کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1323442 | 1499859 | 2015 | 6 صفحه PDF | دانلود رایگان |
• A coordinatively unsaturated lateral-(np2bimy)2Mo(CO)3 complex was prepared.
• Crystal structure analysis showed tilted coordination and significant ligand bending.
• DFT calculations prove steric reasons for the benzoNHC ligand distortions.
• There are no interactions between the empty d-orbital and the ligand π-system.
• An isomeric trigonal bipyramidal structure is 36 k cal/mol less stable.
Reaction of free dineopentyl-benzimidazoline-2-ylidene 1 (ligand: np2bimy) with (η3-cycloheptatriene)Mo(CO)3, molar ratio 3:1, provides the coordinatively unsaturated lateral-(np2bimy)2Mo(CO)3 complex 2. Crystal structure analysis of 2 reveals an almost ideal cis-square pyramidal geometry with tilted coordination of the metal, interplanar angles of the np2bimy ligands to the C4Mo plane of about 70° and significant bending of the N-heterocyclic carbene rings towards each other. Quantum chemical calculations (B97-D/6-31G(d)[Mo:cc-pVTZ-PP] level of theory) reproduce this peculiar structure and show it to be more stable by 36 kJ/mol than the second energy-minimum structure with trigonal bipyramidal geometry and the carbene ligands in the axial positions. Calculations indicated no significant Mo–C(II) back-bonding or interactions of the empty d-orbital with adjacent p-orbitals of the ligands, implying that the ligand distortions, tilted coordination and the occurrence of a free coordination site are caused by the spatial demand of the N-substituents.
A coordinatively unsaturated lateral-(np2bimy)2Mo(CO)3 complex was prepared and structurally characterized. DFT calculations indicate steric reasons for the tilted coordination and ligand bending and 36 k cal/mol lower stability of a trigonal bipyramidal isomer.Figure optionsDownload as PowerPoint slide
Journal: Journal of Organometallic Chemistry - Volume 783, 1 May 2015, Pages 22–27