Synthesis, Crystal Structure, Vibrational Spectroscopy and Thermal Behavior of the First Alkali Metal Hydrated Hexaborate:K2[B6O9(OH)2

Abstract

AbstractNew hydrated potassium hexaborate K2[B6O9(OH)2] has been synthesized under mild solvothermal conditions. The structure was determined by single‐crystal X‐ray diffraction and further characterized by FT‐IR, Raman spectra and DTA‐TG. It crystallizes in the monoclinic system with space group P21/n, a=0.9036(2) nm, b=0.66052(18) nm, c=1.5997(4) nm, β=91.862(4)°, V=0.9543(4) nm3 and Z=4. Its crystal structure consists of K–O polyhedra and 1‐D stepped polyborate chains constructed by new [B6O9(OH)2]2− fundamental building blocks. 1‐D polyborate chains contain 3,8‐membered boron rings. Adjacent chains are further linked via H‐bonding interactions into 2‐D layers. The K+ cations reside not only between the layers but also in the 8‐membered boron rings of the chains, compensating the negative charges of the borate chains and holding the layers together into the 3‐D structure through bonding with oxygen atoms of the chains.