119009-98-2Relevant articles and documents
Use of pyrazolyl ligands for the formation of a bimetallic cobalt-ruthenium complex
Shi, Yifan,Arif, Atta M.,Ernst, Richard D.
, p. 1899 - 1905 (2011)
A straightforward route to Ru(pyz)2(Hpyz)4 (Hpyz = pyrazole) has been developed. This has been found to react readily with a modified Co(pyrazolylborate)Cl complex in the presence of triethylamine as an HCl acceptor to yield a bimetallic cobalt-ruthenium complex, in which the two metals are each six-coordinate, and bridged by three pyrazolyl anions. Both species have been characterized structurally, as has a modified Co(pyrazolylborate)2 complex.
Steric effects in polypyrazolylborate ligands. Poly(3-isopropylpyrazolyl)borates: Ligands of intermediate steric requirements
Trofimenko, Swiatoslaw,Calabrese, Joseph C.,Domaille, Peter J.,Thompson, Jeffery S.
, p. 1091 - 1101 (2008/10/08)
The synthesis, structures, and coordination chemistry of a series of polypyrazolylborate ligands, [HnB(3-isopropylpyrazol-1-yl)4-n]- and [HB(3-isopropyl-4-bromopyrazol-1-yl)3]-, are presented. These ligands are made by the reaction of tetrahydroborate ion with the appropriate pyrazole. A series of metal complexes was prepared and characterized by analytical and spectroscopic data. In addition, four complexes were characterized by means of X-ray diffraction techniques. The complex Co(HB(3-isopropyl-4-bromopyrazol-1-yl)3)(NCS) crystallizes in the tetragonal space group P421m with four molecules per unit cell of dimensions a = 17.450 (3) ? and c = 9.025 (1) ? at -70°C. Least-squares refinement of 160 variables led to a value of the conventional R index (on F) of 0.042 and of Rw of 0.033 for 879 reflections with I > 3.0σ(I), The geometry about the Co(II) ion, which is coordinated to three pyrazolyl nitrogen atoms and the nitrogen atom of the thiocyanate group, is tetrahedral. The isopropyl group and the bromine atom are in the 3- and 4-positions of the pyrazolyl ring, respectively. The complex Co(B(3-isopropylpyrazol-1-yl)4)2 crystallizes in the monoclinic space group C2/c with four molecules in a unit cell of dimensions a = 15.276 (3) ?, b = 19.856 (5) ?, c = 19.274 (3) ?, and β = 109.37 (1)° at -70°C. Least-squares refinement of 309 variables led to a value of the conventional R index of 0.057 and of Rw of 0.050 for 2800 reflections with I > 3.0σ(I). The geometry about the Co(II) ion, which is coordinated to four pyrazolyl nitrogen atoms from two ligands, is tetrahedral. The isopropyl group is in the 3-position of each pyrazolyl ring. The complex Co(HB(3-isopropylpyrazol-1-yl)2(5-isopropylpyrazol-1-yl))2 crystallizes in the triclinic space group P1 with one molecule in a unit cell of dimensions a = 9.076 (2) ?, b = 10.784 (2) ?, c = 11.079 (1) ?, α = 108.66 (1)°, β = 93.35 (1)°, and γ = 100.12 (1)° at -70°C. Least-squares refinement of 232 parameters led to a value of the conventional R index of 0.037 and of Rw of 0.045 for 3581 reflections with I > 3.0σ(I). The geometry about the Co(II) ion, which is coordinated to six pyrazolyl nitrogen atoms from two ligands, is octahedral. The isopropyl group is in the 3-position for two rings, whereas for the third, this group is in the 5-position. The complex Co(HB(3-isopropyl-4-bromopyrazol-1-yl) 2(5-isopropyl-4-bromopyrazol-1-yl))2 crystallizes in the triclinic space group P1 with one molecule per unit cell of dimensions a = 10.164 (1) ?, b = 10.236 (2) ?, c = 12.938 (2) ?, α = 111.08 (1)°, β = 99.26 (1)°, and γ = 106.28 (1)° at -70°C. Least-squares refinement of 259 variables led to a value of the conventional R index of 0.037 and of Rw of 0.032 for 2950 reflections with I > 3.0σ(I). The geometry about the Co(II) ion and ring substitution patterns are the same as those for the octahedral complex described above, with the addition of a bromine atom in the 4-position of each ring. These last two structural studies reveal a unique feature of these new ligands: rearrangement of the mode of coordination by a pyrazolyl group in octahedral complexes to relieve steric crowding. The results presented here indicated that these ligands have properties that are unique and transitional from those of the previously reported, relatively unhindered ligands such as [HnB(pyrazolyl-1-yl)4-n]- to the sterically bulky ligands [HnB(3-R-pyrazol-1-yl)4-n]-, where R = tert-butyl and phenyl groups.
