The synthesis of rhodium(III) and iridium (III) half sandwich complexes [Cp*M(PEt 3)(S-R-S)], M = Rh, Ir; S-R-S = naphthalene-1,8-dithiolate (NaphthS 2 , a), acenaphthene-5,6-dithiolate (AcenapS 2 , b) and biphenyl-2,2'-dithiolate (BiphenS 2 , c) is reported. We also describe the isolation of a new compound acenaphthene-1,8-dithiol. All complexes have been fully characterised using multinuclear NMR spectroscopy and single crystal X-ray diffraction. The ligands naphthalene-1,8-dithiol (H 2 a), acenaphthene-1,8-dithiol (H 2 b), 1,1'-biphenyl-2,2'dithiol (H 2 c) and benzene-1,2-dithiol (H 2 d) have also been characterised by single crystal Xray diffraction. With the exception of the electron transfer mimics the coordination chemistry of 1,1'biphenyl-2,2'dithiolate has seen little investigation. Two molybdenum based complexes have been synthesised with one bearing an Mo oxygen triple bond.[23, 24] A derivatised version of the ligand has been bound to copper[25] with mono-and dinuclear nickel complexes also reported.[26] There has also been two reports on methods to synthesise titanocene-2,2'-dithiolatobiphenyl.[27, 28] Herein we describe the synthesis of a series of dithiolato complexes bound to rhodium(III) and iridium(III) metal centres. We also report the isolation of a new dithiol, acenaphthene-1,8-dithiol, along with crystallographic studies of naphthalene-1,8-dithiol, 1,1'-biphenyl-2,2'dithiol and benzene-1,2-dithiol. All new complexes and the new dithiol have been fully characterised principally by multinuclear NMR spectroscopy, elemental analysis and single crystal X-ray diffraction. Results and Discussion The diprotic pro-ligands naphthalene-1,8-dithiol [Naphth(SH) 2 ] (H 2 a), acenaphthene-5,6dithiol [Acenap(SH) 2 ] (H 2 b) and 1,1'-biphenyl-2,2'-dithiol [Biphen(SH) 2 ] (H 2 c) were synthesised from their respective disulfides naphtho[1,8-cd]-1,2-dithiole,[32] 5,6dihydroacenaphtho[5,6-cd]-1,2-dithiole[31] and dibenzo[c,e]-1,2-dithiin[33] (Scheme 1). The reduction of disulfides was performed using NaBH 4 ,[34] which was followed by an acidic workup after which all three pro-ligands were isolated as colourless solids, each possessing only a mild thiol odour. Benzene-1,2-dithiol (H 2 d) was prepared according to literature and purified by distillation to afford a colourless liquid with a strong thiol odour (Scheme 1).[35] H 2 a, H 2 c and H 2 d were isolated and spectroscopically characterised earlier,[33, 34, 36] for completeness we report their X-ray structures here. In contrast, H 2 b was not isolated previously, and we report full spectral characterisation as well as its X-ray structure.

The synthesis of a range of rhodium(iii) and iridium(iii) half sandwich complexes with aryl dithiolato ligands of varying geometry and flexibility are reported. These include dinuclear [Cp*M(S-R-S)]2 complexes 3b and 4b, M = Rh, Ir; S-R-S = naphthalene-1,8-dithiolate (b) and four dinuclear complexes bearing bridging dithiolate ligands [(Cp*M)2(μ2-Cl)(μ2-S-R-S)]Cl 3c, 4c, 5b, 6b, M = Rh, Ir; S-R-S = naphthalene-1,8-dithiolate (b) or acenaphthene-5,6-dithiolate (c). The introduction of a less rigid biphenyl dithiolate backbone resulted in the tetranuclear dicationic complex [(Cp*Rh)4(S-R-S)3]Cl2 (3d), S-R-S = biphenyl-2,2'-dithiolate (d) with dithiolate ligands in two different bridging modes. All new complexes were fully characterised by multinuclear NMR, IR, Raman and MS spectroscopy and single crystal X-ray diffraction.