This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021 New J. Chem. Cite this: DOI: 10.1039/d1nj03128g Assembly of discrete and oligomeric structures of organotin double-decker silsesquioxanes: inherent stability studies† Pushparaj Loganathan, a Renjith S. Pillai, ab Velusamy Jeevananthan, a Ezhumalai David, c Nallasamy Palanisami, c Nattamai S. P. Bhuvanesh d and Swaminathan Shanmugan * a Double-decker silsesquioxane (DDSQ), a type of incompletely condensed silsesquioxane, has been used as a molecular precursor for synthesizing new organotin discrete and oligomeric compounds. The equimolar reaction between DDSQ tetrasilanol (DDSQ-4OH) and Ph 2 SnCl 2 in the presence of triethylamine leads to obtaining discrete [Ph 4 Sn 2 O 4 (DDSQ)(THF) 2 ](1). The change of sterically bulky aryl Ph 2 SnCl 2 precursor to linear alkyl n Bu 2 SnCl 2 led to the isolation of oligomeric [ n Bu 4 Sn 2 O 4 (DDSQ)] (2). The structures of compounds 1 and 2 have been demonstrated using single-crystal X-ray diffraction measurements. Indeed, the formation of oligomeric organotin DDSQ compound (2) was determined using GPC and MALDI-TOF mass spectroscopy. In compound 1, the geometry of the tin atom is five- coordinated trigonal bipyramidal by two phenyl groups, two Si–O from DDSQ and one tetrahydrofuran. Compound 2 contains four coordinated two peripheral tin atoms and two five-coordinated central tin atoms, in which, the fifth coordinating oxo groups in the central tin atoms create the bridge between two different DDSQ units that leads to the formation of oligomeric structure. Density functional theory calculations on organotin DDSQs infer that the obtained lattice energy for compound 1 is far higher than for the case of compound 2, which indicates that the crystal of compound 1 is better stabilized in its crystal lattice with stronger close packing via intermolecular interactions between discrete molecules with coordinated THF compared to the crystal of compound 2. The greater stability arises mainly due to the sterically bulkier phenyl groups attached to the tin centers in compound 1, which provide accessibility for accommodating the THF molecule per tin via Sn–THF bonding, while contrarily the smaller n-butyl groups aid the polymerization of the four repeating units of [SnSi 4 O 7 ] or two Sn 2 O 4 (DDSQ) through m-oxo groups. Both compounds 1 and 2 were chosen to be promising precursors for the synthesis of ceramic tin silicates. The thermolysis of 2 at 1000 1C afforded the mixture of crystalline SnSiO 4 and SiO 2 but the same mixture was only formed by thermolysis of 1 at relatively higher temperature (1500 1C), which infers that compound 1 is more stable than compound 2 that is in good synergy with theoretical lattice energy. Introduction Discrete molecular cages and polymeric frameworks containing Si–O–M linkages have been gaining much attention owing to their resemblance to naturally existing frameworks viz. zeolites. 1–5 Nevertheless, the rational design of such frame- works is extremely difficult that can be partially adjudged to the irregular coordination modes shown by SiO 4 4À groups and also to their poor solubility in most organic solvents. These obscurities can be systematically tackled using suitable organic-soluble syn- thons that need to be developed at molecular level for mechanistic investigations. Silsesquioxanes have turned out to be soluble model systems for answering various queries related to zeolites a Department of Chemistry, Faculty of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur-603203, Tamil Nadu, India. E-mail: shanmugs2@srmist.edu.in, shanmugan0408@gmail.com b Department of Chemistry, Christ University, Bangalore-56029, Karnataka, India c Centre for Functional Materials, Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore-632014, Tamil Nadu, India d X-ray Diffraction Laboratory, Department of Chemistry, Texas A&M University, College Station, TX 77842, USA † Electronic supplementary information (ESI) available. CCDC 2085328 and 2085329. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/d1nj03128g Received 26th June 2021, Accepted 29th September 2021 DOI: 10.1039/d1nj03128g rsc.li/njc NJC PAPER Published on 29 September 2021. Downloaded by INDIAN INSTITUTE OF TECHNOLOGY BOMBAY on 10/23/2021 4:41:12 AM. View Article Online View Journal