-218 Tomioka K, see Iguchi M (2003) 5 37-60 Tomooka K, see Hodgson DM (2003) 5 217-250... 

Scheme 4 Oxidative-addition of NCAs to zerovalent cobalt and nickel complexes...

In 1977, Fahey and Mahan described the first C-F oxidative addition of hexafluo-robenzene (C ) to the zerovalent nickel complex [Ni(cod)(PEt3)j] [11], The reaction was very slow and led, after several days at 30-35°C, to the formation of trani-[Ni(CgF3)(F)(PEt3)2] in very poor yield (7%). The use of [NiCPEtj) ] for the same reaction by Perutz and co-workers 20 years later allowed for a better conversion but the reaction rate remained slow (4 weeks were necessary to obtain 48% of the desired product) [12],... 

Figure 13. Nanoparticle synthesis through hydrogenolysis of zerovalent metal complexes. (Reprinted from Ref [53], 2007, with permission from Wiley-VCH.)...

Pringle found that zerovalent metal complexes were active catalysts (Scheme 5-3) for the addition of PH3 to formaldehyde (see also Scheme 5-2, Eq. 1). 

The same reaction sequence was monitored by uv-visible spectroscopy and despite the lack of optical data for the zerovalent binary iron-isocyanide complexes, comparison with the spectrum for FeCCO) (18) reveals a close similarity. After the photolysis the original spectrum [an intense absorption at 232 nm with two shoulders at 297 and 340 nm] had decayed to be replaced by a new spectrum consisting of two bands at 220 and 382 nm. 

The first transition metal isonitrilate complex reported was the tetrahedral Co-1 complex [Co(C=NPh )4] where Ph = 2,6-Me2C6H3,96 characterized by a crystal structure analysis. Oxidation yields the zerovalent dimer Co2(C=NPh )8, which features two bridging isonitrile groups. 

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