Catalytic synthesis of vinylphosphanes via calcium-mediated intermolecular hydrophosphanylation of alkynes and butadiynes

The calcium complex [(thf)₄Ca(PPh₂)₂] (1) is a very effective catalyst for the hydrophosphanylation of substituted alkynes of the type R-CC-R (R = Me, Ph) yielding (E)-1,2-diphenyl-1-diphenylphosphanylethene (2a) and (Z)-1-phenyl-2-diphenylphosphanyl-1-propene (2b). The calcium-mediated hydrophosphanylation of butadiynes of the type R-CC-CC-R (R = Me, SiMe₃, Ph, Mes, tBu) proceeds less selectively and diverse products are obtained such as 1,4-substituted 1,4-bis(diphenylphosphanyl)-1,3-butadienes (3), 1,4-diphenyl-1,2-bis(diphenylphosphanyl)-1,3-butadiene (4), and 1,4-di(tert-butyl)-1,4-bis(diphenylphosphanyl)buta-1,2-diene (5). Besides these regioisomers also several configuration isomers with respect to the C=C double bonds [(E)/(Z) isomerism] are obtained. A catalytic cycle can be formulated with the first addition of a Ca-P bond of the catalyst 1 to a CC triple bond always leading to the formation of an intermediate with the newly formed C-P bond in 1-position whereas the remaining phosphanido calcium fragment binds to the carbon in 2-position. The addition of a second diphenylphosphane is much faster and therefore, only two-fold hydrophosphanylated butadiynes are observed. Neither addition products with only one HPPh₂ group nor those with more than two PPh₂ substituents are obtained.     

Synthesis and characterization of ruthenium heterocyclic-thiocarboxylate complexes

The cyclopentadienyl ruthenium complexes CpRuL₂SCO-het (Cp = η⁵-C₅H₅; L₂ = 2PPh₃ (1), dppe (2)) bearing heterocyclic thiocarboxylate ligands have been synthesized from the reaction of CpRuL₂SH with heterocyclic acid chlorides (ClCO-2-C₄H₃S (a); ClCO-2-C₄H₃O (b); ClCO-1-C₄H₈N (c)). Bubbling of CO gas through a THF solution of (1) produced the mixed carbonyl–phosphine complexes CpRu(PPh₃)(CO)SCO-het (3) with high yields. Complexes (1)-(3) were characterized by spectroscopic methods (i.r., ¹H-n.m.r., ³¹P-n.m.r.) and elemental analysis. The molecular structure of CpRu(PPh₃)₂SCO-2-C₄H₃S (1a) verifies that the thiocarboxylate ligands bind via the sulfur atom (Ru–S = 2.406(2) Å).     

Crystallographic and computational study of the structure of copper(II) 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl

The reaction of M(OAc)₂ with 2,2′-bis(2-hydroxybenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl (H₂L1) allows the synthesis of 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl complexes of Cu(II) (CuL1), Co(II) (CoL1) and Ni(II) (NiL1) that were characterized by elemental analysis, FTIR spectroscopy and for CuL1 also by X-ray crystallography verifying a tetradentate binding mode of L1 via an (ONNO) motif of the two phenolic oxygen atoms and two azomethine nitrogen atoms. Recrystallization from a solvent mixture of dichloromethane and methanol promotes the formation of methanol adducts. Different binding modes of the methanol–complex were investigated using density functional theory calculations and binding energies, and thermodynamic data of the interaction are reported. The results show that the favored interaction occurs when the methanol molecule acts as a Lewis acid weakly binding via an O–H···O hydrogen bridge to a phenoxide moiety leading to an elongation of the respective M–O bond.

     

Spatial evaluation of radionuclide concentrations and the associated radiation hazards using the Kriging method

Spatial variations of natural and artificial radiation hazards are evaluated by combining high-resolution gamma spectrometry with the Kriging method. The coupling of both methods was applied on radionuclides’ concentration measurements of northern Jordan soil, and the generated smooth surfaces had mean standardized error and root mean square standardized error values ranging from 6?×?10^?3 to 26?×?10^?3 and from 0.89 to 1.19, respectively. The spatial assessment shows that some radiation hazard indices are higher than the global average values. The produced maps show that the observed increase in uranium and thorium concentrations could be related to the spread of phosphate-rich rock compositions.     

Oxidation products of calcium and strontium bis(diphenylphosphanide)

The tetrahydrofuran adducts [(thf)(4)M(PPh(2))(2)] (M = Ca, Sr) are air sensitive and can easily be oxidized by chalcogens. Metalation of diphenylphosphane oxide, diphenylphosphinic acid, and diphenyldithiophosphinic acid as well as salt metathetical approaches of the potassium salts with MI(2) allow the synthesis of [(thf)(4)Ca(OPPh(2))(2)] (1), [(dmso)(2)Ca(O(2)PPh(2))(2)] (2), [(thf)(3)Ca(O(2)PPh(2))I](2) (3), [(thf)(3)Ca(S(2)PPh(2))(2)] (4), [(thf)(2)Ca(Se(2)PPh(2))(2)] (5), [(thf)(3)Sr(S(2)PPh(2))(2)] (6), [(thf)(3)Sr(Se(2)PPh(2))(2)] (7), and [(thf)(2)Ca(O(2)PPh(2))(S(2)PPh(2))](2) (8), respectively. The diphenylphosphinite anion in 1 contains a phosphorus atom in a trigonal pyramidal environment and binds terminally via the oxygen atom to calcium. The diphenylphosphinate anions act as bridging ligands leading to polymeric structures of calcium bis(diphenylphosphinates). Therefore strong Lewis bases such as dimethylsulfoxide (dmso) are required to recrystallize this complex yielding chain-like 2. The chain structure can also be cut into smaller units by ligands which avoid bridging positions such as iodide and diphenyldithiophosphinate (3 and 8, respectively). In general, diphenyldithio- and -diselenophosphinate anions act as terminal ligands and allow the isolation of mononuclear complexes 4 to 7. In these molecules the alkaline earth metals show coordination numbers of six (5) and seven (4, 6, and 7).