Hydrido chloride complexes

The first examplesof group 9 complexes supported by tridentate PSiP ligation were reported by Stobart and coworkers in 1997 [36]. Treatment of the hydrosilane 5 with [Ir(COD)Cl]2 (COD, 1,5-cyclooctadiene) afforded the five-coordinate hydrido chloride complex 38 (Scheme 6.10). Alternatively, treatment of 5 with trans-Ir(PPh3)2(CO)Cl afforded a 3 1 mixture of the six-coordinate hydrido carbonyl chloride isomers 39 and 40. Reaction of the 39/40 mixture with SnCl2 led to the synthesis of the six-coordinate Ir-SnClj complex as another pair of stereoisomers (41 and 42) in the same 3 1 ratio. Treatment of the 39/40 mixture with IiAlH4 led to the formation of a mixture of dihydrido carbonyl stereoisomers (43-45, Scheme 6.10), which is proposed to include the c-PSiP complex 45 as a minor component. Complexes 38 and 42 were crystaUographicaUy characterized. 

The detailed decomposition (P-H ehminahon) mechanism of the hydrido(alkoxo) complexes, mer-crs-[lr(H)(OR)Cl(PR 3)3] (R = Me, Et, Pr R = Me, Et H trans to Cl) (56, 58, 60), forming the dihydrides mer-cis-[lr H)2Cl PR )2] (57, 59) along with the corresponding aldehyde or ketone was examined (Scheme 6-8). The hydrido(ethoxo) as well as the hydrido(isopropoxo) complexes 60 could also be prepared by oxidative addition of ethanol and isopropanol to the phosphine complexes 39 [44]. In the initial stage of the P-H elimination, a pre-equiUbrium is assumed in which an unsaturated pentacoordinated product is generated by an alcohol-assisted dissociation of the chloride. From this intermediate the transition state is reached, and the rate-determining step is an irreversible scission of the P-C-H bond. This process has a low... 

In their early studies, Schwartz and co-workers [5, 80] reported the zirconocene hydrido chloride [Cp2Zr(H)Cl] (1) as a reagent capable of reacting under mild conditions with a variey of non-functionalized alkenes to form isolable alkylzirconi-um(lV) complexes Cp2Zr(R)Cl in which the zirconium is attached to the least-hindered terminal primary carbon, irrespective of the original location of the double bond in the olefin chain. As an example, at room temperature in benzene, 1-octene, cis-4-octene and trows-4-octene all yield the n-octylzirconocene derivative (Scheme 8-6) [80]. 

The details of the cupric salt reaction with the palladium adduct are not clear. Exchange to form a cupric alkyl is one possibility or complex formation,"probably with chloride bridges between the palladium adduct and cupric chloride, may occur with subsequent anion shift from palladium to carbon or perhaps an Sn2 displacement of the complex metal group by an anion may occur. Rearrangements producing 1,3 and 1,4 substituted products from linear olefins have also been observed. For example, 1-butene produced several percent of 1,3- and 1,4-chloro acetates and diacetates under the reaction conditions used 16>. "Hydrido-palladium acetate or chloride" -complexes would seem to be likely intermediates in these arrangements. 

A convenient method for the synthesis of zirconocene hydrido chloride, isobutyl hydride, and dihydride complexes has been developed using the BuTi reagent.452 Thus, the reaction of Cp Cp"ZrCl2 with BuTi reagent gives... 

The alkenyl complexes / 7 r-[Fe(X)(CH=CHC6Hs)(dmpe)2] (X = C1, N3, SCN), which resemble 107, were obtained by a completely different synthetic method. This consists in quantitative anion-induced rearrangement of the hydrido-acetylide complex /ra r-[FeH(C CG6Hs)(dmpe)2] in methanol solution containing chloride, azide, or... 

The T-shaped complex Rh(N2)[FIC(CFl2CFl2P(/-Bu)2)2], prepared by elimination of FlCl with sodium hydride from the hydrido chloride RhH(Cl)[FIC(CFl2CFl2P(/-Bu)2)2], reacted with CO2 yielding the first 16-electron rhodium-carbon dioxide complex that was spectroscopically characterized (Scheme 11). ... 

The mechanism involves the formation of a nucleophilic ferrate species from the iron(IIl) salt and ter/-butylmagnesium chloride. It undergoes oxidative addition to the aryl halide. Transmetalation with the Grignard reagent leads to an alkyliron compound. The latter is not preferentially prone to reductive elimination to form alkylated arenes. Instead, P-hydride elimination and subsequent reductive elimination of the hydrido-iron complex reforms the iron(-II) catalyst releasing isobutene and the defiinctionalized arene (Scheme 4-226). ... 

Due to the low oxidation state of the metal in carbonyliron complexes and ferrates, these species can be applied for the reduction of various carbonyl compounds. Initially, these reagents have been applied in stoichiometric amounts. First examples describe the hydrogenation of a,p-unsaturated carbonyl compounds by carbonyl(hydrido)ferrate complexes to give saturated carbonyl compounds or saturated alcohols. Low valent iron species for the reduction of carbonyl compounds and imines can also be generated in situ from iron(II) chloride and lithium powder in the presence of 4,4 -di-rert-butylbiphenyl. Catalytic versions have been developed subsequently. Thus, pentacarbonyliron functions as a precatalyst for the hydrogenation of aldehydes and ketones in the presence of a tertiary amine as solvent (Scheme 4-322). The catalytically active system probably consists of (tetracarbonyl)(hydrido)ferrate and the protonated amine. ... 

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