Frustrated Lewis Pairs and Ring-Opening of THF, Dioxane, and Thioxane

The reaction of tBu(2)PH and B(p-C6F4H)(3) in THF afforded tBu(2)(H)P(CH2)OB(p-C6F4H3 (1). Similarly, reactions of N-bases with a THF solution of B(C6F5)(3) led to the formation of the THF-ring-opening products C5H3Me2N(CH2)(4)OB(C6F5)(3) (2), C6H5CH2NIMe2(CH2)(4)OB(C6F5)(3) (3), and Me2NC(6)H(4)NMe(2),(CH2)(4)OB(C6F5)(3)(4). THF-ring-opening also occurs with aliphatic amines to form the compounds Me3N(CH2)(4)OB(C6F5)(3) (5), Et3N(CH2)(4)OB(C6F5)(3) (6), Me2N(CH2)(2)NMe2(CH2)(4)-OB(C6F5)(3) (7), and tBuHN(CH2)(2)NH/Bu(CH2)(4)OB(C6F5)(3) (8). In related chemistry, reactions of B(C6F5)(3),1,4-dioxane, and the appropriate base yielded tBu(3)P(CH2)(2)O(CH2)2OB(C6F5)(3) (10), C6H5-CH2NMe2(CH2)(2)O(CH2)(2)OB(C6F5)(3) (11), ((tBuN)(2)C3H2)(CH2)(2)O(CH2)(2)OB(C6F5)(3) (12), Me2NC6-H4NMe2(CH2)(2)O(CH2)2OB(C6F5)(3) (13), and C5H3Me2N(CH2)(2)O(CH2),OB(C6F5)(3) (14). In a related fashion, the thioxane adduct (C6F5)(3)B(SC4H8O) (15) reacted with N,N-dimethylbenzylamine, N,N,N ',N '-tetramethyl-p-phenylenediamine, 2,6-lutidine, or tBu(3)P to give the corresponding ringopened products L(CH2)(2)S(CH2)(2)OB(C6F5)3 (l = tBu(3)P (16), C6H5C6H2NMe2 (17), Me2NC6H4NMe2 (18), and C5H3Me2N (19)). The crystal structures of 1-7, 10-12, 14, 18, and 19 are reported.