Methylallyl complexes

The role of complexes 23-28 as catalyst precursors in the ring closing metathesis reactions was investigated. Three different diene substrates diethyldiallyl-malonate (29), diallyltosylamine (30). and dielhyldi(2-methylallyl)malonate (31) were added to the NMR tubes containing a solution of 5 mol% of catalyst precursor in an appropriate deuterated solvent. The NMR tubes were then kept at the temperatures reported in Table X. Product formation and diene disappearance were monitored by integrating the allylic methylene peaks in the H NMR spectra and the results are presented in Table X and the catalytic transformations are depicted in Scheme 3. 

Complexes with unsaturated ligands (a-vinyl. a-allyl, and alkynyl) have been reported, each prepared from Fe(TPP)CI with the appropriate Grignard (vinyl, 2- methylvinyl.2,2-dimethylvinyl,allyl,or2-methylallyl)orlithiumreagent(LiC= C-n-Pr or LiC CPh) and observed by NMR spectroscopy (Scheme 4). The vinyl and alkynyl complexes are stable in solution at 25 C, whereas the allyl species decompose quickly if allowed to warm to room temperature. All were too reactive to be purihed by chromatography. The vinyl and allyl complexes show characteristic low spin behavior, although the temperature dependence of the vinyl... 

MandyPhos Initial attempts to synthesize defined chelating biphosphine complexes by reacting (1) with established Ruthenium(II) precursors such as [Ru(COD)Cl2]x, [Ru(benzene)Cl2]2, [Ru(p-cymene)Cl2]2, (COD)Ru(Methylallyl)2,... 

Another substituted derivative of BINAP was used by Lemaire et al. [109]. The ammonium salt catalysts (7 and 8, Fig. 41.10) were prepared in situ from the bro-mohydrates and [Ru( /3-2-methylallyl)2(/72-COD)], and immobilized in several ionic liquids. By comparative studies of the hydrogenation of ethyl acetoacetate, the best results were obtained with imidazolium- and pyridinium-containing ionic liquids. No significant ee was observed with the phosphonium salt. This observation was attributed to problems of solubility and to the ability of complexation for the phosphonium ion. From the anionic side, use of the [BF4] anion appeared superior compared to [PF6] and [(CF3S02)2N]A... 

Butadiene d4 complexes were obtained (i) from [NbCU(dmpe)2] and magnesium butadiene (equation 87) j706 (ii) by dimerization of ethylene using alkylidenes (equation 88) 707 or (iii) by metal vapor techniques (equation 89), which yielded sublimable methylallyl derivatives.70 Compound (62) could not be prepared by Na/Hg reduction of (22) in the presence of butadiene. Compound (63) is also accessible from [TaH2ClL4] (Scheme 9). 

The hydrogenation of trans-l-phenyl-1,3-butadiene has been discussed49 in terms of the mechanism originally proposed,45 and 773-allyl species were invoked. NMR studies on the hydrogenation of butadiene have shown that Tj -but-2-enyl and r 3-l-methylallyl complexes are present in the reaction mixture. With isoprene, an q1 -methylbut-2-enyl complex was observed.50 By using a two-phase system and a phase-transfer catalyst, the turnover numbers attainable with conjugated dienes can be increased to about 30.51... 

A more general route to these anionic manganese complexes has recently been described34 35 and involves Red-Al reduction of [Mn(2-methylallyl)(CO)4] to yield [Mn(butene)(CO)4]r which reacts with a variety of both cyclic and acyclic dienes or polyenes to give [Mn(Tj4-diene)(CO)3] or [Mn(tj4-polyene)(CO)3] complexes in moderate to good isolated yields (equation 10). 

Another allyl compound which reacts stoichiometrically with carbon dioxide is (fj5-C5H5)2Ti(l-methylallyl) (120). The titanium acetate complex which is formed is interesting in that the carbon dioxide carbon atom is attached to the substituted end of the allyl. It seems unlikely, then, that the product is the result of C02 insertion into the -methylallyltitanium bond in view of the fact that methyl-substituted allyls tend to form fj -complexes in which the metal is bonded to the least substituted end of the allyl. One possible explanation offered by the authors is that the allyl is bonded to titanium at the methylene carbon, but that rearrangement occurs subsequent to adduct formation [Eq. (49)]. 

The complex formed in situ from bis(2-methylallyl)cycloocta-l,5-dienerutheni-um(II) [(COD)Ru[met]2l, a phosphine, and (TfO Sc has been found to catalyse efficiently the anti-Markovnikov addition of imides (RCO NH to terminal alkynes (g) R C CH to produce enimides R,CH=CHN(OCR)2. Depending on the phosphine employed, E- and Z-isomers can be accessed stereoselectively 96... 

A series of substituted phosphine complexes of palladium have been synthesized by displacement of the allyl ligand from (2-methylallyl)PdCl2 with excess phosphine, and 13C n.m.r. studies have shown that the equilibrium (1) lies well to the left ... 

The first transition metal catalysis using BINAP-ruthenium complex in homogeneous phase for enantioselective hydrogenation of P-ketoesters was developed by Noyori and co-workers [31]. Genet and co-workers described a general synthesis of chiral diphosphine ruthenium(II) catalysts from commercially available (COD)Ru(2-methylallyl)2 [32]. These complexes preformed or prepared in situ have been found to be very efficient homogeneous catalysts for asymmetric hydrogenation of various substrates such as P-ketoesters at atmospheric pressure and at room temperature [33]. 

Other i73-allyl ruthenium complexes of type 44 have been prepared from la with allylmercury chlorides (allyl, methallyl, crotyl, 1-and 2-phenylallyl, and l-acetyl-2-methylallyl) (45). 

Alkyl-2,3-dihydrodiboroles on treatment with bis(/7 -allyl)- or bis( -methylallyl)nickel give the tetradecker complexes 2 [ML = = Ni( -... 

In this context, it is worth reporting that another route to bis-NHC-Pd(O) complexes has proven efficient. A Pd(II) source, such as the dimer [Pd(2-methylallyl)Cl]2 (83) (equation 10) reacted with sodium malonate in the presence of free NHC ligand. Reduction of Pd(II) to Pd(0) and coordination of two NHCs afforded [(NHC)2Pd] in quantitative yield. This route proved very useful for the synthesis of catalyst (84) developed by Glorius et al. ... 

Addition of allyl- (or 2-methylallyl-) magnesium chloride to an ethereal slurry of ( j -Cp IrCl2)2 results in the formation of air-sensitive yellow needles of Cp (t/ -allyl) chloroiridium (Cp = CjMej) complexes in 55-80% yield after crystallization from toluene-hexane . 

The reaction of the polymeric diene complexes, [RuCl2(diene)]u [diene = cod (1,5-cydooctadiene), nbd (2,5-norbomadiene)], with allylic Grignard reagents gives white bis(allylic) complexes, Ru(allyl)2(diene) (allyl = C3H5, 2-methylallyl), which contain asymmetrically bonded allyl ligands (Eq. 5.2) [10],... 

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