Syntheses of Nonracemic Ortho-Mercurated and Ortho-Ruthenated Complexes of 2-[Tricarbonyl(η6-phenyl)chromium]pyridine

The reaction of racemic orthomercurated (η6-arene)tricarbonylchromium complexes with bis[(?6-cymene)ruthenium(II)dichloride] affords the corresponding dinuclear (Cr,Ru) products with moderate yields, which have been satisfactorily characterized by X-ray diffraction analysis. The synthesis of nonracemic orthomercurated (η6-arene)tricarbonylchromium complexes has been attempted starting from enantio-enriched homo- and heteroleptic Pd(II) bischelated complexes. Both enantiomers of ortho-mercurated 2-[tricarbonyl(?6-phenyl)chromium]pyridine have been synthesized by reaction of a heteroleptic Pd(II) bischelated with HgCl2. The two mercury(II) complexes were also submitted to a transmetalation reaction with bis[(?6-cymene)ruthenium(II)dichloride] and yielded the corresponding nonracemic (Cr, Ru) products, with enantiomeric excesses ranging from 82 to 89% as suggested by 1H NMR analyses in the presence of BINPHAT anion

Chloride-Promoted Synthesis of Cis Bis-Chelated Palladium(II) Complexes from Ortho-Mercurated Tricarbonyl(η6-arene)chromium Complexes

A new method of synthesis of homo- and heteroleptic cis bis-chelated Pd(II) species by a transmetalation reaction of the ortho-mercurated 2-[tricarbonyl(η6-phenyl)chromium]pyridine with a series of bis(µ-chloro) palladacyclic aromatic compounds in the presence of a large excess of the chloride salt [NMe4]Cl is reported. These (CO)3Cr-bound bis-chelated Pd(II) species can be designed for the preparation of enantiopure planar chiral cyclopalladated (η6-arene)Cr(CO)3 complexes. The study of the mechanism of this transmetalation reaction reveals the key role of the excess of chloride salt, which is necessary for the isolation of persistent heteroleptic bis-chelated Pd(II) complexes. This method was further applied to the synthesis of highly enantioenriched (+) and (-) samples of the ortho-chloropalladated 2-[tricarbonyl(η6-phenyl)chromium]pyridine, whose enantiopurity was assessed with the aid of diamagnetic Λ and Δ TRISPHAT salts used as chiral shift 1H NMR agents. The absolute configurations of the two enantioenriched complexes were obtained from the corresponding absolute structures determined by X-ray diffraction analyses. The molecular structures of six new heteroleptic bis-chelated Pd(II) complexes are reported

Novel Heteroleptic cis-(C^N2)Pd(II) Chelates for the Preparation of Enantiopure Planar Chiral Cyclopalladated 2-[tricarbonyl(η6-phenyl)chromium]pyridine

In the presence of large amounts of [Me4N]Cl, the reaction of ortho-chloromercurated 2-[(n6-phenyl)tricarbonylchromium]pyridine with µ-chloro cyclopalladated aromatic compounds yields a series of new heteroleptic heterodinuclear cis-(C^N)2Pd(II) complexes, which are valuable precursors of planar chiral cyclopalladated (n6-arene)Cr(CO)3 complexes