356 E.S. Raper et al. Transition Met. Chem., 13, 356-360 (1988) Iron(II) complexes of imidazoline-2-thiones: the crystal structure of dichlorobis(1-methylimidazoline-2-thione)iron(II) Eric S. Raper*, Peter Carry, James R. Creighton and Angela Miller Department of Chemical and Life Sciences, The Polytechnic, Newcastle upon Tyne NEi 8ST, UK William Clegg* Department of Inorganic Chemistry, The University, Newcastle upon Tyne NEi 7RU, UK Summary Imidazoline-2-thione (imtH2) and 1-methylimidazoline- 2-thione (mimtH) react with FeC12-4H20 in rigorously anhydrous media producing complexes of general for- mula Fe(LH)2C12. Infrared and electronic spectra as well as room temper- ature magnetic moments are consistent with mononu- clear, pseudotetrahedral species. The crystal structure of [Fe(mimtH)2CU confirms this arrangement. The com- plex crystallises in a triclinic unit celt (a = 7.376(2), b = 7.595(2), c = 15.043(4) •. c~ = 76.80(1) ~ fl = 79.60(1) ~ y = 61,90(1)~ V=721.13~3; space group=P]~, Z=2). Final conventional R from 2267 observed data (F >4a(F)) is 0.0271. Average bond lengths are 2.353A (Fe--S) and 2.265 ~ (Fe--C1). Angles at the metal range from 91.5(1) ~ to 114.5(1) ~ . Thermal degradation of the complexes in flowing air involves sequential loss of halogen and ligand with -Fe20 3 as the final product. The decomposition is exothermic in flowing dinitrogen, Introduction A number of heterocyclic thiones and their derivatives have been reported to coordinate to iron(II) (1-8) and to iron(iii)(2, 4-11). Neutral (thione) and de-protonated (thio- late) forms of the ligands usually generate high-spin complexes with pseudo-tetrahedral or pseudo-octahedral environments about the metal. Homoleptic complexes are generally not observed with neutral ligands (z-5, 9-12) but are commonly observed for the deprotonated ligands(3, 6-8). A variety of donor sites have been proposed for the neutral ligands, largely on the basis of spectroscopic data, since definitive structural evidence is relatively scarce for such complexes. The heterocyclic imido-nitrogen atom has been pro- posed as the donor site for both iron(II) and iron(III) complexes of benzoxazoline-2-thione t2) and thiazolidine- 2-thione (1). Monodentate thione-S donation has been proposed for the iron(II) complex of pyridine-2-thione (5). Pyrimidine-2-thione is believed to S, N chelate to iron(II) by comparison with the crystal structure of the corre- sponding cobalt(II) complex (4). Crystallographic studies of the tris-thiolato complexes of iron(II) with pyrimidine-2-thiolate (6-s) and pyridine-2- thiolate(6, 7) have established S, N-chelating ligands and distorted octahedral environments about the metal. We now report iron(II) complexes with the neutral ligands, imidazoline-2-thione (imtH2) and 1- methylimidazoline-2-thione (mimt H), (1) and (2). * Authors to whom all correspondenceshould be directed. H N N R R=H R=Me (1) and (2) Experimental Starting materials Imidazoline-2-thione (imt H2) (1) and 1-methyl- imidazoline-2-thione (mimt H) (2), were supplied by the Aldrich Chemical Company and were used as supplied. The FeC12'4H20 was supplied by BDH. Chemical analysis C, H, N analyses were performed by the Department of Chemistry, Leeds University. Preparations [Fe( imt H2) 2Cl2] (3) FeC12.4H20 (0.199g, 1 mmol) in a minimum volume of deoxygenated triethylorthoformate was added dropwise to imtH2 (0.1174 g, 1 mmol) in a minimum volume of the same solvent with a little absolute EtOH (ca. 5 cm 3) to aid dessolution. The resultant dark brown solution was deoxygenated with N 2 and placed in the refrigerator for 24-48 h. The resultant bright yellow solid was filtered and washed with EtOH (2 • 10cm 3) and Et20 (5cm 3) and dried in vacuo. Yield: 62%. (Found: C, 22.3; H, 1.9; N, 17.2; Fe, 17.9. Calcd: C, 22.0; H, 2.4; N, 17.1; Fe, 17.9%). Fe(mimt H) ~Cl2(4 ) FeClz.4H20 (0.1457g, l mmol) in a minimum vol of deoxygenated HC(OEt)3 was added dropwise to mimtH (0.1926 g, 1.5 mmol) in a minimum vol of the same solvent. The resultant dark brown solution was stirred in ice for 2 h under N2. The solution was then refrigerated for 24 h. The green-yellow solid obtained was filtered, washed with EtOH (2 x 10 cm 3) and Et20 (5 cm 3) and dried in vacuo. Yield: 92%. [Fe(mimt H )zClz] (Crystals) FeC12.4H20 (0.1946g, l mmol) in a minimum vol of 1M HC1 was added to mimtH (0.4591g, 4mmol) in a minimum vol of absolute EtOH. An excess of HC(OEt)3 was added as a dehydrating agent. The solution was 0340-4285/88$03.00+ .12 9 1988 Chapman and Hall Ltd