Synthesis, crystal structure and hydroformylation activity of triphenylphosphite modified cobalt catalysts

Abstract

The dinuclear complex [Co 2 (CO) 6 {P(OPh) 3 } 2 ] (2) has been synthesised and was fully characterised. The solid state structure revealed a trans diaxial geometry, no bridging carbonyls, and Co-Co and Co-P bond lengths of 2.6722(4) and 2.1224(4) Å, respectively. Catalysed hydroformylation of 1-pentene with 2 was attempted at temperatures in the range 120 to 210 °C and pressures between 34 and 80 bar. High pressure spectroscopy (HP-IR and HP-NMR) was used to detect hydride intermediates. High pressure infrared (HP-IR) studies revealed the formation of [HCo(CO) 3 P(OPh) 3 ] (4) at ca. 110 °C, but at higher temperatures absorption bands corresponding to [HCo(CO) 4 ] (3) were observed. The hydride intermediate 4 has also been synthesised and characterised. Upon increased ligand concentration, HP-IR studies showed the formation of new carbonyl absorption bands due to a higher substituted cobalt carbonyl complex-[HCo(CO) 2 {P(OPh) 3 } 2 ] (5), which is believed to be catalytically less active. Complex 5 has been synthesised independently and was fully characterised. A low temperature crystal structural study of 5 revealed a trigonal bipyramidal structure with a trans H-Co-CO arrangement and two equatorial phosphite ligands, the Co-P bond lengths being 2.1093(8) and 2.1076(8) Å, respectively.

Crystal structure of N,N-bis(diphenylphosphanyl)cyclohexylamine, C30H31NP2

“…The modular structure of the ligands enables "tuning" of the catalyst activity and selectivity through systematic variation of the donor atoms, their substituents, and the ligand backbone framework. There are numerous examples of crystal structures of such PNP-pincer ligands [1][2][3][4][5][6] and metal complexes [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Diphosphinoamine (PNP) and other P donor ligands [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] with various substituents on both the P and N atoms have been applied to several catalytic reactions such as methoxycarbonylation [17], metathesis [18], hydroformylation [19] and C-H activation [24].…”

Understanding chemistry from combined X-ray and quantum mechanical studies

“…In pioneering studies we could demonstrate that these CCs not only influence the geometry of coordination compounds [3] and solids but also serve as controlling parameters for important chemical reactions like the activation of chemical bonds in catalytic reactions [4]. Furthermore, in covalent solids such as transition metal oxides and carbides they appear to signal electron localization phenomena which are reflected by metal-to-insulator transitions or the suppression of superconductivity [5].…”

“…This is the case of the early metal activation of the alkanes C-H bonds ("agostic" interaction), whose features we catalogued [2]. As another topic, the systematic study of series of structures allowed revising the parameters for the redox coupling/uncoupling between sulphido anions, namely the dichotomies 2S 2 4-/S 4 2-or 2S 2-/S 2 2-over one or more metal centers [3] The lecture will also illustrate how some key structures can be used as milestones along complicate patterns of reactivity also in processes of bio-catalytic relevance, such as the modeling of hydrogenases [4].…”

“…The second axis will concern symmetry breakings which take place in crystallographic superspaces. There, the new degrees of freedom come from the aperiodicity of the materials allowing very original structural instabilities [3]. [ X-ray diffraction has developed structural chemistry, hence the understanding of the matter and its behavior.…”

Phasing by SAD and molecular replacement inPHASER

“…This presentation deals with a number of model systems in industrial process and metal based drugs chemistry and will discuss the importance of known structures, coupled with the kinetic behaviour, on the reaction mechanisms thereof. The solution behaviour of some homogeneous catalytic processes and model pharmaceuticals will be described, illustrating the importance of the detailed ground state structures as obtained primarily from X-ray diffraction, but integrated with spectroscopic and other techniques [1][2][3][4][5][6][7]. Moreover, different activated states, and the utilization of reaction kinetics, coupled with computational techniques, to produce overarching and more holistic perspectives on the complete reaction mechanisms, will be discussed.…”