Reduction of [RuCl2(diene)]n (diene = norbornadiene (bicyclo[2.2.1]hepta-2.5-diene) or 1,5-cyclooctadiene) by means of zinc powder in the presence of norbornadiene (NBD) in refluxing acetonitrile affords a mixture of two new ruthenium(II) complexes of empirical formula RuC1C21H25, in which three NBD molecules are involved. The structures of the cocrystallizing complexes [bicyclo[2.2.1]hepta-2,5-diene-(2,3,5,6-η)]chloro[3-(tricyclo[2.2.1.02,6]heptan-3-yl-kH3)-endo-bicyclo- [2.2.1]hept-5-en-2-yl-(2,5,6-7))]ruthenium(II) and [bicyclo[2.2.1]hepta-2,5-diene-(2,3,5,6-η)]endo-3-(bicyclo[2.2.1]hept-5- en-2-yl-kH2)-endo-bicyclo[2.2.1]hept-5-en-2-yl-(2,5,6-η)]chlororuthenium(II) were determined by single-crystal X-ray diffraction methods. These two isomers, differing only in the nature of the third noncoordinated NBD moiety, were found in the crystal in a ratio 86:14, respectively. Proton NMR spectroscopy of these complexes indicates a strong interaction between the ruthenium(II) atom and a hydrogen atom of the hydrocarbon ligand (-3.74 for the major isomer, -2.83 for the minor isomer), which was further substantiated by the X-ray structure determination of this complex. Relevant crystal data are as follows: space group Cj-Pi; a = 7.389 (2), b = 13.271 (4), c = 9.439 (3) Å; a = 105.37 (2)°, β = 101.18 (2)°, γ = 92.80 (2)°; V = 861.3 Å3 at -150 °C; Z = 2; pokd = 1.59 (1), pcaled = 1.590 g cm-3. The molecules, including hydrogen atoms, were refined on E1, including F02 < 0 (6762 unique data collected at -150 °C), to values for R and Rv on F2 of 0.050 and 0.072. For the portion of data where F02 > 3a(F02) (5788 reflections), the values for R and Fw on F are 0.028 and 0.036. The primary coordination sphere is composed of one chloro, one alkyl, and three olefin ligands. Two metal-olefin bonds are provided by a free norbornadiene molecule. The third such bond is provided by a substituted norbornenyl molecule; the other olefin bond of its norbornadiene parent is now involved in (i) a metal-alkyl bond approximately trans to the chloro ligand and in (ii) a covalent bond to a nortricyclyl derivative of norbornadiene for the major component and a (second) norbornenyl derivative for the minor component. A pseudooctahedral geometry is completed by an unusually close Ru-HCR3 contact of 2.10 (3) A with the otherwise dangling nortricyclyl (or norbornenyl) component. The Ru-Cl separation is 2.483 (1) A.; the Ru-Csn3 separation is 2.099 (2) A. and the six Ru-Colcfm separations range from 2.110 (2) to 2.353 (2) A. The C=C bond lengths (1.422 (2), 1.400 (2), and 1.385 (2) A) are correlated with the Ru-Colefin separations. For the related complex [Ru(C21H25)(CH3CN)] [CF3S03], generated by the reaction of RuClC21H25 with silver triflate in an acetonitrile solution, an even stronger interaction between the ruthenium(II) center and the hydrogen atom was inferred from the NMR spectrum (δ -4.93). Formation of the RuC1C21H25 moiety from the active intermediate complex RuHCl(NBD)2 by an Ru-H insertion followed by an Ru-C insertion into olefinic bonds is postulated.
ASJC Scopus subject areas
- Colloid and Surface Chemistry