The reaction of CH3NH2with SnX2, CH3NH3SnX3(X=Cl, Br, I), and BiI3– The first Sn(II)‐Ammine complexes as intermediates

Abstract

AbstractIn order to understand the “molten salt approach” for CH3NH3PbI3, we have investigated the interaction of gaseous CH3NH2with PbX2(X=Cl, Br, I) and MAPbX3(MA=CH3NH3+;X=Cl, Br, I) and characterised the first ammine complexes of Pb(II). In continuation, we have extended our work to the corresponding Sn(II) halides, i. e. SnX2(X=Cl, Br, I) and MASnX3(X=Cl, Br, I). WithX=iodine we have obtained cubic [Sn(CH3NH2)6]I2, which is isotypic to the lead compounds withX=I and Br showing a close similarity to the K2PtCl6type due to the octahedra [Sn(CH3NH2)6]2+. Release of CH3NH2yields [Sn(CH3NH2)4I]I. Here, Sn2+is fivefold coordinated by 4 CH3NH2ligands and one I−as a square pyramid with the I−in an equatorial position. Charge neutrality is achieved by a second I−anion with a significant longer distance of 4.29 Å, completing the square pyramid to a distorted octahedron. WithX=Br and Cl, only one compound forms, Sn(CH3NH2)5Br2and Sn(CH3NH2)5Cl2, respectively. Both structures are isotypic and crystallize in an orthorhombic structure with square‐pyramidal [Sn(CH3NH2)5]2+units. For all representatives with mixed ligands, the interaction withX−is significantly weaker than with CH3NH2. H‐bridges N−H⋅⋅⋅Xcontribute to the interaction between the Sn(CH3NH2)4X2units. All compounds show high sensitivity to moisture and limited thermal stability. They decompose in air to CH3NH3Xand a white amorphous residue, probably Sn(OH)X. The reaction of CH3NH2with BiI3results in (CH3NH3)4(CH3NH2)BiI7according to traces of moisture.