Phosphorus bond strengths

Table 3. Bond lengths (A), bond dissociation energies (kcal/mol), a- and n-bond strengths (kcal/mol), charges on phosphorus (e), and orbital energies (eV) for first row transition metal complexes ML =PH ...

Attempting to rationalize the strength of a metal-phosphorus bond in terms of the collective a, tt, and steric capacity of a coordinated phosphine is a difficult matter. Refer to the series you developed in Problem 11.13 and predict which ligands would form the strongest and the weakest M—P bonds. 

The stability of the olefin complexes seems to be determined by the steric and electronic characters of both the phosphorus ligand and the olefin (22). For example, ethylene complexes have only been isolated for the cases with sterically large ligands such as P(0-o-tolyl)3 and PPh3 however, maleic anhydride forms a stable isolable complex with the smaller P(0-p-tolyl)3 ligand. The nickel-ethylene bond strength is estimated to be 39 kcal/mol based on values of 36 kcal/mol for 1-hexene and 42 kcal/mol for acrylonitrile [when L = P(0-o-tolyl)3] (22). 

In many ways the phosphates provide the richest field for CBC s (chemically bonded ceramics) because of the P—O bond strengths and the coordination demands of pentavalent phosphorus. Among silicates, room temperature hydration reactions seem to be possible only with Ca-compounds the magnesium and aluminum anhydrous silicates phases simply do not react. This book documents for the reader the wide application of these separate chemistries as true chemically bonded ceramics. 

A148. C. T. Mortimer, Reaction Heats and Bond Strengths. Pergamon, Oxford, 1962. 201 pp. Metal-carbon and metal-halide bonds are considered in Chapter 8, and bond strengths in silicon, phosphorus, and sulfur compounds in Chapter 10. 

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