Donor bridged isomers

Ge to the isolation of RCIGe------GeRCl with a weak Ge—Ge interaction [ i(Ge—Ge) 

The dibridged structures (48, M = Si) are substantially stabilized also by amino and hydroxy bridging groups, i.e. I IS i(/zNI 12)28 i 11 is by 10 kcalmol-1 more stable and HSii/i-OHjjSiH is by only 3.2 kcalmol-1 less stable than the corresponding RHSi=SiRH disilenes311. 

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Another interesting aspect of reactivity within this class of complexes is interconversion of syn and anti isomers, as has been observed with Tc-PnAO complexes substituted at the central carbon of the propylene bridge [67], The same phenomenon has been described for DMSA complexes and will be discussed in the section on S-donor groups. 

In the tetra-bridged phosphocavitands containing four donor P(0)R groups, the P=0 bonds can adopt the inward (f) or outward (o) orientations relatively to the molecular cavity. Only the ini isomer with the four P=0 groups oriented inwards can benefit from both cooperativity of P=0 binding and r-in-teractions with the aromatic cavity of the resorc[4]arene framework [19, 63]. The complexation properties of new iiii tetra-phosphonatocavitands 12b-12d and 12g towards metal ions were characterized by extraction of the metal picrate from water to chloroform solution containing the host compound (Fig. 4). 

The tris(2-cyanoethyl)phosphine can act either as a monodentate phosphorus donor ligand or as a bidentate mixed donor ligand. The red square planar [NiX2L<2] complexes (X = Cl, Br) transform in the solid state into blue six-coordinate isomers which have a polymeric structure involving bridging bidentate ligands (Scheme (2).1178,1184,1192... 

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