Hydrido-hydroxy complex

Later, in the study of the reactivity of the (PCP)Rh(I) complex (38), Kaska and coworkers [20] realized that the reaction of this compound with CO2 was, in fact, a CO2 reducing process to water and CO in what amounted to be a reversal of the water gas shift reaction. In fact, the reaction of the hydrido-hydroxy complex (45) with CO afforded complex (40) quantitatively (Scheme 2.24). 

In 2003, Morales-Morales and Jensen reported [35] on the reactivity of different (PCP)Ir derivatives with carbon monoxide. Thus, direct reactions of the dihydride species (82) (in the presence of TBE), dinitrogen (83), and hydrido-hydroxy (84) afforded the (PCP)Ir(I) carbonyl complex (85) (Scheme 2.38). Worth noting is the reaction of compound (84) with CO, which besides complex (85) also affords a very small amount of a pale yellow air sensitive (PCP)Ir(I) carboxyl compound (86) (Scheme 2.38). The structure of this compound was unequivocally determined by single-crystal X-ray diffraction analysis. 

Cyclic imides are accessible by a similar methodology. Reaction of dodeca-carbonyltriiron with primary amines gives an amine(carbonyl)iron complex that reacts with an alkyne under double carbonyl insertion to a ferracycle. Treatment of this complex with an excess of primary amines leads to a nucleophilic attack of the amine at the carbonyl function displacing the carbonyliron moiety presumably under formation of an alkene(hydrido)iron complex that may reduce the carbonyl groups to hydroxy groups. 

The mechanism involves formation of a reactive 16-electron tricarbonyliron species by sequential loss of two carbon monoxide ligands and coordination of allyl alcohol to pentacarbonyliron (Scheme 4-291). Oxidative addition under activation of the sp C-H bond adjacent to the hydroxy group leads to an Ti -allyl(hydrido)iron complex. Subsequent reductive elimination transfers the hydrido ligand to the 3-position of the allyl ligand to afford an ri -alkene(tricarbonyl)iron complex. Dissoziation of the enol ligand releases a 14-electron tricarbonyliron complex that will start the catalytic cycle de novo by complexation of allyl alcohol. The enol will finally tautomerize to the ketone. In total, a formal [l,3]-hydride shift is achieved at the allyl alcohol. ... 

Recently, a somewhat different synthetic approach has been reported. Halcrow et al. (215) synthesized a series of five-coordinate copper(II) complexes comprising a tridentate tris(pyrazolyl)borate ligand and a bidentate phenol derivative. Neutral complexes [Cun(TpPh)(bidentate phenolate)] were synthesized and structurally characterized [Tpph] = hydrido-tris(3-phenylpyrazol-l-yl)borate. The species [Cun(TpPh)(2-hydroxy-5-methyl-3-methylsulfanylbenzaldehydato)] can electro-chemically be converted to the (phenoxyl)copper(II) monocation, which has been characterized in solution by UV-vis spectroscopy. It displays two intense absorption maxima at 907 nm (e = 1.2 x 103 M 1 cm-1), and 1037 (1.1 x 103 M l cm-1), resembling in this respect the radical cofactor in GO (Fig. 7). 

The rapid, acid-catalyzed hydrolysis of the polycyclic phosphite 2,8,9-trioxa-l-phosphaadamantane (L) produces two isomeric hydrolysates, 3-a-oxo-3-fi-hydrido-7-fi-hydroxy-2,4-dioxa-3-phosphahicyclo (3.3.1) nonane (Isomer A), and 3-fi-oxo-3-a-hydrido-7-ff-hydroxy-2,4-dioxa-3-phosphabicyclo (3.3.1) nonane (Isomer B), the configurations of which were tentatively postulated on the basis of infrared and PNMR spectra. Each isomer dehydrates to L under vacuum at 120°C., as well as in the presence of Cu+ or PhiC+ ions to give [CWLJ+ and [P/i3CL]+, respectively. With hydrated metal ions, L forms complexes of the general formula [M(L -HiO)A](X ), where X = BFa or ClOi and M = Mn+, Zn+, Fe+, and Cd+. Of the isomers, only A forms the identical complexes with these ions as well as Ni+. Infrared evidence is presented which is consistent with the postulate that L HiO is an enolform of A bound to the metal through phosphorus. 

B. R. Sutherland, M. Cowie, Hydroxy- and hydrido-bridged binuclear complexes of iridium synthesis, characterization, and attempts to model binuclear water-gas shift catalysts. Structure of [Ir2(CO)2(.mu.-H.Cl)(Ph2PCH2PPh2)2], Organometalhcs 4 (1985) 1637-1648. 

In the early 1970s, Clark and Kurosawa [121] intensively investigated the mechanism of stoichiometric and catalytic isomerization of terminal and internal olefins (1-butene, allyl ethers) with phosphine-modified platinum hydrido complexes such as fcr ws-[HPt(PR3)2(acetone)]X. Later, Toniolo et cd. [122] showed that the isomerization rate is strongly dependent on the temperature. Hydroxy groups being a constituent of allyl alcohols may also control isomerization [121]. 

The reaction of alcohols with styrene or 1,1-diphenylethene in the presence of iron(III) chloride leads to addition products under C-C bond formation (Scheme 4—276). This includes a C pS-H bond activation at the hydroxy function. A variety of primary alcohols has been employed in this reaction accessing structurally diverse secondary alcohols. The reaction is proposed to proceed via iron(IV) hydrido complexes and alkyl radical intermediates. ... 

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