Insertion Reactions into the Boron–Boron Bonds of Barrelene-Type 1,2-Diaminodiboranes(4)

Abstract

Double lithiation of 9,10-dihydroanthracene (DHA) or 6,13-dihydropentacene (DHP) with nBuLi, followed by the addition of B2(NMe2)2Cl2, affords 9,10-DHA-9,10-diyl- (1a) or 6,13-DHP-6,13-diyl-bridged B2(NMe2)2 (1p) in good yields. Upon treatment with Pt(PEt3)3 in C6H6 at 60 °C, both compounds cleanly insert a Pt(PEt3)2 moiety into their B–B bonds to furnish the corresponding diboryl Pt(II) complexes 2a and 2p. Compound 2a reacts with excess tBuCCH to give an equimolar mixture of the B–(tBu)C═C(H)–B-bridged 9,10-DHA 3 and Pt(η2-tBuCCH)(PEt3)2 (4). The addition of isocyanides to either the Pt(II) complex 2a or the Pt-free species 1a yields bicyclic products, in which a 9,10-DHA-9,10-diyl fragment is spanned by a B–C(═NR)–B linker (R = tBu (5), iPr (6)). Both 5 and 6 are extremely prone to hydrolysis. In the case of 6, a water-induced rearrangement reaction leading to a B–C-bridged 9,10-DHA 8 was observed.