1314469-75-4Relevant academic research and scientific papers
Coordination behavior and coligand-dependent cis/trans isomerism of calcium bis(diphenylphosphanides)
Langer, Jens,Al-Shboul, Tareq M. A.,Younis, Fadi M.,Goerls, Helmar,Westerhausen, Matthias
, p. 3002 - 3007 (2011)
The salt metathesis reaction of KPPh2 with CaI2 and SrI2 in THF yields the corresponding complexes [(THF) 4Ae(PPh2)2] [Ae = Ca (1), Sr]. Depending on the crystallization conditions, cis- or trans-[(THF)4Ca(PPh 2)2] can be isolated. In solution, a fast equilibrium converts these isomers into each other leading to a single set of resonances in the NMR spectra. The THF ligands can be replaced by stronger Lewis bases, such as N-methylimidazole (MeIm), which leads to the formation of [(MeIm) 4Ae(PPh2)2] [Ae = Ca (2a), Sr (2b)]. The use of tetradentate hexamethyltriethylenetetramine (hmteta) fixes a cis configuration yielding [(hmteta)Ca(PPh2)2] (3). All compounds are very air and moisture sensitive, therefore a few crystals of the partially oxidized product [(hmteta)Ca(PPh2)(OPPh2)] (4) were also obtained. [(L)4Ca(PPh2)2] is an effective hydrophosphanylation catalyst. To predetermine and fix a cis or trans arrangement of the phosphanide anions, the neutral coligand sphere of four Lewis base donors, such as four THF molecules or one hmteta ligand, was altered. Copyright
