Abstract
The [2+3] cycloaddition reaction (which is greatly accelerated by microwave irradiation) of the bis(azido)platinum(II) compound cis-[Pt(N-3)(2)(PPh3)(2)] (1) with 4-cyanobenzaldehyde (2) furnishes the (NN2)-N-2-bonded isomer of bis[5-(4-formylphenyl)tetrazol-2-ate) platinum(II) trans-[Pt{N4CC6H4- (4-CH=O)}(2)(PPh3)(2)] (3a) as the major product, along with the (NN2)-N-1-bonded isomer 3b. Treatment of 3a with 2-dimethyl-aminoethylamine (4), in refluxing methanol, gives the corresponding (NN2)-N-2-bonded bis[(E)-5-(4-{[2-(dimethylamino)ethylamino]methyl}phenyl)tetrazol-2-ate] platinum(II) complex trans-[Pt{N4CC6H4(4-CH=NCH2CH2NMe2)}(2) (PPh3)(2)] (6) in good yield. An alternative route involves the reaction of 4-cyanobenzaldehyde (2) with diamine 4 to give the E isomer of 4-{[2-(dimethylamino)ethylimino]methyl}benzonitrile N CC6H4(4-CH=NCH2CH2NMe2) (5), followed by the reaction of the latter with bis (azido) platinum (11) complex 1 to afford 6 in similar yield, The reaction of 6 with MCl2 (M = Pd, Ni, Zn, Cu), at room temperature for 3 h regenerates complex 3a as a result of the Schiff base hydrolysis, along with the diamine complex [MCl2(NH2CH2CH2NMe2)] (7). Treatment of 6 with ZnCl2 for 36 h affords a mixture of 3a with its substitution products [Pt{HN4CC6H4(4-CH=O)}(NH2CH2CH2NMe2)(PPh3)]Cl-2 (9; isolated in the tetrazole form) and cis[PtCl2(PPh3)(2)] (10) and diamine complex 7 (M = Zn). The [2+3] cycloaddition reactions of cis-[Pt(N-3)(2)(PPh3)(2)] (1) with unsubstituted dicyanobenzenes 11 [1,2-C6H4(CN)(2) (11a), 1,3-C6H4(CN)(2) (11b), 1,4-C6H6(CN)(2) (11c)] occur regioselectively and give the corresponding (NN2)-N-2-bonded bis[5-(cyanophenyl)tetrazol-2-ate] trans-[Pt(N4CC6H4R)(2)(PPh3)(2)] complexes 12 (R = 2-CN 12a, 3-CN 12b, 4-CN 12c). The isolated compounds were characterized by IR, H-1 NMR, C-13 NMR and P-31(H-1) NMR (metal complexes) spectroscopy, elemental analyses, ESI-MS and X-ray structural analyses (for 3a, 5 center dot HCl, 7, 9 and 12a). ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)