Intra- and intermolecular interactions and water pincer in the crystal structure of a 3-P(O)Ph2 substituted 1,2,3,6-tetrahydrophosphinine oxide hydrate

Single crystal X-ray structure analysis of 3-diphenylphosphinoxido-1-phenyl-4-chloro-1,2,3,6-tetrahydrophosphinine oxide (1)·H2O provided experimental proof for a transannular P[double bond, length as m-dash]O⋯HC type interaction. The embedded water molecule bridges two P[double bond, length as m-dash]O groups of the P-heterocycle via intra-associate hydrogen bonds. Theoretical calculations showed that the conformation of the hetero-ring alters only slightly due to the presence of the water molecule. Thus 1 behaves as a preorganized host molecule for water, presenting a minimum ring-size molecular environment for water binding.