Divalent Heteroleptic Ytterbium Complexes – Effective Catalysts for Intermolecular Styrene Hydrophosphination and Hydroamination

New
heteroleptic Yb­(II)–amide species supported by amidinate and
1,3,6,8-tetra-tert-butylcarbazol-9-yl ligands [2-MeOC6H4NC­(tBu)­N­(C6H3-iPr2-2,6)]­YbN­(SiMe3)2(THF) (6) and [1,3,6,8-tBu4C12H4N]­Yb­[N­(SiMe3)2]­(THF)n (n =
1 (7), 2 (8)) were synthesized using the
amine elimination approach. Complex 6 features an unusual
κ1-N,κ2-O,η6-arene coordination mode of the amidinate
ligand onto Yb­(II). Complexes 7 and 8 represent
the first examples of lanthanide complexes with π-coordination
of carbazol-9-yl ligands. Complexes 6 and 7, as well as the amidinate–Yb­(II)–amide [tBuC­(NC6H3-iPr2-2,6)2]­YbN­(SiMe3)2(THF) (5),
are efficient precatalysts for the intermolecular hydrophosphination
and hydroamination of styrene with diphenylphosphine, phenylphosphine,
and pyrrolidine to give exclusively the anti-Markovnikov monoaddition
product. For both types of reaction, the best performances were observed
with carbazol-9-yl complex 7 (TONs up to 92 and 48 mol/mol
at 60 °C, respectively).