HOESY NMR Research Articles

Cationic Bis- and Tris(η2-(pyrazol-1-yl)methane) Acetyl Complexes of Iron(II) and Ruthenium(II): Synthesis, Characterization, Reactivity, and Interionic Solution Structure by NOESY NMR Spectroscopy

The complexes trans,cis-M(PMe3)2(CO)2(Me)I (M = Fe and Ru, 1a,b) react with bis- and tris(pyrazol-1-yl)methane, in the presence of NaBPh4, affording trans-[M(PMe3)2(CO)(COMe)(pz2-CH2)]BPh4 (2a,b) and trans-[M(PMe3)2(CO)(COMe)(η2-pz3-CH)]BPh4 (3a,b), respectively (pz = pyrazolyl ring). The reactions of 1b with 5,5‘-Me2-pz2-CH2 and 3,5‘-Me2-pz2-CH2 produce trans-[Ru(PMe3)2(CO)(COMe)(5,5‘-Me2-pz2-CH2)]BPh4 (4) and trans-[Ru(PMe3)2(CO)(COMe)(3,5‘-Me2-pz2-CH2)]BPh4 (5), respectively. A mixture of trans,cis-[Ru(PMe3)2(CO)2(η1-3,3‘-Me2-pz2-CH2)(Me)]BPh4 (6) and trans-[Ru(PMe3)2(CO)(COMe)(3,3‘-Me2-pz2-CH2)]BPh4 (7) is obtained from reaction of 1b and 3,3‘-Me2-pz2-CH2. The reactions of 2−7 with nucleophiles either give back the starting complex (Nu = I-) or analogous complexes (Nu = Br- and Cl-) or produce decomposition products of the complexes (Nu = I2, Br2, Cl2, and OMe-). The solid state structures of 2b and 3b were obtained using single-crystal X-ray diffraction. For all complexes, 2−7 as well as complex 8 (analogue to 2a, having a BF4- counterion instead of BPh4-), the ion-pair structures and the localization of the counterion in solution with respect to the organometallic moiety were investigated by the detection of interionic contacts in the 1H-NOESY and 19F{1H}-HOESY NMR spectra.