A P,O,P′-tridentate mixed-donor scorpionate ligand: 6-[4,6-bis(diphenylphosphino)-10H-phenoxazin-10-yl]hexan-1-ol

The title compound, C42H39NO2P2, is a P,O,P′-tridentate scorpionate-type ligand and has one molecule in the asymmetric unit. The angles involving the P atoms range from 100.21 (7) to 104.89 (7)°. The N-hexanol group was found to be disordered and was refined over two positions with final occupancies of 0.683 (3) and 0.317 (3) which affected the C—O and C—N bond lengths. The bond lengths for C—O range from 1.402 (2) to 1.415 (2) Å and for C—N from 1.410 (2) to 1.448 (3) Å for the major disorder component; the corresponding ranges for the minor disorder component are 1.429 (3)–1.408 (3) and 1.474 (3)–1.474 (4) Å.

The title compound, C 42 H 39 NO 2 P 2 , is a P,O,P 0 -tridentate scorpionate-type ligand and has one molecule in the asymmetric unit. The angles involving the P atoms range from 100.21 (7) to 104.89 (7) . The N-hexanol group was found to be disordered and was refined over two positions with final occupancies of 0.683 (3) and 0.317 (3) which affected the C-O and C-N bond lengths. The bond lengths for C-O range from 1.402 (2) to 1.415 (2) Å and for C-N from 1.410 (2) to 1.448 (3) Å for the major disorder component; the corresponding ranges for the minor disorder component are 1.429 (3)-1.408 (3) and 1.474 (3)-1.474 (4) Å .

S1. Comment
The title compound (I) was synthesized as part of our on going investigation of scorpionate type ligands based on the nixantphos backbone (Marimuthu et al.,2008a,b). Scorpionate ligands coordinate to metal centres to give unique types of coordination compounds. These compounds exhibit a characteristic type of geometry, enforced by the pincers and the third donor which comes across the plane (formed by metal and pincers) to coordinate to the metal (Pettinari, 2004). The common feature of most scorpionate ligands is that they uniformly contain a single type of donor atom, typically N- (Trofimenko, 1993), O-(Leung, 2007), or P-(Mayer et al., 1994. In contrast, this research is focused on the preparation of chelating P-donor ligands based on a nixantphos backbone functionalized by various hard and soft donors that serve as the third binding site of the ligands. The funtionalized N-hexanol group was found to be disordered and was refined over two positions with final occupancies of 0.68 and 0.32. If the nixantphos moiety is considered as the 'head′ of the compound (I) and the hexanol chain as its 'tail′, then the packing in (I) can be described as stacked in a 'head′ to 'tail′ arrangement. Due to this arrangement several intermolecular interactions especially of type O2-H···O1 are observed between the 'heads′ and 'tails′ of adjacent molecules. The H···O1 interatomic lengths range from 2.733 to 3.346 Å.
Although these are unusually long for classical hydrogen bonding (Chen and Craven, 1995;Monge et al., 1978), the interactions are significant in maintaining the integrity of the disordered crystal structure. The bond angles involving the P atoms range from 100.21 (7) ° to 104.89 (7) °.

S2. Experimental
A two part synthesis involving: a) alkylation (Reymond et al., 1996), and b) deprotection (van der Veen et al., 2000) was adapted from literature. Nixantphos (0.20 g, 0.36 mmol) was dissolved in 4 ml of dry DMF to which NaH (0.22 g, 0.54 millimol, 60% dispersed in mineral oil) was added, followed by the addition of (6-bromohexyloxy)(tertbutyl)dimethylsilane (0.18 g, 0.63 millimol). The resulting mixture was stirred overnight at 100 °C. The reaction was cooled to room temperature and hydrolysed with 10 ml of water. The organic phase was extracted with 4 x 15 ml ethyl acetate and the combined fractions dried over sodium sulfate. Thereafter the solvent was removed in vacuo and the residue chromatographed with 10% hexane/ethyl acetate to give the protected precursor of the title compound (I). The precursor was dissolved in 25 ml THF, and 2.5 equivalents of tetra-n-butylammoniumflouride trihydrate was added. The reaction was left to stir overnight at room temperature and was followed by aqueous work-up. The resulting crude product of compound (I) was chromatographed with 20% hexane/ethyl acetate and recrystalized from a solution of dichloromethane/ethanol (1:1) to yield 23% of pale yellow crystals of pure (I). m.p. 440-441 K.

S3. Refinement
Non-hydrogen atoms were first refined isotropically followed by anisotropic refinement by full matrix least-squares calculations based on F2 using SHELXTL. Hydrogen atoms were first located in the difference map then positioned geometrically and allowed to ride on their respective parent atoms. The N-hexanol group was found to be disordered and was refined over two positions using a combination of SADI, SAME, DELU and SIMU restraints, with final occupancies of 0.683 (3) and 0.317 (3).
All hydrogen atoms were first located in the difference map then positioned geometrically and allowed to ride on their respective parent atoms (C -H = 0.95 -0.99 Å) with U iso (H) = 1.2 U eq (C) for aryl H or 1.5 U eq (C) for alkyl.  Molecular structure of the title complex. Thermal ellipsoids are shown at 50% probability levels.

Special details
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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.