Synthesis, molecular structure and stability of fused bicyclic Δ4-1,2,4-oxadiazoline Pt(II) complexes

The reaction of trans-[PtCl2(NCR)(2)] (R-1 = CH2CO2Me (1a), R-2 = CH2C; (1b)) with pyrroline N-oxide -O+(N) under bar =CHCH2(C) under barH(2)CMe(2) (4), at room temperature for 15 min, furnishes via [3+2] cycloaddition the fused bicyclic Delta(4)-1,2,4-oxadiazoline Pt(II) complexes trans-[PtCl2((N) under bar =C(R)O (N) under barC(H)CH2CH2(C) under bar Me-2}(2)] (R-1 = CH2CO2Me (5a), R-2 = CH2Cl (5b)). compounds 5a and 5b were refluxed in CH2Cl2 for 1 week to afford the derived ketoimine Pt(II) complexes trans-[PtCl2{N(C(=O)(R))=(C) under bar CH2CH2C(Me-2)(N) under barH)(2)] (R-1 = CH2CO2Me (6a), R-2 = CH2Cl (6b)), respectively, as a result of the N-O bond cleavage of the oxadiazoline ring in 5. The complexes were characterized by IR, H-1 and C-13 NMR spectroscopies, ESI+-MS and elemental analyses. OFT calculations show that the Pt(II)-catalysed [3+2] cycloaddition reaction (4 + 10 -> 11) is spontaneous and exergonic. In addition, the reaction is completely regioselective yielding a unique oxadiazoline. Moreover, the molecular structure, spectroscopic and electronic properties of complex 5b were predicted, and the optimized geometry showed a slightly distorted square planar arrangement around the Pt(II) centre. (C) 2015 Elsevier Ltd. All rights reserved.