Synthesis, Structure, And Reactivity Of N-heterocyclic Organic Boranes

In this dissertation, several organic boron compounds supported by the aromatic imine ligand L'H [L'H=ArN=C('Bu)CH2Si(CH3)3, Ar=2,6-iPr2C6H3], pyrrole ligand L2 with substituents (L2=2-C(H)O-5-tBu-C4H2NH), andβ-diketiminato ligand L3H[L3H=ArNC(Me)CHC(Me)N(H)Ar, Ar=2,6-Me2C6H3] were synthesized and fully characterized. Their reduction reactions and other properties have also been studied.1. Dihaloboranes L1BBr2 (1) and 2 based on the ligand L1 and L2, were synthesized and fully characterized. Reduction of 1 with KC8 resulted in the formation of a C-C coupling product{[BrBC(H)(TMS)C(H)(tBu)N(Ar')]2, Ar'= 2-lPr-6-C(H)(Me)2-C6H3},3. in which C-H activation of methine (isopropyl) on the ligand was observed. The structure of product obtained from the reduction of 2 with KC8 was not determined.2. The chloroborane L3BHC1 (4) was prepared by the reaction of L3Li with BHCl2·SMe2, and has been fully characterized. Reaction of 4 with 1 equiv ItBu [(tBuNCH)C:] yielded a dehydrohalogenated borane 5 {[ArNC(CH2)CHC(CH3)NAr]BH, Ar=2,6-Me2C6H3}, in which one of theβ-methyl groups on the P-diketiminato ligand backbone is deprotonated during the reaction.3. Reaction of borane 5 with 1 equiv elementary sulfur (or selenium) yielded the first stable monomeric thioxoborane (or selenoxoborane){[HC(CMe)2(NAr)2]BE, E= S, or Se; Ar= 2,6-Me2C6H3} featuring well-defined B=E (E=S, Se) double bonds.4. Reaction of borane 5 with 1 equiv water resulted in the formation of addition product 11{[HC(CMe)2(NAr)2]BHOH, Ar=2,6-Me2C6H3}. Treatment of 5 with 2 equiv water yielded a dihydroxyborane 12{[HC(CMe)2(NAr)2]B(OH)2, Ar= 2,6-Me2C6H3}.5. Reaction of 5 with 1 equiv Lewis acid B(C6F5)3 yielded the boron cation compound 13{{ArNC[CH2B(C6F5)3]CHC(CH3)NAr)BH,Ar=2,6-Me2C6H3}, which could be converted to a dications(boron and lithium)compound 14 {{[ArNC(CH2B(C6F5)3)]2CH}BHLi(THF)4,Ar=2,6-Me2C6H3}upon treatment with 1 equiv Lewis base LiN(TMS)2.