Crystal structure of bis(3,3-dimethyl-2-oxobutyl)diphenylphosphonium bromide chloroform monosolvate

In the title salt solvate, C24H32O2P+·Br−·CHCl3, the P atom has a distorted tetrahedral geometry, and the planes of the phenyl rings form a dihedral angle of 71.86 (14)° with one another. The bromide anion is disordered and was modelled over three positions (occupancy ratio 0.50:0.35:0.15). The crystal also contains one disordered chloroform solvent molecule that was modeled over three positions (occupancy ratio 0.50:0.35:0.15). Weak intermolecular interactions (C—H⋯Br and C—H⋯O) exist between the complex cation and the bromide anion fragments. The resulting supramolecular structure is an oval-shaped arrangement of phosphonium salt molecules that surround the disordered bromide anion.

ion is engaged in a variety of weak interactions with nearby hydrogen atoms, with interatomic H···Br distances ranging from 2.70 to 2.97 Å. In the fragment that has the highest occupancy ratio (50%), a weak CH···Br interaction is also present between the chloroform molecule and bromide ion. Based on the amount of disorder present in this structure, it is clear these intermolecular interactions are quite weak in nature.

S3. Synthesis and crystallization
The title compound was prepared via an Arbuzov reaction between bromopinacolone and an excess of iso-propoxydi-

S4. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. The positions of all hydrogen atoms were calculated geometrically and refined to ride on their parent atoms, with U iso (H) = 1.2U eq (C) for methine, methylene and aryl groups, and U iso (H) = 1.5U eq (C) for methyl groups.
The disordered bromide ion was modelled over three positions with a 50:35:15 occupancy ratio. An EADP instruction was included in the refinement to constrain the thermal ellipoids of these fragments to the same size and shape. The disordered chloroform molecule was also modelled in three parts with a 50:35:15 occupancy ratio.  Weak intermolecular interactions (denoted with dashed lines) found throughout the crystal lattice of the title compound (Table 1). Only the major position of the disordered fragments are shown. The aryl rings, tert-butyl groups, and all hydrogen atoms not involved in these interactions have been omitted for clarity. This drawing is done as a ball and stick with standard CPK colors. Symmetry codes: (i) 3/2 -x, -1/2 + y, 3/2 -z; (ii) 3/2 -x, 1/2 -y, 1 -z.

Data collection
Bruker SMART APEX CCD area-detector diffractometer Radiation source: sealed tube Graphite monochromator Detector resolution: 8 pixels mm -1 ω and φ scans Absorption correction: multi-scan (SADABS; Bruker, 2013) T min = 0.667, T max = 0.745 25767 measured reflections 5090 independent reflections 3862 reflections with I > 2σ(I) Special details Experimental. SADABS-2012/1 (Bruker, 2013 was used for absorption correction. wR2(int) was 0.0613 before and 0.0433 after correction. The Ratio of minimum to maximum transmission is 0.8956. The λ/2 correction factor is 0.0015. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.