9.10-Dihydro-9.10-diboraanthracenes, Organoboranes. ElectrochemistryA series o f alkyl and amino derivatives of the tricyclic organoborane system 9,10-dihydro-9.10-diboraanthracene was synthesized and examined. The reactions o f 9,10-dichlor-9,10-dihydro-9,10-diboraanthracene ( l a ) with suitable reagents yield the corresponding alkyl, aryl or amino derivatives lc -h , respectively. The compounds have been characterized by 'H, 13C and 1!B NM R spectroscopy. X-ray structure analyses have shown that the amino derivatives have bent structures, while the H 2N compound lh is planar. Calculations were carried out to study the reasons for the deformation of som e o f the amino-substituted derivatives. These calculations indicate that steric reasons are responsible for the deformation. Electrochemical investigations show reversible reductions of the dimethyl derivative l c leading to the radical anion and the dianion. Both anions have been structurally characterized by X-ray diffraction studies.

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The reduction of the 18-VE complexes (q5-C5H5)Ni[q5-(CR1),(BRZ),CR3] (2a, b) with potassium in THF leads to the paramagnetic anions 2-, which react with NiBr, . DME to give the triple-decker complexes (q5-C5H5)Ni [p,q5-

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Synthesis and S tructure o f B enzyl S ubstituted D erivatives of the D inickel T riple-D ecker C om plex ,w-?75,?75-(2 ,3 -D ih y d ro -l,3 -diborolyl)-(?73-allyl)(774-l ,5 -hexadiene)dinickel W alter Siebert, Stefan H uck und H an s Pritzkow Nickel, //-775,?75-(2 ,3-Dihydro-l,3-diborolyl)(?73-allyl)(?74-l,5-hexadiene)dinickel, Polydecker ComplexesHydroboration of phenyl-and mesitylethyne with in situ formed HBC12 leads to an isome ric mixture of l,l-bis(dichloroboryl)-2-phenylethane (4a) and l,l-bis(dichloroboryl)-l-phenylethane (4b) (ratio 3 : 1) and regioselectively to l,l-bis(dichloroboryl)-2-mesitylethane (4c). Treatment of 4a/b and 4c with BI3 gives the corresponding tetraiodo compounds 5, which undergo redox reactions with butyne-2 to form the l,3-diiodo-4,5-dimethyl-2,3-dihydro-l,3diborole derivatives 6a/b and 6c. Reactions of the diiodo-l,3-diboroles with AlMe3 or LiMe result in the formation of the very air-sensitive pentaorganyl-l,3-diboroles la, lc and the hexaorganyl-l,3-diborole lb.The mixture of la/b as well as lc react with bis(?/3-allyl)nickel to give black products, which are chromatographed on silica with hexane as eluent. The brown solids were recrystallized from pentane to give the light-brown crystals of i M-j/5,7;5-[2-benzyl-l,3 ,4 ,5 -tetramethyl-2 ,3-dihydrol,3-diborolyl](/73-allyl)(»74-l,5-hexadiene)dinickel (2a, 34%) and //-?/5,»75-[2-(2 ,4 ,6-trimethylbenzyl)-l,3 ,4 ,5-tetramethyl-2,3-dihydro-l,3-diborolyl](?73-allyl)(?74-l,5-hexadiene)dinickel (2c, 43%). lb does not react with Ni(C3H5)2 to form any triple-decker. The compositions of the new compounds follow from spectroscopic and analytical data, and from X-ray structure analyses of 6a and of 2a. The structure of the ?74-l,5-hexadiene-?73-allyl-dinickel triple-decker 2a finally disproved the alternative tris(allyl)dinickel arrangement.