Reaktionen von tricarbonyl-chrom-η6λ3-phosphorin-komplexen zu tricarbonyl-chrom-η6λ5-phosphorin-ylid-komplexen

The tricarbonylchromium η⁶π⁶ complexes of 2,4,6-triphenyl- and 2,4,6-tri-t-butyl-λ³-phosphorins 3a and 3b add nucleophiles regio- and stereo-specifically to the phosphorus atom in the exo-position giving the λ⁴-phosphorin anions which now add electrophiles in the endo position, giving η⁵π⁶-λ⁵-phosphorin ylide complexes 5a and 5b, respectively. The ¹H, ¹³C and ³¹P NMR spectra of 3a and 3b and especially 5a and 5b are discussed with respect to the stereoisomeric complexes 5a having two different exocylic substituents at the phosphorus atom, synthesized from e.g. 1-ethyl-1-methyl-2,4,6-triphenyl-λ⁵-phosphorin and Cr(CO)₆. The tricarbonylchromium-1,1,-dialkyl or alkyl-aryl-2,4,6-tri-t-butyl-λ⁵-phosphorin 5b can only be synthezised from tricarbonylchromium-2,4,6-tri-t-butyl-λ³-phosphorin by addition of nucleophiles and electrophiles since the corresponding λ⁵-phosphorin derivatives are not available. By removal of the tricarbonylchromium residue from the λ⁵-phosphorin-ylide complexes 5b, however, also 2,4,6-tri-t-butyl-λ⁵-phosphorins can be prepared.