Synthesis, structure and spectral properties of dithiocarbamato bridged dirhenium(III,II) complexes: A combined experimental and theoretical study Suman Mallick a , Mrinal Kanti Ghosh a , Manoj Mohapatra b , Sudip Mohapatra c , Swarup Chattopadhyay a,⇑ a Department of Chemistry, University of Kalyani, Kalyani, Nadia 741235, WB, India b Radiochemistry Division, RLG, Bhabha Atomic Research Centre, Mumbai 400085, India c Department of Chemistry, Missouri University of S & T, Rolla, MO 65409, USA article info Article history: Received 19 May 2014 Received in revised form 14 July 2014 Accepted 20 July 2014 Available online xxxx SI: Metal-metal bonded compounds Keywords: Dirhenium(III,II) Dithiocarbamate Paramagnetic Edge-shared bioctahedra Density functional theory abstract Sodium salts of dimethyldithiocarbamate, diethyldithiocarbamate and pyrrolidinedithiocarbamate react with the multiply bonded paramagnetic dirhenium(III,II) complex Re 2 (l-O 2 CCH 3 )Cl 4 (l-dppm) 2 , 1 (dppm = Ph 2 PCH 2 PPh 2 ) in refluxing ethanol to afford the paramagnetic substitution products of the type Re 2 (g 2 -S,S) 2 (l-S,S)(l-Cl) 2 (l-dppm), where S,S represents the dithiocarbamato ligands [S,S = S 2 CNMe 2 , 4(L Me ); S 2 CNEt 2 , 4(L Et ) and S 2 CN(CH 2 ) 4 , 4(L Pyr )]. These are the first examples of dirhenium complexes that contain bridging dithiocarbamato ligand along with the dppm ligand. These complexes have very similar spectral (UV–Vis, IR, EPR) and electrochemical properties which are also reported. The identity of 4(L Et ) has been established by single-crystal X-ray structure determination (Re–Re distance 2.6385 (9) Å) and is shown to have edge-shared bioctahedral structure. The electronic structure and the absorption spectra of the complexes are scrutinized by the density functional theory (DFT) and time-dependent density func- tional theory (TD-DFT) analyses. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction The multiply bonded paramagnetic dirhenium(III,II) complex Re 2 (l-O 2 CCH 3 )Cl 4 (l-dppm) 2 1 (dppm = Ph 2 PCH 2 PPh 2 ), with the r 2 p 4 d 2 d /1 electronic configuration has been prepared almost 25 years ago and its solid state structure was also determined in the year 1988 [1]. Since then efforts have been made to develop the reaction chemistry of this useful synthon 1. Although there has been a flurry of compounds prepared using the other two mul- tiply bonded dirhenium(II,II) synthons Re 2 Cl 4 (l-dppm) 2 2 [2] and cis-Re 2 (l-O 2 CCH 3 ) 2 Cl 2 (l-dppm) 2 3 [1] and an extensive chemistry which has now been developed involving 2 and 3 as the starting materials, there exist few examples of complexes in which 1 has been used as synthon. The substitutional lability of the l-O 2 CCH 3 ligand in 1 has been demonstrated by its reaction with carboxylic acids in a fashion similar to that of cis-Re 2 (l-O 2 CCH 3 ) 2 Cl 2 (l-dppm) 2 . The reaction of 1 with isonicotinic acid affords the expected dirhenium(III,II) complex Re 2 (l-O 2 CC 5 H 4 N)Cl 4 (l-dppm) 2 [3] whereas with terephthalic acid the centrosymmetric ‘‘dimer-of-dimers’’ l-terephthalate complex [(l-dppm) 2 Cl 4 Re 2 ] 2 (l-O 2 CC 6 H 4 CO 2 ) [4] is formed. Similar dicarboxylate-bridged complexes are isolated with the use of adipic acid, fumaric acid and 4,4 0 -biphenyldicarb- oxylic acid [3]. When trans-1,4-cyclohexanedicarboxylic acid is used the reduced Re 2 4+ complex cis-Re 2 (l-O 2 CC 6 H 10 CO 2 Et) 2 Cl 2 (l- dppm) 2 was obtained [3]. On the other hand the reactions of 1 with tetrafluoro terephthalic acid and 1,1 0 -ferrocene dicarboxylic acid afford the known Re 2 Cl 4 (l-dppm) 3 complex [3]. When 1 is made to react with acetylene dicarboxylic acid the paramagnetic l- alkyne complex Re 2 (l-Cl)(l-g 2 -HCCH)Cl 4 (l-dppm) 2 [5] is formed whereas when 2-butynoic acid is used the diamagnetic l-carbyne complex Re 2 (l-Cl)(l-CCH 2 CH 3 )Cl 4 (l-dppm) 2 [5] is isolated by decarboxylation method. All the reactions cited above show that 1 contains labile l-O 2 CCH 3 group in combination with substitutionally inert dppm and Cl ligands, but none has yet been reported in which the dppm and the Cl ligands have been replaced by other suitable chelating or bridging ligands. Of the diverse array of dirhenium complexes that are known [6], few have been isolated that contain dithiocar- bamate ligand in the coordination sphere. The only compounds that we are aware of are the Re(IV)–Re(IV) dimer, Re 2 (l-S) 2 (S 2- CNR 2 ) 4 and the Re(III)–Re(III) dimer [Re 2 (l-SS 2 CNR 2 ) 2 (S 2 CNR 2 ) 3 ] + where R = Me and i Bu [7]. No other dithiocarbamato complexes of dirhenium are known where there is at least one Re–Re bond http://dx.doi.org/10.1016/j.ica.2014.07.047 0020-1693/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +91 33 25828750; fax: +91 33 25828282. E-mail address: icskc@klyuniv.ac.in (S. Chattopadhyay). Inorganica Chimica Acta xxx (2014) xxx–xxx Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica Please cite this article in press as: S. Mallick et al., Inorg. Chim. Acta (2014), http://dx.doi.org/10.1016/j.ica.2014.07.047