Ruthenium carbonyl 1,4-diaza-1,3-butadiene (R-DAB) complexes. Reactivity of Ru2(CO)5(R-DAB) toward molecular hydrogen. Molecular structure of H2Ru4(CO)8(R-DAB)2, containing an unique linear chain of four ruthenium atoms

Abstract

Hx,) reacts smoothly at 90 °C with molecular hydrogen to yield the oxidative addition product H2Ru2(CO)5(R-DAB). The same product can be obtained when Ru2(CO)6(R-DAB) (R = ¿-Pr, c-Hx, f-Bu) is used as starting material. In the products, which are characterized by FD-mass, IR, and NMR spectroscopy, the R-DAB ligand is in a tie-bonding mode. The NMR spectra indicate that the two hydride atoms are bonded (presumably terminally) to the same Ru atom. Ru3(CO)8(neo-Pent-DAB) reacts with H2 to yield both known H4Ru4(CO)12 and novel H2Ru4(CO)8(neo-Pent-DAB)2. The latter compound can also be obtained from the reaction of Ru2(CO)5(neo-Pent-DAB) with H2. Possible reaction routes are discussed. An X-ray crystal structure determination established the molecular geometry of this tetranuclear Ru-a-diimine complex. Crystals of H2Ru4(CO)8(neo-Pent-DAB)2 are monoclinic of space group C2/c with cell constants = 18.399 (7) k,b = 8.725 (3) A, c = 29.177 (8) A, ß = 110.43 (4)°, and Z = 4. A total of 1318 reflections have been used in the refinement resulting in a final R value of 0.038 (Rw = 0.064). The molecule possesses a pseudo-Cy, symmetry. Surprisingly, the four Ru atoms are located in a linear chain arrangement which is very unusual. The Ru(l)-Ru(2)-Ru(2)* angle is 176.48 (6)°. The Ru-Ru distances are in the range expected for single Ru-Ru bond lengths (Ru(l)-Ru(2) = 2.806 (2) A, Ru(2)-Ru(2)* = 2.745(2) A). Ru(l) is coordinated by two terminal carbonyls and Ru(2) by one. The central Ru(2)-Ru(2)* bond is symmetrically bridged by two carbonyls. The neo-Pent-DAB ligand is -, -'-bonded to Ru(l) with equal Ru(l)-N bond lengths of 2.09 (1) A and r)2-C=N,7)2-C'=N' bonded to Ru(2) with an average Ru-(2)-ligand atom distance of 2.30 (5) A. Likewise, the C-N and C-C bond lengths within the a-diimine part are equal (1.36(3) A) which is consistent with an 8e-bonding mode. The hydride ligands could not be located directly, however; the geometry around Ru(l) and the NMR data strongly indicate a terminal (on Ru(l)) bond position, which is quite unusual in a polynuclear metal carbonyl complex. Electronically, this species can be considered as electron precise, i.e., a 66e complex having three metal-metal bonds.

Homo- and Hetero-Oligonuclear Complexes of Platinum Group Metals (PGM) Coordinated by Imine Schiff Base Ligands

“…The examples of such coordination motif may be found both in simple 1,4-diazabutadiene ligands as reported by Abbel et al (Figure 7a; FIMNAR) [142] as well as in the case of more extended ligands as in the 1,2-diiminobenzene Ru complex, which shows interesting electrochemical properties (Figure 7b; AROQAZ) [122]. [143], GIRCAL [144], GLXRUA10 [145] and GLXRUB10 [146] and (g) unusual linear Ru4 cluster based on the 6e μ2-κ 2 -N,N':η 2 -C'=N' ligating 1,2diimine ligand [143] (CSD Refcode DEXBIR). Solvent molecules and hydrogen atoms were omitted for clarity.…”

“…Similar 8e donating μ2-κ 2 -N,N':η 2 -C=N:η 2 -C'=N' coordination scheme of DAB ligands are observed for example in oligonuclear metal carbonyl complexes (trinuclear Os [144] (GIRCAL), Ru [143] (CUXFIK), binuclear Ru [145] (GLXRUA10) and tetranuclear Ru [146] (GLXRUB10; Figure 7cf)).…”

“…Similar 8e donating µ 2 -κ 2 -N,N':η 2 -C=N:η 2 -C'=N' coordination scheme of DAB ligands are observed for example in oligonuclear metal carbonyl complexes (trinuclear Os [144] (GIRCAL), Ru [143] (CUXFIK), binuclear Ru [145] (GLXRUA10) and tetranuclear Ru [146] (GLXRUB10; Figure 7c-f However, the possible η 5 -like coordination mode may be disturbed, and "slipped" complexes are also observed with only one η 2 -C=N ligation and rarely encountered three-membered PdCN ring (Scheme 1l,m). An example may be a 6e donor µ 2 -κ 2 -N,N':η 2 -C'=N' coordination mode of DAB ligand, which was reported for monohydride metal carbonyl complexes of Ru [147] or described by Owen et al dipalladium unit with the η 2 -coordination mode [148] (Figure 8a,b; WAGKOE, OKAYUU).…”

Binuclear Complexes of Ruthenium and Osmium Containing Metal Metal Bonds

“…92 The same product is obtained on reaction o f (49) (R 1 = R 2 = Pr', Cy) with H 2 . 92 Further reaction of (77) with hydrogen at 90 °C leads to reduction o f the coordinated dab ligand with the formation of [Ru 2 H 2 (CO) 5 (Pr i NCH 2 CH 2 NPr i )] (78a)*, which reacts readily with carbon monoxide to give [Ru 2 (CO) 6 (Pr i NCH 2 CH 2 NPr i )] (78b)*.…”

“…92 The same product is obtained on reaction o f (49) (R 1 = R 2 = Pr', Cy) with H 2 . 92 Further reaction of (77) with hydrogen at 90 °C leads to reduction o f the coordinated dab ligand with the formation of [Ru 2 H 2 (CO) 5 (Pr i NCH 2 CH 2 NPr i )] (78a)*, which reacts readily with carbon monoxide to give [Ru 2 (CO) 6 (Pr i NCH 2 CH 2 NPr i )] (78b)*. 93 The electronic structure o f the latter, containing a sixelectron bridging ji,fi'-l,2-ethanediyldiamido ligand, has been determined using SCF first-principle discrete variational Xa calculations and gas-phase UV-photoelectron spectroscopy.…”