Observation and Interpretation of Structural Variety in Alkaline Earth Metal Derivatives of Diphosphanyldisiloxane

Alkaline earth metal derivatives of the diphosphanyldisiloxane O(Si i Pr 2 PH 2 ) 2 ( 1 ) were obtained by reactions of 1 with MgBu 2 and M{N(SiMe 3 ) 2 } 2 (M = Ca, Sr, Ba), respectively. The metal complexes formed were characterised by elemental analysis, NMR spectroscopy, and IR spectroscopy as well as by single‐crystal structure analysis. The solid‐state structures depend on the metal ion involved. The magnesium derivative crystallizes from thf as a trimer and exhibits a six‐membered Mg 3 P 3 ring. In contrast, the Ca und Sr derivatives show a dimeric structure via formation of M 2 P 2 rings (M = Ca, Sr). Eventually, the Ba derivative forms a dimeric structure with an octahedral P 4 Ba 2 moiety. Quantum chemical investigations indicate that the structural variety is a consequence of accessibility and spatial extent of the d‐orbitals of the alkaline earth metal atoms.