The syntheses and solid-state structures of K(BH2(RCN4)(2))-(18-crown-6) (R = H, Me, NMe2, and NiPr2) are described. Complexes where R = H and Me have B-N bonds to N-1 of the tetrazolyl groups and form one-dimensional polymers, whereas those with R = NMe2 and NiPr2 possess isomeric B-N bonds to N-2 of the tetrazolyl moieties and adopt chelating kappa(3)-N,N',H-coordination modes to the potassium ion.