B-substituted group 1 phosphides: synthesis and reactivity

Abstract

1-Boryl-8-phosphinonaphthalenes 1-BCy₂-8-PCl₂-C₁₀H₆ (1) and 1-BCy₂-8-PPhCl-C₁₀H₆ (2) were prepared and used as starting materials for the synthesis of B-substituted phosphides. The reduction of 1 and 2 by Mg provided neutral compounds [1-BCy-8-PCy-C₁₀H₆]₂ (3) and [1-BCy₂-8-PPh-C₁₀H₆]₂ (4). Compound 3 represents the dimer of phosphinoborane 1-BCy-8-PCy-C₁₀H₆ while complex 4 is a rare example of a discrete B ← P coordinated diphosphine. The reduction of 2 by Na or K in THF yielded B-substituted group 1 phosphides [Na(THF)₃]⁺[1-BCy₂-8-PPh-C₁₀H₆]⁻ (5) and {[K(THF)₂]⁺[1-BCy₂-8-PPh-C₁₀H₆]⁻}_∞ (6), which structurally resembled bulky group 1 phosphides. Complex 5 showed easy activation of elemental chalcogens E (E = O, S, Se) to give B-substituted chalcogenophosphinites {[Na(THF)₂]⁺[1-BCy₂-8-P(E)Ph-C₁₀H₆]}₂ (E = O (7), S (8), Se (9)) as the products of chalcogen insertion into the P–Na bond. Importantly no oxidation to dichalcogenophosphinates was observed. Compound 5 is tolerant of the CO polar bonds in organic substrates and the reactions of 5 with 2,3-butanedione or an acyl chloride provided {[Na(THF)₂]⁺[1-BCy₂-8-P{CHC(O)C(Me)O}Ph-C₁₀H₆]⁻}₂ (10) and [1-BCy₂-8-P{C(O)tBu}Ph-C₁₀H₆] (11). Finally, B-coordinated phosphatetrylenes [1-BCy₂-8-P(SnL)Ph-C₁₀H₆] (12) and [1-BCy₂-8-P(PbL)Ph-C₁₀H₆] (13) (L is {2,6-(Me₂NCH₂)C₆H₃}⁻) were also prepared by substitution reactions of 5.