MOLECULAR-DYNAMICS OF DIORGANOTIN(IV) MERCAPTOCARBOXYLATES FROM VARIABLE-TEMPERATURE SN-119 MOSSBAUER-SPECTROSCOPY

The molecular dynamics of the diorganotin(IV) 3-mercaptopropionate com plexes R2Sn(S(CH2)2COO] (R = Me, Et,n-Bu, n-Oct, Ph), as well as of th e mercaptoacetates R2Sn(SCH2COO), the mercaptosuccinates R2Sn[SCH(COO) CH2COO(H)] and the mercaptosalicylates R2Sn[(2-)SC6H4COO] (R = Me, Ph) , have been investigated by variable-temperature Sn-119 Mossbauer spec troscopy. The complexes behave as Debye solids with the exception of n -Bu2Sn(IV) and Ph2Sn(IV) mercaptopropionates; the former compound seem s to occur in two different solid-state modifications, as characterize d by the respective absolute recoil-free fractions. Mean-square displa cements of the Mossbauer nuclei suggest the general occurrence of mono dimensional polynuclear systems. Application of the effective vibratin g mass model evidences two strictly congeneric series consisting of th e Alk2Sn(IV) and Ph2Sn(IV) complexes, respectively. On fingerprint cri teria, monodimensional polynuclear structures are assumed, which turn to oligonuclear ones for the 3-mercaptopropionates of n-Bu2Sn(IV) (cyc lic, ref. 6) and Ph2Sn(IV).