Synthesis and reactions of new 1,2- and 1,3-cyclopentadienyl disubstituted cobalt sandwich compounds (h 5 -C 5 H 3 R 2 )Co(h 4 -C 4 Ph 4 ) (R]CH 2 OH, CHO, C^CH, CH 2 N 3 , CH 2 NH 2 , CH 2 OAc, CH]NPh) Nem Singh, Bhanu P.R. Metla, Anil J. Elias * Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India article info Article history: Received 31 May 2012 Received in revised form 9 July 2012 Accepted 16 July 2012 Keywords: Cyclopentadienyl Cyclobutadiene Cobalt bis(hydroxymethyl) bis(azidomethyl) abstract Synthesis and characterization of a series of 1,3- and 1,2-cyclopentadienyl disubstituted derivatives of h 5 - C p Co(h 4 -C 4 Ph 4 ) has been described. The 1,3- and 1,2-cyclopentadienyl diester derived cobalt sandwich compounds {h 5 -C 5 H 3 [C(O)OMe] 2 }Co(h 4 -C 4 Ph 4 ) were prepared by literature procedure and were sepa- rated by column chromatography. The reduction of these diester derivatives using LiAlH 4 gave the bis(hydroxymethyl) derivatives, [1,3-h 5 -C 5 H 3 (CH 2 OH) 2 ] Co(h 4 -C 4 Ph 4 ) 1 and [1,2-h 5 -C 5 H 3 (CH 2 OH) 2 ] Co(h 4 -C 4 Ph 4 ) 2 which were oxidized to the dialdehydes [1,3-h 5 -C 5 H 3 (CHO) 2 ]Co(h 4 -C 4 Ph 4 ) 3 and [1,2-h 5 - C 5 H 3 (CHO) 2 ]Co(h 4 -C 4 Ph 4 ) 4 by using tetrapropylammonium perruthenate along with N-methyl mor- pholine oxide. Reaction of the dialdehydes with (chloromethyl)triphenylphosphonium chloride/n-BuLi followed by elimination of HCl using n-BuLi resulted in the 1,2- and 1,3-cyclopentadienyl disubstituted dialkynes [1,3-h 5 -C 5 H 3 (C^CH) 2 ]Co(h 4 -C 4 Ph 4 ) 5 and [1,2-h 5 -C 5 H 3 (C^CH) 2 ]Co(h 4 -C 4 Ph 4 ) 6. The reactions of 1 and 2 with NaN 3 in acetic acid resulted in the bis(azidomethyl) derivatives [1,3-h 5 -C 5 H 3 (CH 2 N 3 ) 2 ] Co(h 4 -C 4 Ph 4 ) 7 and [1,2-h 5 -C 5 H 3 (CH 2 N 3 ) 2 ]Co(h 4 -C 4 Ph 4 ) 8. Heating of bis(hydroxymethyl) compounds 1 and 2 in acetic acid at 85e90  C resulted in the formation of bis(2-acetoxymethyl) derivatives [1,3-h 5 - C 5 H 3 (CH 2 OAc) 2 ]Co(h 4 -C 4 Ph 4 ) 9 and [1,2-h 5 -C 5 H 3 (CH 2 OAc) 2 ]Co(h 4 -C 4 Ph 4 ) 10. The reactions of 1 and 2 with thiophenol in the presence of trifluoroacetic acid in dichloromethane gave bis(phenylmethyl thi- oether) derivatives 11 [1,3-h 5 -C 5 H 3 (CH 2 SPh) 2 ]Co(h 4 -C 4 Ph 4 ) and [1,2-h 5 -C 5 H 3 (CH 2 SPh) 2 ]Co(h 4 -C 4 Ph 4 ) 12. The click reaction of the 1,2-dialkyne 6 with benzyl azide resulted in the 1,2-bis(triazole) derivative 13. The 1,3-diazide 8 was reduced to bis(aminomethyl) derivative [1,3-h 5 -C 5 H 3 (CH 2 NH 2 ) 2 ]Co(h 4 -C 4 Ph 4 ) 14. Condensation of the 1,3-dialdehyde 3 with aniline resulted in the 1,3-bis(phenylimino) derivative 15. All the new compounds synthesized in this study were characterized by 1 H and 13 C NMR, FT-IR, HRMS, CHN analysis. The compounds 2e6, 8 and 10 have also been structurally characterized by single crystal X-ray diffraction analysis. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Aryl rings with functional groups at the 1,2 and 1,3 positions and heteroaryl rings with functional groups flanking the heteroatom are excellent precursors for preparing a wide variety of chelating and multidentate ligands. The classic examples for such bidentate ligands are the chiral box (bis oxazoline) ligands which, along with metal compounds have been used extensively in asymmetric catalysis [1e5]. Achiral bidentate ligands have also been prepared from 1,2 to 1,3-disubstituted aryl rings, the latter being used extensively for the preparation of pincer type complexes [6e8]. Recently there has been a surge of activity in preparing such bidentate ligands using stable metal sandwich compounds, espe- cially with ferrocene as the substrate [9e14]. 1,2- and 1,3- disubstitution of a Cp ring of ferrocene can be achieved with rela- tive ease and many examples of multiple phosphine, amine and heterocycle derived ferrocenes are available in the literature [15e19]. Such compounds have shown promising activity in diverse areas such as antitubercular agents, as receptors for recognition of barbiturates and glucose sensors [20e22]. Apart from realizing bidentate ligands, the ferrocene scaffold has also been derivatized with terminal alkyne units at the 1 and 2 positions to prepare novel alkyne linked multiferrocenyl assemblies [23e28]. Among non-ferrocenyl, highly stable and easily accessible sandwich compounds, (h 5 -Cp)Co(h 4 -C 4 Ph 4 ) has attracted consid- erable interest especially for the synthesis of chiral and sterically * Corresponding author. Tel.: þ91 11 26591504. E-mail address: eliasanil@gmail.com (A.J. Elias). Contents lists available at SciVerse ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem 0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jorganchem.2012.07.023 Journal of Organometallic Chemistry 717 (2012) 99e107