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2645 1,2,3-Triborolane aus Norbornenderivaten, Allylbenzol und Dehalogenierungsprodukten von Dichlor(diisopropy1amino)boran; 2,4,5-Tris(diisopropylamino)-2,4,5-triborabicyclo [ 1.1 .l] pentan -Products of Dichloro(diisopropy1amino)borane; 2.4,5-Tris(diisopropylamino)-2.4.5-triborabicyclo[l.l.l]pentane -Bicyclus or Carborane? The new 1,2,3-tris(diisopropylamino)triborolanes 1. 2, 3 and 4 have been prepared by treatment of mixtures of 2-norbornene (A), 5-methylene-2-norbornene (B), 5-ethylidene-2-norbornene (C) and allylbenzene (D) with dichloro(diisopropylamino)borane with Na/K alloy in hexane. The corresponding species 5, derived from 2,5-norbornadiene (E), is relatively unstable and by a retro Diels-Alder reaction gives 2,3,4-tris(diisopropylamino)-l,5-dicarba-closo-pentaborane(5) (6). The compounds are characterized by chemical analyses, MS and NMR ('H, "B, I3C, lSN) and 1, 4 and 6 also by X-ray structure analyses.Die elektronische Absattigung, die das Bor durch Aminogruppen iiber n-Donorbindungen erfahrt, hat zur Folge, dalj borreiche Bor-Kohlenstoff-Verbindungen nicht als Carboranpolyeder", sondern als klassisch gebundene Verbindungen auftreten2). Wie wir an einem ersten Beispiel, ausgehend vom Dicyclopentadien, zeigen konnten 3), kann man so 1,2,3-Triborolane, die zuerst als ubergangsmetallkomplexe erhalten wurden4), auch unkomplexiert herstellen. 2,5-Norbornadien (E): das zunachst gebildete Triborolanderivat 5 zersetzt sich beim Erhitzen im Sinne einer retro-Diels-Alder-Reaktion unter Abspaltung von Cyclopentadien und Bildung des 2,4,5-Tris(diisopropylamino)-2,4,5triborabicyclo[l.l.l]pentans 6, das im Prinzip das Skelett des 1,5-Dicarba-closo-pentaborans(5) enthalt. Jedoch zeigt 6 A C +3CI2'BY.+6Na/K 1. 2. 3. 4; 5 A.B,C.D;E -6 (N0,K)CI Y = N[CH(CH3)2]2 -C5H6 3 4 Ergebnisse und DiskussionEbenso werden d e 1,2,3-Triborolanderivate 1, 2 und 3 gebildet, wenn man vom Norbornen (A), 5-Methylen-2-norbornen (B) bzw. 5-Ethyliden-2-norbornen (C) ausgeht, wobei auch bei den beiden letzteren Edukten nur die endocyclische Doppelbindung reagiert. Bei der Umsetzung rnit Allylbenzol (D) jedoch wird das in Position 4 mit dem Benzylrest substituierte Triborolan 4 isoliert. Wieder anders reagiert das 5

Twofold Borylation of Benzene Derivatives with (Diisoalkylamino)boradiyl Units The reaction of subvalent boron species generated by the defluorination of difluoro(diorganylamino)borane with Na/K alloy in the presence of 1,4‐disubstituted benzene derivatives leads to products which contain two (diorganylamino)boradiyl units and two remaining double bonds which are located on the substituted C atoms. Compounds 5 to 8 exhibit structures based on a 2,8‐diborabicyclo[3,2,1]octa‐3,6‐diene skeleton while 9 shows a skeleton with a 1,3a,4,6a‐tetrahydroborolo[3,2‐b]borole structure. The latter structure corresponds to that of 1 obtained in the same reaction with benzene. The compounds are characterized by elemental analyses and spectroscopically [MS, NMR (1H, 11B, 13C, 15N, 19F, 29Si)]. X‐ray structure analyses are presented for 1, 6, 7, 8, and 9.

Products of RC6H,*5BNR', are the highest borylated species to be formed in reactions between dehalogenation products of F,BN(i-Pr), with monoalkylbenzenes. The structures are cages, each consisting of a five-, six-, and seven-membered ring, in which the carbon skeleton has been split into C,, C,, and C3 units, as shown by singlacrystal X-ray structure determinations. Mass spectroscopic and 'H, llB, and 13C NMR and elemental analyses are reported.Generally, reactions of the six-electron species carbene with aromatic compounds lead to the addition of only one carbene molecule to a benzene ring.' Due to the anticipated higher reactivity of the four-electron species borene, multiple additions to aromatic rings might occur. Mass spectrometric studies of the system ClzBN(i-Pr)2/C6H6/ Na,K2 indicated that up to six "BN(i-Pr)z" units can be added to benzene. Upon substitution of the benzene ring with methyl groups, only a reduced number of formal "borene" units will react, as one double bond or a cyclopropane ring will be left or formed, respectively, at the carbon atom carrying the alkyl Therefore, toluene and other monoallrylated benzenes should add at most five "borene" units. However, it should be noted that the formation of these products can be also explained by stepwise radical reactions/eliminations from borenoids.Here we report for the first time the isolation and structures of such species formed in the reaction of toluene, tert-butylbenzene, and isopropylbenzene with sodium/ potassium alloy and F2BN(i-PrI2 in glyme. The cage compounds la, lb, and IC each consist of a seven-, six-, and five-membered ring with the remaining double bond fixed at the alkylated C atom in the seven-membered ring. NPrl. NPr$ R=Me, t-Bu, i -P r l i : R = Me 1L.R:t-Bu l_r: R= i -Pr -In these reactions, la (R = CH3), which is merely a byproduct of the tetraborylated s p e~i e s ,~ is isolated only in 0.6% yield after repeated distillation and recrystallization of the first solid formed! l b (R = t-Bu) is obtained, (1) *%gib, M., Ed. Methoden der Organieche Chemie (Houben-Weyl); (2) Meller, A.; Bromm, D.; Mnringgele, M.; Bbhler, D.; Elter, G. J. (3) Meller, A,; Seebold, U.; Maringgele, W.; Noltemeyer, M.; Sheldrick, G. Thieme Vlg.: Stuttgart-New York, 1989; Vol. E19b. Organomet. Chem. 1988,347, 11. G. M. J. Am. Chem. SOC. 1989,111,8299. 2097 Figure 1. Structure of lb. Selected bond lengths (pm) and anglea (deg) (m = mean): Bl-C2 = 158.0 (41, B1-C8a = 160.7 (4), B3-C2 = 160.9 (4), B9-C2 = 158.5 (4), B9-C5 = 161.8 (4), B3-C3a = 159.3 (4), B4-C3a = 157.9 (3), B4-C5 = 160.7 (4), B&C7 = 156.6 (4), B W 8 a = 158.1 (4), B-N = 141.6 (m), N-C = 147.5 (4) (m), C W 7 = 134.8 (4), C H 6 = 153.9 (3), C3a-C8a = 160.9 (3), C6-CMe3 = 154.9 (3); (BlC2B3) = 91.1 (2), (B2C3aC8a) = 91.9 (2), (C6C7B8) = 130.5 (2). however, in a yield of 32% while IC (R = i-Pr) is isolated in 22% yield (based on FzBN(i-Pr)2).6 l b was prepared by dropwise addition of 210 g (1.41 mol) of F2BN(i-Pr)2 to a stirred suspension of 98 g (2.87 mol) of Na/K alloy (1:4) in 1.2 L of 1,2...

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