Borabenzene Adducts of Ylidic Lewis Bases. Syntheses\nand Structures of 3,5-Me₂C₅H₃BCH₂PPh₃,\n3,5-Me₂C₅H₃BCH(SiMe₃)PPh₃, and C₅H₅BN(Ph)PPh₃¹

Abstract

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