Stefan Schutte

Palladium-catalyzed cross-methylation of aryl triflates by intramolecularly stabilized dialkyl-aluminum, -gallium and -indium reagents

Abstract Several phenyl and naphthyl triflates undergo catalytic cross-methylation with the monomeric and dimeric dimethyl-aluminum, -gallium and -indium complexes 1a , 1b , 1c , 3a , 3b and 3c in the presence of either PdCl 2 (PPh 3 ) 2 , Pd(PPh 3 ) 4 or Pd(binap)(OAc) 2 . 4-Bromophenyl triflate reacts selectively via the triflate function. Structural features of the substrate and the methylating agent, as well as the nature and quality of the palladium catalyst have a considerable influence on the cross-coupling process.

Si(CH2CH2SnH3)4 — a unique organotin hydride featuring 12 SnH units in a dendritic molecule. Single-crystal X-ray structures of tetrakis(2-stannylethylene)silane and tetrakis[2-(triphenylstannyl)ethylene]silane

Abstract Fourfold hydrostannation of tetravinylsilane affords the first generation metallodendrimer Si(CH2CH2SnPh3)4 (1). Selective bromination yields Si(CH2CH2SnBr3)4 (2), which can be reduced by LiAlH4 to give Si(CH2CH2SnH3)4 (3), containing 12 reactive SnH bonds. These novel dendritic organotin compounds were characterized by elemental analysis, spectroscopic studies (1H-, 13C-, 119Sn-NMR; IR) and by single-crystal X-ray structure determination. The molecular structures of 1 and 3 reveal increased conformational constraint in 1; the average SnH bond length in 3 is 1.60(7) A.

Facile Access to NaOC≡As and Its Use as an Arsenic Source to Form Germylidenylarsinidene Complexes

A facile, one-pot synthesis of [Na(OC≡As)(dioxane)x ] (x=2.3-3.3) in 78 % yield is reported through the reaction of arsine gas with dimethylcarbonate in the presence of NaOt Bu and 1,4-dioxane. It has been employed for the synthesis of the first arsaketenyl-functionalized germylene [LGeAsCO] (2, L=CH[CMeN(Dipp)]2 ; Dipp=2,6-i Pr2 C6 H3 ) from the reaction with LGeCl (1). Upon exposure to ambient light, 2 undergoes CO elimination to form the 1,3-digerma-2,4-diarsacyclobutadiene [L2 Ge2 As2 ] (3), which contains a symmetric Ge2 As2 ring with ylide-like Ge=As bonds. Remarkably, the CO ligand located at the arsenic center of 2 can be exchanged with PPh3 or an N-heterocyclic carbene iPr NHC donor (iPr NHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) to afford the novel germylidenylarsinidene complexes [LGe-AsPPh3 ] (4) and [LGe-As(iPr NHC)] (5), respectively, demonstrating transition-metal-like ligand substitution at the arsinidene-like As atom. The formation of 2-5 and their electronic structures have been studied by DFT calculations.

Studies on the Thermolysis of Ether-Stabilized Lu(CH2SiMe3)3. Molecular Structure of Lu(CH2SiMe3)3(THF)(diglyme)

Lu(CH2SiMe3)3(THF)2 (2) decomposes slowly at room temperature with formation of Me4Si. In order to understand the mechanism of this elimination process, Lu(CH2SiMe3)3([D8]-THF)2 (1), Lu(CH2SiMe3)3(THF)(DME) (3), and Lu(CH2SiMe3)3(THF)(diglyme) (4) were prepared. The results of 1H NMR spectroscopic studies of the decomposition in solution exclude an α- as well as a β -H elimination mechanism and point towards a γ -H elimination. The molecular structure of 4 has been determined by single crystal X-ray diffraction.