Structural Diversity in the Solid-State Structures of the Rubidium and Cesium Salts of 2,6-Dimesitylphenylphosphane

A coordination environment reminiscent of a paddle-wheel is exhibited by aryl groups about one of the two cesium ions in CsP(H)Dmp (Dmp=2,6-dimesitylphenyl; structure depicted on the right), which has now been synthesized and is found to exhibit Cs⁺{Cs₂[P(H)Dmp]₃}⁻ contact ion pairs in the solid state. In contrast, the analogous rubidium compound displays a Rb₄P₄ cube as the central structural motif.     

[Hydroxy­tris­(penta­fluoro­phenyl)­borato‐O][N‐iso­propyl‐2‐(iso­propyl­amino)­troponiminato‐N]­methyl­indium(III)

The title complex, [In(CH₃)(C₁₈HBF₁₅O)(C₁₃H₁₉N₂)], crystallizes as an ion pair linked by a μ‐hydro­xo bridge. There are two independent mol­ecules in the asymmetric unit that exhibit essentially identical metric parameters, but different conformations.     

Constructor graph description of hydrogen bonding in a supra­molecular assembly of N,N′‐bis­(2‐hydr­oxy‐1‐methyl­ethyl)phthalamide

Hydrogen bonds of four types (N—H⋯O=C, N—H⋯OH, O—H⋯O=C and O—H⋯OH) connect mol­ecules of the title compound, C₁₄H₂₀N₂O₄, in the crystal into sheets folded into a zigzag pattern. The inter­molecular inter­actions are discussed in terms of the first‐ through fourth‐level graph sets, and a constructor graph helps visualize the supra­molecular assembly.     

Transformations of tetrahydrobenzo[b][1,6]naphthyridines and tetrahydropyrido[4,3-b]pyrimidines under the action of dimethyl acetylene dicarboxylate

10-Cyanotetrahydrobenzo[b][1,6]naphthyridines 3, 4 undergo addition of DMAD, followed by a Stevens rearrangement of the intermediate ylide to yield methyl dioates 8 and 9. An alternative transformation sequence starts with migration of the dimethyl butenedioate anion to the carbon of the CN group, followed by the addition of 1 mol of water, to provide succinates 10 and 11. In contrast, tetrahydropyrido[4,3-b]pyrimidines 5-7 undergo a tandem cleavage process, involving one molecule of solvent. The resulting enamines are easily cleaved by strong acids, to give dihydropyrymidinylethylamines, which are scarcely available by other synthetic means.     

Synthesis and characterization of dimetallic oxorhenium(V) and dioxorhenium(VII) compounds, and a study of stoichiometric and catalytic reactions

Chelating dithiolate ligands--e.g., mtp from 2-(mercaptomethyl)thiophenol, edt from 1,2-ethanedithiol, and pdt from 1,3-propanedithiol--stabilize high-valent oxorhenium(V) against hydrolytic and oxidative decomposition. In addition to the dithiolate chelating to a single rhenium, one sulfur forms a coordinate bond to the other rhenium. In one arrangement this gives a dimer with a nearly planar diamond core with different internal Re-S distances. The new compounds are [MeReO(edt)](2) (2) and [MeReO(pdt)](2) (3), which can be compared to the previously known [MeReO(mtp)](2) (1). Another mode of synthesis leads to [ReO](2)(mtp)(3) (5) and [ReO](2)(edt)(3) (6). They, too, have similar Re(2)S(2) cores that involve donor atoms from two of the dithiolate ligands; the third dithiolate chelates one of the rhenium atoms. Gentle hydrolysis of 1 affords [Bu(n)4][[MeReO(mtp)](2)(mu-OH)] (7) in low yield. It appears to be the first example of this structural type for rhenium. The use of dithioerythritol as a starting material allowed the synthesis of a dioxorhenium(VII) compound, [MeReO(2)](2)(dte) (8). Its importance lies in understanding the role such compounds are believed to play as intermediates in oxygen atom catalysis. Ligation of the dimers 1-3 converts them into monomeric compounds, MeReO(dithiolate)L. These reactions go essentially to completion for L = PPh(3), but reach an equilibrium for L = NC(5)H(4)R. With R = 4-Ph, the values of K/10(3) L mol(-1) for the reactions (1-3) + 2L = 2MeReO(dithiolate)L are identical within 3 sigma: 1.15(3) (1), 1.24(4) (2), and 1.03(16) (3). The rates of monomer formation follow the rate law -d ln [dimer]/dt = k(a)[L] + k(b)[L](2). These trends were found: (1) phosphines are slow to react compared to pyridines, (2) the edt dimer 2 reacts much more rapidly than 1 and 3. Dimer 1 and MeReO(mtp)PPh(3) both catalyze oxygen atom transfer: PicO + PPh(3) --> Pic + Ph(3)PO. Compound 1 is ca. 90 times more reactive, which can be attributed to its lability toward small ligands as opposed to the low rate of displacement of PPh(3) from the mononuclear catalyst. The kinetics of this reaction follows the rate law -d[PicO]/dt = k[PicO][1]/[1 + kappa[PPh(3)]], with k = 5.8 x 10(6) L mol(-1) s(-1) and kappa = 3.5 x 10(2) L mol(-1) at 23 degrees C in benzene. A mechanism has been proposed to account for these findings.     

An example of the refinement of positional disorder modeled as compositional disorder in [5‐(2‐formylphenyl)‐10,15,20‐triphenylporphyrinato]nickel(II)

The title compound, [Ni(C₄₅H₂₈N₄O)], crystallizes in the space group I2d and resides on a crystallographic fourfold rotoinversion axis with only a quarter of the complex in the asymmetric unit. The complex displays positional disorder as the one aldehyde group on the ligand can be located at four different positions. It was necessary to model this as compositional disorder to obtain a correct model and refinement. The practical approach to the refinement is explained.