Cyclocondensation of the (Z)-1,2-bis[chloro(dialkylamino)boryllethenes 6 a -c and 1,2-bis[chloro(diisopropylamino)-boryllbenzene (8a) with the lithium phosphides Li2P -C6H5, LizP -C6F5, LizP -CGH2(fBu),, (LiPH2 . dme], and P(SiMe,),, yields the 2,5-dihydro-lH-l,2,5-phosphadiboroles 1 a -c, 2b. c, 3a-c, 412,512, 9a. Compounds 4c.5c.9a are characterized by an X-ray structure analysis. Due to the B -N n bond, these derivatives are monomeric with little contribution of B -P R interaction. However, low-temperature 'H-NMR studies show that the P-inversion barrier is distinct lower (10-15 kcal mol-') than for PH, and organophosphanes (ca. 35 kcal mol-*).This may be a result of favorable B -P n interaction in the transition state of the inversion at phosphorus. Reaction of the B-methyl-substituted 1,2-bis(chloromethylboryl)benzene (8b) with P( SiMe,), gives the 1 ,Zdihy dro-1 H-l,2,5-benzophosphadiborole 9b which forms the dimer (9b)z below 40°C by an intermolecular B -P acceptor-donor bond. The structure of (9b)2 is confirmed by an X-ray crystal structure analysis. Treatment of 1 c with oxygen, sulfur, or selenium leads to the corresponding 1,2,5-chalcogenadiborole derivatives 10, 11 and 12. By this process, the phenylphosphorus group is eliminated as the pentamer (C&-P)5 in 25% yield. Reaction of 1 c with MezBBr gives the Lewis acid-base adduct 13 bearing an h304-coordinated phosphorus and one four-coordinated boron atom. n complexation of l c with the (CO),Fe fragment leads to the iron complex 15 (X-ray diffraction analysis). Deprotonation of 3 c with MeLi gives the P-Li-substituted phosphadiborole [3 c-H]Li which reacts with MeI, Me2SiC12, Me,SiCl to form the Pmethylated and -silylated derivatives 14a. 14b, 2c. Reaction of 2 b with one equivalent of MeOH at -78°C in pentane does not give the expected P-unsubstituted compound 3b. Instead, B -P ring cleavage is observed with formation of H2P -SiMe, and (Z)-1,2-bis[(diethylamino)methoxyboryl]ethene. Darstellung und EigenschaftenZur Synthese der P-phenylsubstituierten Derivative
Reactions of (Z)-1,2-diborylethenes [HC -B(C1)RlZ with LiPH2 and LiP(SiMe& lead to the 2,5-dihydro-lH-l,2,5-phosphadiboroles 1 a -d in good yields. 1 a, b react with (Me3C)2Hg to give yellow 2a (56%) and 2b (go%), which are also obtained from 1 c, d and TlCl or C2C16, respectively. The constitution of 2b is established by an X-ray structure analysis. 2a reacts with Cr(C0)3(CH3CN)3 to yield the bis(pentacarbony1)chromium complex 4a, whereas 2b and Fe(C0)3(C8H,4)2 form the bis(tricarbony1iron) compex 5 b. Spectroscopic studies and Xray structure analyses of 4a and 5 b show that in 4a the chromium atom is ql-bound to phosphorus, whereas in 5b the iron interacts with all atoms of the folded CzBzP ring.Fruhere Untersuchungen haben gezeigt, da13 Bor-funktionalisierte (2)-1 ,ZDiborylethene zum Aufbau neuartiger BorHeterocyclen geeignet sind 1,2). Fiinf-und sechsgliedrige C,B,X,-Ringgeruste (n = 1, 2) rnit X = Schwefel, Stickstoff und Phosphor reprasentieren vielseitige n-Komplexliganden in der Ubergangsmetallchemie, die iiber Olefin-und Heteroatom-Donor-sowie Bor-Akzeptor-Funktionen verfugen2). Von Derivaten der phosphorhaltigen Heterocyclen 2,s-Dihydro-1 H-1,2,5-phosphadiborol 1 3, und 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborin 34' rnit dem C2B2P-bzw. C2B2P2-Ringgerust sind Metallkomplexe bekannt.
ds-l,2-Bis(diisopropylamino-trimethyltin-boryl)hex-3-ene, rra«s-l,2-Bis(diisopropylamino-trimethylthin-boryl)etheneTrimethyltinlithium reacts with z-l,2-bis(diisopropylamino-chloro-boryl)ethene deriva tives 4a (R = Et) and 4b (R = H) to give the ds-l,2-bis(diisopropylamino-trimethyltin-boryl)-hexene-3 (2a) and, surprisingly, the frarts-l,2-bis(diisopropylamino-trimethyltin-boryl)-ethene (5 b) respectively. The constitution of 2 a and 5 b is derived from spectroscopic data, and confirmed by X-ray structure analyses. The formation of the trans-product 5 b probably occurs via a radial intermediate.
Synthesis and Reactions of lJ.2.2-Tetraborylethane Derivatives *Reaction of (Z)-1,2-bis(dichloroboryl)ethene with B2C14 leads to l,l,Z,Z-tetrakis(dichloroboryl)ethane ( l a ) in 90% yield. Substitution of the chlorine atoms in l a results in the formation of the iodo and amino derivatives 1 b and 1 c, d. Compound 1 b reacts with alkynes to give the 2,2'-linked 2,3-dihydro-1,3-diborole derivatives 2b, c which are aminated to yield 2d, e. Dehalogenation of 1 d leads to the organoboron C2B4 cage 3d.The heterobicyclic compound 4d with two fused phosphadiborolane rings is obtained from Id and LiPH2. Reaction of 4d with (C0)3Fe(C8H14)2 gives the unusual diiron complex 5d. The constitutions of the new compounds are derived from spectroscopic data and are proven for 2e, 4d and 5d by X-ray structure analyses.
and 31P-NMR spectroscopy as well as an X-ray structure analysis of 2. Lowtemperature 'H-NMR studies show that the inversion barrier at P is distinctly lower than that of related unsaturated compounds. This might be the result of a favorable B-P-n interaction in the transition state of the inversion at the phosphorus atom. Reaction of 1 with S8 or CS2 leads to the 1,2,5-thiadiborolane 3. . DME] in Toluol bei 120°C entsteht 2 das in Form farbloser, maI3ig luftstabiler Kristalle anfallt, die sich sehr gut in aromatischen Solventien und THF losen. Das 1,2,5-Thiadiborolan 3 wird aus 1 und S8 in Toluol erhalten. Die NMRKontrolle der Umsetzung gab keinen Hinweis auf ein Zwischenprodukt rnit der B-S-P-B-Sequenz; 3 kristallisiert in Form farbloser, unangenehm riechender Kristalle, die ebenfalls gut loslich in organischen Losungsmitteln sind. Einen weiteren Zugang zum 1,2,5-Thiadiborolan 3 ermoglicht die Umsetzung von 1 rnit CS2 in Petrolether bei Raumtemperatur. Im Rahmen unserer
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