Transformation of trigonal planar B4 into zigzag B4 units within the new boride series Ti2–xM1+x–δIr3+δB3 (x = 0.5 for M = V–Mn, x = 0 for M = Mn–Ni and δ < 0.2)

Abstract

In metal‒rich borides, numerous boron fragments Bn (n = 2, 3, 4, 5, 6) have been discovered, the B4 units being the most versatile with four different shapes (bent, zigzag, trigonal planar and tetrahedral). We report on the new boride series Ti2-xM1+x–δIr3+δB3 (x = 0.5 for M = V–Mn, x = 0 for M = Mn–Ni and δ < 0.2), in which a structural change occurs by successive substitution of the 3d transition metal M = V, Cr, Mn, Fe, Co and Ni. It is found that the change in structure from the Ti1+xOs2‒xRuB2‒type structure (P6‾2m, no. 189) to the Ti1+xRh2‒x+yIr3‒yB3‒type (Pbam, no. 55) leads to a change of B4 shape from trigonal planar B4 (M = V–Mn) to zigzag B4 fragment (M = Mn–Ni). Even though there is no group‒subgroup relationship between the two structures, we present how the Ti1+xOs2‒xRuB2‒type structure can easily be geometrically derived from the Ti1+xRh2-x+yIr3-yB3‒type.