Syntheses, Crystal and Solution Structures, Ligand‐Exchange, and Ligand‐Coupling Reactions of Mixed Pentaarylantimony Compounds

Abstract

All possible combinations of mixed pentaarylantimony compounds bearing p-methylphenyl and p-trifluoromethylphenyl groups were synthesized; ArnTol5-nSb (n=0-5: Ar=p-CF3C6H4, Tol=p-CH3C6H4): Tol5Sb (1), ArTol4Sb (2), Ar2Tol3Sb (3), Ar3Tol2Sb (4), Ar4TolSb (5), and Ar5Sb (6). Compounds 2-5 are the first well-characterized examples of mixed acyclic pentaarylantimony species. The structures of 2-6 were determined by X-ray crystallography to feature trigonal-bipyramidal (TBP) geometry with the more electronegative p-trifluoromethylphenyl substituents selectively occupying the apical positions. Consideration of the chemical shifts of the ipso carbons of the aryl and tolyl groups suggested that the solution structures of 1-6 were also TBP, although their pseudorotation could not be frozen even at -80 degrees C. Ligand-exchange reactions (LERs) took place between 1 and 6 at approximately 60 degrees C in [D6]benzene and all six species 1-6 were found in the equilibrium mixture. The relative stabilities of 1-6 were determined quantitatively by comparison of the observed molar ratios of 1-6 in equilibrium with calculated statistical molar ratios, and Ar2Tol3Sb (3) was found to be the most stable. The ligand-coupling reactions (LCRs) of 2-5 in solution were greatly accelerated by adding Cu(acac)2 or Li+TFPB- (TFPB: [3,5-(CF3)2 C6H3]4 B), whereby the rate becomes comparable to the LER. The use of flash vacuum thermolysis (FVT) allowed the LCR to occur with very little ligand-exchange; the exception ArTol4Sb had very fast ligand-exchange. The selectivities of the LCRs were calculated from the yield of the biaryls synthesized by using FVT. These results were highly consistent with reactions catalyzed in solution, in which bitolyl was not obtained at all. The experimental results suggested that the LCR of pentaarylantimony compounds proceeds in the manner of apical-apical coupling.

Formation of epoxides from pentacoordinated organoarsenic compounds with a β-hydroxyethyl group

“…Two mechanisms for the epoxide formation can be considered (Scheme 7). One is the S N 2 reaction, in which the alkoxide anion attacks the a-carbon, and the other is the ligand coupling reaction (LCR), 12 in which hexacoordinate intermediates once formed after deprotonation decompose to give the epoxide. 13 The four broad signals A observed in the above-described reaction (Fig.…”

Solid‐State and Solution Structure of a Hypervalent AX5 Compound: Sb(C6F5)5

“…As far as we know, all previous attempts to detect the limiting slow‐exchange spectrum in homoleptic organopnictogen(V) derivatives, ER 5 , have failed 16. Efforts to widen the frequency range of the observed nucleus by introducing fluorinated substituents as in Sb{C 6 H 4 (CF 3 )‐4} 5 did not yield any improvement 16a. No better results were attained when the methyl group in SbMe 5 was replaced by the sterically demanding CH 2 SiMe 3 , as Sb(CH 2 SiMe 3 ) 5 also gave a single type of ligand down to 153 K 21.…”

Desoxyfluorierung von Phosphanoxiden: Ein allgemeiner Weg zu fluorierten Organophosphor(V)‐Verbindungen und noch mehr

“…Fluorarsanen 45 umgesetzt (Schema 6). Im Gegensatz zu vielen ihrer Phosphorhomologen können Difluortriaryl‐λ 5 ‐stibane mittels Säulenchromatographie aufgereinigt werden und haben als Vorläufer von fünfwertigen Organoantimonverbindungen in der Hauptgruppenchemie Anwendung gefunden [28–31] . Als Folge der zur Synthese nötigen harschen Reaktionsbedingungen (Verwendung von AsF 3 ,IF 5 , HF usw.)…”

“…Im Gegensatz zu vielen ihrer Phosphorhomologen kçnnen Difluortriaryl-l 5 -stibane mittels Säulenchromatographie aufgereinigt werden und haben als Vorläufer von fünfwertigen Organoantimonverbindungeni nd er Hauptgruppenchemie Anwendung gefunden. [28][29][30][31] Als Folge der zur Synthese nçtigen harschen Reaktionsbedingungen (Verwendung von As-F 3 ,IF 5 ,H Fu sw.) sind Difluortriaryl-l 5 -arsane bislang wenig erforscht, sie haben aber potenzielle Anwendungen als Fluorierungsreagenzien. [32] Eine detaillierte Untersuchung zur Anwendung der DOF Methode auf Antimon-und Arsenoxide sprengt den Rahmen dieser Studie,a ber diese ersten Ergebnisse dienen als aussichtsreiches "Proof-of-Concept" fürd ie Anwendung der Oxalylchlorid/KF-basierten Desoxyfluorierung auch auf andere Gruppe-15-Elementverbindungen.…”