N-Heterocyclic carbene, carbodiphosphorane and diphosphine adducts of beryllium dihalides: synthesis, characterisation and reduction studies

Reaction of several N-heterocyclic carbenes, a carbodiphosphorane, and bis(diphenylphosphino)ethane (DPPE) with [BeX 2 (OEt 2 ) 2 ] (X = Br or I) have yielded a variety of beryllium dihalide adduct complexes, all of which were crystallographically characterised. Attempts to reduce the compounds to low oxidation state beryllium complexes using a variety of reducing agents have been carried out, but were of limited success. However, reaction of [(IPr)BeBr 2 ] (IPr = :C{(DipNCH) 2 }; Dip = 2,6-diisopropylphenyl) with the aluminium( i ) heterocycle, [:Al( Dip Nacnac)] ( Dip Nacnac = [HC(MeCNDip) 2 ] − ) afforded the adduct complex, [{(IPr)(Br)Be(μ-H)} 2 ], while reduction of [(IPr)BeBr 2 ] with potassium naphthalenide gave the beryllium naphthalenediyl complex, [(IPr)Be(C 10 H 8 )]. Furthermore, reaction of [{(DPPE)BeI 2 } ∞ ], with [:Al( Dip Nacnac)] led to insertion of the Al centre of the heterocycle into a Be-I bond, and formation of a rare example of an Al-Be bonded complex, [(DPPE)( i )Be-Al( i )( Dip Nacnac)]. A variety of C- and P-donor adduct complexes of beryllium dihalides have been synthesised. Attempts to reduce these have led to N-heterocyclic carbene adducts of beryllium hydride and naphthalenediyl fragments, and a rare example of a Be-Al bonded complex.