Ethylene-PtCl

The utility of fragment orbitals can be documented in many different situahons. Here only two examples, ahcene ML and CpMLs complexes, are covered. We start with Zeise s salt, ethylene PtCls. A PtCls fragment is d the electron occupancy for the five fragment orbitals is shown on the left side of Figure 18(a). The empty 2ai PtCft" hybrid interacts with and stabihzes the n orbital of the ethylene hgand while filled b2 is stabihzed by ethylene tt. The same basic pattern... 

Similarly, the vinyl group of trimethylvinylsilane is hydrolyzed by a catalytic amount of Zeise s salt [(QH PtCls]- in moist acetone (37). In this study, the intermediate ir-complex formed [(Me3SiC2H3)PtCl3 ] from the displacement of ethylene on Zeise s anion by the vinylsilane was isolated and shown to hydrolyze to Zeise s anion and hexamethyldisiloxane in moist acetone [Eqs. (63-64)]. 

The importance of steric interactions with cis hgands can be more clearly seen in alkene substituent effects. The barrier increases significantly in the PtCl(acac)(ene) series where ene = substituted ethylene compared to ene = ethylene. The m-Cl2(DMSO)Pt(alkene) series (6)-(9), studied by Boucher aud Bosuich, is particularly instructive. The rotatiou iu the ethylene begins to produce broadening about -47 °C, whereas the propene conformers broaden at —20 °C and... 

Although a variety of platinum(II)-ethylene complexes have been described (268), those most frequently encountered are Zeise s salt, K[(C2H4)PtCls] H20, and Zeise s dimer, [(C2H4)PtCl2]2- These have been employed for preparation of many other platinum(II)-olefin complexes and have been the subject of much research. 

Asymmetric Influence from the trans Ligand. As shown later, when an asymmetric nitrogen is in the trans position of the complexes of the type trans N,//)-[PtCl(L-am)(ethylene)], asymmetry is introduced by the substitution of tbn for the ethylene in organic solvents. 10.) L-Alanine, L-phenylalanine, and L-valine fail to introduce asymmetry on the incoming tbn in the equilibrated state. However, L-proline, N- and C-substituted L-proline and even -substituted L-valine induce asymmetry. (Table V) There must be some electronic interaction from the asymmetric nitrogen upon the olefin through platinum(II). 

Figure 11. Difference in CD between two complexes of the type trans(N,//)-[PtCl( L-aminocarhoxylate)( ethylene ) with and without substituent on the nitrogen (10)...

Figure 12. Projection of the square planar complexes (10) A, trans(N,//)-[PtCl-(-substituted L-am)(ethylene)] B, S,S-trans-2-butene moiety.

The cis-isomer cis(N,//)-[PtCl(L-pro)(ethylene)] gives only a weak CD in this region (Figure 13). 

Table V. Kinetic and Thermodynamic Optical Yield of trans-(N,//)-[PtCl(L-am)(olefin)] on the Reaction of the Corresponding Ethylene Complexes with Olefins (22)...

Ethylene inserts into the Pt—H bond of trans-PtCl(C2H4XPEt3)2-... 

Dimethyldiethylphosphonium iodide, (CH3)aP(C2H5)2l, is obtained by treating methyldiethylphosphine with methyl iodide. The corresponding chloride decomposes when heated into ethylene and a distillate which yields dimethylethylphosphine when treated with sodium hydroxide. The chloride forms a platinichloride, 2C6H16PCI. PtCl. ... 

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