Heteropolynuclear palladium complexes with pyrazolate and its 3-tert-butyl derivatives: the effect of heterometal ions on the rate of isomerization

Chemistry : a European Journal
Keisuke UmakoshiMasayoshi Onishi

Abstract

The heteropolynuclear complexes [Pd(2)M'(2)(mu-pz)(6)] (M'=Ag (1), Au (2); pzH=pyrazole), HT-[Pd(2)M'(2)(mu-3-tBupz)(6)] (M'=Ag (3 a), Au (4 a); 3-tBupzH=3-tert-butylpyrazole), and HH-[Pd(2)Au(2)(mu-3-tBupz)(6)] (4 b) have been prepared and some of them were structurally characterized. When 3-tert-butylpyrazolate was employed as a bridging ligand, two linkage isomers (head-to-tail (HT) and head-to-head (HH)) arise from the difference in orientation of the substituent groups on the pyrazolate bridges between the two Pd atoms. (1)H NMR spectroscopy has been used to identify and to follow the reversible stereochemical rearrangement of the HH isomer of [Pd(2)Ag(2)(mu-3-tBupz)(6)] (3 b) to form the HT isomer 3 a in CDCl(3) and the HT isomer of [Pd(2)Au(2)(mu-3-tBupz)(6)] (4 a) to form the HH isomer 4 b in C(6)D(6). Kinetic studies of the reaction have established the rate law to be -d(HH)/dt=d(HT)/dt=k(2)[HH]-k(1)[HT] for 3 b and -d(HT)/dt=d(HH)/dt=k(1)[HT]-k(2)[HH] for 4 a, where k(1) and k(2) denote the rate of isomerization from the HT to the HH isomer and that from the HH to the HT isomer, respectively. For typical runs at 50 degrees C in C(6)D(6), k(1)=13.8x10(-5) s(-1), k(2)=18.6x10(-5) s(-1), and K(eq)=k(2)/k(1)=1.24 for 3 b,...Continue Reading

References

Jul 19, 2002·Chemical Communications : Chem Comm·Peter BaranRaphael G Raptis
Apr 16, 2003·Inorganic Chemistry·Guang Yang, Raphael G Raptis
Jul 17, 2003·Chemistry : a European Journal·Juan ForniésL Francisco Martín
Sep 10, 2004·Dalton Transactions : an International Journal of Inorganic Chemistry·Xiaoming LiuMalcolm A Halcrow

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Citations

Dec 10, 2015·Dalton Transactions : an International Journal of Inorganic Chemistry·María-José Fernández-RodríguezPeter G Jones
Mar 11, 2009·Dalton Transactions : an International Journal of Inorganic Chemistry·Malcolm A Halcrow
Jan 20, 2011·Dalton Transactions : an International Journal of Inorganic Chemistry·Shao-Hua YanLin-Pei Jin
Sep 23, 2014·Dalton Transactions : an International Journal of Inorganic Chemistry·Jun YoshidaJun Okabayashi

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