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42806-B3
Compounds of Bidentate Phosphines with Metallocene Backbones: Electrochemistry and Catalysis

Chip Nataro, Lafayette College

����������� Undergraduates in my lab have continued to investigate the properties of bidentate phosphines that have metallocene backbones.� To date our work has focused on the synthesis, electrochemistry and structural analysis of compounds containing either� ���������

1,1'-bis(diphenylphosphino)metallocene (metallocene = ferrocene (dppf), ruthenocene (dppr) or osmocene (dppo)) or 1,1'-bis(dialkylphosphino)ferrocene (alkyl = i-propyl (dippf), cyclohexyl (dcpf) or t-butyl (dtbpf)).� �

In the past year, we have completed an investigation of the asymmetric compound 1-diphenylphsophino-1'-ditertbutylphosphinoferrocene (dppdtbpf).� The oxidation of dppdtbpf is chemically reversible.� Upon complexation, the oxidation of dppdtbpf is typically chemically and electrochemically reversible.��� A series of phosphine sulfide, phosphine selenide and mixed phosphine sulfide/selenide compounds of dppdtbpf were prepared and characterized (Figure 1).� The electrochemistry of these complexes is complicated if there is at least one selenium present.

Figure 1.� X-ray structures of C₃₀H₃₆FeP₂SSe.

����������� We have also been investigating the synthesis, electrochemistry and reactivity of a series of CpRu(P-P)H complexes (P-P = dppf, dppr, dppo, dippf or dppc).� The reaction we have been examining is the transfer of the hydride ligand from the ruthenium center to an iminium cations (Figure 2).� During this time we developed a collaboration with Jack Norton at Columbia University and we are currently working on a manuscript detailing this work.

�

Figure 2.� Hydride transfer reaction.

-CF₃ group, the dtbpf gave the most efficient catalyst.� Additional catalytic studies are currently underway.�

Finally, we have continued or investigation of commercially available chiral, bidentate phosphines with metallocene backbones.� We have examined the electrochemistry and complexation of a series of Taniaphos and Walphos ligands (Figure 3). �The electrochemistry of the ligands displays multiple oxidation waves that are not greatly influenced by R or R'.� Upon complexation, the electrochemistry typically

Taniaphos

Walphos

Figure 3.� Taniaphos and Walphos ligands.

simplifies to a single, chemically and electrochemically reversible wave.� The structures of three new compounds were reported and the bite angles for Taniaphos and Walphos were examined (Figure 4).

Figure 4.� X-ray structures of [(P-P)PdCl₂] (P-P = Taniaphos or Walphos).

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