Transition Metal Complexes of Optically Active Tris(pyrazolyl)hydroborates

Daniel D. LeCloux, Michael C. Keyes, Masahisa Osawa, Veronica Reynolds, William B Tolman

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The synthesis and characterization of a series of complexes of the recently reported (LeCloux, D. D.; Tokar, C. J.; Osawa, M.; Houser, R. P.; Keyes, M. C.; Tolman, W. B. Organometallics 1994, 13, 2855–2866) ligands tris(7(R)-isopropyl-4(R)-methyl-4,5,6,7-tetrahydroindazolyl)hydroborate (TpMenth) and tris(7(S)-tert-butyl-4(R)-methyl-4,5,6,7-tetrahydroindazolyl)hydroborate (TpMementh) are presented. Specific complexes prepared are TpMenthMIICl (MII= ZnII, NiII, CoII, CuII, MnIIFeII), TpMementhZnIICl, TpMenthMII(NO3) (MII = CuII,NiII), TpMenthMII(OAc) (MII = CuII, NiII), TpMenthRhI(CO)2) TpMenthTiIV cl3, and TpMenth*TiIVCl3, where TpMenth* is an isomerized version of TpMenth in which one pyrazolyl group is attached to boron via the more, rather than the less, hindered N atom. Structural hypotheses are proposed on the basis of analytical and spectroscopic data for all compounds and X-ray crystal structures for TpMenthZnCl, TpMementhZnCl, TpMenthNi(OAc), and TpMenth*TiCl3. Pseudooctahedral 4-coordinate (TpMenthMCl and TpMementhZnCl), distorted square pyramidal 5-coordinate [TpMenthM(OAc) and TpMenthM(NO3)], and octahedral 6-coordinate (TpMenthTiCl3 and TpMenth*TiCl3) metal ion geometries were identified. IR and NMR data indicated that TpMenthRh(CO)2 exists as a mixture of 4- and 5-coordinate isomers. The combined synthetic, spectroscopic, and structural data for the complexes we have synthesized suggest that the chiral Tp ligands have effective steric properties similar to those of achiral variants with 3-tert-butyl or 3-isopropyl substituents on the pyrazolyl rings. X-ray data for TpMenthZnCl: orthorhombic, space group P212121 (No. 19), at −101 °C, a = 9.658(7) Å, b = 17.717(7) Å, c = 20.058(6) Å, V = 3444(5) Å3, Z = 4, R = 0.063 and Rw = 0.049 for 4055 reflections with I > 2σ(I) and 379 parameters. X-ray data for TpMementhZnCl: orthorhombic, space group P212121 (No. 19), at 24 °C, a = 11.170(4) Å, b = 14.829(9) Å, c = 23.063(9) Å, V = 3820(5) Å3, Z = 4, R = 0.055 and Rw = 0.056 for 4566 reflections with I > 2σ(I) and 407 parameters. X-ray data for TpMenthNi(OAc): orthorhombic space group P212121 (No. 19), at 24 °C, a = 10.139(5) Å, b = 18.248(8) Å, c = 19.700(8) Å,V= 3645(5) Å3, Z = 4, R = 0.043 and Rw = 0.039 for 3721 reflections with I > 2σ(I) and 406 parameters. X-ray data for TpMenth*TiCl3·CH2Cl2: orthorhombic, space group P212121 (No. 19), at —100 °C, a = 10.335(8) Å, b = 15.430(7) Å, c = 25.11(1) Å, V= 4004(7) Å3, Z = 4, R = 0.070 and Rw = 0.071 for 3831 reflections with I > 2σ(I) and 424 parameters.

Original languageEnglish (US)
Pages (from-to)6361-6368
Number of pages8
JournalInorganic chemistry
Issue number26
StatePublished - Dec 1 1994


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