Organometallic Chemistry
Planar Chiral Metallocenes
Pincer Complexes
Molecular Gears

We have developed methods for the synthesis of palladium and platinum bisoxazoline pincer complexes 11,2 and 2.3,4 Both are obtained from easily synthesised 1,3-bisoxazolines. Palladium in introduced by initial regioselective lithiation followed by transmetallation, and platinum is introduced directly by heating with potassium tetrachloroplatinate. In both cases, subsequent halide abstraction generates cationic complexes containing a single exchangeable coordination site, the axis of which is also the C2-axis of the molecule.

We are actively investigating the use of these as Lewis acid catalysts, and have found them to be especially efficient for aldehyde silylcyanation,5 and for C-C bond forming reactions of nitrile substrates. In addition, we have also demonstated the synthesis of related Nickel pincer complex 3,6 and platinum bisimine derivatives 4.7,8 The latter are available in three simple steps from commercially available starting materials, and represent the most accessible examples of this class of organometallic. In addition, we recenty published a comprehensive review on the synthesis of chiral pincer complexes and their application to asymmetric catalysis.9

X-ray crystal structures of two new platinum pincer complexes,
left R = Me and right R = H.4
[1] M. A. Stark and C. J. Richards, Tetrahedron Letters, 1997, 38, 5881. [2] M. A. Stark, G. Jones and C. J. Richards, Organometallics, 2000, 19, 1282. [3] J. S. Fossey and C. J. Richards, Organometallics, 2004, 23, 367. [4] J. S. Fossey, G. Jones, H. V. Nguyen, C. J. Richards, M. A. Stark and H. V. Taylor, Tetrahedron: Asymmetry, 2004, 15, 2067. [5] J. S. Fossey and C. J. Richards, Tetrahedron Lett., 2003, 44, 8773. [6] J. S. Fossey and C. J. Richards, J. Organomet. Chem. 2004, 689, 3056. [7] J. S. Fossey and C. J. Richards, Organometallics, 2002, 21, 5259. [8] J. S. Fossey, M. L. Russell, K. M. A. Malik and C. J. Richards, J. Organomet. Chem., 2007, 692, 4843. [9] Chiral Pincer Complexes and Their Application to Asymmetric Synthesis. C. J. Richards and J. S. Fossey, in The Chemistry of Pincer Type Complexes, ed D. Morales-Morales and C. M. Jensen, Elsevier, Ameterdam, 2007.