Bis(phosphinimino)methanides as ligands in divalent lanthanide and alkaline earth chemistry - synthesis, structure, and catalysis |
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| Authors: | Tarun K Panda |
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| Institution: | Institut für Chemie, Freie Universität Berlin Fabeckstrasse 34-36, 14195 Berlin, Germany |
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| Abstract: | Divalent bis(phosphinimino)methanide lanthanide complexes of composition {(Me3SiNPPh2)2CH}EuI(THF)]2 and {(Me3SiNPPh2)2CH}YbI(THF)2] have been prepared by a salt metathesis reactions of K{CH(PPh2NSiMe3)2} and LnI2. Further reactions of these complexes with K(THF)nN(PPh2)2] led selectively to the heteroleptic amido complexes {(Me3SiNPPh2)2CH}Ln{(Ph2P)2N}(THF)] (Ln = Eu, Yb). The ytterbium complex can also be obtained by reduction of {CH(PPh2NSiMe3)2}Yb{(Ph2P)2N}Cl] with elemental potassium. The single crystals of {(Me3SiNPPh2)2CH}Ln{(Ph2P)2N}(THF)] contain enantiomerically pure complexes. As a result of the similar ionic radii of the divalent lanthanides and the heavier alkaline earth metals some similarities in coordination chemistry of the bis(phosphinimino)methanide ligand were anticipated. Therefore, MI2 (M = Ca, Sr, Ba) was reacted with K{CH(PPh2NSiMe3)2} to give {(Me3SiNPPh2)2CH}CaI(THF)2], {(Me3SiNPPh2)2CH}SrI(THF)]2, and {(Me3SiNPPh2)2CH}BaI(THF)2]2, respectively. As expected the Sr and Eu complexes and the Ca and Yb complexes are very similar, whereas for the Ba compound, as a result of the large ion radius, a different coordination sphere is observed. For all new complexes the solid-state structures were established by single crystal X-ray diffraction. In the solid-state the {CH(PPh2NSiMe3)2}− ligand acts as tridentate donor forming a long methanide carbon metal bond. Thus, all complexes presented can be considered as organometallic compounds. {(Me3SiNPPh2)2CH}YbI(THF)2] was also used as precatalyst for the intramolecular hydroamination/cyclization reaction of different aminoalkynes and aminoolefines. Good yields but moderate activities were observed. |
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| Keywords: | Alkaline earth metals Bis(phosphinimino)methanides Catalysis Hydroamination Lanthanides P N ligands |
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