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Coordination of Lanthanide Triflates and Perchlorates with N,N,N‘,N‘-Tetramethylsuccinamide

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journal contribution
posted on 29.09.2000, 00:00 by Brian M. Rapko, Bruce K. McNamara, Robin D. Rogers, Grant A. Broker, Gregg J. Lumetta, Benjamin P. Hay
Compounds formed from the reaction of N,N,N‘,N‘-tetramethylsuccinamide (TMSA) with trivalent lanthanide salts possessing the poorly coordinating counteranions triflate (CF3SO3-) and perchlorate (ClO4-) have been prepared and examined. Structural features of these Ln−TMSA compounds have been studied in the solid phase by thermogravimetric analysis, infrared spectroscopy, and, in selected cases, by single-crystal X-ray diffraction and in solution by infrared spectroscopy. Eight-coordinate compounds, [Ln(TMSA)4]3+, derived from coordination of four succinamide ligands to the metal ion could be formed with all lanthanides examined (Ln = La, Pr, Nd, Eu, Yb, Lu). Structural analyses by single-crystal X-ray diffraction were performed for the lanthanide triflate salts Ln(C8H16N2O2)4(CF3SO3)3:  Ln = La, compound 1, monoclinic, P21/n, a = 11.0952(2) Å, b = 19.2672(2) Å, c = 24.9759(3) Å, β = 90.637(1)°, Z = 4, Dcalcd = 1.586 g cm-3; Ln = Nd, compound 2, monoclinic, C2/c, a = 24.6586(10) Å, b = 19.3078(7) Å, c = 11.1429(4) Å, β = 90.450(1)°, Z = 4, Dcalcd = 1.603 g cm-3; Ln = Eu, compound 3, monoclinic, C2/c, a = 24.4934(2) Å, b = 19.3702(1) Å, c = 11.1542(1) Å, β = 90.229(1)°, Z = 4, Dcalcd = 1.617 g cm-3; Ln = Lu, compound 5, monoclinic, C2/c, a = 24.2435(4) Å, b = 19.6141(2) Å, c = 11.2635(1) Å, β = 90.049(1)°, Z = 4, Dcalcd = 1.626 g cm-3. X-ray analysis was also carried out for the perchlorate salt:  Ln = Eu, compound 4, triclinic, P1̄, a = 10.9611(2) Å, b = 14.6144(3) Å, c = 15.7992(2) Å, α = 106.594(1)°, β = 91.538(1)°, γ = 90.311(1)°, Z = 2, Dcalcd = 1.561 g cm-3. In the presence of significant amounts of water, 7-coordinate compounds with mixed aquo−TMSA cation structures [Ln(TMSA)3(H2O)]3+ (Ln = Yb) and [Ln(TMSA)2(H2O)3]3+ (Ln = La, Pr, Nd, Eu, Yb) have been isolated with structural determinations by single-crystal X-ray diffraction obtained for the following species:  Yb(C8H16N2O2)3(H2O)(CF3SO3)3, compound 6, monoclinic, P21/n, a = 8.9443(3) Å, b = 11.1924(4) Å, c = 44.2517(13) Å, β = 93.264(1)°, Z = 4, Dcalcd = 1.735 g cm-3; Yb(C8H16N2O2)3(H2O)(ClO4)3, compound 7, monoclinic, Cc, a = 19.2312(6) Å, b = 11.1552(3) Å, c = 19.8016(4) Å, β = 111.4260(1)°, Z = 4, Dcalcd = 1.690 g cm-3; Yb(C8H16N2O2)2(H2O)3(CF3SO3)3, compound 8, triclinic, P1̄, a = 8.6719(1) Å, b = 12.2683(2) Å, c = 19.8094(3) Å, α = 75.815(1)°, β = 86.805(1)°, γ = 72.607(1)°, Z = 2, Dcalcd = 1.736 g cm-3. Unlike in the analogous nitrate salts, only bidentate binding of the succinamide ligand to the lanthanide metal is observed. IR spectroscopy studies in anhydrous acetonitrile suggest that the solid-state structures of these Ln−TMSA compounds are maintained in solution.

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