Dune艧 G, Chapple PM, Kahlal S, Roisnel T, Carpentier JF, Saillard JY, Sarazin Y. Barium phosphidoboranes and related calcium complexes.
Dalton Trans 2024;
53:6892-6905. [PMID:
38567539 DOI:
10.1039/d4dt00487f]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The attempted synthesis of [{Carb}BaPPh2] (1) showed this barium-phosphide and its thf adducts, 1路thf and 1路(thf)2, to be unstable in solution. Our strategy to circumvent the fragility of these compounds involved the use of phosphinoboranes HPPh2路BH3 and HPPh2路B(C6F5)3 instead of HPPh2. This allowed for the synthesis of [{Carb}Ae{PPh2路BH3}] (Ae = Ba, 2; Ca, 3), [{Carb}Ca{(H3B)2PPh2}路(thf)] (4), [{Carb}Ba{PPh2路B(C6F5)3}] (5), [{Carb}Ba{O(B(C6F5)3)CH2CH2CH2CH2PPh2}路thf] (6), [Ba{O(B(C6F5)3)CH2CH2CH2CH2PPh2}2路(thf)1.5] (7) and [Ba{PPh2路B(C6F5)3}2路(thp)2] (8) that were characterised by multinuclear NMR spectroscopy (thp = tetrahydropyran). The molecular structures of 4, 6 and 8 were validated by X-ray diffraction crystallography, which revealed the presence of Ba鈰疐 stabilizing interactions (ca. 9 kcal mol-1) in the fluorine-containing compounds. Compounds 6 and 7 were obtained upon ring-opening of thf by their respective precursors, 5 and the in situ prepared [Ba{PPh2路B(C6F5)3}2]n. By contrast, thp does not undergo ring-opening under the same conditions but affords clean formation of 8. DFT analysis did not highlight any specific weakness of the Ba-P bond in 1路(thf)2. The instability of this compound is instead thought to stem from the high energy of its HOMO, which contains the non-conjugated P lone pair and features significant nucleophilic reactivity.
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