Coordination complexes of phosphorus-carbon compounds

5 n-Coordination complexes of phosphorus-carbon compounds (1) Diphosphenes (R-I =P-R) 

Diphosphenes contain the -P=P- group, the majority of which adopt a trans-configuration. For example, the stable compound 

Various coordination modes of diphosphenes toward transition metals involve a and jt interaction with the metal center, as listed in Table 15.5.4. 

Many metal complexes containing the 1,2 or 1,3-diphosphacyclobutadiene ring have been characterized, and Fig. 15.5.8 shows the structures of some examples. 

The phosphinine rings (PC5R5, P2C4R4. P6) are analogs of benzene and form sandwich structures with the transition metals. In r 6-phosphinine complexes, the phosphinine rings are all planar. 

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