UNCORRECTED PROOF 1 2 Organoplatinum(II) complexes with phosphite ligands 3 Ahmad R. Esmaeilbeig * , Hamid R. Samouei, Mehdi Rashidi 4 Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, Iran 5 6 8 article info 9 Article history: 10 Received 13 March 2008 11 Received in revised form 21 April 2008 12 Accepted 23 April 2008 13 Available online xxxx 14 Keywords: 15 Organoplatinum(II) complexes 16 Phosphite ligands 17 Multinuclear NMR 18 19 abstract 20 The phosphite complexes cis-[PtMe 2 L(SMe 2 )] in which L = P(O i Pr) 3 , 1a, or L = P(OPh) 3 , 1b, were synthe- 21 sized by the reaction of cis,cis-[Me 2 Pt(l-SMe 2 ) 2 PtMe 2 ] with 2 equiv. of L. If 4 equiv. of L was used the 22 bis-phosphite complexes cis-[PtMe 2 L 2 ] in which L = P(O i Pr) 3 , 2a, or L = P(OPh) 3 , 2b, were obtained. The 23 reaction of cis-[Pt(p-MeC 6 H 4 ) 2 (SMe 2 ) 2 ] with 2 equiv. of L gave the aryl bis-phosphite complexes cis- 24 [Pt(p-MeC 6 H 4 ) 2 L 2 ] in which L = P(O i Pr) 3 , 2a 0 , or L = P(OPh) 3 , 2b 0 . Use of 1 equiv. of L in the latter reaction 25 gave the bis-phosphite complex along with the starting complex in a 1:1 ratio. 26 The complexes failed to react with MeI. The reaction of cis,cis-[Me 2 Pt(l-SMe 2 ) 2 PtMe 2 ] with 2 equiv. of the 27 phosphine PPh 3 gave cis-[PtMe 2 (PPh 3 ) 2 ] and cis-[PtMe 2 (PPh 3 )(SMe 2 )] along with unreacted starting 28 material. Reaction of cis-[PtMe 2 L(SMe 2 )], 1a and 1b with the bidentate phosphine ligand bis(diphenyl- 29 phosphino)methane, dppm = Ph 2 PCH 2 PPh 2 , gave [PtMe 2 (dppm)], 8, along with cis-[PtMe 2 L 2 ], 2. The reac- 30 tion of cis-[PtMe 2 L(SMe 2 )] with 1/2 equiv. of the bidentate N-donor ligand NN = 4,4 0 -bipyridine yielded 31 the binuclear complexes [PtMe 2 L(l-NN)PtMe 2 L] in which L = P(O i Pr) 3 , 3a, or L = P(OPh) 3 , 3b. 32 The complexes were fully characterized using multinuclear NMR ( 1 H, 13 C, 31 P, and 195 Pt) spectroscopy. 33 Ó 2008 Published by Elsevier B.V. 34 35 36 1. Introduction 37 Phosphorus(III) ligands, especially phosphines and phosphites, 38 have extensively been used as auxiliary ligands in forming transi- 39 tion metal complexes. These ligands are very useful as they present 40 wide varieties of steric effects and electronic properties when coor- 41 dinated to transition metals. Thus, by changing the substituents at 42 the phosphorus atom, it is possible to greatly manipulate the 43 chemical behavior of their complexes. 44 Although organoplatinum complexes with phosphines, PR 3 , as 45 ligands are widely studied and the complexes have been involved 46 in many chemical transformations, the related organoplatinum 47 complexes with phosphite ligands, P(OR) 3 , have been far less 48 investigated [1]. One important reason for this disparity is that 49 the phosphites usually perform the ‘‘classical” Arbuzov rearrange- 50 ment during which a phosphonate molecule is formed, and this 51 property is often retained when they are coordinated to a transi- 52 tion metal [2]. Secondly, the platinum–phosphite complexes are 53 usually very soluble in organic solvents and easily form oils [3]. 54 In the present study, using suitable starting materials, we have 55 synthesized some primary organoplatinum(II) complexes contain- 56 ing the phosphite ligands L = P(O i Pr) 3 or P(OPh) 3 , of formula cis- 57 [PtMe 2 L(SMe 2 )], cis-[PtMe 2 L 2 ], or cis-[Pt(p-MeC 6 H 4 ) 2 L 2 ]. Some 58 reactions of the complexes, including reactions with the bidentate 59 N-donor, 4,4 0 -bipyridine, were also investigated. 60 2. Results and discussion 61 2.1. Synthesis and reactions of the complexes 62 The synthetic methods used to prepare the desired complexes 63 are described in Scheme 1. The reaction of organoplatinum(II) pre- 64 cursors cis-[PtR 2 (SMe 2 ) 2 ] (R = p-MeC 6 H 4 ) or cis,cis-[R 2 Pt(l-SMe 2 ) 2 - 65 PtR 2 ] (R = Me) with 2 equiv. or 4 equiv., respectively, of the 66 phosphite ligand L, L = P(O i Pr) 3 or P(OPh) 3 , in benzene gave cis- 67 [PtR 2 L 2 ], 2. When cis,cis-[Me 2 Pt(l-SMe 2 ) 2 PtMe 2 ] was reacted with 68 2 equiv. of L, the monosubstituted complexes cis-[PtMe 2 L(SMe 2 )], 69 1, were formed. Note that reaction of the starting complex cis- 70 [PtR 2 (SMe 2 ) 2 ] (R = p-MeC 6 H 4 ) with 1 equiv. of L did not give the 71 expected monosubstituted complexes cis-[PtR 2 L(SMe 2 )] and 72 instead the corresponding complexes 2 were obtained along with 73 the unreacted starting complex, in a 1:1 ratio. When 2 equiv. of 74 PPh 3 was reacted with 1 equiv. of cis,cis-[Me 2 Pt(l-SMe 2 ) 2 PtMe 2 ], 75 the di-substituted complex cis-[PtMe 2 (PPh 3 ) 2 ] was formed along 76 with the monosubstituted complex, cis-[PtMe 2 (PPh 3 )(SMe 2 )] in 77 an approximately 1:2 ratio, and small amount of the starting 78 complex. 79 All these observations could be explained in terms of the 80 p-acceptor ability or nucleophilicity of the phosphorus ligand. In 81 all these substitution reactions, it is known that they normally 82 proceed via a penta-coordinated intermediate involving bonding 83 of the incoming phosphorus ligand with the empty 6p z orbital of 84 the square-planar starting complex to form a square-pyramidal 85 species [5]. As such, the dimethylplatinum complexes 0022-328X/$ - see front matter Ó 2008 Published by Elsevier B.V. doi:10.1016/j.jorganchem.2008.04.034 * Corresponding author. E-mail address: esmaeilbeig@chem.susc.ac.ir (A.R. Esmaeilbeig). Journal of Organometallic Chemistry xxx (2008) xxx–xxx Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem JOM 15460 No. of Pages 8, Model 5G 19 May 2008 Disk Used ARTICLE IN PRESS Please cite this article in press as: A.R. Esmaeilbeig et al., J. Organomet. Chem. (2008), doi:10.1016/j.jorganchem.2008.04.034