Mononuclear dpp-Bian Gallium Complexes: Synthesis, Crystal Structures, and Reactivity toward Alkynes and Enones

Treatment
of (dpp-Bian)­Ga–Ga­(dpp-Bian) (1)
(dpp-Bian = 1,2-bis­[(2,6-diisopropylphenyl)­imino]­acenaphthene) with
iodine gives (dpp-Bian)­Ga­(I)–Ga­(I)­(dpp-Bian) (2), which reacts in situ with K­(C5H4CH2CH2NMe2) (KCpDo) or K­(OCH2CH2NMe2) (KORDo) to produce the
monomeric species (dpp-Bian)­GaCpDo (3) and
(dpp-Bian)­GaORDo (4), respectively. Complex 3 reacts with PhCCH to give the paramagnetic derivative
(dpp-Bian)­Ga­(CCPh)2 (5), while compound 4 is inert toward this alkyne. In contrast, monomeric (dpp-Bian)­Ga­(S2CNMe2) (6) reacts with PhCCH
and HCCH to give the cycloaddition products [dpp-Bian­(PhCCH)]­Ga­(S2CNMe2) (7) and [dpp-Bian­(HCCH)]­Ga­(S2CNMe2) (8). The related compounds
[dpp-Bian­(MeCCC­(O)­OMe)]­Ga­(S2CNMe2) (9) and [dpp-Bian­(CH2CHC­(Me)­O)]­Ga­(S2CNMe2) (10) have been obtained in
the reactions of complex 6 with methyl 2-butynoate and
methyl vinyl ketone, respectively. New complexes have been characterized
by 1H NMR (3, 4, and 7–10) and ESR (5) spectroscopy; their
molecular structures have been established by single-crystal X-ray
analysis. The catalytic activity of complex 6 in the
hydroamination and hydroarylation of alkynes has been examined.