An examination of the 1H-{11B}, 11B-{1H}, and 31P-{1H} NMR behaviour of the compounds [M(B5H8)(X)(dppe)] has been made [M = Ni, Pd and Pt; X = halogen; dppe = bis(diphenylphosphino)ethane]. Some relaxation phenomena are rationalised, and it is concluded that all the compounds examined have a static metallo-nido-penta-borane structure in which the metal atom occupies a bridging position between two basal boron atoms. Some temperature and solvent effects are also presented and briefly discussed. © 1979, Walter de Gruyter. All rights reserved.