Cyclisierung von (Fluorsilyl)phosphanen zu 1,3‐Diphospha‐2,4‐disilacyclobutanen – Kristallstrukturuntersuchungen

Abstract

Lithiiertes ferf-Butylphosphan reagiert mit Di-ferf-butyldifluorsilan und Difluorbis[methyl(trimethylsilyl)amino]silan zu den (Fluorsily1)phosphanen 1 und 2 sowie zum (Di-terf-butylsilandiy1)-bisphosphan 3. Die cyclischen Verbindungen 4 und 5 werden durch die Umsetzung von 1 und 2 mit ferf-C,H9Li erhalten. Dilithiiertes 3 reagiert mit Dichlorphenylphosphan zum 1,2,3-Triphospha-4-silacyclobutan 6. Nach Kristallstrukturanalysen besitzen 4 und 5 jeweils planare Si,P2-Ringe mit Si-P-Bindungen zwischen 224.1 (1) und 228.0(1) pm. Cyclisation of (Fluorosi1yl Ergebnisse und DiskussionDie Silicium-Element-Wasserstoff-Gruppierung neigt, wie Erfahrungen aus der Silicium-Stick~toff-~*'), Silicium-Sa~erstoff-~) oder auch der Silicium-Phosphor-Chemie 5, zeigen, leicht zu Folgereaktionen wie der Kondensation. Durch Einfuhrung sperriger Substituenten, z. B. der tert-Butylgruppe, werden die Kondensationsreaktionen erschwert . In Kombination mit aciden Element-Wasserstoff-Gruppen unterscheiden sich (Fluorsily1)-Verbindungen in ihrem Reaktionsverhalten wesentlich von anderen Silicium-Halogen-Verbindungen. Die hohe Si -F-Bindungsenergie (586 kJ/mol) verrin-0

Flash Vacuum Thermolysis: First Gas-Phase Generation of Unhindered Silylidenephosphanes and Characterization by Photoelectron Spectroscopy

“…The geometrical parameters calculated (MP2/ LANL1DZ) for its methyl counterpart 1e correspond to a nonplanar form with a dihedral angle of 15.0° and the phosphorus substituents in a trans configuration (Figure ). These parameters are in agreement with the crystal structure determination performed on 1,2,2,3,4,4-hexa- tert -butylcyclodisilaphosphane 2 Geometrical parameters (bond lengths in angstroms; bond angles in degrees) of 4e optimized at the MP2/6-31G(d) level and of 1e and 4d optimized at the MP2/LANL1DZ level. …”

“…The presently known 2,2,4,4-tetramethylcyclodisilaphosphanes (2,2,4,4-tetramethyl-1,3-diphospha-2,4-disilacyclobutanes) are limited to 1,3-di- tert -butyl, , 1,3-diphenyl, , and 1,3-bis(chlorodimethylsilyl) derivatives. A few cyclodisilaphosphanes substituted on silicon by groups other than methyl have been also described, − as well as 1,3,5-triphenyl-2,2,4,4,6,6-hexamethylcyclotrisilaphosphane, and triphosphatrisilacyclohexanes …”

Structure of 1,3-di-tert-butyl-2,2,4,4-tetraisopropylcyclodisilazane, C20H46N2Si2

“…We conclude that (BUESi.NBu)2 is probably too crowded to be stable, at least with a planar central Si2N 2 ring of the form always observed so far for cyclodisilazanes. In contrast, (BUESi.PBu)2 has been prepared and structurally characterized (Clegg, Haase, Klingebiel & Sheldrick, 1983); in this molecule, however, the mean Si-P bond length is 2.259 A, so steric crowding is much smaller.…”

Structures and Energetics of Some Silicon−Phosphorus Compounds: SiHmPHn, SiHmPHnSiHo, and (SiH3)3P. An ab Initio Molecular Orbital Study

“…The structures of about 200 SiP compounds have been determined by X-ray crystallography . A few of the more interesting ones include Si−P analogues of cyclobutane, bicyclobutane, spiropentane, hexane, norbornane, adamantane, and cubane . Some of these, along with simpler silylphosphines, have found uses as ligands in transition metal complexes. , Silicon−phosphorus single bonds are remarkably reactive .…”