Modular Assembly of a Chiral Bis(oxazolinyl)carbene: A New Meridionally Coordinating Tridentate Spectator Ligand

A highly modular assembly of meridionally
coordinating tridentate bis(oxazoline)carbene ligands
(“BoxCarb”) is reported, in which the coupling of the
oxazoline units with the central imidazolidene ring
occurs by means of chemically orthogonal reaction steps.
Reaction of the imidazolium salt (iPr)2-BoxCarbH+Br-
4 with [Rh(OtBu)(nbd)]2 at temperatures below −30 °C
gave a thermally unstable rhodium(I) species, which was
directly reacted at −78 °C with 1 molar equiv of bromine,
giving the rhodium(III) compound [RhBr3((iPr)2-BoxCarb)] (5). An X-ray diffraction study established the
meridional tricoordination of the ligand. Reacting 4 with
0.5 molar equiv of Ag2O gave the silver(I) complex 6,
which was converted with [PdCl2(COD)] in CH2Cl2 to
give the cationic square planar palladium(II) complex
[PdCl((iPr)2-BoxCarb)]Cl (7).