2-(Trimethylsilyl)-λ3 -Phosphinine: Synthesis, Coordination Chemistry, and Reactivity.

The [4+2] cycloaddition reaction between 2-pyrone and Me3 Si-C≡P gives the corresponding 2-(trimethylsilyl)-λ3 -phosphinine in good yields as a rather air and moisture stable, colorless oil. Insight into the regioselectivity of the pericyclic reaction was obtained with the help of deuterium-labeling experiments. The silyl-phosphinine acts as a ligand for the preparation of a Cu(I) and the first crystallographically characterized phosphinine-Ag(I) complex. The title compound was further used as a starting material for an alternative preparation of the parent phosphinine C5 H5 P by means of protodesilylation with HCl. C5 H5 P reacts with CuBr⋅S(CH3 )2 to give an infinite Cu(I)Br coordination polymer. DFT calculations shed light on the influence of the -Si(CH3 )3 group on the electronic properties of the aromatic phosphorus heterocycle.

3-Bromo-2-Pyrone: An Alternative and Convenient Route to Functionalized Phosphinines.

The facile access to 3-bromo-2-pyrone allows the preparation of 6-bromo-2-trimethylsilyl-phosphinine by a [4+2] cycloaddition with Me3 Si-C≡P for the first time. The regioselectivity of this reaction could be verified by means of single crystal X-ray diffraction of the corresponding W(0) complex. In the presence of ZnBr2 and dppp (1,3-bis(diphenylphosphino)propane) as a bidentate ligand, the bromo-phosphinine quantitatively undergoes a Negishi cross-coupling reaction with PhLi that selectively leads to 6-phenyl-2-trimethylsilyl-phosphinine. This heterocycle could again be characterized by means of X-ray diffraction as a W(0) complex. These results describe a new and convenient route to 2,6-disubstituted phosphinines that makes use of readily available starting materials.

Clicking the Arsenic-Carbon Triple Bond: An Entry into a New Class of Arsenic Heterocycles.

Arsaalkynes can undergo regioselective and quantitative [3+2] cycloaddition reactions with organic azides to give hitherto unknown 3H-1,2,3,4-triazaarsole derivatives. The reaction product was obtained as a white, air- and moisture-stable solid, and the presence of a planar, five-membered arsenic heterocycle was unambiguously verified by means of X-ray crystallography. DFT calculations gave insight into the electronic structure of these novel compounds compared to tetrazoles and triazaphospholes. The coordination chemistry towards Re(I) was investigated and compared with the structurally related phosphorus-containing ligand. These preliminary investigations pave the way for a new class of arsenic heterocycles and fill the gap between the azaarsoles already known.

One-Pot Synthesis of 5-Hydroxy-4H-1,3-thiazin-4-ones: Structure Revision, Synthesis, and NMR Shift Dependence of Thiasporine A.

An annulation of arylthioamides with 3-bromopyruvic acid chloride to 5-hydroxy-4H-1,3-thiazin-4-ones has been developed. The initial condensation affords two regioisomeric thiazolinone intermediates in a temperature-dependent manner. The synthesis of the 2-aminophenylthiazinone derivative led to the revision of the previously proposed structure of thiasporine A. Synthesis of the revised structure and NMR analysis revealed that thiasporine A had been isolated as a carboxylate.

[Ln(BH4)2(THF)2] (Ln = Eu, Yb)--a highly luminescent material. Synthesis, properties, reactivity, and NMR studies.

The divalent lanthanide borohydrides [Ln(BH(4))(2)(THF)(2)] (Ln = Eu, Yb) have been prepared in a straightforward approach. The europium compound shows blue luminescence in the solid state, having a quantum yield of 75%. Nonradiative deactivation of C-H and B-H oscillator groups could be excluded in the perdeuterated complex [Eu(BD(4))(2)(d(8)-THF)(2)], which showed a quantum yield of 93%. The monocationic species [Ln(BH(4))(THF)(5)][BPh(4)] and the bis(phosphinimino)methanides [{(Me(3)SiNPPh(2))(2)CH}Ln(BH(4))(THF)(2)] have been prepared from [Ln(BH(4))(2)(THF)(2)]. They show significantly lower or no luminescence. Using the diamagnetic compound [{(Me(3)SiNPPh(2))(2)CH}Yb(BH(4))(THF)(2)], we performed a 2D (31)P/(171)Yb HMQC experiment.