{2,6-Bis[(2,6-diisopropylphosphanyl)oxy]-4-fluorophenyl-κ3 P,C 1,P′}(1H-pyrazole-κN 2)nickel(II) hexafluorophosphate

The title compound, [Ni(C18H30FO2P2)(C3H4N2)]PF6, was prepared by halide abstraction with TlPF6 in the presence of CH3CN in CDCl3 from the respective neutral pincer chlorido analogue followed by addition of pyrazole. The PO—C—OP pincer ligand acts in typical trans-P2 tridentate fashion to generate a distorted square-planar nickel structure. The Ni—N(pyrazole) distance is 1.925 (2) Å and the plane of the pyrazole ligand is rotated 56.2 (1)° relative to the approximate square plane surrounding the NiII center in which the pyrazole is bound to the NiII atom through its sp 2-hybridized N atom. This Ni—N distance is similar to bond lengths in the other reported NiII pincer-ligand square-planar pyrazole complex structures; however, its dihedral angle is significantly larger than any of those for the latter set of pyrazole complexes.

The title compound, [Ni(C 18 H 30 FO 2 P 2 )(C 3 H 4 N 2 )]PF 6 , was prepared by halide abstraction with TlPF 6 in the presence of CH 3 CN in CDCl 3 from the respective neutral pincer chlorido analogue followed by addition of pyrazole. The PO-C-OP pincer ligand acts in typical trans-P 2 tridentate fashion to generate a distorted square-planar nickel structure. The Ni-N(pyrazole) distance is 1.925 (2) Å and the plane of the pyrazole ligand is rotated 56.2 (1) relative to the approximate square plane surrounding the Ni II center in which the pyrazole is bound to the Ni II atom through its sp 2 -hybridized N atom. This Ni-N distance is similar to bond lengths in the other reported Ni II pincer-ligand square-planar pyrazole complex structures; however, its dihedral angle is significantly larger than any of those for the latter set of pyrazole complexes.

Experimental
Crystal data [Ni(C 18 H 30 FO 2 P 2 )(C 3 H 4 N 2 )]PF 6 M r = 631.12 Monoclinic, P2 1 =n a = 9.0380 (9) Å b = 20.1878 (16)  resorcinol and diisopropylchlorophosphine in THF in the presence of triethylamine, and then anhydrous NiCl 2 was added to form the (PO-C-OP)NiCl complex. Chloride abstraction with TlPF 6 in the presence of CH 3 CN from this species followed by addition of pyrazole afforded an excellent yield of the cationic complex whose structure is shown below in Detailed lists of dimensions are available in the archived CIF.

Experimental
The first step entailed generating a neutral nickel(II) halido pincer complex, abbreviated as Pr{Ni F }Cl. An anhydrous solution of 5-fluororesorcinol (330 mg, 2.58 mmol) in THF was prepared in a 100-ml Kontes Teflon screw-cap flask inside a glovebox. To this solution was added via syringe 1.50 ml NEt 3 (10.77 mmol) followed by 850 µL of ClPPr i 2 (5.34 mmol); immediately a large volume of white precipitate formed. The flask was brought out of the glovebox and heated for 20 minutes at 80 °C; thereafter the flask was returned to the glovebox, where 0.57 grams of anhydrous NiCl 2 (4.40 mmol) was added to afford an orange mixture. After 24 h under heavy stirring at 80 °C, the resulting green-yellow mixture was filtered through a plug of Celite and concentrated under vacuum. This solution was layered with pentane and left overnight in a -30 °C freezer to give dark yellow-brown crystals of Pr{Ni F }Cl (608 mg, 52% yield).
Complex I, [Ni(C 3 H 2 N 2 )(C 12 H 16 FO 2 P 2 )]PF 6 , abbreviated as Pr{Ni F }(Pz)]PF 6 , was prepared as follows. Pr{Ni F }Cl (32.4 mg, 0.0799 mmol) was stirred at ambient temperature for 24 h with TlPF 6 (Strem Chemicals; 1.15 mol equiv.) in CDCl 3 (Cambridge Isotopes Lab; 1.25 ml) to which 25 µL CH 3 CN (Fisher reagent) had been added. The resulting mixture was supplementary materials sup-2 Acta Cryst. (2012). E68, m1282-m1283 filtered to remove insoluble TlCl and excess TlPF 6 . To the resulting yellow-orange solution of Pr{Ni F }(CH 3 CN)]PF 6 was added a slight excess of solid pyrazole (Aldrich; 5.7 mg), and the reaction solution was stirred one hour. Then it was subjected to vapor diffusion with 30 ml me thyl tert-butyl ether (MTBE; Fisher reagent) at 22 °C for 3 days. The very pale yellow liquid of the resulting mixture was removed from the vial by a small-diameter syringe needle, and the rodlike orange crystals were washed twice with 1.5 ml of MTBE, removed from the vial, and then air-dried overnight in the dark (91% yield). The complex was characterized by NMR at 24 °C in CDCl 3 . Unusual features of the spectra are discussed below the data tabulation. Pincer Aryl: ipso δ 115.49(t of d; 4 J F-C =2.9 Hz, 2 J P-C =21 Hz) ortho δ 168.55 (d of t; 3 J F-C =15 Hz, 2 J P-C~7 .4 Hz) meta δ 94.89(d of t; 2 J F-C =33 Hz, 4 J P-C~6 .6 Hz) para δ 165.16 (d; 1 J F-C =246 Hz Pr i 2 P: methyne, δ 27.66(t; 1 J P-C =11 Hz) methyls δ 16.58(t; 2 J P-C =11 Hz), δ 16.41(s) Integrals recorded for 1 H signals of Pr{Ni F }(Pz)]PF 6 match expected values except for the low-field pyrazole N-H resonance in which strong hydrogen-bonding to the hexafluorophosphate counterion is likely. Overlap of 1 H triplets for the inequivalent isopropyl methyl groups created by different rotation rates around the Ni-Pz, P-C, and C-C bonds affords pseudo-quartets centered at δ 1.35 and δ 1.08 (Fig. 2). The same rotational phenomena generate a more unusual 13 C-NMR methyls pattern (Fig. 3), in which a triplet at δ 16.58 ( 2 J P-C =11 Hz) and singlet at δ 16.41 (no measurable P-C coupling observed) of equal intensity appear. Recording the 13 C-NMR spectrum with longer relaxation delay (4 s versus 1 s) or at 44 °C affords no change in this pattern.

Refinement
Hydrogen atoms were placed in calculated positions and allowed to ride during subsequent refinement, with U iso (H) = 1.2U eq (C) and C-H distances of 0.93 Å for the H atoms on the pyrazole carbons, U iso (H) = 1.2U eq (N) and an N-H distance of 0.86 Å for the H atom on the pyrazole N, U iso (H) = 1.2U eq (C) and C-H distances of 0.98 Å for the H atoms on the tertiary carbons, and U iso (H) = 1.5U eq (C) and C-H distances of 0.96 Å for the methyl H atoms.

Computing details
Data collection: CAD-4-PC (Enraf-Nonius, 1993); cell refinement: CAD-4-PC (Enraf-Nonius, 1993); data reduction:     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 > 2σ(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.