A. MCAULEY, S. SUBRAMANIAN, and T. W. WHITCOMBE. Can. J. Chem. 67, 1650 (1989). The Ni(I1) complex, ~i ( H t a m )~~+ (tam = pentaerythrityl tetraamine), has been prepared under controlled conditions. In this ion, three of the four amino groups of each ligand are coordinated to yield an octahedral structure which shows tetragonal and trigonal distortion. The fourth amino group is protonated in each case and binds strongly to the counter ion so4*-. The crystal structure (triclinic, P i , a = 8.913(3), b = 9.775(2), c = 7.505(3), a = 102.61(4)", P = 106.28(4)", y = 96.40(3)") has been refined, converging to final values ofR = 0.0347 and R,,, = 0.0386. The three dimensional nature of the hydrogen bonding in the crystal structure has been described. Differences in Ni-N bond lengths are observed. A transient nickel(II1) species is generated chemically or electrochemically. The esr spectrum is consistent with a low spin d7 centre and is axial in nature.Key words: nickel, pentaerythrityl tetraamine, hydrogen bonding, oxidation.A. MCAULEY, S. SUBRAMANIAN et T. W. WHITCOMBE. Can. J. Chem. 67, 1650 (1989). Optrant dans des conditions contr61ies, on a pripari le complexe de Ni(II), N i ( H t a~n )~~+ (tam = pentatrythrityl tttraamine). Dans cet ion, trois des quatre groupements amints de chacun des ligands sont coordonnis pour donner une structure octaedrique qui prtsente une distorsion tttragonale et trigonale. Dans chaque cas, le quatritme-groupement amini est protone et il se lie fortement au contre-ion ~0 4~' .On a affini la structure cristalline (triclinique, PI, a = 8,913(3), b = 9,775(2) et c = 7,505(3) A, a = 102,61(4), P = 106,28(4) et y = 96,40(3)") jusqu'i des valeurs finales de R = 0,0347 et R,,. = 0,0386. On decrit la nature tridimensionnelle des liaisons hydrogenes dans la structure cristalline. On a observt des differences dans les longueurs des liaisons Ni-N. I1 y a gkniration chimique ou Clectrochimique d'une espece transitoire de Ni(II1). Le spectre rpe est en accord avec un centre d7 de faible spin et de nature exiale.