Synthesis and Structure Determination of Rh−diene Complexes with the Hydridotris(3,5-diisopropylpyrazolyl)borate Ligand, Tp^iPrRh(diene) (diene = cod, nbd):  Dependence of the ν(B−H) Values on the Hapticity of the Tp^iPrLigand (κ²vs κ³)¹

Abstract

Rhodium-diene complexes with the Tp iPr ligand, Tp iPr Rh(diene) (Tp iPr ) hydridotris(3,5-diisopropylpyrazolyl)borate; diene ) 1,5-cyclooctadiene (cod) (1), norbornadiene (nbd) (2)), are prepared by treatment of [Rh(µ-Cl)(diene)] 2 with KTp iPr or TlTp iPr . The structure of 1, characterized by X-ray crystallography, contains the κ 2 -coordinated Tp iPr ligand, and its central Rh atom adopts a square-planar geometry, whereas the unit cell of 2 contains two independent molecules: a square-planar structure with a κ 2 -coordinated Tp iPr ligand similar to 1 and a trigonal-bipyramidal one with a κ 3 -coordinated Tp iPr ligand. Although 1 H and 13 C NMR spectroscopy does not provide any information concerning the coordination geometry due to the interconversion between the square-planar and trigonal-bipyramidal structures, which occurs at a rate much faster than the NMR time scale, IR analysis reveals that the bands observed around 2470 and 2540 cm -1 are assigned to the B-H stretching vibrations of the square-planar and trigonal-bipyramidal structures, respectively. Thus, the ν(B-H) value can be used as an indicator of the hapticity of a Tp iPr ligand (κ 2 (∼2470 cm -1 ) vs κ 3 (>2530 cm -1 )) as compared with related Tp iPr ML n -type complexes.

Bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine − A Versatile Ligand for Complexation in RhI Cationic Complexes

“…The pyrazolyl-nitrogen to Rh distances are slightly different but are in the range found for hydridotris(pyrazolyl)borate rhodium complexes. [15,16] The N4ϪRh1 bond is significantly longer than the N1ϪRh1 bond, and this is certainly the consequence of the steric crowding around rhodium as there are no electronic reasons to justify this difference. This is evident if we consider the positioning of the 1,5-cyclooctadiene ligand.…”

“…This is evident if we consider the positioning of the 1,5-cyclooctadiene ligand. The atoms C15, C18, N1, and N4 lie in a plane, which is usually [16] defined by the pyrazolyl nitrogen atoms and the middle of the olefinic carboncarbon bonds. The rhodium atom lies 0.1 Å out of that coordination plane.…”

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

“…The position of the BϪH stretch in infrared spectra has been recognized as an indicator for the coordination mode of the Tp ligand (i.e., κ 3 versus κ 2 coordination). [54,55] It has, however, only very recently been realized that the frequency of this band also corresponds to the electron density on the metal ion to which it is coordinated and, more specifically, to its oxidation state. Thus, O'Hare and co-workers have just published a series of mixed-sandwich complexes containing both the Cp and the Tp ligand or the 3,5-dimethyl derivative thereof, several of them in the adjacent M II and M III oxidation states (M ϭ V, Cr, Co, Ni).…”

Denticity Changes of Hydrotris(pyrazolyl)borate Ligands in RhI and RhIII Compounds: Fromκ3- to Ionic “κ0”-Tp′

“…[21] As shown in Figure 2, there is no bonding interaction [22] between the Rh III center and Before closing, some comments on the application of the n(BÀH) [17] and d ( 11 B{ 1 H}) [18] criteria to ascertain the k n -Tp ' denticity in the above complexes appear appropriate. Referring for convenience and simplicity to the Tp Me2 derivatives, the n(B À H) stretching frequencies of 2 (2518 cm 2) and À 5.6 (3) also point in the same direction.…”