This paper reports about the electrospray ionization mass spectrometric and quantum chemical study of unique coupling reaction of dihydroxybenzaldehydes in strong basic medium, which in the presence of (SnCl4)-Cl-IV yielded series of condensation products through the homo Dies-Alder reaction of the bicyclohexyl-4,6,4',6'-tetraene-2,3,2',3'-tetraone (2). In contrast to the known coupling reaction products catalyzing by diversity of Cu-I/Cu-II, Ag-I-, Au-0/Au-III/Au-I-, Zn-II-, Pd-0/Pd-III/Pd-II- and/or Pt-II-organometallics, yielding the substituted biphenyls, benzo-[c]-cromenes, condensation products of 5,6,11, 12-tetraoxo-tricyclo[6.2.2.02,7]dodeca-3,9-diene-1,4-dicarbaldehyde (14) type from 2,3-dihydroxybenzaldehyde particularly, and/or substituted aldehydes by Reimer-Tiemann reaction, in the presence of SnIV- Cl-4, the formation of above dimeric adducts is chiefly process, explained with Sn-IV -> Sn-II redox process. The known product 14 is obtained at trace concentrations, producing further dimeric 5,6,11,12,5',6',11',12'-octaoxo-[4,4']bi[tricyclo[6.2.2.02,7]dodecyl]-3,9,3',9'-tetraene-1,1'-dicarbaldehyde adduct (15). The catalyzing organometallic precursor is a binuclear Se-complex (I), where the metal ion is bonded covalently in Cl-Sn-C manner. A second metal ion is bidentately coordinated to adjacent O=C- groups, forming a five membered chelate ring. The Cl- and OH--terminal ligands completed the SnO3Cl chromophore. The experimentally evidenced complex I exhibited a significant thermodynamics stability of Delta G = -52996.80 kcal mol(-1), a value different than Delta(Delta G) =vertical bar 52945 vertical bar kcal mol(-1) towards the corresponding quantities of other structurally proposed analogous of Sn-II, Sn-IV or Sn-II/Sn-IV organometallics II-IV on the base of the MS elemental compositions and isotopic shapes. (C) 2013 Elsevier B.V. All rights reserved.