Functionalized Homoleptic <i>cis</i>- and <i>trans</i>-<i>C,N</i>-<i>o</i><i>rtho</i>-Chelated Aminoaryl Platinum(II) Complexes

For the synthesis of corner building blocks with a 90° angle, to be used for the construction of larger structures, several homoleptic platinum(II) complexes [Pt(η2-C,N)2] (10−14), as both cis- and trans-isomers, have been prepared starting from newly synthesized ortho-lithiated (dimethylamino)methyl arene ligands. The aryl groups of these arylplatinum(II) complexes contain additional substituents such as halides or methyl, naphthyl, or (dimethylamino)methyl groups. With these functionalities on the aryl rings the cis/trans ratio could be tuned. The presence of steric groups ortho to the metal center (methyl or naphthyl) favors the formation of planar-chiral cis-isomers. The trans-isomers isomerize irreversibly to the thermodynamically favored cis-isomers upon heating. The arylplatinum(II) complexes were used in various substitution reactions. Addition of a stronger coordinating ligand changes the denticity of the C,N-attached ligands. The halide functionalities were exploited for chemoselective lithiation and subsequent transmetalation reactions in order to synthesize the SnMe3-functionalized [Pt(C,N)2] complexes. A Suzuki−Miyaura C−C coupling reaction on one of these complexes was also performed, resulting in the preparation of a mixed trinuclear palladium/platinum complex (25). The crystal structure determinations of four functionalized cis-[Pt(C,N)2] complexes, cis-12·Et2O, cis-14·xC6H6, 19, and 25·xCH2Cl2, are reported. With these structures it is shown that depending on the substituents, the degree of planarity around the platinum center can be tuned.