Structures, spectroscopy, and a mechanism of formation of linked-norbornadiene complexes of ruthenium(II). Interaction of ruthenium(II) with alicyclic hydrogen atoms

Abstract

The electronic structure of M O (~-B U S )~, as studied by a UV photoelectron spectroscopy and X,-SW MO calculations, will be a subject of a separate paper. ~~Since the molecular structure of tetrakis(alcoho1ato)molybdenum( IV) compound has not been studied by X-ray diffraction, of the rather rare class of mononuclear tetracoordinate d2 species. Acknowledgment. We thank Japan Synthetic Rubber Co., Ltd., this work contributes to our knowledge on the structural chemistry for the partial financial support and Climax Molybdenum c o * for the generous gift Of pentachloride* Supplementary Material Available:Table listing observed and (16) Otsuka, S.; Yoshida, T.; Matsumoto, M.; Nakatsu, K. J. Am. Chem. d c u l a t e d structure factors (1 page). Ordering information is SOC. 1976, 98, 5850. given on any current masthead page. Abstract: Reduction of [RuC12(diene)], (diene = norbornadiene (bicyclo[2.2.1] hepta-2.5-diene) or 1,s-cyclooctadiene) by means of zinc powder in the presence of norbornadiene (NBD) in refluxing acetonitrile affords a mixture of two new ruthenium(I1) complexes of empirical formula R U C I C~, H~~, in which three NBD molecules are involved. The structures of the wrystalking complexes [bicyclo[2. 2.l]hepta-2,5-diene-(2,3,5,6-~)]ch~oro[~-(tricyclo[2.2,l.02~6]heptan-3-yl-~H3)-endo,endo-bicyclo-[2.2.1] hept-5-en-2-yl-(2,5,6-v)]ruthenium(II) and [bicyclo[2.2.l]hepta-2,5-diene-(2,3,5,6-v)][endo-3-(bicyclo[2,2.1] hept-5-en-2-yl-~~)-endo,endo-bicyclo[ 2.2.11 hept-5-en-2-y1-(2,5,6-?)lchlororuthenium(11) 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(I1) atom and a hydrogen atom of the hydrocarbon ligand (6 -3.74 for the major isomer, 6 -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 grou C, !--PT; a = 7.389 (2), b = 13.271 (4), c = 9.439 (3) A; a = 105.37 (2)", = 101.18 (2)", y = 92.80 (2)O; V = 861.3 i3 at -150 OC; Z = 2; pobd = 1.59 (l), pcald = 1.590 g ~m -~. The molecules, including hydrogen atoms, were refined on lbz, including F: < 0 (6762 unique data collected at -150 "C), to values for R and R, on lbz of 0.050 and 0.072. For the portion of data where F: > 3a(F,2) (5788 reflections), the values for R and R, 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...

Chiral phosphine ligands in asymmetric synthesis. IV. Hydrosilation of ketones, and the structure of (bicyclo[2.2.1]hepta-2,5-diene)[N,N-dimethyl-1(R)-(o-(bis(tert-butyl)phosphino)phenyl)ethylamine]rhodium(I) perchlorate

“…All dimensions within the dibutphos ligand are normal, and they and other dimensions in the cation correspond well with those in related complexes (17,27,28). The geometry of the norbornadiene ligand is unexceptional (29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). Weighted leastsquares planes and selected torsion angles have been deposited as Tables SVI and S V I I .~…”

Two‐Step Synthesis of Heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14] tetradecane from Norbornadiene: Mechanism of the Cage Assembly and Post‐synthetic Functionalization

“…Only recently has a practical protocol for its synthesis based on Ru‐catalysis been reported [17] . Although still not studied in detail, cumulative evidence suggests that the cage closure starts with the formation of an endo‐endo NBD dimer A , which evolves through a sequence of consecutive olefin insertion steps into B [16b, 18] . Final C−H oxidative addition followed by C−C reductive coupling are probably the last steps of the cycle, delivering 7 and regenerating the Ru active species (Scheme 1).…”

Catalytic Cage Formation via Controlled Dimerization of Norbornadienes: An Entry to Functionalized HCTDs (Heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14]tetradecanes)

“…W ith fascinating highly symmetrical structures, carbocyclic cage compounds hold great promise for use as pharmaceuticals (e.g., amino-adamantanes), 1 energetic (e.g., nitrocubanes and CL-20), 2 and photonic/electronic materials (e.g., fullerenes). 3 In particular, HCTD (heptacyclo-[6.6.0.0 2,6 .0 3,13 .0 4,11 .0 5,9 .0 10,14 ]tetradecane) represents a unique class of cage molecules (Figure 1). 4 Analogous to cubanes and adamantanes, HCTD can be considered a distinct repository of cyclopentanes with D 2d symmetry.…”

“…The prior mechanistic study 8 suggested that forming the undesired PCTD was initiated by a Ru−H-mediated 1,2addition of NBD. 10 Thus, it is logical to hypothesize that one key to promote the desired cage formation would be to avoid forming a ruthenium−hydride species, which indicates that choosing an appropriate ruthenium precatalyst would be critical. From a practical viewpoint, the study was initiated by examining a range of commercially available Ru(II) salts in combination with appropriate reductants, e.g., Mn or Zn.…”

“…The prior mechanistic study suggested that forming the undesired PCTD was initiated by a Ru–H-mediated 1,2-addition of NBD . Thus, it is logical to hypothesize that one key to promote the desired cage formation would be to avoid forming a ruthenium–hydride species, which indicates that choosing an appropriate ruthenium precatalyst would be critical.…”