Synthese und Struktur von benzylsubstituierten Derivaten des Dinickel-Tripeldeckerkomplexes μ-η⁵,η⁵(2,3–Dihydro–1,3-diborolyl)-(η³–allyl)(η⁴–1,5–hexadien) dinickel / Synthesis and Structure of Benzyl Substituted Derivatives of the Dinickel Triple-Decker Complex μ–η⁵, η⁵–(2 ,3–Dihydro–1,3 -diborolyl)– (η³–allyl)(η⁴– 1,5 -hexadiene)dinickel

Abstract

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.