Highly Active Hydroformylation Catalysts: Synthesis, Characterisation and Catalytic Performance
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Highly Active Hydroformylation Catalysts: Synthesis, Characterisation and Catalytic Performance Elisabetta Piras • Bernhard Powietzka • Frederik Wurst Doreen Neumann-Walter • Hans-Jo¨rg Gru¨tzmacher • Thomas Otto • Thomas Zevaco • Olaf Walter
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Received: 7 March 2013 / Accepted: 14 April 2013 / Published online: 15 May 2013 Ó Springer Science+Business Media New York 2013
Abstract The phoszone ligand [(Ph2P)(bis-3,5-CF3-Ph)] NN=CH(penta-fluoro-Ph) transformed in liquid CO2 at room temperature in presence of [Rh(cod)2]OTf into [Rh(cod)(g2P,P0 -Ph2POPPh2)]OTf. Replacing the O-atom in Ph2POPPh2 by a PrN-group leads to the ligand PrN(PPh2)2 acting similarly as a bidentate ligand in [Rh(cod)(g2-P,P0 -PrN(PPh2)2)] OTf. Hydroformylation of 1-octene with in situ catalysts formed by the ligands with [Rh(cod)2]OTf showed hydroformylation activities at 50 % conversion of 16,000 h-1 (PrN(PPh2)2/[Rh(cod)2]OTf) and 24,000 h-1 (phoszone/ [Rh(cod)2]OTf), respectively. Keywords Homogeneous catalysis Activity Hydroformylation Isomerisation
hydroformylation of 1-octene [11]. Already the introduction of some fluorinated positions in the ligands of metal complexes could increase the solubility of the pre-catalyst in supercritical carbon dioxide [12]. Therefore it seemed logical to studying the activity of the Rh-complexes of the phoszone ligand 1 in supercritical carbon dioxide offering the possibility by the use of this solvent to enhance the reactivity further [13, 14]. This could have been well the case as for highly active catalysts in the more phase hydroformylation mass transfer could become the rate limiting step which could be overcome by the application of supercritical carbon dioxide as the solvent creating a single phase system [13, 14]. In this publication we describe how experiments with the phoszone ligand 1 lead to the development of highly active Rh-catalysts for the hydroformylation of 1-octene.
1 Introduction Hydroformylation is one of the best studied catalytic reactions [1, 2]. However, only few highly active catalysts are known in the literature [3–10]. The phoszone ligand 1 bearing fluorinated side chains (Fig. 1) forms in the presence of [Rh(cod)2]OTf or [Rh(cod)2]BF4 an in situ Rh-catalyst with an exceptionally high activity in the
Dedicated to the memory of Prof. Ivano Bertini. E. Piras B. Powietzka F. Wurst D. Neumann-Walter T. Otto T. Zevaco O. Walter (&) IKFT, Campus Nord, KIT, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany e-mail: [email protected] E. Piras H.-J. Gru¨tzmacher Laboratorium fu¨r Anorganische Chemie, Wolfgang-Pauli-Street. 10, ETH Ho¨nggerberg, HCI H 131, 8093 Zurich, Switzerland
2 Results and Discussion Preliminary hydroformylation experiments with an in situ catalyst system containing the ligand 1 and [Rh(cod)2]OTf as the pre-catalyst showed a very high catalytic activity with tofs of more than 20,000 h-1 [11]. Our attempts to study the complex chemistry of the ligand 1 towards Rh-complex fragments present in [Rh(cod)2]OTf or [Rh(cod)2]BF4 un
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