RuCl, 2 complex

Selective oxidation of alcohols. Primary alcohols are oxidized by this RuCL complex about 50 times as rapidly as secondary alcohols. Use of benzene as solvent is critical lor this high selectivity. Little or no reaction occurs in CH3CN, THF, or DMF. Most oxidants, if they show any selectivity, oxidize secondary alcohols more rapidly than primary ones. However, ruthenium-catalyzed oxidations with N-mcthylmorpholine N-nxide and oxidations with PCC4 proceed about three times as rapidly with primary alcohols as with secondary ones. 

Ruthenium, in the presence of osmium, can be determined after reduction of RUO4 in 6-10 M HCl (RuCle complex) (Os does not interfere in the determination of Ru) [8]. Ruthenium can be determined also as various chloride complexes combined with SnCb ions [54,70]. Such a complex has been used for determining Ru in the presence of Os, by derivative spectrophotometry [71]. This method has also been used for determining Ru in the presence of Rh after the reaction with octadecyldithiocarbamate [72] and triazine derivatives (in picrate medium) [73]. Simultaneous determination of Ru and Os by derivative spectrophotometry can be performed after absorption of volatile RUO4 and OSO4 in water [7]. 

Dinitrogen complexes are molecules that contain dinitrogen bound to a metal. The first dinitrogen complex, [Ru(N2) (NH ) ], was reported in 1965 as a product of the interaction of hydrazine and RuCl (aq) (18). There are hundreds of complexes in the 1990s with dinitrogen as a ligand (19,20). 

Binary Compounds. The mthenium fluorides are RuF [51621 -05-7] RuF [71500-16-8] tetrameric (RuF ) [14521 -18-7] (15), and RuF [13693-087-8]. The chlorides of mthenium are RUCI2 [13465-51-5] an insoluble RuCl [10049-08-8] which exists in an a- and p-form, mthenium trichloride ttihydrate [13815-94-6], RuCl3-3H2 0, and RuCl [13465-52-6]. Commercial RuCl3-3H2 0 has a variable composition, consisting of a mixture of chloro, 0x0, hydroxo, and often nitrosyl complexes. The overall mthenium oxidation state is closer to +4 than +3. It is a water-soluble source of mthenium, and is used widely as a starting material. Ruthenium forms bromides, RuBr2 [59201-36-4] and RuBr [14014-88-1], and an iodide, Rul [13896-65-6]. 

Figure 11.10 Complexes containing bent NO groups (a) fIr(CO)Cl(NO) PFh3)iJ , and (b) [RuCl NO)2(PFh3)2]. ...

Complexes 206 (E = P, R = CH2CH2NMc2, CH2NMc2, R = R = Me, R = H) were utilized as ligands with respect to [Cp RuCl]4 (970M2862). Their properties... 

Dimethyl-, 3,5-diphenyl-, and 3,5-di-tert-butylpyrazolato potassium salts with [Cp RuCl]4 give the first structurally proven -coordinated complexes 48 (R = Me, t-Bu, Ph) in the azole series (99JA4536). 

Dimesitylimidazolium chloride in the presence of potassium tert-butylate reacts with [RuCl2(PCy3)2(=CHPh)] or [RuCl2(PCy3)2(=CHCH=CMe2)] to yield the mixed phosphine-carbene complexes [RuCL(L)(PCy3)(=CHPh)] or... 

It appeared to be a logical consequence to transfer this synthetic principle to more suitable metals like ruthenium and introduce bulky, kinetically stabilizing ligands at the metal. An interesting example for this approach is the complex 78. The latter is synthesized from Cp RuCl(PR3)2 with ClMgCH2SiMe2H through 77 by a thermal Si — H activation reaction. 

The reaction of the coordinatively unsaturated ruthenium amidinates with [Cp RuCl]4 tetramer or [CpRufMeCNlsJPFg provides access to novel amidinate-bridged dinuclear ruthenium complexes (Scheme 146), which in turn can be transformed into cationic complexes or hydride derivatives. In these complexes, a bridging amidinate ligand perpendicular to the metal-metal axis effectively stabilizes the highly reactive cationic diruthenium species. 

Ruthenium complexes have also been reported as active species for enan-tioselective Diels-Alder reactions. Faller et al. prepared a catalyst by treatment of (-)-[( ] -cymene)RuCl(L)]SbF6 with AgSbFe resulting in the formation of a dication by chloride abstraction [95]. The ligand was (-l-)-IndaBOx 69 (Scheme 36) and the corresponding complex allowed the condensation of methacrolein with cyclopentadiene in 95% conversion and 91% ee. As another example, Davies [96] prepared the complex [Ru(Fl20)L ( i -mes)] [SbFe]2 (with 70 as L in Scheme 36), and tested its activity in the same reaction leading to the expected product with similar activity and lower enan-tioselectivity (70%). 

Fig. 1. P MAS NMR spectrum of (a)Ru-BrNAP/PTA/y-Al203, and (b)Ru-BINAP crt rlex In order to find the characteristics of the immobilized catalyst, asymmetric hydrogenation of the prochiral C=C bond was performed as a model reaction. Firstly, three different homogeneous Ru-BINAP complexes including [RuCl2((R)-BINAP)], [RuCl((R)-BINAP)(p-cymene)]Cl and [RuCl((R)-BINAP)(Benzene)]Cl were immobilized on the PTA-modified alumina. Reaction test of immobilized catalysts showed that [RuCl2((R)-BINAP)] was the most active and selective so all the experiment were done using this catalyst afterwards.

Madsen and co-workers have reported an important extension to the amine alkylation chemistry, in which oxidation takes place to give the amide product [13]. A ruthenium NHC complex is formed in situ by the reaction of [RuCl Ccod)] with a phosphine and an imidazolium salt in the presence of base. Rather than returning the borrowed hydrogen, the catalyst expels two equivalents of H. For example, alcohol 31 and benzylamine 27 undergo an oxidative coupling to give amide 32 in good isolated yield (Scheme 11.7). 

Another method for reductive dimerization has been developed in hy-drosilylation. NiCl2-SEt2 is an effective catalyst in silylative dimerization of aromatic aldehydes with a hydrosilane (Scheme 12) [40]. A catalytic thiolate-bridged diruthenium complex [Cp RuCl(/ 2-SPrI)2RuCp ][OTf] also induces the conversion to 1,2-diaryl-1,2-disiloxyethane [41]. A dinuclear (siloxyben-zyl)ruthenium complex is considered to be formed, and the homolytic Ru - C bond fission leads to the siloxybenzyl radicals, which couple to the coupling product 14. 

Zheng et al. treated potassium [l,2,4]diazaphospholides, obtained from the reaction of 3,5-disubstituted-[l,2,4]diazaphospholes with metallic potassium in THF, with [Cp RuCl]4 to afford [(T75-dp)RuCp ] type pseudoruthenocene complex (106) (Scheme 33). Sandwich structure with almost eclipsed orientation of two n-bonded ligands has been confirmed by X-ray crystal structure determination [110], Catalytic application of [(rf-dp)RuCp ] complexes in the Heck reaction has also been investigated [111]. 

Reactions with Other Substrate Complexes. The ruthenium analog of 45, coordinatively unsaturated RuCl(NO)(PPh3)2, also yields methylene and ethylidene complexes on treatment with diazomethane and diazoethane (39,85). 

RuCl2(=CCl2)(CO)(PPh3)2 reacts with NH3 to give a cyanide complex, RuCl(CN)(CO)(NH3)(PPh3)2, presumably via a CNH complex which is deprotonated (19). 

Alternatively, arene displacement can also be photo- rather than thermally-induced. In this respect, we studied the photoactivation of the dinuclear ruthenium-arene complex [ RuCl (rj6-indane) 2(p-2,3-dpp)]2+ (2,3-dpp, 2,3-bis(2-pyridyl)pyrazine) (21). The thermal reactivity of this compound is limited to the stepwise double aquation (which shows biexponential kinetics), but irradiation of the sample results in photoinduced loss of the arene. This photoactivation pathway produces ruthenium species that are more active than their ruthenium-arene precursors (Fig. 18). At the same time, free indane fluoresces 40 times more strongly than bound indane, opening up possibilities to use the arene as a fluorescent marker for imaging purposes. The photoactivation pathway is different from those previously discussed for photoactivated Pt(IV) diazido complexes, as it involves photosubstitution rather than photoreduction. Importantly, the photoactivation mechanism is independent of oxygen (see Section II on photoactivatable platinum drugs) (83). 

Fig. 18. The dinuclear complex [ RuCl(ri6-indane)>2(p-2,3-dpp)]2+ (21) can be photoactivated to yield highly reactive and potentially cytotoxic ruthenium species and the arene indane, which could be used as a fluorescent probe.

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