Application of Trianionic Pincer Ligands to Reactions Involving Group VI Alkylidynes, Metal-Metal Multiple Bonds, and Group IV Amides; Master's thesis

摘要

In an effort to isolate a pincer-support tungsten alkylidyne, several new tungsten alkylidenes and a ditungsten compound have been isolated, supported by the previously reported OCO3- pincer ligand 3,3 -di-tert-butyl-2, 2 -di-(hydroxy-kappaO)-1,1 :3 ,1 -(terphenyl-2 -yl-kappaC2 ) (tBuOCO 1). When the tBuOCO ligand precursor is treated with W(OAr)2(CH2(CH3)3)- (aC(CH3)3) (OAr= 2,6-diisopropylphenoxide) in benzene, the alkylidene complex tBuOCO- W(=CH(CH3)3)(O-2,6-iPr2-C6H3) (3) results and was characterized by a combination of one and two dimensional NMR spectroscopy, single-crystal X-ray crystallography, and combustion analysis. To aid in the final abstraction, W(CH2(CH3)3)3(aC(CH3)3) was next combined with 1, but the reaction resulted in a complicated mixture of products. From this mixture, two closely related structural isomers of the form (tBuOCO)(CH3) (3CCH=)W(-tBuOCHO) W-(=CHC(CH3)3tBuOCO) (4 and 5) were isolated. This bridged, dinuclear complex was analyzed by single-crystalX-ray crystallography. Finally, the reaction of (NMe2)3WaW(NMe2)3 with two equivalents of 1 results first in (tBuOCHO)(NMe2)WaW(NMe2) (tBuOCHO)(7) and after prolonged heating, (tBuOCHO)W(mu-NMe2)2(mu-O)W (tBuOCHO) (8). These complexes were analyzed by a combination of NMR spectroscopy,single-crystal X-ray crystallography, and combustion analysis. The exactmechanism of formation for 8 is not yet know, but it potentially represents a rare example of the oxidative addition of water to an earlytransition metal.