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

Abstract

The complexes trans,cis -M(PMe 3 ) 2 (CO) 2 (Me)I (M = Fe and Ru, 1a, b ) react with bis- and tris(pyrazol-1-yl)methane, in the presence of NaBPh 4, affording trans- [M(PMe 3 ) 2 (CO)(COMe)(pz 2 -CH 2 )]BPh 4 ( 2a, b ) and trans- [M(PMe 3 ) 2 (CO)(COMe)(η 2 -pz 3 -CH)]BPh 4 ( 3a, b ), respectively (pz = pyrazolyl ring). The reactions of 1b with 5,5‘-Me 2 -pz 2 -CH 2 and 3,5‘-Me 2 -pz 2 -CH 2 produce trans- [Ru(PMe 3 ) 2 (CO)(COMe)(5,5‘-Me 2 -pz 2 -CH 2 )]BPh 4 ( 4 ) and trans- [Ru(PMe 3 ) 2 (CO)(COMe)(3,5‘-Me 2 -pz 2 -CH 2 )]BPh 4 ( 5 ), respectively. A mixture of trans,cis- [Ru(PMe 3 ) 2 (CO) 2 (η 1 -3,3‘-Me 2 -pz 2 -CH 2 )(Me)]BPh 4 ( 6 ) and trans -[Ru(PMe 3 ) 2 (CO)(COMe)(3,3‘-Me 2 -pz 2 -CH 2 )]BPh 4 ( 7 ) is obtained from reaction of 1b and 3,3‘-Me 2 -pz 2 -CH 2 . 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 = I 2, Br 2, Cl 2, 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 BF 4 - counterion instead of BPh 4 - ), 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 1 H-NOESY and 19 F{ 1 H}-HOESY NMR spectra.