Simultaneous First- and Second-Sphere Coordination. Organopalladium Metalloreceptors for Water, Ammonia, Amines, Hydrazine, and the HydraziniumIon

Article abstract of DOI:10.1021/ic00126a040

The complexes [Pd(L)(CH3CN)][BF4] (L(3) = 5,8,11-trioxa-2,14-dithia[15]-m-cyclophane and L(5) = 5,8,11,14,17-pentaoxa-2,20-dithia[21]-m-cyclophane) were prepared by palladation of the respective thiacyclophane employing [Pd(CH3CN)4][BF4]2. These metalloreceptors were reacted with various small substrates (H2O, NH3, NH2R, NHR2, NH2NH2 and NH2NH3(1+)) capableof simultaneously coordinating to the Pd center and hydrogen-bonding with the peripheral ether oxygens. (Pd(L(3))(NH3)][BF4] crystallized in the space group Pbca with a = 21.377(4) ?, b = 21.656(5) ?, c = 9.437(6) ?, V = 4368(2) ?**3, and Z = 8. The structure refined to R = 6.41% and Rw = 7.03% for 659 reflections with Fo**2 > 3σ(Fo**2). [Pd(L(3))(NH2NH2)][BF4] crystallized in the space group P1- with a = 11.652(3) ?, b = 12.669(4) ?, c = 8.356(1) ?, α = 94.13(2)°, β = 94.34(2)°, γ = 117.21(1)°, V=1090.3(5) ?**3 and Z = 2. The structure refined to R = 2.81% and Rw= 3.40% for 2709 reflections with Fo**2 > 3σ(Fo**2). [Pd(L(5))(H2O)][BF4] crystallized in the space group P1- with a = 11.076(3) ?, b= 15.147(5) ?, c = 8.586(2) ?, V = 1284(1) ?**3, and Z = 2.The structure refined to R = 3.14% and Rw = 4.06% for 2275 reflections with Fo**2 > 3σ(Fo**2). [Pd(L(3) )(NH2NH3)][CF3SO3]2 crystallized in the space group P21/c with a = 11.906(4) ?, b = 17.19(1) ?, c= 15.313(4) ?, β = 111.18(2)°, V = 2923(4) ?**3, and Z = 4. The structure refined to R = 3.13% and Rw = 4.25% for 2954 reflections with Fo**2 > 3σ(Fo**2). [Pd(L(5))(NH2NH3)][BF4]2 crystallized in the space group P1- with a = 9.391(3) ?, b = 18.292(5) ?,c = 9.107(2) ?, α = 94.46(3)°, β = 102.02(2)°, γ = 103.51(2)°, V = 1474.5(8) ?**3, and Z = 2. Thestructure refined to R = 3.69% and Rw = 4.58% for 3059 reflections withFo**2 > 3σ(Fo**2). Each complex shows evidence of hydrogen bonding between the Pd-bound substrate and the peripheral oxygen atoms. The major hydrogen-bonding sites are the oxygen atoms adjacent to the thioether atoms, while the extent of the hydrogen bonding is dependent on the size of the polyether ring and the orientation of the substrate. Controlling the number of hydrogen bonds formed results in selective binding of primary amines (two hydrogen bonds) over secondary amines (one hydrogen bond) and tertiary amines (no hydrogen bonds) as determined by competition reactions monitored by (1)H NMR spectroscopy.