Reactions of β-diketiminato group 2 silylamides, [HC{(Me)CN(2,6-iPr2C6H3)}2M(THF)n{N(SiMe3)2}] (M = Mg, n = 0; M = Ca, Sr, n = 1), and an equimolar quantity of pyrrolidine borane, (CH2)4NH·BH3, were found to produce amidoborane derivatives of the form [HC{(Me)CN(2,6-iPr2C6H3)}2MN(CH2)4·BH3]. In reactivity reminiscent of analogous reactions performed with dimethylamine borane, addition of a second equivalent of (CH2)4NH·BH3 to the Mg derivative induced the formation of a species, [HC{(Me)CN(2,6-iPr2C6H3)}2Mg{N(CH2)4 BH2NMe2BH3}], containing an anion in which two molecules of the amine borane substrate have been coupled together through the elimination of one molecule of H2. Both this species and a calcium amidoborane derivative have been characterised by X-ray diffraction techniques and the coupled species is proposed as a key intermediate in catalytic amine borane dehydrocoupling, in reactivity dictated by the charge density of the group 2 centre involved. On the basis of further stoichiometric reactions of the homoleptic group 2 silylamides, [M{N(SiMe3)2}2] (M = Mg, Ca, Sr, Ba), with (CH3)2NH·BH3 and iPr2NH·BH3 reactivity consistent with successive amidoborane β-hydride elimination and [R2N
BH2] insertion is described as a means to induce the B–N dehydrocoupling between amine borane substrates.