Reactions of carbene-stabilized borenium cations. Issue 6 (22nd January 2020)

• Record Type: Journal Article
• Authors: Lam, Jolie; Cao, Levy L.; Farrell, Jeffrey M.; Stephan, Douglas. W.
• Is Part Of: Dalton transactions. Volume 49:Issue 6(2020)
• Page Start: 1839
• Page End: 1846
• Publication Date: 2020-01-22
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt04731j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A borenium cation containing BH bond is shown to react with olefins, alkynes vinyl-pyridine and phosphinoalkene. Related reactivity of C3-borenium cations with the FLP, P t Bu3 /B(C6 F5 )3 is shown to give the zwitterionic borenium-borate species. Abstract : In this paper we probe the reactivity of the borenium cations [C3 H2 (NCH2 C6 H4 )(NCH2 Ph)BH][B(C6 F5 )4 ] 2 and [C3 H2 (NCH2 C6 H4 )2 B][B(C6 F5 )4 ] 3 . The reactions of 2 with cyclohexene or 3, 3-dimethyl-1-butene gave the alkyl-aryl borenium salts [PhCH2 (CHN)2 CCH2 C6 H4 BR][B(C6 F5 )4 ] (R = Cy 4, CH2 CH2 t Bu 5 ) while the corresponding reactions with diphenylacetylene, 1-hexyne and 1-phenyl-1-propyne gave the aryl–alkenyl borenium cation salts [PhCH2 (CHN)2 CCH2 C6 H4 BC(R 1 )C(H)R 2 ][B(C6 F5 )4 ] (R 1 = R 2 = Ph 6, R 1 = H, R 2 = C4 H9 7, R 1 = Me, R 2 = Ph 8a, R 1 = Ph, R 2 = Me 8b ). In contrast, the reaction of 2 with ethynyldiphenylphosphane or 2-vinylpyridine lead to the formation of the adducts, [PhCH2 (CHN)2 CCH2 C6 H4 B(H)P(Ph2 )CCH][B(C6 F5 )4 ] 9, [PhCH2 (CHN)2 CCH2 C6 H4 B(H)NC5 H4 C(H)CH2 ][B(C6 F5 )4 ] 10, respectively, while the more bulky donor H2 CC(Ph)PMes2 gave 1, 2-hydroboration of the phosphinoalkene affording [PhCH2 (CHN)2 CCH2 C6 H4 BCH2 CH(Ph)PMes2 ][B(C6 F5 )4 ] 11 . In another vein of reactivity, one or two equivalents of the FLP, P t Bu3 /B(C6 F5 )3 is shown to react with 3 to give the zwitterionic borenium-borate species [C2 H2 (NCH(BC(CHNCH2 C6 H4 )2 )C6 H4 )(NCH(B(C6 F5 )3 )C6 H4 )CB] 12 and the anionic bis-borate species[ t Bu3 PH][C2 H2 (NCH(B(C6 F5 )3 )2 C6 H4 )2 CB] 13 . The implications of these findings are discussed.