More than 70 equilibrium constants K between acids and bases, mainly phosphine derivatives, have been measured in tetrahydrofuran (THF) at 20 °C by 1 H and/or 31 P NMR. The acids were chosen or newly synthesized in order to cover the wide pK R THF range of 5-41 versus the anchor compound [HPCy 3 ]BPh 4 at 9.7. These pK R THF values are approximations to absolute, free ion pK a THF and are obtained by crudely correcting the observed K for 1:1 ion-pairing effects by use of the Fuoss equation. The acid/base compounds include 14 phosphonium/phosphine couples, 17 cationic hydride/neutral hydride couples, 9 neutral polyhydride/anionic hydride couples, 14 dihydrogen/hydride couples, and 4 other nitrogen-and phosphorus-based acids. The effects on pK R of the counterions BAr′ 4and BF 4vs BPh 4and [K(2,2,2-crypt)] + versus [K(18-crown-6)] + are found to be minor after correcting for differences in inter-ion distances in the ion-pairs involved. Correlations with ν(M-H) noted here for the first time suggest that destabilization of M-H bonding in the conjugate base hydride is an important contributor to hydride acidity. It appears that Re-H bonding in the anions [ReH 6 (PR 3 ) 2 ]is greatly weakened by small increases in the basicity of PR 3 , resulting in a large increase in the pK R of the conjugate acid ReH 7 (PR 3 ) 2 . Correlations with other scales allow an estimate of the pK R THF values of more than 1000 inorganic and organic acids, 20 carbonyl hydride complexes, 46 cationic hydrides complexes, and dihydrogen gas. Therefore, many new acid-base reactions can be predicted and known reactions explained. THF, with its low dielectric constant, disfavors the ionization of neutral acids HA over HB + , and therefore separate lines are found for pK R THF (HA) and pK R THF (HB + ) when plotted against pK a DMSO or pK a MeCN . The crystal structure of [Re(H) 2 (PMe 3 ) 5 ]BPh 4 is reported.

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Addition of excess HOSO2CF3 (HOTf) to CpRu(L)H (1) (L = dfepe = PR2CH2CH2PR2, R = C2F5) in CD2Cl2 under N2 produces a mixture of [CpRu(L)(H)2]+ (2a), [CpRu(L)(H2)]+ (2b), and CpRu(L)(OTf) (3) in a ratio of 1:5:2. Salts of the acid [HOEt2]+ are not strong enough to protonate 1. Complexes 2 slowly eliminate H2 to give 3; this reaction is slowed by adding excess HOTf. Of all such complexes [CpRu(PR2CH2CH2PR2)(H2)]+, R = alkyl and aryl, the dihydrogen complex 2b has the greatest acidity (similar to that of HOTf) and the related HD complex has the greatest J HD (29.1 Hz) because of the electron-withdrawing substituents R = C2F5. The reaction of 3 with 1 atm H2(g) proceeds much faster in the presence than in the absence of 1 equiv of HOTf to produce 1 and HOTf. This is a rare example of the production of a strong acid from H2(g) where the intermediate dihydrogen complex has been characterized. Reaction of Cp*Ru(L)Cl (4), Cp* = C5Me5, in dry CH2Cl2 at −78 °C with AgX salts under H2(g) (1 atm) gives mixtures of Cp*Ru(L)H (5) and [Cp*Ru(L)(H)2]+ (6), which have been identified by 1H NMR. 6 is deprotonated by traces of water or by PPh3 to give Cp*Ru(L)H (5). The addition of excess HOTf to mixtures of 5 and 6 under H2(g) produces 6. Complexes 3, 4, and 5 have been characterized by single-crystal X-ray diffraction. Complexes CpRu(L)Cl, 1, 4, and 5 have very positive redox potentials that indicate that the dfepe ligand has the electron-withdrawing power close to that of two carbonyl ligands.

The 2H solid state NMR spectra and relaxation data of a transition metal g2-dideuterium complex, namely T 1 have been measured in the temperature regime from 5.4 to 320 K. trans-[Ru(D 2)Cl(PPh 2 CH 2 CH 2 PPh 2) 2 ]PF 6 , In the sample, coherent and incoherent exchange processes on the time scale of the quadrupolar RuÈD 2 interaction have been found, leading at low temperatures to a tunnel splitting of the 2H NMR spectrum. With increasing temperature a slight increase of the tunnel splitting is observed, in conjunction with a strong increase of the incoherent exchange process, which Ðnally, at temperatures above 20 K, destroys the tunnel splitting and determines the spectral line shape. For the description of the experimental spectra a Liouville formulation of the AlexanderÈBinsch NMR line shape theory, adapted for exchanging deuterons, is employed. It is shown that the whole evaluation of the 2H magnetization takes place in four 2D and two 4D subspaces of the 81D Liouville space, leading to a drastic simpliÐcation of the numerical e †orts in the simulation of the spectral line shapes. The height of the tunnel barrier calculated from the value of the tunnel splitting is 270 meV (6.22 kcal mol~1). The incoherent exchange rates extracted from the spectra and from relaxation data T 1 are analyzed in terms of a Bell tunneling model, with a temperature dependent e †ective potential.