trans-W(Cmesityl)(dmpe)₂H:  Revealing a Highly Polar W−H Bond and H-Mobility in Liquid and Solid State

Abstract

The isotopomeric complexes trans-W(Cmesityl)[(C(H,D)3)2PCH2CH2P(C(H,D)3)2]2(H,D) 1-4 were prepared. 2 (W(Cmesityl)(dmpe)2D) was used to study the Deuterium Quadrupole Coupling Constant (DQCC) and the ionicity of the W-D bond (DQCC=34.1 kHz; ionicity 85%). 1 (W(Cmesityl)(dmpe)2H) shows several dynamic exchange processes in solution, such as HW/HW, HW/ortho-Memesityl, and HW/H2 exchanges observed by NMR in combination with deuterium labeling studies and double label crossover experiments. Except for the HW/H2, these reactions comprise elementary steps, which also appear along the isomerization pathway of 1 into (2,3,5-trimethylphenylcarbyne)(dmpe)2WH (5) at 60 degrees C. 5 was characterized by an X-ray diffraction study. In the solid state only an HW/Mep exchange process prevails appearing at higher temperatures, which was identified by NMR and by Quasielastic Neutron Scattering. The latter also provided an activation barrier of 5 kcal/mol and a "jump width" for the moving H nucleus in agreement with the HW...Mep distance of the X-ray diffraction study of 1.

Efficient Carbene and Carbyne Formation in Molybdenum(0) and Tungsten(0) Dinitrogen Complexes

“…These assignments are completely supported by X-ray crystallography data showing slightly distorted octahedral structures with equivalent MoC (1.853 (3) Å) and WC (1.853 (2) Å) bond lengths (Figure ; see the Supporting Information for full details). The WC bond length of 2b is intermediate between those for trans -(dmpe) 2 (H)WC(2,3,5-CMe 3 C 6 H 2 ) (1.838(9) Å) and trans -(dmpe) 2 (H)WCMes (1.863(6) Å) . The isolation of carbyne hydride complexes 2a , b is noteworthy, in that these species can be obtained in high yield in a single step from the easily accessible corresponding dinitrogen precursors in contrast to multiple ligand-exchange steps required to access trans -(dmpe) 2 (H)WCMes from W(CO) 6 .…”

“…When the W analogue 1b was heated together with 3,3-diphenylcyclopropene, a similar reaction was observed and a dark green product was isolated with spectral data that are quite similar to those reported for trans-(dmpe) 2 W(H)(CMes). 12 On the basis of these spectral data, we assigned the products in the reactions of 1a,b with 3,3-diphenylcyclopropene as the trans carbyne hydride complexes 2a and 2b shown in eq 1.…”

Self-assembled PEG–carboxymethylcellulose nanoparticles/α-cyclodextrin hydrogels for injectable and thermosensitive drug delivery

“…The uniformly distributed hydrophobic nanoparticles core and the hydrophobic-hydrophobic interactions between the HCPT and BA molecules inner shell of the nanoparticles can improve the strength of the hydrogels to a certain extent. 29 Thus, for these viscoelasticity, the CMC-BA/HCPT hydrogel can be an efficient injectable material for drug delivery.…”

The effect of the geometry of extrusion head flow channels on the adiabatic extrusion of low density polyethylene

“…In conventional extrusion, the heat for plasticizing the material is supplied indirectly from the heaters via the extruder's barrel and head [3,4]. Adiabatic extrusion is a process wherein heat is generated by internal friction in the material being processed and by external friction of this material against the barrel and screw surface [5,6]. In high speed extrusion, heat is generated in the same manner as in adiabatic extrusion; however, the amount of the generated heat is so vast that the extruder should be left to cool down at intervals.…”