Hydride compounds cationic complexes

P Pr3)2. The protonation of OsHMe(CO)2(P Pr3)2 with a diethyl ether solution of HBF4 in the presence of acetone leads to the quantitative formation of the cationic hydride complex [OsH(CO)2 ii1-OCMe2 (P,Pr3)2]BF4. If water instead of acetone is used as a Lewis base, the aquo hydride compound [0sH(C0)2(H20) (P Pr3)2]BF4 is obtained also in excellent yield. 

The Ir(III)-amido-hydrido complex 43 was isolated by reacting the electron-rich neutral phosphine-cyclooctene complex 42 according to Equation 6.13 [7] (note the cis arrangement of the hydride and amide function). Likewise, the cationic complex 44 reacted in neat aniline to afford a 50/50 mixture of the N—H (45) and C—H (46) activation products that was isolated as a light orange powder (Equation 6.14). Compound 45 was separated from 46 and purified in 49% overall yield. 

Hydride abstraction from dienyl tricarbonyl iron complexes furnishes cationic dienyl tricarbonyl iron complexes. For example, reaction of the diene-iron tricarbonyl complex (115) with triphenyhnethyl hexafluorophosphate followed by trimethylsilyl cyanide furnished with excellent regio- and stereoselectivity a new diene iron tricarbonyl complex (116) (Scheme 170). Excellent regio- and stereoselectivity is seen upon reaction of the cationic complex (116) with trimethylsilyl cyanide (TMS-CN) (Scheme 170). Reduction of the nitrile affords a spirocyclic lactam complex. Intramolecular cyclization of in situ formed enols furnishes spirocyclic compounds again with excellent stereoconfrol (Scheme 171). An interesting example of hydride transfer from a cyclohexadiene ring to a pendant aldehyde followed by nucleophilic addition is seen in Scheme 172. 

In a subsequent work, Castarlenas and Esteruelas disclosed the synthesis of another cationic complex [(IPr)Os(OH)(p-cymene)][OTf] (45), which was an efficient pre-catalyst for transfer hydrogenation (Equation (7.11)). Several aliphatic and aromatic aldehydes could be reduced in high yields and high turnover numbers, whereas under these same experimental conditions, acetophenone reacted only very slowly. Regarding the activation of the pre-catalyst, the authors provided strong NMR evidence that, in the presence of isopropanol, compound 45 was converted into a cationic acetone-hydride complex [(IPr)0s(H)(0=C(CH3)2)][0Tf], which most likely acted as the active species for transfer hydrogenation. 

Cationic rings are readily reduced by complex hydrides under relatively mild conditions. Thus isoxazolium salts with sodium borohydride give the 2,5-dihydro derivatives (217) in ethanol, but yield the 2,3-dihydro compound (218) in MeCN/H20 (74CPB70). Pyrazolyl anions are reduced by borohydride to pyrazolines and pyrazolidines. Thiazolyl ions are reduced to 1,2-dihydrothiazoles by lithium aluminum hydride and to tetrahydrothiazoles by sodium borohydride. The tetrahydro compound is probably formed via (219), which results from proton addition to the dihydro derivative (220) containing an enamine function. 1,3-Dithiolylium salts easily add hydride ion from sodium borohydride (Scheme 20) (80AHC(27)151). 

The most electrophilic site in the cationic dH Ru and Os arylcarbyne complexes is not the carbyne carbon, but the para position of the aryl ring. As noted in Section II, B,2, hydride reduction of these compounds affords zero-valent vinylidene species ... 

A similar involvement of palladium hydride, palladium alkyl, and palladium acyl complexes as intermediates in the catalytic cycle of the Pd-catalyzed hydroxycarbonylation of alkenes was reported for the aqueous-phase analogs. The cationic hydride PdH(TPPTS)3]+ was formed via the reduction of the Pd11 complex with CO and H20 to [Pd(TPPTS)3] and subsequent protonation in the acidic medium. The reaction of the hydride complex with ethene produced two new compounds, [Pd(Et)(TPPTS)3]+ and Pd(Et)(solvent)(TPPTS)2]+. The sample containing the mixture of palladium alkyl complexes reacted readily with CO to afford trans-[Pd(C(Q)Et)(TPPTS)2]+.665... 

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