Syntheses of Ortho-Mercurated and -Palladated (η6-Arene)tricarbonylchromium Complexes

The selective ortho mercuration of tricarbonylchromium derivatives of 2-phenylpyridine, N, N -dimethylbenzylamine, (1 S )-1-(dimethylamino)-1-phenylethane, and 2-phenyl-2-oxazoline by Hg(OAc) 2 is reported. The mercurations of the latter (η 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 (1 S )-1-(dimethylamino)-1-phenylethane was stereoselectively orthomercurated. The conversion of the chloromercurated complexes, e.g. (η 6 -Ar-HgX)Cr(CO) 3, into the corresponding homoleptic trinuclear [(η 6 -Ar)Cr(CO) 3 ] 2 Hg complexes was readily carried out by reaction with Me 4 NCl in boiling acetone. In almost all cases, the so-called symmetrization reaction afforded a mixture of two diastereomers, except for the derivative of (1 S )-1-(dimethylamino)-1-phenylethane, which afforded a unique “symmetrized” product. This result suggests that the “symmetrization” reaction occurred with retention of the configuration of the mercury-bound ipso carbon atom. The trimetallic and bimetallic mercurated (η 6 -arene)Cr(CO) 3 complexes were readily converted into cyclopalladated binuclear complexes upon transmetalation with Pd(II) salts. The structures of two ortho-mercurated compounds and two ortho-palladated complexes are reported.