Intramolecular H...H interactions between hydrogen-bond proton donors and transition metal hydrides can be extended to intermolecular cases by cocrystallization of ReH5(PPh3)(2)L and suitable hydrogen-bond donors, as is shown in the neutron and X-ray crystal structures of 6 (L = PPh3; donor = indole) and 7 (L = imidazole; donor = lattice imidazole of solvation), respectively. Short N-H...H-Re distances are found for these unconventional hydrogen bonds in both cases: 6, 1.734(8) Angstrom; 7, 1.68(3) Angstrom (sum of van der Waals radii for H...H = 2.4 Angstrom). IR data indicate a correlation between the pK(a) of the hydrogen-bond donor and the strengths of the H...H interactions. DFT calculations on ReH5(PH3)(3) . NH3 show the presence of a significant attractive interaction between the rhenium fragment and the proton donor, independent of the Re-H bonds chosen. Experimentally, the least hindered Re hydride is involved in the interaction in each case. The influence of the occupied metal d orbital (Re(V), d(2)) is minimal. Molecules like OPPh3 that can act as a hydrogen-bond acceptor do not show an attractive interaction with the Re complex, as confirmed by the absence of an attractive potential between ReH5(PH3)(3) and OPH3.
|Titolo:||Intermolecular N-H center dot center dot center dot H-Re interactions involving rhenium polyhydrides|
|Parole Chiave:||molecular-structure; hydrogen-bond; complexes; IR; crystal|
|Settore Scientifico Disciplinare:||Settore CHIM/03 - Chimica Generale e Inorganica|
|Data di pubblicazione:||apr-1997|
|Appare nelle tipologie:||01 - Articolo su periodico|