Catalytic Activation of Heterocumulenes by an Organo-f-Complex

Moris S. Eisen, Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa, Israel
Isabell S. R. Karmel, Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa, Israel
Matthias Tamm, Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Braunschweig, Germany

The activation of heterocumulenes, such as carbodiimides, isocyanates, thioisocyanates and carbon disulfide is an atom efficient, waste free synthetic approach, yielding the respective guanidines and related systems, which find a wide application as synthons in organic synthesis as well as ligands for a variety of transition metals, lanthanides and actinides. Several lanthanide coordination complexes have been shown to be active for the insertion reactions of amines and phosphines into the central NCE (E = N, O, S) linkage of heterocumulenes.¹ In addition, Evans et al. have shown the stoichiometric reactivity of (C5Me5)An(CH3)2 (An = U, Th) toward aliphatic carbodiimides, furnishing mixed pentamethylcyclopentadienyl amidinate actinide (IV) complexes.² Hence, it was interesting to investigate the conceptual question whether this process can be incorporated into a catalytic cycle using catalytic amounts of actinide coordination complexes.

Recently, we have reported on the reactivity of mono(imidazolin-2-iminato) actinide (IV) complexes in the catalytic dimerization of aldehydes, displaying a high catalytic activity and selectivity toward the asymmetrically substituted ester, when Th(Im^DippN)(N(TMS)2)3 was used as catalyst.3 Therefore, Th(Im^DippN)(N(TMS)2)3 was used for catalytic activation of carbodimides with primary and secondary amines, phosphines and thiols, yielding the respective insertion products (Scheme 1). In addition, heterocumulene systems, such as PhNCO, PhNCS and CS2 were also catalytically activated using amines, phosphines and thiols, furnishing the insertion products in high yields under mild conditions.

Scheme 1: Actinide mediated activation of heterocumulenes.

1. Behrle, A. C.; Schmidt, J. A. R. Organometallics 2013, 32, 1141-1149, and references therein.
2. Evans, W. J.; Walensky, J. R.; Ziller, J. W.; Rheingold, A. L. Organometallics 2009, 28, 3350-3357.
3. Karmel, I. S. R.; Fridman, N.; Tamm, M.; Eisen, M. S. J. Am. Chem. Soc. 2014, 136, 17180-17192.