Zirconium monohydrides

Tetraneopentyl zirconium reacts in the same way as tetraneopentyl titanium to give, on a silica (soo), a tris(neopentyl) monografted species [32]. Treatment under H2 of this surface species yields silica-supported zirconium hydrides [33], which have been characterized as a mixture of mono- (65-70%) and bis- (35-30%) hydrides based on double quanta NMR experiments (Scheme 2.11) [34]. Interestingly, the double quantum experiment allows us to prove not only the presence of the two hydrides and the monohydride of zirconium by the presence or the absence of the double quanta correlation but also to detect the through space magnetic interaction between the zirconium monohydride and the silicon di-hydride, proving thus the spatial arrangement on the surface. This confirms the mechanism by which these hydrides have been formed on the surface. 

Thanks to recent advances in soHd-state NMR spectroscopy, the zirconium bis-hydride [(=SiO)2ZrH2] (lb) (20-35%) was found to be generated simultaneously to the major zirconium monohydride [(=SiO)3Zrft] (la) (80-65%) during hydroge-nolysis of the single site sihca or silica-alumina supported [(=SiO)ZrNp3] [14],... 

The initial slopes obtained are different from the first loading to the third, indicating clearly that there is not one unique zirconium monohydride site on the surface of silica, thus showing the heterogeneity of oxide surface, which leads to different active sites. 

Reaction of this well-characterized species with dry hydrogen at 150°C leads to the formation of zirconium hydride and the evolution of alkanes.257 Hafnium and titanium monohydride can be obtained in the same way.258... 

Magnesium hydride, 4463 Magnesium-nickel hydride, 4464 Plutonium(III) hydride, 4509 Poly (germanium dihydride), 4415 Poly (germanium monohydride), 4413 Potassium hydride, 4427 Rubidium hydride, 4450 Sodium hydride, 4444 f Stibine, 4510 Thorium dihydride, 4489 Thorium hydride, 4540 Titanium dihydride, 4490 Titanium-zirconium hydride, 4491 Trigermane, 4421 Uranium(III) hydride, 4511 Uranium(TV) hydride, 4541... 

Magnesium—nickel hydride, 4458 Plutonium(III) hydride, 4504 Poly(germanium dihydride), 4409 Poly(germanium monohydride), 4407 Potassium hydride, 4421 Rubidium hydride, 4444 Sodium hydride, 4438 f Stibine, 4505 Thorium dihydride, 4483 Thorium hydride, 4535 Titanium dihydride, 4484 Titanium—zirconium hydride, 4485 Trigermane, 4415 Uranium(III) hydride, 4506 Uranium(IV) hydride, 4536 Zinc hydride, 4486 Zirconium hydride , 4487 See COMPLEX HYDRIDES, PYROPHORIC MATERIALS See entry LANTHANIDE—TRANSITION METAL ALLOY HYDRIDES... 

Surface zirconium hydrides 1 result from hydrogenolysis of the Zr-C bonds of A at 150°C. A monohydride zirconium supported complex is the major species formed, but some zirconium dihydrides are present along with surface silanes, [Sijj-H, the product of reduction of siloxane bridges by the very reducing zirconium hydrides [6]. These latter are catalytically inert. The surface zirconium hydrides are stable up to 200°C under vacuum or hydrogen. Complexes 1 were fiilly characterized by physical techniques (in situ IR, EXAFS) and their chemical reactivity determined (towards O2, H2O, R-X, ROH, olefins) [6]. 

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