| Abstrakt: |
The synthesis of a series of Fe, Co, and Ni complexes supported by an iPrPNPhP (iPrPNPhP = PhN(CH2CH2PiPr2)2) pincer ligand is described. These complexes were characterized using IR, UV–vis, NMR, and Mössbauer spectroscopy, as well as X-ray crystallography. There are major differences in the stability, reactivity, and spectroscopic features of the iPrPNPhP-supported complexes in comparison to related complexes supported by iPrPNHP (iPrPNHP = HN(CH2CH2PiPr2)2) and iPrPNMeP (iPrPNMeP = CH3N(CH2CH2PiPr2)2) ligands, which have been used for a plethora of catalytic applications. These differences likely arise because the nitrogen donor in iPrPNPhP is a poorer σ- donor in comparison to the corresponding nitrogen donor in iPrPNHP or iPrPNMeP. As a result, it was not possible to isolate the types of carbonyl hydride complexes with the iPrPNPhP ligand that have been heavily utilized in catalysis with iPrPNHP and iPrPNMeP ligands. A comparison of the catalytic performance of (iPrPNRP)FeH(κ2-BH4) (R = Me, Ph) for additive-free formic acid dehydrogenation shows that both complexes give similarly low activity, emphasizing the need for complexes that also contain π-acceptor carbonyl ligands to generate highly active catalysts. |
