Cyclodiphosphazane appended with pyridyl functionalities: Reactivity, transition metal chemistry and structural studies Guddekoppa S. Ananthnag a , Joel T. Mague b , Maravanji S. Balakrishna a, * a Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India b Department of Chemistry, Tulane University, New Orleans, LA 70118, USA article info Article history: Received 20 October 2014 Received in revised form 15 December 2014 Accepted 16 December 2014 Available online 24 December 2014 Keywords: Cyclodiphosphazane Multi dentate Transition metal complex Chelation Coordination X-ray structure abstract A pyridyl functionalized cyclodiphosphazane, cis-{(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 (1) was synthesized by reacting pyridine-2-methanol with cis-{(m-N t Bu)PCl} 2 . The reactions of cis-{(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 with chalcogenides in appropriate stoichiometry afforded both mono and bis-chalcogenides. The treatment of 1 with ML 2 Cl 2 (M ¼ Pd or Pt; L 2 ¼ COD, (SMe 2 ) 2 ) in 1:1 molar ratios resulted in the for- mation of mononuclear complexes, [MCl 2 {(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 ](8 M ¼ Pd; 9 M ¼ Pt), whereas the 1:2 reactions produced binuclear complexes [(MCl 2 ) 2 {(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 ] (10 M ¼ Pd; 11 M ¼ Pt). The reaction of 1 with [Ru(h 6 -p-cymene)(m-Cl)Cl] 2 afforded [((h 6 -p-cymene)RuCl 2 ) 2 {(m-N t Bu) P(OCH 2 C 5 H 4 N-o)} 2 ](13). Reaction of [Rh(m-Cl)(COD)] 2 with 1 in a 1:2 molar ratio yielded the mono- nuclear complex, [{(CO)RhCl} 2 {(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 ] (14), while the 1:1 reaction of [Rh(m- Cl)(CO) 2 ] 2 with 1 produced a binuclear complex [((CO)RhCl{(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 ](15). The treatment of 1 with AuCl(SMe 2 ) resulted in the formation of a binuclear complex [(AuCl) 2 {(m-N t Bu) P(OCH 2 C 5 H 4 N-o)} 2 ](16). The reaction of 1 with 2 equiv of CuBr gave coordination polymer [{Cu(m- Br)} 2 {(m-N t Bu)P(OCH 2 C 5 H 4 N-o)} 2 ] n (17). The crystal structures of 5, 8e10, 13 and 17 were established by single-crystal X-ray diffraction studies. © 2014 Elsevier B.V. All rights reserved. Introduction Hemilabile P,N donor ligands have received much attention due mainly to the structural diversity of their metal complexes and their usefulness in homogeneous catalysis [1e8]. These bidentate ligands can show either monodenate (h 1 -P) or chelating (h 2 -N,P) modes of coordination depending on the metal reagents and the reactions conditions. The slight difference in the Lewis acidity of donor atoms make them ideal suited for catalytic applications. The selective dissociation of one of the donor atoms from the metal center generates a vacant site on the metal for substrate coordi- nation. They can temporarily stabilize the reactive and coor- dinatively unsaturated intermediates during catalytic processes [9,10]. In this context, a large number of hemilabile P,N ligands have been developed and successfully employed in cross coupling reactions [11,12], hydroformylation [13,14], hydrogenation [15,16] and many other organic transformations [17e22]. The cyclodiphosphazanes or diazadiphosphetidienes are satu- rated four-membered inorganic rings containing alternating phosphorus and nitrogen atoms which generally show mono- dentate and bridged bidentate modes of coordination. A chelating mode of coordination is ruled out due to the rigid N 2 P 2 framework as the lone pairs on the phosphorus atoms are disposed away from each other. However, if donor functionalities are appended to the N 2 P 2 rings, it is then possible to form up to two chelate rings involving the ring phosphorus and the hetero donor atom on each side. Beside this they can also exhibit various other coordination modes [23e25]. In this context, we have synthesized several cyclodiphosphazane derivatives and studied their extensive coor- dination chemistry [26e29]. As an extension of our interest in cyclodiphosphazane system, in this paper, we describe the transi- tion metal complexes of cyclodiphosphazane appended with pyr- idyl groups. Results and discussion The reaction of 2 equiv of pyridine-2-methanol with cis-{(m- N t Bu)PCl} 2 in the presence of triethylamine yielded cis-{(m-N t Bu) * Corresponding author. Fax: þ91 22 5172 3480/2576 7152. E-mail addresses: krishna@chem.iitb.ac.in, msb_krishna@iitb.ac.in (M.S. Balakrishna). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem http://dx.doi.org/10.1016/j.jorganchem.2014.12.022 0022-328X/© 2014 Elsevier B.V. All rights reserved. Journal of Organometallic Chemistry 779 (2015) 45e54