Journal
POLYHEDRON
Volume 119, Issue -, Pages 403-411Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.poly.2016.09.016
Keywords
Platinum(II); Triphenylphosphine; Dinuclear complexes; Divergent ligands; Cis-trans isomerism
Categories
Funding
- University di Pisa
- University di Pisa-Progetti di Ricerca di Ateneo [PRA_2015_0055]
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Dinuclear platinum(II) complexes [{PtCl2(PPh3)}(2)(mu-N-N)], where N-N is a divergent bidentate nitrogen ligand, were prepared by reacting cis-[PtCl2(PPh3)(NCMe)] with N-N in a Pt/N-N molar ratio 2. The (trans,trans)-isomers were obtained as kinetic products and recovered in good yields and high purity {1, N-N = pyrazine (pyrz); 2, N-N = 4,4'-bipyridyl (bipy); 3, N-N = piperazine (pipz); 4, N-N = p-xylylendiamine (xylN(2))}. Cis[PtCl2(PPh3)(NCMe)] was also reacted with the tridentate divergent ligand 2,4,6-tris-(pyrid-4'-yl)1,3,5-triazine (py3TRIA) in molar ratio 3 with formation of the trinuclear (trans, trans,trans)-[{PtCl2(PPh3)}(3)(mu-py3TRIA)], 5. On the other hand, the treatment of cis-[PtCl2(PPh3)(NCMe)] with the monodentate pyridine (py) produced a mixture of both trans-PtCl2(PPh3)(py)] (6a) and cis-[PtCl2(PPh3)(py)] (6b). The reactions of cis-[PtCl2(PPh3)(NCMe)] with N-N = pyrz, bipy, pipz, carried out with a Pt/N-N molar ratio 1, were monitored by P-31 NMR spectroscopy. Equilibria were observed in solution, involving dinuclear (trans-trans)-[{PtCl2(PPh3)}(2)(t-N-N)], mononuclear [PtCl2(PPh3)(N-N)] and free N-N. The addition of an excess of the divergent ligand allowed the complete conversion to the corresponding mononuclear complexes. With the heteroaromatic ligands both geometric isomers were observed (7a, 7b and 8a, 8b, for pyrz and bipy derivatives, respectively) while with pipz the trans-isomer only was detected, 9. In the system involving bipy, the scarcely soluble dinuclear (cis,cis)-[{PtCl2(PPh3)}(2)(mu-bipy)], 2b, was also obtained. Products 2, 2b, 3.2(CHCl3) and 6a.0.5(C2H4 Cl-2) were structurally characterized by single crystal X-ray diffraction methods. (C) 2016 Elsevier Ltd. All rights reserved.
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