Cationic bis- and tris(eta(2)-(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)-(pz(2)-CH2)]BPh4 (2a,b) and trans-[M(PMe3)(2)(CO)(COMe)(eta(2)-pz(3)-CH)]BPh4 (3a,b), respectively (pz pyrazolyl ring). The reactions of 1b with 5,5'-Me-2-pz(2)-CH2 and 3,5'-Me-2-pz(2)-CH2 pro duce trans-[Ru(PMe3)(2)(CO)(COMe)(5,5'-Me-2-pz(2)-CH2)]BPh4 (4) and trans-[Ru(PMe3)(2)(CO)(COMe)(3,5'-Me-2-pz(2)-CH2)]BPh4 (5), respectively. A mixture of trans,cis-[Ru(PMe3)(2)(CO)(2)(eta(1)-3,3'-Me-2-pz(2)-CH2)(Me)]BPh4 (6) and trans-[Ru(PMe3)(2)(CO)(COMe)(3,3'-Me-2-pz(2)-CH2)]BPh4 (7) is obtained from reaction of 1b and 3,3'-Me-2-pz(2)-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 = 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 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 H-1-NOESY and F-19{H-1}-HOESY NMR spectra.