Counter phases

DETERMINATION OF INTERACTION COEFFICIENTS FOR ALLOYS AND STABILITY OF COUNTER-PHASES... 

J The concept of counter-phases. When a stable compound penetrates from a binary into a ternary system, it may extend right across the system or exhibit only limited solubility for the third element. In the latter case, any characterisation also requires thermodynamic parameters to be available for the equivalent metastable compound in one of the other binaries. These are known as counter-phases. Figure 6.16 shows an isothermal section across the Fe-Mo-B system (Pan 1992) which involves such extensions for the binary borides. In the absence of any other guide-... 

Figure 6.16. Counter phases in the Fe-Mo-B system (a) the section FeB-MoB and (b) the section Fe3B2-MosB2 (from Pan 1992 and Miodotvnik 1994).

The term Counter Phase Transfer Catalysis (CPTC) was coined by Okano214,215 to describe biphasic reactions catalysed by water soluble transition metal complexes which involve transport of an organic-soluble reactant into the aqueous phase where the catalytic reaction takes place. Similarly, Mathias and Vaidya564,565 gave the name Inverse Phase Transfer Catalysis to describe this kind of biphasic catalysis which contrasts with classical Phase Transfer Catalysis where the reaction occurs in the organic phase and does not involve formation of micelles.389,564... 

New tools for such biphasic reactions are inverse- or counter-phase transfer catalysts, which are able to transport lipophilic molecules from the organic phase into the aqueous phase. An advantage of the inverse- or counter-PTC is its applicability to reactions not only with ionic salts but also with non-ionic reagents soluble in water. Such carriers were first reported by Mathias and Vaidya and by us in 1986 [3, 4], and three types of carriers are known at present. Mathias and Vaidya found that pyridine derivatives react with acid halides in the organic phase to form the pyridinium salts, which transfer into the aqueous phase [3]. This catalysis was... 

Fig. 2 Mechanisms for inverse- and counter-phase transfer catalyses mixed system of inverse PTC and water-soluble metal catalyst (left) ...

The inverse-PTCs with no steric limitations are hydrophilic phosphine complexes, which are able to transport the lipophilic substrates capable of forming complexes with transition metals. These hydrophilic phosphine complexes differ essentially from the other inverse-PTCs in that they have the functions of both inverse-PTCs and transition metal catalysts by themselves. Therefore we named these catalysts counter-phase transfer catalysts [4]. 

Mechanism of the Counter-phase Transfer Catalytic Reaction... 

The counter-phase transfer catalysis via jr-allyl—palladium complexes exhibits an unusual solvent effect [16]. Both the reduction with sodium formate and the car-... 

Although counter-phase transfer catalysis has not yet attracted much attention, it is a very promising method for solving some of the problems of organometallic catalyses. Since transition metal complexes are capable of interacting with a wide variety of organic compounds, great development of counterphase catalysis is expected. 

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