Crystal structure of 1,3-di-tert-butyl-2-chloro-1,3,2-di­aza­phospho­rinane − a saturated six-membered phospho­rus nitro­gen heterocycle with a partially flattened chair conformation and a long P(III)—Cl bond

Colourless blocks of 1,3-di-tert-butyl-2-chloro-1,3,2-di­aza­phospho­rinane, C(11)H(24)ClN(2)P (1), were obtained by sublimation in vacuo slightly above room temperature. The asymmetric unit of the monoclinic crystal structure of the six-membered N-heterocyclic compound is defined by one mol­ecule in a general position. The six-membered ring of the mol­ecule adopts a cyclo­hexane-like chair conformation; the chair at one side is to some extent flattened as a result of the approximately trigonal–planar coordination of both nitro­gen atoms. In detail, this modified chair conformation is characterized by an angle of 53.07 (15)° between the plane defined by the three carbon atoms and the best plane of the two nitro­gen atoms and the two carbon atoms bound to them, and an angle of 27.96 (7)° between the latter plane and the plane defined by the nitro­gen and phospho­rus atoms. The tert-butyl groups are oriented equatorially and the chloro substituent is oriented axially. The P—Cl bond length of 2.2869 (6) Å is substanti­ally longer than the P—Cl single-bond length in PCl(3) [2.034 Å; Galy & Enjalbert (1982 ▸). J. Solid State Chem. 44, 1–23]. Inspection of the inter­molecular distances gives no evidence for inter­actions stronger than van der Waals forces. The closest contact is between the Cl atom and a methyl­ene group of a neighbouring mol­ecule with a Cl⋯C distance of 3.7134 (18) Å, excluding a significant influence on the P—Cl bonding.