Ruthenium complexes amidines

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. 

Complexation via amidinate units was found in ruthenium complexes containing tri- and pentacyclic trifluoromethylaryl-substituted quinoxalines. The complex fragment [(tbbpy)2Ru] (tbbpy = bis(4,4 -di-ferf-butyl-2,2 -bipyridine) has been employed in these compounds which have all been structurally characterized by X-ray diffraction. ... 

The catalytic activation of allylic carbonates for the alkylation of soft car-bonucleophiles was first carried out with ruthenium hydride catalysts such as RuH2(PPh3)4 [108] and Ru(COD)(COT) [109]. The efficiency of the cyclopen-tadienyl ruthenium complexes CpRu(COD)Cl [110] and Cp Ru(amidinate) [111] was recently shown. An important catalyst, [Ru(MeCN)3Cp ]PF6, was revealed to favor the nucleophilic substitution of optically active allycarbonates at the most substituted allyl carbon atom and the reaction took place with retention of configuration [112] (Eq. 85). The introduction of an optically pure chelating cyclopentadienylphosphine ligand with planar chirality leads to the creation of the new C-C bond with very high enantioselectivity from symmetrical carbonates and sodiomalonates [113]. 

By using ruthenium complexes derived from [RuCl2(p-cymene)]2/AgOAc, oxidative alkenylations of amidines with substituted acrylates provided diversely substituted 1-iminoisoindolines (Eq. (7.52)) [48]. The resulting product was proposed to form in a process of oxidative alkenylation, intramolecular aza-Michael addition, and dehydrogenation. 

Novel ruthenium-amidinate complexes of the type (j -CgHsRlRufamidina-te)X (R = Me, OMe, F X = Cl, Br, OTf) and [Ru(amidinate)(MeCN)4][PF6] have been synthesized by photochemical displacement of the benzene ligand in (j -CgHglRufamidinatelX by substituted arenes or MeCN. The acetonitrile ligands of [Ru(amidinate)(MeCN)4][PF6] are easily replaceable by other cr-donor ligands (L) such as pyridines, phosphines, and isocyanides to afford the corresponding derivatives [Ru(amidinate)(MeCN) (L)4 ][PF6] n — 1, 2). These reactions are summarized in Scheme 142. ... 

Chlorination of the Cp Ru(amidinate) complexes is readily achieved by treatment with CHCI3, while oxidative addition of allylic halides results in formation of cationic Ti-allyl ruthenium(IV) species (Scheme 243). °... 

Pentamethylcyclopentadienyl complexes CpjAnX, 4, 207 Cp AnX2 and Cp AnX, 4, 206 Cp MX compounds, 4, 62 with iridium amidinates, 7, 366 mono(Cp ) actinide(IV) compounds, 4, 207 with Ni-C cr-bonded ligands, 8, 108-109 with rhodium, 7, 152 with ruthenium, 6, 632 tris(Cp ) actinide(IV) compounds, 4, 219 with zirconium amidinates, 12, 730 l, 2, 3, 4, 5 -Pentamethyl-l-formylruthenocene, preparation, 6, 643... 

Besides mononuclear, dinuclear complexes were also applied successfully as Kharasch addition catalysts (Fig. 38) [200, 201]. Ruthenium amidinate complex... 

The observation that the Ru(amidinate)C5Me5 complex could generate the first allyl ruthenium(IV) complex containing a nitrogen ligand led to the use of this complex as catalyst for simple allyl substitution of allylcarbonates [111]. Re-... 

The family of Ru(II)-Cp ATRA catalysts was recently extended to novel ruthenium amidinate complexes 12 and 13 [40]. Complex 12 displays two successive one-electron oxidation waves in cyclic voltammetry, assigned to Ru(II)/Ru(III) and Ru(III)/Ru(IV) oxidation steps, respectively. This opens the door to chemical transformations of organic molecules on 12 either byway of one-electron redox processes [i.e.,Ru(II) to Ru(III) or Ru(III) to Ru(IV)],or via two-electron processes [i.e., Ru(II) to Ru(IV)]. 

Imidazoles have been widely studied. Although the binding is usually through the N atom (9-XXIIIa), in some Run, Ru111, Fe°, and Cr° complexes it is possible to have C-bonded groups (9-XXIIIb). The C-bonded entity can be regarded as a carbene (9-XXIIIc) or as a C-bound amidine (9-XXIIId). An example of a C-bonded species is the ruthenium(II) complex obtained as follows ... 

This researeh was extended to include non-symmetrical amidinate complexes of the same type with mixed Cp and Cp ligands, such as the cationic species [Cp Ru 2-PrN=C(Me)NPr )RuCp(L)] (138 L = none, NCMe, CNBu , PMc3 BF4 salts). For 138 (L = CNBu ), there is NMR evidence that the isonitrile ligand switches between the ruthenium centers. Coordinatively unsaturated intermediates play a key role in catalytic processes, and thus complexes 138 (L = none PFe salt) and 135 (PFe salt) were found to catalyze the atom-transfer radical cyclization of A7-allyl trichloroacetamides. It was discovered that the greater protection offered by the steric bulk of the Cp" ligand led to the superior performance of 135 (PF salt). ... 

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