Molecular structures of three coordinate zinc and cadmium complexes that feature β-diketiminato and anilido-imine ligands

A series of zinc and cadmium complexes of the β-diketiminato and anilido-imine classes of ligands, namely [BDIAr], [AIAr] and [AIAr,NPr2i], have been synthesized and structurally characterized by X-ray diffraction. For example, the zinc and cadmium alkyl compounds [AIAr]ZnEt and [AIAr]CdMe have been synthesized via the reactions of [AIAr]H with Et2Zn and Me2Cd, respectively, while [AIAr]ZnN(SiMe3)2 has been obtained by treatment of [AIAr]H with Zn[N(SiMe3)2]2. Single crystal X-ray diffraction studies establish that the metal centers in each of these complexes are trigonal planar. Comparison of the molecular structures of [AIAr]CdMe and [BDIAr]CdMe demonstrates that the cadmium methyl moiety lies in the plane of the annulated [AIAr] ligand, whereas there is considerable displacement for [BDIAr]CdMe. [AIAr,NPr2i]Li, an anilido-imine ligand that incorporates a CH2CH2NPr2i tether, has been synthesized via a sequence involving condensation of 2-fluorobenzaldehyde with H2NCH2CH2NPr2i, followed by treatment with ArNHLi. X-ray diffraction demonstrates that the lithium has a T-shaped coordination environment which is supplemented by an agostic interaction with a C–H bond of one of the isopropyl groups of the NPr2i moiety. However, while the NPr2i group of the tether coordinates to lithium in [AIAr,NPr2i]Li, it does not coordinate to the zinc center of [AIAr,NPr2i]ZnMe. The structure of [AIAr,NPr2i]ZnMe is also in marked contrast to that reported for [AIAr,NMe2AIAr,NMe2]ZnMe, in which the NMe2 group does coordinate to the zinc center. The M–C bonds of [AIAr,NPr2i]ZnMe, [BDIAr]ZnEt and [BDIAr]CdMe are cleaved by B(C6F5)3 to give the perfluorophenyl derivatives [AIAr,NPr2i]ZnC6F5, [BDIAr]ZnC6F5 and [BDIAr]CdC6F5. Interestingly, the C6F5 groups are almost orthogonal to the planes of the chelating ligands in the zinc complexes, [AIAr,NPr2i]ZnC6F5 and [BDIAr]ZnC6F5, whereas the C6F5 and [BDIAr] ligands of [BDIAr]CdC6F5 reside in the same plane. In addition to 1:1 [AIAr,NPr2i]ZnX complexes, it is also possible to synthesize the 2:1 complex [AIAr,NPr2i]2Zn which is consistent with the [AIAr,NPr2i] ligand being less sterically demanding than the [BDIAr] ligand.

A series of zinc and cadmium complexes of the β-diketiminato and anilido-imine classes of ligands, namely [BDIAr], [AIAr] and [AIAr,NPr2i], have been synthesized and structurally characterized by X-ray diffraction.Figure optionsDownload as PowerPoint slide