F. Rochon, Viorel Buculei
Jun 10, 2004
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Influential Citations
39
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Journal
Inorganica Chimica Acta
Abstract
Complexes of the types cis - and trans -Pt(amine) 2 I 2 were studied by spectroscopic methods, especially by multinuclear NMR spectroscopy. In 195 Pt NMR, the cis diiodo compounds with primary amines were observed between −3342 and −3357 ppm in acetone, while the trans compounds were found between −3336 and −3372 ppm. For the secondary amines, the chemical shifts were observed at lower fields. In 1 H NMR, the trans complexes were observed at higher fields than the cis compounds, while in 13 C NMR, the reverse was observed. The 2 J ( 195 Pt– 1 H) and 3 J ( 195 Pt– 1 H) coupling constants are larger for the cis compounds (ave. 67 and 45 Hz, respectively) than for the trans isomers (ave. 59 and 38 Hz). In 13 C NMR, the values of 2 J ( 195 Pt– 13 C) and 3 J ( 195 Pt– 13 C) were also found to be larger for the cis complexes (ave. 17 and 39 Hz versus 11 and 28 Hz). There seems to be a slight dependence of the p K a values of the protonated amines or the proton affinity in the gas phase with the δ (Pt) chemical shifts. The crystal structures of eight diiodo complexes were determined. These compounds are cis -Pt(CH 3 NH 2 ) 2 I 2 , cis -Pt(n-C 4 H 9 NH 2 ) 2 I 2 , cis -Pt(Et 2 NH) 2 I 2 , trans -Pt(n-C 3 H 7 NH 2 ) 2 I 2 , trans -Pt( iso -C 3 H 7 NH 2 ) 2 I 2 , trans -Pt(n-C 4 H 9 NH 2 ) 2 I 2 , trans -Pt(t-C 4 H 9 NH 2 ) 2 I 2 and trans -Pt(Me 2 NH) 2 I 2 . The Pt–N bond distances located in trans position to the iodo ligands were compared to those located in trans position to the amines. The Pt–N bond in cis -Pt(Et 2 NH) 2 I 2 are much longer than the others, probably caused by the steric hindrance of the two very bulky ligands located in cis positions.