Crystal chemistry of complex indium(III) and other M(III) halides, with a discussion of M—Cl bond lengths in complex M(III) chlorides and of the structures of and hydrogen bonding in (NH4)2[InCl5(H2O)], K3InCl6•nH2O, (MeNH3)4[InCl6]Cl, and (Me2NH2)4[InCl6]Cl

Abstract

The crystal chemistry of complex In(III) halides is discussed and compared with that of other Group III elements and Fe(III), with critical comments and analysis of the available information. The cation/anion packing types occurring among A+[M3+X4] halides are classified according to volume per formula unit and the relative ionic sizes of M, X, and A, and the structural trends in this class of compounds are identified. The effect of systematic factors responsible for variation in M(III)—Cl bond lengths is examined in detail. It is shown that the mean M(III)—Cl bond lengths in [MClnLm]ε(M = Al, Ga, Fe, In, Tl; L = Cl or a neutral ligand) complexes can be approximated, to within about 0.02 Ă, by a linear function of the coordination number CN = n + m and the charge ε over the range 3 ≤ CN ≤ 6 and.−3 ≤ ε ≤2. This analytical expression provides a norm for comparing M(III)—Cl bond lengths and demonstrates that the CN is always a more important factor than ε in determining the variation in the mean bond length and that it becomes dominant when M is small. The crystal structure of (Me2NH2)4[InCl6]Cl (P21212, a = 10.156(4) Å, b = 13.007(4) Å, c = 8.751(3) Å, Z = 2) has been determined and those of (NH4)2InCl5(H2O)] (Pnma, a = 13.953(4) Å, b = 10.086(5) Å, c = 7.152(3) Å, Z = 4), K3InCl6•nH2O (I4mm, a = 15.659(8) Å, c = 18.106(5) Å, Z = 14) and (MeNH3)4[InCl6]Cl (P2/n, a = 16.113(3) Å, b = 7.446(2) Å, c = 16.163(4) Å, β = 103.75(2)°, Z = 4) redetermined. The water in K3InCl6•nH2O appears to be in part zeolitic; the hydrate examined contained more water than the monohydrate reported previously. Hydrogen bonding in these and related structures is described and discussed in detail; descriptions of the hydrogen-bonding schemes in (NH4)2[InCl5(H2O)] and (MeNH3)4[InCl6]Cl constitute the main improvement over earlier structure determinations.