only evidence for a species of composition BS2 has so far come from mass spectrometry and thermal analysi~[~.'~.During our studies on binary and ternary boron sulf i d e~~' .~' we have now obtained a new boron disulfide of molecular formula B8Sib by two different routes. Rapid heating of a B2S,/S mixture (molar ratio 1 : 1.5) to ca. 300 "C at ca. bar in a sealed quartz glass which has been graphitized or protected by a boron nitride coating, in a twozone furnace with a sharp temperature profile (300/1OO "C) leads to deposition of a crystalline product within a narrow region in the colder zone of the reaction tube. The colorless needles are up to 2 mm long, extremely sensitive to hydrolysis, and decompose above 115 " C in a sealed vessel under normal pressure (Nz).The compound [elemental analysis B : S = 1 : 2.01(2)] forms monoclinic crystals (space-group P2,/c), a = 12.158(3), V = 1040.4 A3, pLalL=1.913, pexp=1.90(2) g cm-'. As shown by the complete X-ray structure analysis (1349 diffractometer data, R = 5.5%), solid boron disulfide is made up of discrete exactly planar BsSi6 molecules whose porphine type skeleton contains four 1,2,4,3,5-trithiadiborolane rings linked by sulfur bridges. Figure 1 shows the molecular structure with distances and angles averaged over chemically equivalent bonding parameters. Within the limits of experimental accuracy the molecule has Dlh symmetry (exact symmetry in the crystal is C,). The average B-S bond length (1.811 A)b=4.089 (1), ~=21.961(4) A, @= 107.65(3)", Z = 16 BS2, Fig. I. BXSlh molecule with bond lengths [A] and bond angles (u=0.003 A and 0.1 ', respectively).corresponds approximately to that in B& (1.808 il") and once again, in agreement with the planarity of the molecule, is indicative of strong ( p -p )~ interactions. The significant difference between the two types of B-S bond lengths in the five-membered rings (Fig. 1) provides the first confirmation of the differing T bond orders estimated by CNDO calculations on trithiadiborolane~l~~. The similarity of the structural characteristics to those of dimethyl-and dichloro-1,2,4,3,5trithiadiborolane in the gas phase161 demonstrates the remarkable, substituent-independent constancy of the bonding in the stable five-membered ring.A second synthetic route leading to BsSlb was found in the thioIysis of the halogenated trithiadiborolanes described by Schmidt and SiebertI7]. Thus reaction of 3,5-dibromo-1,2,4,3,5-trithiadiborolane with trithiocarbonic acid as an HZS generatorl'l in dilute CS, solution according to affords the porphine-like B8Si6 in ca. 6% yield along with polymeric (B2S& chains made up of S-linked B2S3 five-membered rings['l. Cyclization can be promoted in the reaction mixture by addition of d X or d9-transition metal compounds; the geometry of the BXSi6 molecule permits formation of interesting transition metal complexes having square-planar coordination of the tetradentate ligand (transannular S . . . S distance in B,S,,,: 4.667 A).In addition to other fragmentation products, the mass spectrum shows B2S; as f...
Several transamination reactions of B2(NMe2)4 (1a) with secondary amines have led to mixed tetraaminodiborane(4) compounds B2(NMe2)4 ‐ n(NR2)n (2–4), and B2(NC5H10)4 (1d) has been characterized by an X‐ray structure analysis which reveals the presence of a rather long B–B bond (1.75 Å). However, tetraaminodiboranes(4) of type R2N(Me2N)B‐B(NMe2)NR2 are more readily accessible from LiNR2 and B2(NMe2)2Cl2. Similarly, amination of B2(NMe2)2Cl2 with N,N'‐dimethylethylenediamine (7) yields B‐[bis(dimethyl‐amino)boryl]‐N,N'‐dimethyl‐1,3,2‐diazaborolidine (8), while reactions with Li(Me)N–CH2–CH2–N(Me)Li (9) lead also to 2,3‐bis(dimethylamino)‐1,4‐dimethyl‐1,4,2,3‐diazadiborinane (10) as the kinetically controlled product. This is further substantiated by the reaction of the B2(NMe2)2Br2 with 9 which gives exclusively the corresponding 1,4,2,3‐diazadiborinane 11. Diborane(4) dihalides B2(NMe2)2X2 (X = Cl, Br) react only in a 1:1 ratio with tmp‐B=N‐CMe3 (13) leading to 14a, b. However, both a 1:1 and a 1:2 methoxyboration of 13 has been observed with B2(OMe)4 with formation of 15 and 16.
A Convenient Synthesis of Diboron TetrabromideTetramethoxydiborane(4) and boron tribromide react at ambient temperature with formation of diboron tetrabromide (yield 50%). methyl bromide and diboron trioxide.This makes B2Br4 readily accessible for further studies.Dibortetrahalogenide kdnnen eine Schlusselfunktion in der Organobor-Chemie ubernehmen, wie ihre stereospezifische cis-Addition an Acetylene und Olefine zu 1 ,2-Diborylderivaten2), die Ringoffnung von Cyclopropanen zu 1,3-Diborylpropanen?) oder die Synthese von Thiadiborolenen und anderer Heterocyclen4) belegen. Gleiches gilt fur Subverbindungen des Bors, etwa den Zugang zu Tetrab~rtetrahalogeniden~) und weiteren polyedrischen Bor(I)-Species6), deren Chemie noch wenig untersucht ist. Voraussetzung dafur ist allerdings eine einfache Synthese von Dibortetrahalogeniden.1925 entdeckten Srock und Mitarbb.') das an Luft selbstentzundliche BzCb, das in geringen Mengen bei der elektrischen Entladung zwischen Zinkelektroden durch fliissiges Bortrichlorid anfiel. Die Einfuhrung von Hg-Elektroden und die Entladung durch gasformiges Bortrichlorid brachten eine wesentliche Ausbeutesteigerung und ermoglichten die Entwicklung eines kontinuierlichen Verfahrens*). Aber erst die Reaktion von Kupferatomen mi1 BC1, unter Anwendung der Cokondensationstechnik fuhrte zur weiteren Ausbeutesteigerung und bedeutete zugleich einen wesentlichen methodischen Fort~chritt~). Jedoch erfordern alle diese Verfahren und andere, hier nicht genannte, einen relativ hohen apparativen Aufwand.Versuche, Dibortetrahalogenide iiber metathetische Reaktionen aus einfachen Ausgangsverbindungen zu gewinnen, liefern z. T. gute Ausbeuten, setzten sich aber als praparative Verfahren nicht durch. Dies gilt etwa fur die Darstellung von Diborterrafluorid aus (BO), oder Bz(OR)., mit Schwefeltetrafluorid'O) oder die Umsetzung von (BO), mit Bortrichlorid") (Ausbeuten bis 50% a n B2F4 oder 13% an B2Cb). RO, ,OR Br, / B r RO' OR Br' B r B-B, + 4 BBr, -B-B, 4 ROBBr, 1 2 3 ROBBr, -B203 + 3 R B r + BBr, R = CH, ( 2 ) Wir fanden nun, daL3 das bei Raumtemperatur flussige Dibortetrabromid (2), das bisher durch Umhalogenierung von B2C4 mit BBr3 dargestellt wurde, durch Einwirkung von Bortribromid auf Chem.
Boron compounds of type (alkyl)2B—B(alkyl)2, which have been sought for more than 40 years, have been independently synthesized by two research teams almost simultaneously and by the same pathway. Stepwise replacement of the methoxy groups of (1) by alkyl groups gave the tetraalkyldiboranes (4), (5) (RMe), and (6) (R=tBuCh2). Tetra‐tert‐butyldiborane could not be prepared, while the silylborane (7), RSiMe3, could.
Einen B6‐Ring in Sesselkonformation enthält die Titelverbindung (1), die aus Destillationsrückständen bei der Enthalogenierung von [(CH3)2N]2BCl kristallisiert. (1) ist der erste Homocyclus des Bors und zugleich die erste Bor(I)‐Verbindung ohne Elektronenmangel.
Magnetische Kernresonanzdaten (1'B,'3C.'4N und 'I9Sn) fur eine Reihe von E-und N-(Trimethylstanny1)aminoboranen (2 -8) wurden ermittelt. Sie werden vergleichend diskutiert. Die Kopplungskonstanten 3J(119SnBN'3C) und 3J("9SnNB13C) der trans zur (CH3)3Sn-Gruppe stehenden "C-Atome sind gr6Der als fur cis-stindige in Analogie zu 3J('19SnCC13C) in Alkenylstannanen. 6" B-und 6l4N-Werte werden von Substituenten in Aminoboranen in gleicher Weise beeinfluot wie 6I3C in Alkenen. Zum Vergleich werden die NMR-Parameter einiger Aminoborane sowie des bisher unbekannten Borats (CH3)3SnBH< herangezogen. NMR Spectroscopic Studies of Boron Compounds, XVIII')A Multinuclear Study (1'B~3C,'4N,119Sn) of B-and N-(Trimethylstannyl)aminoboranes and of a Trihydrido(1rimethylstannyl)borate Ion NMR Data (11B,13C,14N, and 'I9Sn) for a series of B-and N-(trimethylstanny1)aminoboranes (2-8) were determined. These are discussed comparatively. It follows that the coupling constants 3J("9SnBN13C) and 3J(1'9SnNB'3C) are larger for compounds with the (CH3)3Sn group trans to a 13C atom than for a cis orientation, analogously to 3J(119SnCC'3C) in alkenylstannanes. Substituents influence 6"B and 6I4N of aminoboranes in the same way as they influence S13C of olefins. NMR Parameters of some aminoboranes are used for comparison as well as those of the hitherto unknown (CH3)3SnBH; anion.Den Doppelbindungscharakter der BN-Bindung in Aminoboranen belegen iibereinstimmend verschiedene physikalische Methoden, darunter auch NMR-spektroskopische Untersuchungen -9). Er geht etwa hervor aus den 'H-NMR-spektroskopish bestimmten Rotationsbameren in Verbindungen des Typs R,B -NRR' und RR'B-NRZ3) oder aus dem Gang der 611B-2,4) und Si4N-Werte5) in der Reihe R,-,,B(NRi),, (n = 0-3). '3C-NMR-Daten6-8), 6"O-Wertel) und "CIchemische Verschiebungeng) stiitzen die aus den "B-und I4N-NMR-Spektren abgeleiteten Folgerungen. Dabei zeigt sich, daR erst die Summe der Information aus allen NMR-Daten zu einem geschlossenen Bild fiihrt, das bei Aminoboranen deshalb sehr vollsttindig ist, weil alle Kerne in dieser Verbindungsklasse dem Kernresonanzexperiment zugtinglich sind.Ersetzt man B-sttindigen Kohlenstoff durch Sn, dann sollte das Bor insgesamt eine h6here Ladungsdichte erhalten, da das Zinn elektropositiver als Kohlenstoff ist. Analog sollte der Ersatz einer (CH,),C-gegen eine (CH3)3Sn-Gruppe am Stickstoff dem Stickstoff zu einer h6heren ElekChem. Ber. 114(1981)
Die Tetraaminodibor-Verbindung 1 lagert die Trihalogenide EX3 (E = B, Al, Ga; X = CI, Br, I) zu 1 : 1-bzw. 1 : 2-Koordinationsverbindungen an. Von diesen zeigt nur das thermisch stabilere BBr,-Addukt 1 b in Losung im Gegensatz zu den AIC1,-und GaCl,-Addukten kein fluktuierendes Verhalten. Die 1 : 2-Addukte sind starr, und nach NMR-Spektren bildet sich nur die meso-Form. Die Struktur der 1 : 1-Addukte wurde durch Rontgenstrukturanalyse von l g gesichert; die Einkristalle enthielten ein R-konfiguriertes Molekiil. Durch die Addition nimmt der sonst planare Diazaborolidin-Ring Briefumschlag-Konformation an.Contributions to the Chemistry of Boron, 1401)
New tetravinyldistibines, RISbz (where R = vinyl, 16; isopropenyl, 17; l(E)-and 1(Z)-propenyl, 18 and 19; 2-methyl-l-propenyl, 20, and l-methyl-lWpropeny1, 211, have been prepared from the reaction of the corresponding tertiary stibines with active metals in liquid ammonia followed by treatment with 1,2-dichloroethane. While all the distibines show yellow liquid phases, 16 and 17 freeze to violet and orange solids. Compounds 18-21 freeze to yellow solids. 'H NMR, Raman, UV, and mass spectra of 16-21 are discussed.In 1934 Paneth reported the synthesis of tetramethyldistibine, 1, from the reaction of methyl radicals with an antimony mirror.'* This compound shows unusual thermochromic behavior. It is a bright red solid that melts reversibly at 17 OC to a pale yellow liquid. Similarly, solutions of 1 are pale yellow. In the intervening 49 years, six other thermochromic distibines 2,1a 3,2 4: 5,4p5 6,6 and 7' have been reported. Solid-phase colors range from deep yellow for 2 to violet for 4, but the liquid phases are invariably pale yellow (see Figure 1).Crystal structures of l,lb 4,3 and show very similar crystal packing (Figure 2). Each molecule adopts a staggered trans conformation about the Sb-Sb axis. All the antimony atoms are nearly colinear with short Sb-Sb intermolecular contacts. This suggests that the solid-phase colors of the thermochromic distibines are due to electronic interactions along the Sb-Sb-Sb-Sb
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.