Reactivity of the [CpM(PPh 3 ) 2 ] + (M = Ru, Os) fragment with diethyldithiocarbamate R. Lalrempuia a, * , Hauzachin Suante b , Hemant P. Yennawar c , Mohan Rao Kollipara a a Department of Chemistry, School of Physical Sciences, North Eastern Hill University, Shillong 793022, Meghalaya, India b Indian Institute of Technology Kanpur, Kanpur 208016, UP, India c Department of Biochemistry and Molecular Biology, The Pennsylvania State University, PA 16802, USA Received 11 July 2006; accepted 15 September 2006 Available online 29 September 2006 Abstract This paper reports on the reaction of [CpM(PPh 3 ) 2 (L)] +/0 (Cp = g 5 –C 5 H 5 ; M = Os, L = CH 3 CN, DMSO Br; M = Ru, X = Cl, CH 3 CN) with diethyldithiocarbamate (S 2 CNEt 2 À ). The exceptional kinetic stability of [Os–PPh 3 ] compared to [Ru–PPh 3 ] is reflected from the isolation of the monodentate diethyldithiocarbamate complex [CpOs(PPh 3 ) 2 (j 1 -S 2 CNEt 2 )] (3) and the bidentate diethyldithio- carbamate complex [CpRu(PPh 3 )(j 2 -S 2 CNEt 2 )] (5) as the only products. The structure of [CpOs(PPh 3 ) 2 (CH 3 CN)]BF 4 (2 Æ BF 4 ) and 5 were determined by X-ray diffraction. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Osmium; Ruthenium; Dithiocarbamates; Cyclopentadienyl; X-ray diffraction 1. Introduction Dithiocarbamates are versatile ligands, capable of form- ing complexes with all the transition elements and able to stabilize most in a range of oxidation states [1]. The CS 2 À group in dithiocarbamates (dtc) is usually a chelate but a few cases of monodentate dithiocarbamates are known [2]. Recently, Baird et al. have reported the unique chemis- try of amino acid dithiocarbamates with the Ru(III) system where a very interesting CS 2 À elimination phenomenon was observed [3]. As far as the [CpM(PPh 3 ) 2 X] (M = Ru, X = Cl; M = Os, X = Br) systems are concerned, these compounds serve as excellent precursors for various orga- nometallic complexes [4] and show very similar reactivity patterns except that the [Os]–PPh 3 bond is kinetically much more stable. Some dithiocarbamate as well as xanthate complexes have been known in both cases [5]. We have reported earlier, the preparation and reactivity of the ace- tonitrile complex [CpOs(PPh 3 ) 2 (CH 3 CN)]BF 4 (2 Æ BF 4 ) and have demonstrated that this compound is a much more desirable precursor for the preparation of chelate com- plexes of the type [CpOs(PPh 3 )(LL 0 )]BF 4 (LL 0 = bipy, phen) [6]. In pursuance of our interest in the synthesis of new complexes essentially bearing a cyclopentadienyl ligand, we wish to report here the contrasting reactivity behavior of the [CpM(PPh 3 ) 2 ] + (M = Os, Ru) fragment towards diethyldithiocarbamate. 2. Results and discussion The reaction of [CpOs(PPh 3 ) 2 Br] with the sodium salt of diethyldithiocarbamate, Na Æ S 2 CNEt 2 in acetonitrile sol- vent in the presence of NH 4 BF 4 under refluxing conditions lead to the formation of the monodentate [S 2 CNEt 2 ] com- plex [CpOs(PPh 3 ) 2 (j 1 -S 2 CNEt 2 )] (3) and a cationic com- plex, [CpOs(PPh 3 ) 2 (CH 3 CN)]BF 4 (2 Æ BF 4 ). Our earlier attempts to isolate pure 3 from [CpOs(PPh 3 ) 2 Br] and Na Æ S 2 CNEt 2 using methanol as a solvent were unsuccess- ful. The 1 H NMR spectrum showed the presence of a 1:1 ratio of complexes 3 and 2 Æ BF 4 in the crude product, apart from the resonances corresponding to 2 Æ BF 4 , the 0277-5387/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2006.09.042 * Corresponding author. Tel.: +91 389 2335159. E-mail address: lrpa@rediffmail.com (R. Lalrempuia). www.elsevier.com/locate/poly Polyhedron 26 (2007) 867–870