X-ray structural and nuclear magnetic resonance study of open chain and macrocyclic thioether complexes

Abstract

. Can. J. Chem. 68, 1357 (1990). Preparations of the thiophenophane and open chain thioether complexes MX2.BBTE (M = Pd; X = C1, I) (M = Pt; X = C1) (BBTE = 1,2-bis(benzy1thio)ethane) and MX2.L (M = Pd; X = C1, Br, I, SCN) (M = Pt; X = C1) (L = 2,5,8-trithia[9](2,5)thiophenophane) are described. The molecular structure of PdBr2.L which contains a weak thiophene-sulfur-topalladium interaction has been determined: space group P2]/n, a = 8.3569(3), b = 16.3254(15), c = 11.1462(3) A, P = 92.833(4)", Z = 4, Rf = 0.060, R, = 0.058. The electronic, low frequency ir, and I3C nrnr spectra are described. Variable temperature 'H nmr spectra are discussed and it is concluded that the open chain complexes undergo rapid conformational exchange at room temperature but are configurationally rigid unless the temperature is increased. In contrast, the macrocyclic complexes undergo very limited conformational and no configurational exchange up to theu decomposition temperatures. They are also nonfluxional in the same temperature range. Chemical exchange of acidic ligand hydrogens and a metal-ligand dissociative equilibrium were also detected when X = SCN.Key words: thiophene, thioether, macrocyclic metal complexes. On discute des spectres rmn du 'H a tempkrature variable et on en conclut que, a la temptrature ambiante, les complexes avec des chaines ouvertes subissent des tchanges conformationnels rapides; toutefois, ils sont rigides d'un point de vue configurationnel, i moins que l'on augmente la temptrature. Par ailleurs, lorsqu'on soumet les complexes avec des macrocycles B des temptratures allant jusqu'i leurs temptratures de dtcomposition, ils ne subissent que des tchanges conformationnels et configurationnels trts limitts. Dans le cas oil X = SCN, on a aussi dttectt un tchange chimique impliquant les hydrogtnes acides agissant comme ligands ainsi qu'un tquilibre mttal ligand impliquant une dissociation.

Thiophenophane metal complexes IV. Effects from ligand changes outside the coordination sphere

“…For the macro-A complete set of data may be purchased from: The Depository of Unpublished Data, CISTI, National Research Council Canada, Ottawa, Canada KIA OS2. Except for the anisotropic thermal parameters, the data mentioned above have also been deposited with the Cambridge Crystallographic Data Centre, University Chemical Laboratory, 12 Union Road, Cambridge, CB2 lEZ, U.K. cyclic ligand, all thioether sulfur lone pairs are exocyclic in a manner reminiscent of other thiophenophanes as free ligands or in some of their complexes (15)(16)(17)(18)(19). Rigidity imposed by the thiophene units on the macrocyclic ring limits the ring's ability to place its thioether electron pairs endocyclic during complex formation, as has been noted previously in thiophenophane complexes (15).…”

Crystal and solution structure of a pendant-armed macrocyclic complex of palladium(II)

“…There are also several recent examples of fluxionality at Pd(I1) detected by NMR spectroscopy involving both pendant armed and simple macrocyclic ligands (6,7). In particular, several complexes with thia-macrocyclic ligands have been examined (8,9). In the present paper, the synthesis of the ligand 1-thia-4,7-bis(pyridy1methyl)diazacyclononane (py2 [9]aneN2S) (Scheme 1) is reported together with the crystal structure of its palladium(I1) complex.…”

“…The tris(pyridylmethy1)-1,4,7-triazacyclonane (py3 [9]aneN3) complex of Pd(I1) has been shown to contain a square pyramidal PdN5 core, in which the metal-coordinated and -uncoordinated pyridine nitrogens interconvert within the NMR time scale (5). There are also several recent examples of fluxionality at Pd(I1) detected by NMR spectroscopy involving both pendant armed and simple macrocyclic ligands (6,7).…”

“…In the present paper, the synthesis of the ligand 1-thia-4,7-bis(pyridy1methyl)diazacyclononane (py2 [9]aneN2S) (Scheme 1) is reported together with the crystal structure of its palladium(I1) complex. The metal complex provides an interesting contrast to [~d (~~, [ 9 ] a n e~~) ]~+ in that the presence of only two arms prohibits a complete scrambling of the coordination environment but does not preclude the possibility of fluxional NMR spectroscopy.…”

“…The coordination of the [9]aneN2S ring in a facial geometry results in the sulfur atom being positioned axially1 such that the inter-atomic distance is borderline between a "bonding" and "non-bonding" interaction. One method of investigating such potential bonding is to compare the torsional angles within the 9-membered ring of the present complex with those for IS.…”