Hydrido dihydrogen complexes

Fig-1- Basic structures of the metal hydride complexes exhibiting the QEC effect, (a) Trihydride, (b) cA-dihydride, (c) dihydrogen, and (d) hydrido dihydrogen complexes. The symbol Cp denotes variously substituted cyclopentadiene anions. 

Electron Hydrido(dihydrogen) Complexes Reactions of [RuH2(H2)2(PCy3)2] with Halocarbons and Related Reactions... 

Electron Hydrido(dihydrogen) Complexes, Proton Transfer and C-H Activation... 

The dynamic equilibrium between the dihydride /ra 5-Ru(H)2(dppm)2 and the hydrido-dihydrogen complex [(dppm)2HRu(H2)]" "(OR) occurs in the presence of phenol or hexafluoroisopropyl alcohol. ... 

These dianions on stoichiometric protonation, e.g. with H20 in THF, give hydrido anions which, in turn, with an excess of a Bronsted acid, or with an equivalent of benzoic acid, are transformed into labile dihydrogen complexes finally loosing dihydrogen according reaction sequence (19a, b, c) (M = Ru, Os P = OEP, TMP, L = THF] [261, 262],... 

In this manner, the cationic dihydrogen complex 13 can be deprotonated to the catalytically active Ru(II) hydrido complexes. The undesired isomerization of 13 to the dihydride complex 14 can be avoided by lowering the reaction temperature and changing the solvent to THF. 

Both in situ infrared and multinuclear NMR under less severe conditions have been used to gain mechanistic insights. For the hydroformylation of 3,3-dimethyl but-l-ene, the formation and hydrogenolysis of the acylrhodium species Rh(C()R)(C())4( R=CH2CH2Bur) can be clearly seen by IR. NMR spectroscopy has also been very useful in the characterization of species that are very similar to the proposed catalytic intermediates. We have already seen (Section 2.3.3, Fig. 2.7) NMR evidence for equilibrium between a rhodium alkyl and the corresponding hydrido-alkene complex. There are many other similar examples. Conversion of 5.3 to 5.4 is therefore well precedented. In the absence of dihydrogen allowing CO and alkene to react with 5.1, CO adducts of species like 5.6 can be seen by NMR. Structures 5.11 and 5.12 are two examples where the alkenes used are 1-octene and styrene, respectively. 

The first known r -dihydrogen complexes, so-called non-classical hydrido complexes, were the molybdenum and tungsten compounds, M(CO)3(PR3)2(ti -H2) (M = Mo, W R = /-Pr) isolated for the first time by Kubas [35]. In order for the... 

Recent Developments in the Synthesis, Bonding Modes and Reactivity of Hydrido and Dihydrogen Complexes... 

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