Rapid Transfer of Selenium from Tertiary Phosphine Selenides to Tertiary Phosphines

Article abstract of DOI:10.1039/DT9800000871

Selenium transfer between PR3Se and PR3 in solution is rapid on the n.m.r. time scale, and a bimolecular process is indicated.Mixtures of Ph2P(Se)C2H4(Se)PPh2, Ph2(Se)C2H4PPh2, and Ph2PC2H4PPh2 display similar variable-temperature 1H n.m.r. characteristics and their methylene-proton signals coalesce at elevated temperatures.The compound Ph2P(Se)CH2(Se)PPh2 reacts immediately on mixing with Ph2PCH2PPh2 to give exclusively Ph2P(Se)CH2PPh2, whereas solutions of Ph2P(Se)C2H4(Se)PPh2 and Ph2PC2H4PPh2 equilibrate with Ph2P(Se)C2H4PPh2 in 1:1:2 proportions, respectively.The sulphur analogues behave similarly, but react much more slowly.Selenium reacts at ambient temperature with Ph2P(S)CH2PPh2 to form only Ph2P(S)CH2(Se)PPh2, but the action of sulphur on Ph2P(Se)CH2PPh2 leads to a mixture of Ph2P(Se)CH2(Se)PPh2, Ph2P(Se)CH2(S)PPh2, and Ph2P(S)CH2(S)PPh2.Controlling influences and synthetic implications of these reactions are discussed.

Full text of DOI:10.1039/DT9800000871

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