Phosphorus aluminum-carbon bonds

Different elective affinity of elements as compared to carbon. Electropositive elements (Si, B, AI, P) have a considerably larger affinity to electronegative elements than carbon. In other words, silicon, boron, aluminum, phosphorus and other elements form weaker bonds with electropositive elements (H, Si, B, Al, As, Sb, Bi, etc.), and stronger bonds with electronegative elements (O, N, Cl, Br, F, etc.) than carbon. 

The ability of phosphorus-carbon-aluminum cage compounds to function as ligands in transition metal complexes will be briefly illustrated by the example of 82 (R = i-Bu) on reaction with diiron nonacarbonyl. Coordination of the Fe(CO)4 fragment occurs exclusively at the phosphorus atom of the double bond which serves as a two-electron donor (- 83,100 %) (Scheme 6-21) [65]. 

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