Influence of .alpha. branching of the 1,4-substituents on the coordination of 1,4-diazabutadienes in mono-, bi-, tri-, and tetranuclear ruthenium carbonyl complexes. Crystal structure of [.sigma.-N, .sigma.-N', .eta.2-C = N, .eta.2-C = N'-diglyoxal bis(isopropylimine)]octacarbonyltetraruthenium

Ruthenium carbonyl 1,4-diaza-1,3-butadiene (R-DAB) complexes. 5. Syntheses, spectroscopic properties, and reactivity of Ru2(CO)5(alkyl-DAB), a key intermediate in the Ru3(CO)12-alkyl-DAB reaction. Crystal and molecular structure of (1,4-diisopropyl-1,4-diaza-1,3-butadiene)pentacarbonyldiruthenium, Ru2(CO)5(isopropyl-DAB)

“…Thus, in 6 ( -, -', ij2-C=N' or -, µ2-', 772-C=N')-coordinated R-DAB complexes, the imine protons are no longer equivalent and an AX pattern is observed. 3,4,18 The imine proton of the -- coordinated C=N part still absorbs at about 8 ppm, but the proton of the jj2-C=N-coordinated half appears at about 4 ppm, with JAX = 2 Hz. In 8ß( -, -', r;2-C=N, t?2-C'= N')-coordinated R-DAB compounds, both imine protons are again equivalent and give one singlet at about 6 ppm.…”

Preparation and Properties of Carbonyliron Complexes of 1-Aza-4-oxa-1,3-butadiene (α-Imino Ketone) – X-ray Crystal Structures of Fe(CO)3[MeNC(Ph)C(Ph)=O] and Fe2(CO)4[tBuNC(H)(Me)C(O)(O)C(Me)C(H)=NtBu]

“…[66] Thirdly, the stability of complexes 6 depends on the propensity of η 2 -CϭN coordination to a second metal fragment, giving rise to the formation of complexes 7. The propensity of the analogous R-DAB towards η 2 -CϭN coordination has been studied by Staal et al [17] and decreases on going from RCH 2 to R 2 CH to R 3 C for the imine nitrogen substituent on R-DAB. The propensity towards η 2 -CϭN coordination will also depend on the substituent on the imine carbon atom and decreases in the order H Ͼ Me ϾϾ Ph, as has been found in the reactivity of complexes [{C 5 H 4 N-2-C(R 3 )ϭNR 1 }Fe(CO) 3 ] (R 3 ϭ H, Me, Ph) towards Fe(CO) 4 fragments.…”

“…[40,41] Judging from the angles around the iron atom (cf. Table 4) the coordination around the central iron atom in 6g more closely resembles a distorted square-pyramidal geometry (89% along the Berry pseudorotation coordinate [42] ) with the basal plane defined by N(1), C (16)(17)(18), and with Fe(1) 0.353(1) Å above that plane. An ideal tbp or sqp geometry is not possible for these chelate complexes because of the small bite angle of the α-imino ketone (81 ± 1°), a feature also observed in many R-DAB complexes.…”

Binuclear Complexes of Ruthenium and Osmium Containing Metal Metal Bonds

“…55 Further studies have subsequently revealed that mono-, tri-and tetranuclear, as well as binuclear products, are formed in these reactions with the actual product or products o f any particular reaction being dependent on the conditions employed and the a-branching o f the substituents attached to the diazabutadiene. 56 For R 1 = R 2 = Cy, the mononuclear species [Ru(CO) 3 (Cy,Cy-dab)] has been positively identified as the first observable product o f the reaction o f 1,4-diazabutadienes with [Ru 3 (CO) 12 ], leading to the formation of the dinuclear species, [Ru 2 (CO) 6 (Cy, Cy-dab)] (49) (R 1 = R 2 = Cy). 57 Further reaction o f the latter with [Ru 3 (CO) 12 ] at 1 0 0 °C produces the trinuclear compound [Ru 3 (CO) 9 (Cy, Cy-dab)].…”

“…The two azaruthenacyclopentadienyl rings in this species are isolobally related to cyclopentadienyl rings such that the complex is formally isolobal with [Ru 2 Cp 2 (u-CO) 2 (CO) 2 ] . w Subsequent more detailed studies o f the reactions involving the ligands where R' = Me or Ph and R 2 = Pr 1 or Bu l revealed the formation o f dinuclear [Ru 2 (CO) 6 (R'C=CHCH 2 NR 2 )] (55)* and [Ru 2 (CO) 6 (R 1 CH 2 CCHNR 2 )] (56)* in the initial stages o f the reaction, both o f which contain an isomerized R',R 2 -mad ligand that is part of a five-membered azaruthenacycle in (55) and a fourmembered azaruthenacycle in (56). 67 ' Compound (55) contains a p-metallated, formally dianionic enylamido ligand in which the initially abstracted H p atom has been transferred to the carbon a to the nitrogen, while compound (56) contains an a-metallated, formally dianionic azoallyl ligand with the initially abstracted H a atom being transferred to the C p atom.…”