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Lookup NU author(s): Dr Mark Elsegood
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A series of lanthanide complexes containing a chalcogenolate ligand supported by two Tp(Me,Me) (tris-3,5-dimethylpyrazolylborate) groups has been prepared and crystallized and provides direct comparisons of bonding to hard and soft ligands at lanthanide centers. Reaction of [Sm(Tp(Me,Me))2Cl] with NaOR (R = Ph, Ph-Bu(t)) gives [Sm(Tp(Me,Me))2OR] (1a and 1b, respectively) in good yields. Reductive cleavage of dichalcogenides by samarium-(II) was used to prepare the heavier congeners. Complexes of the type [Sm(Tp(Me,Me))2ER] for E = S, R = Ph (2a), E = S, R = Ph-4-Me (2b), E = S, R = CH2Ph (2c), E = Se, R = Ph (3a), E = Se, R = Ph-4-Bu(t) (3b), E = Se, R = CH2Ph (3c), and E = Te, R = Ph (4) have been prepared together with the corresponding complexes with Tp(Me,Me,4-Et) as ancillary. The X-ray crystal structures of 1b, 2b, 3a, 3b, and 4 have been determined. The crystal of 1b (C40H57B2N12OSm·C7H8) was monoclinic, P21/c, a = 10.6845(6) Å, b = 18.5573(11) Å, c = 24.4075(14) Å, β = 91.616(2)°, Z = 4. The crystal of 2b (C37H51B2N12SSm) was monoclinic, P21/n, a = 15.0154(9) Å, b = 13.1853(8) Å, c = 21.1254(13) Å, β = 108.628(2)°, Z = 4. The crystal of 3a (C36H49B2N12SeSm·C7H8) was triclinic, P1̄, a = 10.7819(6) Å, b = 19.3011(10) Å, c = 23.0235(12) Å, α = 79.443(2)°, β = 77.428(2)°, γ = 89.827(2)°, Z = 4. The crystal of 3b (C40H57B2N12SeSm) was triclinic, P1̄, a = 10.1801(6) Å, b = 10.2622(6) Å, c = 23.4367(14) Å, α = 88.313(2)°, β = 86.268(2)°, γ = 62.503(2)°, Z = 2. The crystal of 4 (C36H49B2N12TeSm·C7H8) was monoclinic, P21/c, a = 18.7440(10) Å, b = 10.3892(6) Å, c = 23.8351(13) Å, β = 94.854(2)°, Z = 4. The compounds form an isoleptic series of seven-coordinate complexes with terminal chalcogenolate ligands. Examination of 1b and other crystallographically characterized lanthanide alkoxides suggests that there is little correlation between bond angle and bond length. The structures of 3a and 3b, however, contain molecules in which one of the pyrazolylborate ligands undergoes a major distortion arising from twisting around a B - N bond so as to give an effectively eight-coordinate complex with π-stacking of the phenyl group with one pyrazolyl ring. These distortions shed light on the fluxionality of these systems.
Author(s): Hillier AC, Liu S-Y, Sella A, Elsegood MRJ
Publication type: Article
Publication status: Published
Journal: Inorganic Chemistry
Year: 2000
Volume: 39
Issue: 12
Pages: 2635-2644
ISSN (print): 0020-1669
ISSN (electronic): 1520-510X
Publisher: American Chemical Society
URL: http://dx.doi.org/10.1021/ic9914793
DOI: 10.1021/ic9914793
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