Synthesis and structures of new 1,3,6,2-dioxazaborocanes containing substituents in the ocane fragment

Abstract

H, Ph) were synthesized by the reactions of aryl or methylboronic acids with dialkanolamines. The treatment of (Me 2 NCH 2 CH 2 O) 3 B (15) with MeN(CH 2 CH 2 OH)(CH 2 CPh 2 OH) afforded 2 [2 (dime thylamino)ethoxy] 1,3,6,2 dioxazaborocane (12). 2 Fluoro 1,3,6,2 dioxazaborocanes R 1 N(CHR 3 CHR 2 O)(CH 2 CH 2 O)BF (13: R 1 = PhCH 2 , R 2 = R 3 = H; 14: R 1 = Me, R 2 = R 3 = Ph, threo) were synthesized by the reaction of bis(trimethylsilyl) ethers of the corresponding di alkanolamines with BF 3 •Et 2 O. The new borocanes can be used for the synthesis of the corre sponding germanium derivatives PhCH 2 N(CH 2 CH 2 O) 2 GeX 2 (16, X = OEt; 17, X = Cl), as exemplified by the reaction of compound 6. The structures of erythro MeN(CH 2 CH 2 O)(CHPhCHPhO)BPh (3), threo MeN(CH 2 CH 2 O)(CHPhCHPhO)BPh (4), erythro MeN(CH 2 CH 2 O)(CHPhCHPhO)B(4 MeC 6 H 4 ) (8), and PhCH 2 N(CH 2 CH 2 O) 2 BF (13) were established by X ray diffraction. The coordination polyhedra of the boron atoms in these complexes can be described as distorted tetrahedra. The boron-nitrogen distances (1.705(7)-1.723(3) Å) provide unambiguous evidence for the presence of the B←N transannu lar interaction in these compounds. The structures of the resulting borocanes containing phenyl substituents at the carbon atoms of the ocane skeleton were studied by NMR spectroscopy and quantum chemical density functional theory calculations.

The nature of multiple boron-nitrogen bonds studied using electron localization function (ELF), electron density (AIM), and natural bond orbital (NBO) methods

“…Chemical names of the studied molecules, downloaded from the CSD [17] and the experimental boron-nitrogen bond lengths, r exp (BN), are presented in Table 1. The molecules contain formal single (B-N), double (B=N), and triple (B ≡ N) bonds and cover the range of r exp (B,N) values between 1.220 (dogpiy [55]) and 1.717 Å (ajepah [56]).…”

“…Therefore, 14 formally single B-N bonds in 10 molecules, with the r opt (B,N) lengths between 1.547 and 1.785 Å have been investigated. The molecules, selected from the CSD, are as follows: akesug [75], cofvuo, afucin [76], amikem [77], abemez [78], acipeh [79], abemid [78], ajepel [56], and ajepah [56]. The Lewis structures for all the studied molecules are shown in Scheme 3.…”