Syntheses of ortho-mercurated and -palladated (η6-arene)tricarbonylchromium complexes

The selective ortho mercuration of tricarbonylchromium derivatives of 2-phenylpyridine, N,N-dimethylbenzylamine, (1S)-1-(dimetbylamino)-1-phenylethane, and 2-phenyl-2-oxazoline by Hg(OAc)(2) is reported. The mercurations of the latter (eta (6)-arene)Cr(CO)(3) complexes bearing an endogenous ligand have been carried out in soft conditions with yields ranging from 13 to 83%. The optically active complex of (1S)-1-(dimethylamino)-1-phenylethane was stereoselectively orthomercurated. The conversion of the chloromercurated complexes, e.g. (eta (6)-Ar-KgX)Cr(CO)(3), into the corresponding homoleptic trinuclear [(eta (6)-Ar)Cr(CO)(3)](2)Hg complexes was readily carried out by reaction with Me4NCl in boiling acetone. In almost all cases, the so-called symmetrization reaction afforded a mixture of two diastereomers, except for the derivative of (1S)-1-(dimethylamino)-1-phenylethane, which afforded a unique "symmetrized" product. This result suggests that the "symmetrizatian" reaction occurred with retention of the configuration of the mercury-bound ipso carbon atom. The trimetallic and bimetallic mercurated (eta (6)-arene)Cr(CO)(3) complexes were readily converted into cyclopalladated binuclear complexes upon transmetalation with Pd(II) salts. The structures of two orthomercurated compounds and two ortho-palladated complexes are reported.