Cumulative number of data packages in the Knowledge Network for Biocomplexity until 2007-06-21

This data set records the cumulative number of data packages in the Knowledge Network for Biocomplexity (KNB) data repository through 2007-06-21. A data package represents a set of data files and metadata files that together make a coherent, citable unit for some particular scientific activity. Each data package in the KNB is described by a scientific metadata document and can be composed of one or more data files that contain various segments of the data in question

Lanthanide(III) Di- and Tetra-Nuclear Complexes Supported by a Chelating Tripodal Tris(Amidate) Ligand

Syntheses, structural, and spectroscopic characterization of multinuclear tris­(amidate) lanthanide complexes is described. Addition of K₃[N­(<i>o</i>-PhNC­(O)<i>^t</i>Bu)₃] to LnX₃ (LnX₃ = LaBr₃, CeI₃, and NdCl₃) in <i>N</i>,<i>N</i>-dimethylformamide (DMF) results in the generation of dinuclear complexes, [Ln­(N­(<i>o</i>-PhNC­(O)^<i>t</i>Bu)₃)­(DMF)]₂­(μ-DMF) (Ln = La (<b>1</b>), Ce (<b>2</b>), Nd­(<b>3</b>)), in good yields. Syntheses of tetranuclear complexes, [Ln­(N­(<i>o</i>-PhNC­(O)^<i>t</i>Bu)₃)]₄ (Ln = Ce (<b>4</b>), Nd­(<b>5</b>)), resulted from protonolysis of Ln­[N­(SiMe₃)₂]₃ (Ln = Ce, Nd) with N­(<i>o</i>-PhNCH­(O)^<i>t</i>Bu)₃. In the solid-state, complexes <b>1</b>–<b>5</b> exhibit coordination modes of the tripodal tris­(amidate) ligand that are unique to the 4f elements and have not been previously observed in transition metal systems

Bonding Trends Traversing the Tetravalent Actinide Series: Synthesis, Structural, and Computational Analysis of An^IV(^Aracnac)₄ Complexes (An = Th, U, Np, Pu; ^Aracnac = Ar<i>N</i>C(Ph)CHC(Ph)<i>O</i>; Ar = 3,5‑^<i>t</i>Bu₂C₆H₃)

A series of tetravalent An­(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the actinide series. The neutral molecules are homoleptic with the formula An­(^Aracnac)₄ (An = Th (<b>1</b>), U (<b>2</b>), Np (<b>3</b>), Pu (<b>4</b>); ^Aracnac = Ar<i>N</i>C­(Ph)­CHC­(Ph)<i>O</i>; Ar = 3,5-^<i>t</i>Bu₂C₆H₃) and were synthesized through salt metathesis reactions with actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state. The Th, U, and Pu complexes were structurally elucidated by single-crystal X-ray diffraction and shown to be isostructural in space group <i>C</i>2/<i>c</i>. Analysis of the bond lengths reveals shortening of the An–O and An–N distances arising from the actinide contraction upon moving from <b>1</b> to <b>2</b>. The shortening is more pronounced upon moving from <b>2</b> to <b>4</b>, and the steric constraints of the tetrakis complexes appear to prevent the enhanced U–O versus Pu–O orbital interactions previously observed in the comparison of UI₂(^Aracnac)₂ and PuI₂(^Aracnac)₂ bis<i>-</i>complexes. Computational analysis of models for <b>1</b>, <b>2</b>, and <b>4</b> (<b>1a</b>, <b>2a</b>, and <b>4a</b>, respectively) concludes that both the An–O and the An–N bonds are predominantly ionic for all three molecules, with the An–O bonds being slightly more covalent. Molecular orbital energy level diagrams indicate the largest 5f-ligand orbital mixing for <b>4a</b> (Pu), but spatial overlap considerations do not lead to the conclusion that this implies significantly greater covalency in the Pu–ligand bonding. QTAIM bond critical point data suggest that both U–O/U–N and Pu–O/Pu–N are marginally more covalent than the Th analogues

Bonding Trends Traversing the Tetravalent Actinide Series: Synthesis, Structural, and Computational Analysis of An^IV(^Aracnac)₄ Complexes (An = Th, U, Np, Pu; ^Aracnac = Ar<i>N</i>C(Ph)CHC(Ph)<i>O</i>; Ar = 3,5‑^<i>t</i>Bu₂C₆H₃)

A series of tetravalent An­(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the actinide series. The neutral molecules are homoleptic with the formula An­(^Aracnac)₄ (An = Th (<b>1</b>), U (<b>2</b>), Np (<b>3</b>), Pu (<b>4</b>); ^Aracnac = Ar<i>N</i>C­(Ph)­CHC­(Ph)<i>O</i>; Ar = 3,5-^<i>t</i>Bu₂C₆H₃) and were synthesized through salt metathesis reactions with actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state. The Th, U, and Pu complexes were structurally elucidated by single-crystal X-ray diffraction and shown to be isostructural in space group <i>C</i>2/<i>c</i>. Analysis of the bond lengths reveals shortening of the An–O and An–N distances arising from the actinide contraction upon moving from <b>1</b> to <b>2</b>. The shortening is more pronounced upon moving from <b>2</b> to <b>4</b>, and the steric constraints of the tetrakis complexes appear to prevent the enhanced U–O versus Pu–O orbital interactions previously observed in the comparison of UI₂(^Aracnac)₂ and PuI₂(^Aracnac)₂ bis<i>-</i>complexes. Computational analysis of models for <b>1</b>, <b>2</b>, and <b>4</b> (<b>1a</b>, <b>2a</b>, and <b>4a</b>, respectively) concludes that both the An–O and the An–N bonds are predominantly ionic for all three molecules, with the An–O bonds being slightly more covalent. Molecular orbital energy level diagrams indicate the largest 5f-ligand orbital mixing for <b>4a</b> (Pu), but spatial overlap considerations do not lead to the conclusion that this implies significantly greater covalency in the Pu–ligand bonding. QTAIM bond critical point data suggest that both U–O/U–N and Pu–O/Pu–N are marginally more covalent than the Th analogues