Zeise

Zeise s salt, K[PtCl3(C2H4)]. A ff-elhylene complex, the first such complex isolated. 

The neutral m do-borane B Hio (structure 10) has a basal B-B bond (see p. 159) and this enables it to act as a ligand by displacing ethene from Zeise s salt (p. 930). 

W. C. Zeise prepaied K[Pl(C H4)Cl3) and related compounds though of unknown structure at the time they later proved to be the first organometallic compounds. 

Xanthates (e.g. EtOCSSK) discovered by W. C. Zeise who also prepared the first mercaptan (EtSH) in 1834 (see also p. 930). 

Figure 19.19 Siructute of Ihe anion of Zeise s sail, (PMij -C HilCIjil standard deviations are Pt-CI 0.2pm Pt-C 03pm. and C-C 04pm...

A common property of coordinated alkenes is their susceptibility to attack by nucleophiles such as OH , OMe , MeC02, and Cl , and it has long been known that Zeise s salt is slowly attacked by non-acidic water to give MeCHO and Pt metal, while corresponding Pd complexes are even more reactive. This forms the basis of the Wacker process (developed by J. Smidt and his colleagues at Wacker Chemie, 1959-60) for converting ethene (ethylene) into ethanal (acetaldehyde) — see Panel overleaf. 

Mercaptans were discovered in 1834 by W. C. Zeise (pp. 930, 1167) who named them from the Latin mercurium captans, catching mercury. 

The adoption of a planar structure in these adducts, rather than the sterically more favourable tetrahedral one, is in keeping with a platinum(II) oxidation state. The side-on bonding of the 02 molecule is believed to involve two components, as in Zeise s salt (Figure 3.18). 

Although Zeise s salt is a complex of a 7r-bonding ligand, this compound must be included in an account of the chemistry of these metals, if only as... 

Figure 3.63 Platinum-alkene bonding in Zeise s salt. (Reproduced with permission from S.A. Cotton and F.A. Hart, The Heavy Transition Elements, Macmillan Press Ltd, 1975, p. 126.)...

Hydration of unactivated alkynes is an important method for functionalizing this plentiful hydrocarbon source. Therefore, a variety of metal ions have been proposed as catalysts for this reaction, and almost all of the reported additions of water to terminal alkynes follow the Markonikov rule. The hydration of l-aUcynes with Hg(II) salts in sulfuric acid [85], RuCh/aq.HCl [86, 87], K[Ru (edta-H)Cl] 2H20 [88], RhCl,.3H20/aq. HCl [89], RhCl3/NR4 [90], Zeise-type Pt(II) complexes [91-93], and NaAuCl4 [94] produced exclusively methyl ketones (Eq. 6.46). 

Treatment of the olefin 49 with Zeise s dimer leads to the chloroplatination complex 50 [26], The addition adduct 50 is hydrogenated stereospecifically to the trans-disubstituted chlorocyclohexane 51. The insertion of carbon monoxide into 50, in the presence of methanol, yields the ester 52 stereoselectively. 

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