Dinitrogen ruthenium complexes

It is useful to compare the molecular and electronic stmctures of the bis(imino)pyridine iron dinitrogen complexes with those of the ruthenium congeners reported by Berry and coworkers [32]. Stirring K -( PDI)Ru(q -arene) complexes in non-arene solvents under a dinitrogen atmosphere furnished the bimetallic ruthenium dinitrogen complex [( PDI)Ru]2(P2> l dimeric... 

Historically, the most important ruthenium(II) ammine species is [Ru(NH3)5N2]2+, the first stable dinitrogen complex to be isolated (1965). It was initially obtained by refluxing RuC13 in hydrazine solution (but many... 

Some bis(dinitrogen) complexes exist, generally as m-isomers (presumably this minimizes competition for the metal t2g electron density in 7r-bonding). Unlike ruthenium, osmium(III) dinitrogen complexes do exist, showing osmium(III) to be a better 7r-donor not surprisingly, they are more labile than the osmium(II) species. 

The bulky ruthenium TMP complex Ru(TMP) is very electron deficient in the absence of any coordinating ligand, and a tt-complex with benzene has been proposed. In fact, it readily coordinates dinitrogen, forming the mono- and bis-N adducts Ru(TMP)(N2)(THF) and Ru(TMP)(N2)2, - As a result, the use of the TMP ligand for careful stereochemical control of the chemistry at the metal center, which has been very successful for the isolation of elusive rhodium porphyrin complexes, is less useful for ruthenium (and osmium) because of the requirement to exclude all potential ligands, including even N2,... 

Pell and Armor found entirely different products in alkaline solution. Above pH 8.3, the sole ruthenium product of the reaction of Ru(NH3)g+ with NO was the dinitrogen complex Ru(NH3)5(N2)2+. Under these conditions the rate law proved to be first-order in [Ru(NH3)g+], [NO] and [OH-]. A likely mechanism is the reversible reaction of Ru(NH3)3+ with OH- to give the intermediate Ru(NH3)5(NH2)2+, followed by electrophilic NO attack at the amide ligand and release of water. However, the kinetic evidence does not exclude other sequences. 

The first dinitrogen complex, characterized in 1965, resulted From the reduction of commercial ruthenium trichloride [containing some Ru(lV)] by hydrazine hydrate. The pentuammine(dinitrogen)ruthenium(Il) cation that formed could be isolated in a variety of salts.50 Soon other methods were found to synthesize the complex, such as the decomposition of the pentaammineazido complex, [Ru NH3)3N,Jj+, and even direct reaction with nitrogen gas ... 

The kinetic stability of these osmium(III) dinitrogen species, while less than that of the corresponding osmium(II) complexes, is far greater than for ruthenium(III) and shows that osmium(III) is capable of effective metal-to-ligand donation. Comparisons have been drawn, using electrochemical and pXa data, between the 7r-acceptor properties of CO and N2 in [OsL(NH3)5]3+ (L = CO, N2) species 54 thus, the pKR of [Os(NH3)6]3+ lies near 16,55 that of [Os(N2)(NH3)5]3+ is about 6.6 and that of [Os(NH3)5CO]3+ about 2.5. In basic solution osmium(III) dinitrogen complexes disproportionate to an osmium(II) dinitrogen species and osmiumfVI).64... 

Since 1965, when the first dinitrogen complex with ruthenium(II) was discovered [3a] N2 complexes with several transition metal compounds have been prepared. As with other unsaturated molecules, in these complexes dinitrogen acts both as electron donor and electron acceptor, the latter properties being more pronounced. Different kinds of complex are obtained experimentally and considered theoretically (e.g. see review [3b]). 

The photocatalytic oxidation of N2 by a suspension of Pt/Ti02/Ru02 in an aqueous solution of the ruthenium complex [Ru(HEDTA)N2] was reported by Taqui Khan et al. in a 1989 communication [112]. The complex that was actually used as a starting material was K[Ru(HEDTA)C1]-2H20. Taqui Khan stated that [Ru(HEDTA)Cl] was converted to [Ru(HEDTA)N2] and [(Ru(HEDTA))2N2]2 in situ by photochemical interaction with the irradiated Pt/Ti02/Ru02 in the presence of N2 gas. The dinitrogen complexes were identified by bands in the UV spectrum at 225 and 278 nm, respectively. 

Protonation of coordinated dinitrogen with acidic ruthenium dihydrogen complexes... 

PROTONATION OF COORDINATED DINITROGEN WITH ACIDIC RUTHENIUM DIHYDROGEN COMPLEXES... 

We also employed other ruthenium dihydrogen complexes for the protonation of the coordinated dinitrogen in complex (2b). Typical results are shown in Table 3 [21]. Ammonia is formed in higher yields (up to 79% based on tungsten) when dinitrogen complex (2b) is similarly treated with tra s-[RuCl(r -H2)(dppe)2]X... 

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