Synthesis and coordination chemistry of new estertin (Ⅳ) complexes with multidentate ligands

Abstract

This work deals with the synthesis and characterization of various estertin(IV) complexes involving mixed multidentate ligands for elucidation on the coordination chemistry of organotin(IV) compounds. $CH_3OOCCH_2CH_2SnCl_3$ reacts with the dithiocarbamate(dtc) ligand in appropriate mole ratios to yield crystalline solid products $ROOCCH_2CH_2Sn(S_2CNMe_2)_xC1_{3-x}$ (Ia: R=Me, x=1; IB: R=Me, x=2; Ic: R=Me, x=3). Ia adopts a distorted octahedral geometry with the chelating dtc and ester group via intramolecclar carbonyl oxygen-to-tin coordination. However, in Ib and Ic the intramolecular coordination of the carbonyl group is not allowed in order to accommodate two and three bidentate dtc ligands, respectively. The reaction of Ia series with an equimolar $Na_2S$ yields dimeric sulfides $[CH_3OOCCH_2CH_2Sn(S_2CNR_2)S]_2$ (IIa: R=Me; IIb: R=Et) involving a rare centrosymmetric $Sn_2S_2$ four-membered ring. In these complexes the dtc ligand acts as bidentate and each Sn atom is pentacoordinate with local geometry of a distorted trigonal bipyramid. The reaction of Ia series with diptych ligands $Y(CH_2CH_2XNa)_2$ affords stannatrane products, $ROOCCH_2CH_2Sn(S_2CNMe_2)(XCH_2CH_2)2Y$(IIIa: R=Me, X=S, Y=0; IIIa-1: R=Et, X=S, Y=O; IIIc: R=Me, X=S, Y=S; IIId: R=Me, X=O, Y=NMe; IIId1: R=Et, X=O, Y=NMe). These complexes are regarded as the first hexacoordinate stannabicyclooctanes. For IIIa, however, unusually unsymmetrical chelation of the dtc ligand (sn-S(1), 3.093(1)A; Sn-S(2), 2.493(1)A) along with the endocyclic ring constrain resulted in a highly distorted octahedral arrangement. Diestertin(IV) complexes $(CH_3OOCCH_2)_2Sn(Ch)C1$ (IVa: $Ch=Me_2NCS_2$- (dtc) ; IVb: Ch=bispyrazolylborate (bpb)) also have been synthesized. IVb shows hexacoordinate tin atom with chelating bpb and one ester group via a carbonyl oxygen-to-tin coordination whereas IVa pentacoordinate with only the dtc chelation. The reaction of IVa with $Na_2S$ in the mole ratio of 2:1 migrates the ligands...