A new ONO3- trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

作者：VenkatRamani Sudarsan; Ghiviriga Ion; Abboud Khalil A; Veige Adam S^*

来源：Dalton Transactions, 2015, 44(42): 18475-18486.

DOI：10.1039/c5dt02911b

This report details the synthesis and characterization of the semi-flexible [(ONO)-O-CH2]H-3 (1) ligand and its W(VI)-alkylidene and alkylidyne complexes. The alkylidyne complex [(ONHO)-O-CH2]W (CBu)-Bu-t((OBu)-Bu-t) (2) forms as a result of alcoholysis of 1 with ((BuO)-Bu-t)(3)W (CBu)-Bu-t. Complex 2 evolves to [(ONO)-O-CH2]W (CHBu)-Bu-t((OBu)-Bu-t) (3) through proton migration from the N atom of the pincer ligand to the W C-alpha bond. Deprotonation of 2 or 3 with Ph3PCH2 affords the anionic alkylidyne {CH3PPh3}{[(ONO)-O-CH2]W (CBu)-Bu-t((OBu)-Bu-t)} (4). Complex 4 exhibits pincer-ligand-centered reactivity with electrophiles (H+, Me+, and TMS+), in spite of its enhanced inorganic enamine interaction. Addition of 2 equiv. of HCl to 4 yields the W(VI)-neopentyl complex [(ONO)-O-CH2]W((CH2Bu)-Bu-t)((OBu)-Bu-t)(Cl) (5). MeOTf or TMSOTf addition to 4 generates the dianionic pincer ligated alkylidynes [(ONRO)-O-CH2]W (CBu)-Bu-t((OBu)-Bu-t) (R = Me (6-Me); TMS (6-TMS)). Complexes 2-5 were characterized by multinuclear NMR spectroscopy, and combustion analysis. Complexes 4 and 5 were also characterized by single crystal X-ray diffraction. This work bridges the gap in the series involving W(VI)-alkylidynes ligated to the rigid [CF3-ONO](3-), and the flexible [(ONO)-N-CH2-O-CH2](3-) ligands. DFT computations permit comparison of the inorganic enamine effect within alkylidynes supported by all three trianionic-pincer type ONO ligands.

• 出版日期2015