A Six-Coordinate Tris(3,5-dimethyl-1-pyrazolyl)methane−Thallium(I) Complex with a Stereochemically Inactive Lone Pair: Syntheses and Solid State Structures of {[HC(3,5-Me2pz)3]2Tl}PF6and {[HC(3,5-Me2pz)3]Tl}PF6(pz = Pyrazolyl)

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Abstract
The addition of the tris(pyrazolyl)methane ligand HC(3,5-Me2pz)3 (pz = pyrazolyl ring) to a THF solution of TlPF6 results in the immediate precipitation of {[HC(3,5-Me2pz)3]2Tl}PF6. The structure has been determined crystallographically. The arrangement of the nitrogen donor atoms about the thallium is best described as a trigonally distorted octahedron. The thallium atom sits on a crystallographic center of inversion; thus the planes formed by the three nitrogen donor atoms of each ligand are parallel. The Tl−N bond distances range from 2.891(5) to 2.929(5) Å (average = 2.92) Å. The lone pair on thallium is clearly stereochemically inactive and does not appear to influence the structure. The pyrazolyl rings are planar, but are tilted with respect to the thallium atom so as to open up the N···N intraligand bite distances. The thallium(I) complex with a ligand to metal ratio of 1/1, {[HC(3,5-Me2pz)3]Tl}PF6, is prepared in acetone by the reaction of equimolar amounts of HC(3,5-Me2pz)3 and TlPF6. The structure of the cation is a trigonal pyramid, with Tl−N bond distances that range from 2.64(1) to 2.70(1) Å (average = 2.67) Å. Pyrazolyl ring tilting is also observed in this complex, but the degree of tilting is smaller. Crystal data for {[HC(3,5-Me2pz)3]2Tl}PF6: monoclinic, P21/c, a = 9.210(6) Å, b = 13.36(1) Å, c = 16.067(8) Å, β = 92.48(5)°, V = 1975(2) Å3, Z = 2, R = 0.029. For {[HC(3,5-Me2pz)3]Tl}PF6: monoclinic, P21/n, a = 10.685(2) Å, b = 16.200(5) Å, c = 13.028(3) Å, β = 94.02(2)°, V = 2249.6(8) Å3, Z = 4, R = 0.042.

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