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DOI: 10.1039/A805300F (Paper) Reference Section for: J. Chem. Soc., Dalton Trans., 1998, 3479-3488

Synthesis and dynamic NMR studies of fluxionality in rhenium(I), platinum(II) and platinum(IV) complexes of ‘back-to-back’ 2,2′∶6′,2″-terpyridine ligands

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Andrew Gelling, Matthew D. Olsen, Keith G. Orrell, Anthony G. Osborne and Vladimir Šik

Abstract

Syntheses are given for the following transition metal complexes, [{ReBr(CO)3}2L] (L = L1, L2 or L3), [(PtClMe3)2L1], [(PtIMe3)2L] (L = L2 or L3), [ReBr(CO)3L1], [Pt(C6F5)2L3], [Pt(C6F4CF3)2L] (L = L1 or L2), [{Pt(C6F4CF3)2}2L] (L = L1 or L2) and [ReBr(CO)3PtIMe3L1] where the ligands, L, are the ‘back-to-back’ terpyridine ligands, 6′,6″-bis(2-pyridyl)-2,2′∶4′,4″∶2″,2‴-quaterpyridine (L1), 1,4-bis(2,2′∶6′,2″-terpyridin-4′-yl)benzene (L2) and 6′,6″-bis{2-(4-methylpyridyl)}-2,2′∶4′,4″∶2″,2‴-quaterpyridine (L3). All the complexes undergo 1,4-metallotropic shifts in solution at above-ambient temperatures and restricted rotations of the pendant pyridyl rings at below-ambient temperatures. Activation energies for these processes have been computed from variable temperature one-dimensional bandshape analysis and 2D-exchange spectroscopy (2D-EXSY) NMR experiments. The metallotropic shift energies are very metal-dependent being in the order PtIV < ReI < PtII, with ΔG[hair space] ‡ (298.15 K) values ranging from 62 to 101 kJ mol–1. The fluxions are sensitive only to the local metal-coordination environment, there being negligible electronic interaction between the metal centres in the dinuclear complexes. In the mixed-metal dinuclear complex [ReBr(CO)3PtIMe3L1] it proved possible to measure the different rates of fluxion of the ReI and PtIV moieties.

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