Major CJ, Qu ZW, Grimme S, Stephan DW. The Non-Ancillary Nature of Trimethylsilylamide Substituents in Boranes and Borinium Cations.
Chemistry 2022;
28:e202200698. [PMID:
35262980 PMCID:
PMC9324859 DOI:
10.1002/chem.202200698]
[Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Indexed: 11/21/2022]
Abstract
The known boranes (R(Me3Si)N)2BF (R=Me3Si 1, tBu 2, C6F53, o‐tol 4, Mes 5, Dipp 6) and borinium salts (R(Me3Si)N)2B][B(C6F5)4] (R=Me3Si 7, tBu 8) are prepared and fully characterized. Compound 7 is shown to react with phosphines to generate [R3PSiMe3]+ and [R3PH]+ (R=Me, tBu). Efforts to generate related borinium cations via fluoride abstraction from (R(Me3Si)N)2BF (R=C6F53, o‐tol 4, Mes 5) gave complex mixtures suggesting multiple reaction pathways. However for R=Dipp 6, the species [(μ‐F)(SiMe2N(Dipp))2BMe][B(C6F5)4] was isolated as the major product, indicating methyl abstraction from silicon and F/Me exchange on boron. These observations together with state‐of‐the‐art DFT mechanistic studies reveal that the trimethylsilyl‐substituents do not behave as ancillary subsitutents but rather act as sources of proton, SiMe3 and methyl groups.
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