Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)methane]Mn(CO)(3)}SO3CF3 complexes: comparison of ligand donor properties

The known ligands HC(pz)(3), HC(3,5-Me(2)pz)(3), HC(3-Phpz)(3), and HC(3-(t )Bupz)(3) and the new ligand HC(3-'Prpz)(3) (pz = pyrazolyl ring) are prepa red in CHCl3-H2O using the appropriate pyrazole. an excess of Na2CO3, and t etra-n-butylammonium bromide as the phase transfer catalyst. Using these co nditions, good yields of the ligands are consistently obtained. The new lig and PhC(pz)(2)py (py = pyridyl ring) is prepared in the CoCl2 catalyzed con densation reaction of (pz)(2)S=O and Ph(py)C=O. The reaction of HC(pz)(3), (KOBu)-Bu-t and para-formaldehyde followed by quenching with water yields H OCH2C(pz)(3). All of these ligands, except HC(3-(t)Bupz)(3), react with [Mn (CO)(5)]SO3CF3, prepared in situ from Mn(CO)(5)Br and Ag(SO3CF3), to yield the respective [(ligand)Mn(CO)(3)]SO3CF3 complex. The carbonyl stretching f requencies and C-13-NMR trends of these complexes indicate that the donor a bilities of all of the ligands are fairly similar. The solid state structur e of {[HC(3-'Prpz)(3)]Mn(CO)(3)}(+) shows the HC(3-'Prpz)(3) ligand is trid entate with the iso-propyl groups rotated away from the Mn(CO)(3) core of t he cation relieving any possible steric congestion. (C) 2000 Elsevier Scien ce S.A. All rights reserved.