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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.

Substitution of two chlorine atoms in 1,2-bis(dichloroboryl)ethane with diisopropylamine yields 1,2-bis(chlorodiisopropylaminoboryl)ethane (4), which is reacted with Na/K alloy to give 1,2-bis(diisopropylamino)-1,2-diboretane (5) in 91% yield. 5 crystallizes in the space group P 21/c with the lattice constants a = 6.116(1), b = 16.658(5), c = 17.577(4) Å, β = 99.49(2)°.

Abb. 1. Metallcluster inTh,Br,,D, (kleine Kreise Th, grok offene Kreise Br, schattierte Kreise D rnit 7/8 Besetzung). Kiirzeste Abstlnde [pm] aus Seutronenbeugungsdaten: d(Th-Th) = 386.1(2), d(Th-D) = 223.8(2), Oktaederkanten d(Th-Br') = 294.5(1), Oktaederspitzen d(7'h-BF') = 295.8(1). 41)-D) = 205.0(3). Die D-Atome sind nahezu trigonal planar von Th-Atomen umgeben. Der Th-Th-Abstand ist geringfugig kurzer als in den Verbindungen MTh,Br,, mil M = Fe. Co (d(Th-Th) = 391.8(2)).Bindende H-Th-Wechselwirkungen fuhren lediglich zu einer Absenkung einzelner Orbitalenergien; die antibindenden Kombinationen liegen oberhalb der HOMO-LUMO-Lucke. Damit entspricht die Elektronenbilanz fur Th6Br,,H7 (6 x 4 -15 +7 = 16) genau einer Vollbesetzung aller bindenden Clusterorbitale (zum Vergleich Nb,F,,:6 x 5 -

The elements sulfur, selenium, and tellurium are capable of forming homo-and heteronuclear polycations. Of the tellurium-containing cations, Te;@ [ I i and Tet@,[21 as well as Angew Chem. I n [ . Ed. Engl. 29 (1990) No. 3 $3 VCH Verlagsgesellschaji mbH. 0-6940 Weinheim, 1990 0570-0833i90j0303-0293 3 02.SOjO

Z. Naturforsch. 51 b, 1104Z. Naturforsch. 51 b, -1110Z. Naturforsch. 51 b, (1996; eingegangen am 22. Januar 1996The synthesis and structural properties of organo-bis-dialkylaminochlorboranes X( BNR2C1)2 X = R2NB(CHCH3)2, < 9-C6H4, 1-q-C6H4CH2, and 1.8-C10H6 are reported. The steric influ ence of the alkylamino group and the geometrical situation caused by a chain of sp2 or sp3 hybridized carbon atoms control the formation of intramolecular donor-acceptor bonds. In o ( C 6H4)(BNM e2C l)2 (5) only one amino-boron donor-acceptor bond is observed. The steric influence of the alkyl groups in R2NB(CHCH3BC1NR2)2 is discernible from the formation of two donor-acceptor bonds in 7a (R = Me), whereas 7b (R = /Pr) is a non-bridged species.The reaction of benzomagnesacyclobutene with chlorbis(dimethylamino)borane yields cyclic l-a (C 6H4C H 2)(BNM e2C l)2 (9). 1,8-Dilithionaphthalene reacts with C1B (NR2)