Journal of Organometallic Chemistry 627 (2001) 189 – 200 www.elsevier.nl/locate/jorganchem Further studies on dialkyltin 1,3-dithiole-2-thione-4,5-dithiolates, R 2 Sn(dmit). Crystal structures of orthorhombic- and monoclinic-Et 2 Sn(dmit), and Me 2 Sn(dmit) Gillian M. Allan a , R. Alan Howie a, *, Janet M.S. Skakle a , James L. Wardell a,b , Solange M.S.V. Wardell c a Department of Chemistry, Uniersity of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, UK b Departamento de Quı ´mica Inorga ˆnica, Instituto de Quı ´mica, Uniersidade Federal do Rio de Janeiro, 21945 -970 Rio de Janeiro, RJ, Brazil c Instituto de Quı ´mica, Departamento de Quı ´mica Orga ˆnica, Uniersidade Federal Fluminense, 24020 -150 Nitero ´i, RJ, Brazil Received 8 January 2001; received in revised form 15 February 2001 Abstract The crystal structures of orthorhombic and monoclinic diethyltin bis(1,3-dithiole-2-thione-4,5-dithiolate), [Et 2 Sn(dmit)], ortho -3 and mono -3, and dimethyltin bis(1,3-dithiole-2-thione-4,5-dithiolate) (4) have been determined. Transformation of solid ortho -3 to mono -3 occurs at 139–140°C. Molecules of ortho -3, obtained by recrystallisation from aqueous acetone, and 4, are linked into chains as a result of intermolecular Snthione S(5) interactions: the tin centres are penta-coordinate with distorted trigonal bipyramidal geometries. The intermolecular, SnS(5) thione bonds {3.0083(15) A  in ortho -3 at 150 K [3.037(4) at 298 K], and 3.001(2) and 2.960(2) A  in the two independent molecules of 4 at 150 K}, are considerably longer than the primary intramolecular Sn bonds to the dithiolato S atoms [between 2.440(3) and 2.5235(15) A  ]. The two independent molecules of mono -3, obtained from aqueous methanol, have quite different arrangements: tin atoms in molecule A form two relatively weak intermolecular Snthione S bonds, 3.567(2) and 3.620(3) A  , with the formation of sheets, while those in molecule B form one similar bond, SnS =3.555(2) A  to give chains, with a much longer contact, Sn···S =3.927(2) A  to another chain. The latter is only ca. 0.12 A  less than the van der Waals radii sum for Sn and S. Sulfur–sulfur contacts, within the sum of the van der Waals radii of two S atoms, 3.60 A  , in 3 and 4, not only reinforce the chains but also help to establish 3D networks. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Organotin; 1,3-Dithiole-2-thione-4,5-dithiolate; Crystal structures; Polymorphism 1. Introduction Diorganotin derivatives of 4,5-dimercapto-1,3-dithi- ole-2-thione, H 2 -dmit, 1, have been previously studied [1–3]: both ionic species, [Q][R 2 SnX(dmit)], II [1], and neutral compounds, R 2 Sn(dmit), I, [2,3] have been ob- tained (Q =onium cation; R =Me, Ph, etc.; X =halide or pseudohalide). The compounds, [Q][R 2 SnX- (dmit)], (II: e.g. Q =NBu 4 ,R =Me, X =Cl; Q =1,4- dimethylpyridinium, R =Ph, X =NCS, Br or I/Cl), have similar structures, with non-interacting cation and anions, and with distorted trigonal bipyramidal, five- * Corresponding author. Tel.: +44-1224-272907; fax: +44-1224- 272921. E-mail address: r.a.howie@abdn.ac.uk (R.A. Howie). 0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0022-328X(01)00735-5