Bonding types in phosphorus-carbon compounds

Phosphorus and carbon are diagonal relatives in the Periodic Table. The diagonal analogy stresses the electronegativity of the element (C 2.5 vs P 2.2) which governs its ability to release or accept electrons. This property controls the reactivity of any species containing the element. This section covers the types of phosphorus-carbon bonds and the structures of representative species. 

Phosphinidenes (recommended IUPAC name phosphanylidenes) are unstable species and analogous to the carbenes. The parent compound H-P is a six-electron species that is still unknown, but its organic derivatives can give rise to seven different types of complexes, as listed in Table 15.5.2. 

Phosphaalkenes are tervalent phosphorus derivatives with a double bond between carbon and phosphorus. The observed P=C bond lengths range from 161 to 171 pm (average 167 pm), appreciably shorter than the single P-C bond length of 185 pm. 

Phosphaalkenes may coordinate to transition-metal fragments in various ways  

In rj2 complexes the P-C bond length is longer than that in rj1 complexes or the free ligands. 

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