DOI: 10.1002/zaac.200500301 Reactivity Studies of η 5 - Indenyl and η 5 -Cp* Ruthenium(II) Complexes towards some Polypyridyl Ligands Keisham Sarjit Singh a , Yurij A. Mozharivskyj b , and Mohan Rao Kollipara a, * a Shillong / India, North-Eastern Hill University, Department of Chemistry b Ames, IA / USA, Iowa State University of Science and Technology, Ames Laboratory Received July 9 th , 2005. Abstract. The reaction of [(η 5 -L 3 )Ru(PPh 3 ) 2 Cl], where; L 3 = C 9 H 7 (1), C 5 Me 5 (Cp*) (2) with acetonitrile in the presence of [NH 4 ][PF 6 ] yielded cationic complexes [(η 5 -L 3 )Ru(PPh 3 ) 2 (CH 3 CN)][PF 6 ]; L 3 = C 9 H 7 ([3]PF 6 ) and L 3 = C 5 Me 5 ([4]PF 6 ), respectively. Complexes [3]PF 6 and [4]PF 6 reacts with some polypyridyl ligands viz, 2,3- bis (α-pyridyl) pyrazine (bpp), 2,3-bis (α-pyridyl) quinoxaline (bpq) yielding the complexes of the formulation [(η 5 - L 3 )Ru(PPh 3 )(L 2 )]PF 6 where; L 3 = C 9 H 7 ,L 2 = bpp, ([5]PF 6 ), L 3 = C 9 H 7 ,L 2 = bpq, ([6]PF 6 ); L 3 = C 5 Me 5 ,L 2 = bpp, ([7]PF 6 ) and bpq, ([8]PF 6 ), respectively. However reaction of [(η 5 - C 9 H 7 )Ru(PPh 3 ) 2 (CH 3 CN)][PF 6 ]([3]PF 6 ) with the sterically de- manding polypyridyl ligands, viz. 2,4,6-tris(2-pyridyl)-1,3,5-triazine 1 Introduction Cyclopentadienyl ruthenium(II) bisphosphine complexes [Cp'Ru(PPh 3 ) 2 Cl] (Cp'= Cp, Cp*, indenyl) have been im- mense interest owing to their high reactivity [1], catalytic activity [2] and interesting reactions towards some terminal alkynes [3, 4]. An extensive studied have been carried out on the cyclopentadienyl bisphosphine ruthenium complexes [5-7]. In contrast, the analogous indenyl and Cp* com- plexes have not been much studied. Literature survey re- veals that most of the reaction on indenyl and Cp*ru- thenium(II) phosphine complexes [(η 5 -C 9 H 7 )Ru(L) 2 Cl] (where, L = PPh 3 , PMe 2 Ph, PMePh 2 ) are centered on the reactions towards terminal acetylenes [3, 4]. However, the reaction of the complex [(η 5 -L 3 )Ru(PPh 3 ) 2 Cl] with N-base ligands are virtually unknown except a few report of such complexes appeared in the recent years [8]. It is noteworthy that complexes of indenyl and Cp* are differ from the anal- ogous cyclopentadienyl complexes in certain aspects such as higher reactivity and labile nature of the organic moieties . The higher reactivity of indenyl complexes is attributed to the ring slippage nature from η 5 - to η 3 - and back to η 5 of the indenyl ligand [9]. * Dr. Mohan Rao Kollipara Department of Chemistry, North-Eastern Hill University Shillong-793022 / India Tel. No. +91 364 272 2620; Fax no. +91 364 2550076 e-mail: kmrao@nehu.ac.in mohanraokollipara@yahoo.com 172  2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Z. Anorg. Allg. Chem. 2006, 632, 172-179 (tptz) or tetra-2-pyridyl-1,4-pyrazine (tppz) leads to the formation of unexpected complexes [Ru(PPh 3 ) 2 (L 2 )(CH 3 CN)][PF 6 ] 2 ;L 2 = tppz ([9](PF 6 ) 2 ), tptz ([11](PF 6 ) 2 ) and [Ru(PPh 3 ) 2 (L 2 )Cl][PF 6 ]; L 2 = tppz ([10]PF 6 ), tptz ([12]PF 6 ). The complexes were isolated as their hexafluorophosphate salts. They have been characterized on the basis of micro analytical and spectroscopic data. The crystal structures of the representative complexes were established by X- ray crystallography. Keywords: Ruthenium; Indenyl; Crystal structure; Triazine; Pyra- zine We had earlier reported the syntheses of indenyl, penta- methylcyclopentadienyl ruthenium complexes containing N, N donor Schiff’s base [10] and azine ligands [11]. In con- tinuation of our study, here we wish to report the reaction of [(η 5 -C 9 H 7 )Ru(PPh 3 ) 2 (CH 3 CN)][PF 6 ]([3]PF 6 ) and [(η 5 - C 5 Me 5 )Ru(PPh 3 ) 2 (CH 3 CN)][PF 6 ]([4]PF 6 ) with some poly- pyridyl ligands viz, 3-bis (α-pyridyl) pyrazine (bpp), 2,3-bis (α-pyridyl) quinoxaline (bpq), 2,4,6-tris(2-pyridyl)-1,3,5- triazine (tptz), tetra-2-pyridyl-1,4-pyrazine (tppz). The li- gands involve in the study are shown in scheme 1. In the case of reaction of [η 5 -CpRu(PPh 3 ) 2 Cl] with tppz and tptz, we obtained the complexes of the type [CpRu(PPh 3 )(L 2 )] + ; (L 2 = tppz or tptz ligand), where the Cp ligand remain intact to metal [12]. In contrast, in this present study the reaction of [(η 5 -C 9 H 7 )Ru(PPh 3 ) 2 (CH 3 CN)][PF 6 ]([3]PF 6 ) with tppz or tptz ligand, we isolated unexpected complexes [Ru(PPh 3 ) 2 (L 3 )(CH 3 CN)] 2+ and [Ru(PPh 3 ) 2 (L 3 )(Cl)] + (L 3 = tppz or tptz). The complexes were fully characterized by elemental analyses, 1 H, 31 P{ 1 H} NMR spectroscopy. The molecular structures of the compound ([9](PF 6 ) 2 ) and ([12]PF 6 ) have been determined by X-ray crystallogra- phy. 2 Results and Discussion 2.1 Reaction of ([3]PF 6 ) or ([4]PF 6 ) with bpp and bpq The reaction of ([3]PF 6 ) or ([4]PF 6 ) with excess of bpp or bpq ligand in refluxing methanol affords the complexes [(η 5 -L 3 )Ru(PPh 3 )(L 2 )][PF 6 ] (scheme 2) as the only product