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Derivates of 1,2-diborabenzene

1988; Elsevier BV; Volume: 355; Issue: 1-3 Linguagem: Inglês

10.1016/0022-328x(88)89046-6

1872-8561

Gerhard E. Herberich, B. Heßner, M. Hostalek,

Synthesis and characterization of novel inorganic/organometallic compounds

The 1,2-diboratabenzene derivative Li2[C4H4B2(NMe2)2] (I) reacts with various transition metal compounds to form sandwich and triple-decked complexes such as (C6Me6RuL (III), (C5Me5)RhL (IV), (μ-L)[Rh(COD)]2 (V), NiL2 (VI), Fe(CO)L2 (VII), and Co2(CO)4L2 (VIII), where L is the 1,2-bis(dimethylamino)-1,2-dibora3,5-cyclohexadiene ligand. Barriers to internal rotation around the BN bond are 48(1), 56(1), and 38(1) kJ/mol for III, IV, and V, respectively, while VII and VIII are rigid on the NMR time scale. Nucleophilic substitution reactions at boron were examined for the rhodium complex IV. The Lewis acids BF3·OEt2 and BCl3 bring about substitution to give (C5Me5)Rh[C4H4B2F(NMe2 · BF3)] (XI) and (C5Me5)Rh(C4B2Cl2) (XII), respectively. Attempted substitution with Al2Me6 and with AlH3 in THF effected a novel ring contraction to produce the borole complexes (C5Me5)Rh(C4H4BR) (XIII: R = Me; XIV: R = H); similarly, traces of air transform XII into (C5Me5)Rh(C4H4BCl) (XV). The structure of XII determined by X-ray diffraction confirms the η6-bonding mode of the diboracyclohexadiene ligand.