Borabenzene adducts of ylidic Lewis bases. Syntheses and structures of 3,5-Me2C5H3BCH2PPh3, 3,5-Me2C5H3BCH(SiMe3)PPh3, and C5H5BN(Ph)PPh3

摘要

The methylenephosphorane Ph3PCH2 reacts with 1-chloro-3,5-dimethyl-2- trimethylsilyl)1,2-dihydroborinine (2c) (in a 2/1 ratio) at ambient temperature to produce (triphenylphosphonio)methanide-3,5-dimethylborabenzene, 3,5-Me2C5H3BCH2PPh3 (3), with 1 equiv of (Ph3PCH2SiMe3)Cl (4), and (trimethylsilyl)(triphenylphosphonio)methanide-3,5-dimethylborabenzene, 3,5-Me2C5H3BCH(SiMe3)PPh3 (5), with I equiv of (PMePh3)Cl (6). Both adducts 3 and 5 are yellow crystalline compounds. Treatment of the iminophosphorane Ph3PNPh with an isomer mixture of 1-chloro(trimethylsilyl)dihydroborinines (8) produces N-(triphenylphosphonio)anilide-borabenzene C5H5BN(Ph)PPh3 (9) as brown-yellow crystals. The reaction of PMe3 with 2c affords the colorless trimethylphosphine adduct 3,5-Me2C5H3BPMe3 (10). The structures of the new adducts 3, 5, and 9 are reported. They do not show conjugation between the two remote charge centers, even in the case of the iminophosphorane adduct 9. [References: 44]