Syntheses, homeomorphic and configurational isomerizations, and structures of macrocyclic aliphatic dibridgehead diphosphines; molecules that turn themselves inside out

The diphosphine complexes cis- or trans- 
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 PtCl2(P((CH2)n)3P 
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 ) (n = b/12, c/14, d/16, e/18) are demetalated by MC 
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 X nucleophiles to give the title compounds (P((CH2)n)3)P (3b–e, 91–71%). These “empty cages” react with PdCl2 or PtCl2 sources to afford trans-MCl2(P((CH2)n)3P). Low temperature 31P NMR spectra of 3b and c show two rapidly equilibrating species (3b, 86 : 14; 3c, 97 : 3), assigned based upon computational data to in,in (major) and out,out isomers. These interconvert by homeomorphic isomerizations, akin to turning articles of clothing inside out (3b/c: ΔH‡ 7.3/8.2 kcal mol−1, ΔS‡ −19.4/−11.8 eu, minor to major). At 150 °C, 3b, c, e epimerize to (60–51) : (40–49) mixtures of (in,in/out,out) : in,out isomers, which are separated via the bis(borane) adducts 3b, c, e·2BH3. The configurational stabilities of in,out-3b, c, e preclude phosphorus inversion in the interconversion of in,in and out,out isomers. Low temperature 31P NMR spectra of in,out-3b, c reveal degenerate in,out/out,in homeomorphic isomerizations (ΔG‡Tc 12.1, 8.5 kcal mol−1). When (in,in/out,out)-3b, c, e are crystallized, out,out isomers are obtained, despite the preference for in,in isomers in solution. The lattice structures are analyzed, and the D3 symmetry of out,out-3c enables a particularly favorable packing motif. Similarly, (in,in/out,out)-3c, e·2BH3 crystallize in out,out conformations, the former with a cycloalkane solvent guest inside.

D 5 H (7.16), toluene-d 7 (7.09), or acetone-d 5 (2.05); 13 C, internal CDCl 3 (77.16), C 6 D 6 (128.06), toluene-d 8 (137.48), or acetone-d 6 (29.84); 31 P, external 85% H 3 PO 4 (0.00). IR spectra were obtained on a Shimadzu IRAffinity-1 spectrometer with a Pike MIRacle ATR system (diamond/Zn-Se crystal). Melting points were recorded using a Stanford Research Systems MPA100 (Opti-Melt) automated apparatus. Microanalyses were conducted by Atlantic Microlab. cis-PtCl 2 (P((CH 2 ) 12 ) 3 P) (cis-2b). Higher yield procedure. A three-neck flask fitted with a condenser was charged with cis-1b (0.7523 g, 0.8258 mmol) s2 and CH 2 Cl 2 (800 mL). A solution of Grubbs' catalyst (0.849 g, 0.103 mmol) in CH 2 Cl 2 (50 mL) was added dropwise at 0 °C over 40 min with stirring. The mixture was refluxed. After 18 h, the sample was cooled to room temperature and another charge of Grubbs' catalyst added (0.0854 g, 0.1038 mmol). The mixture was refluxed. After 24 h, the solvent was removed by rotary evaporation. The residue was chromatographed on neutral alumina (4 × 13 cm column) with CH 2 Cl 2 and ethyl acetate. The solvent was removed by rotary evaporation from the ethyl acetate eluates. The light brown/grey solid was transferred to a Fisher-Potter bottle that was charged with PtO 2 (0.0427 g, 0.1880 mmol), was filtered. The filter cake was washed with THF (3 × 5 mL). The solvent was removed from the filtrate by oil pump vacuum, and hexanes (50 mL) added. The suspension was filtered through celite and the filter cake washed with hexanes (3 × 5 mL). The solvents were removed from the filtrate by oil pump vacuum (15 h) to give (in,in/out,out)-3c as a white powder (0.339 g, 0.521 mmol, 91%). s8 (in,in/out,out)-3c using LiCCPh. A Schlenk flask was charged with trans-2c (0.0706 g, 0.0770 mmol) s8 and LiCCPh (0.0403 g, 0.373 mmol) in a glove box, and THF (3 mL) added with stirring. After 4 d, a white precipitate had formed. The solvent was removed by oil pump vacuum, and benzene added. The mixture was shaken. After 5 min, the clear supernatant was transferred by cannula to a second Schlenk flask. The solvent was removed by heating and oil pump vacuum to give (in,in/out,out)-3c as a yellow solid (0.0431 g, 0.0662 mmol, 86%).

Crystallography.
A. out,out-3b. A hexanes solution of (in,in/out,out)-3b was allowed to slowly concentrate under argon at -38 °C. After 7 d, clear plates were collected and data obtained per Table s1. Cell parameters were derived from 45 frames using a 1° scan and refined with 17631 reflections. Integrated intensity information for each reflection was obtained by reduction of the data frames with the program APEX3. s9 Lorentz, polarization, crystal decay, and adsorption corrections were applied, the last with the program SADABS. s10 The space group was determined from systematic reflection conditions and statistical tests. Non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were fixed in idealized positions using a riding model. The absence of additional symmetry or voids was confirmed using PLATON (ADDSYM). s11 The structure was refined (weighted least squares refinement on F 2 ) to convergence. s12 B. out,out-3c. A saturated hexanes solution of (in,in/out,out)-3c was kept at 4 °C. Hexagonal plates were collected and data obtained per Table s1. Integrated intensities for each reflection were obtained by reduction of the data frames with the program SAINT. s13 Cell parameters were obtained and refined with 14394 (1047 independent) reflections. s14 Lorentz, polarization, and adsorption corrections were applied, the last with the program SADABS. s10 The space group was determined from systematic reflection conditions and statistical tests. The structure was solved by direct methods and refined (weighted least squares refinement on F 2 ) using SHELXL-97. s12 Non-hydrogen atoms were refined with anisotropic thermal parameters. The hydrogen atoms were placed in idealized positions, and refined using a riding model.
C. out,out-3e. A CH 2 Cl 2 solution of (in,in/out,out)-3e was allowed to slowly concentrate under a N 2 atmosphere at −35 °C. After 18 d, yellows plates were collected and data obtained per Table s1. Cell parameters were obtained from 45 frames using a 1° scan and refined with 46796 reflections. Integrated intensity information for each reflection was obtained by reduction of the data frames with the program APEX3. s9 Lorentz, polarization, and adsorption corrections were applied, the last with the program SADABS. s10 The space group was determined from systematic reflection conditions and statistical tests. Non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were fixed in idealized positions using a riding model. Elongated or abnormal thermal ellipsoids for all carbon atoms of two methylene chains (related by a C 2 symmetry axis passing through the midpoint of the third chain) indicated possible disorder, which was modeled between two positions with an occupancy ratio of 0.77:0.23. The absence of additional symmetry or voids was confirmed using PLATON (ADDSYM). s11 The structure was refined (weighted least squares refinement on F 2 ) to convergence. s12 D. out,out-3c·2BH 3 ·(C 5 H 9 CH 3 ) and out,out-3c·2BH 3 ·(C 6 H 11 CH 3 ). Hexanes and methylcyclohexane solutions of (in,in/out,out)-3c·2BH 3 were allowed to slowly concentrate at room temperature. Data were obtained on the resulting crystals per Table s1. Integrated intensities for each reflection were acquired by reduction of the data frames with the program SAINT. s13 Cell parameters were obtained from 3960 frames using ω and φ scans and refined with 15936 and 14070 reflections, respectively. s14 Lorentz, polarization, and adsorption corrections were applied, the last with the program SADABS. s10 For out,out-3c·2BH 3 ·(C 5 H 9 CH 3 ), the methylene chains C1 to C14 and C15 to C28 exhibited elongated thermal ellipsoids, suggesting disorder that was modeled with occupancy ratios of 0.81/0.19 (C1 to C14) and 0.52/0.48 (C15 to C28). s15 Restraints were used to keep the bond distances and thermal ellipsoids meaningful. For out,out-2·2BH 3 ·(C 6 H 11 CH 3 ), the thermal parameters of the phosphorus atoms, the boron atoms, and one methylene chain (C1 to C14) were very well defined. The ellipsoids of the other methylene chains (C15 to C28 and C29 to C42) were elongated, indicating possible disorder. At this point the R factor was 12.9%. The restraints SIMU and DELU were applied to the latter two chains, resulting in a final R factor of 13.4%.
Attempts to model the disorder increased the numbers of parameters and restraints, as well as the R factor (>16%).

Rate and 2D NMR Measurements. A
Mass Spectrometry (m/z).  (s7) This coupling represents a satellite (d, 195 Pt = 33.8%) and is not reflected in the peak multiplicity given. (s15) For out,out-3·2BH 3 ·(C 5 H 9 CH 3 ), the numbering of carbon atoms C1-C42 has been changed from that in the CIF to be comparable with out,out-3·2BH 3 ·(C 6 H 11 CH 3 ).      . Peak widths (w 1/2 ) for the 31 P{ 1 H} NMR signal of (in,in/out,out)-3c as a function of solvent and temperature (162 or 202 MHz). Below T c in toluene-d 8 (Figure s1), the peak width is for the major isomer (in,in-3c). Possible interpretations of the data in the chlorinated solvents include, inter alia, (a) that still lower temperatures are required for the decoalescence of the signals of in,inand out,out-3c, or (b) that the K eq has greatly increased from the 97:3 in toluene-d 8 .

Figure s6.
Peak widths (w 1/2 ) for the 31 P{ 1 H} NMR signal of (in,in/out,out)-3e as a function of solvent and temperature (202 MHz). One interpretation of these data is that the barriers for interconverting in,inand out,out-3e are much lower than for the lower homologs.