2-Butene, 2,3-dimethyl rhodium complex

The allylic hydroperoxide, 2,3-dimethyl-3-hydroperoxy-l-butene, III, was detected during the oxidation of TME in the presence of [MCl(CO)-(Ph3P)2] (M = Rh, Ir) and reached a maximum yield of 11% after 3.5 hours when the rhodium complex was used (Figure 1). James and Ochiai (13) have cited spectral evidence for hydroperoxide intermediates, and Fusi et ah (14) obtained evidence which supports the intermediacy of an allylic hydroperoxide during cyclohexene oxidation in the presence of metal complexes. The allylic hydroperoxide (III) which is formed during the oxidation of TME in the presence of [MCl(CO) (Ph3P)2]... 

The water-soluble rhodium complex [Rh(p.-pz)(CO)(TPPTS)]2 (pz = pyrazolate) was used as catalyst precursor during the two-phase catalytic hydroformylation of different olefins at 100 °C, 50 bar (CO H2 = 1 1), 600 rpm, and substrate catalyst ratio of 100 1. A reaction order- 1-hexene > styrene > allylbenzene > 2,3-dimethyl-1-butene > cyclohexene-was found. The experiments also showed that the binuclear catalyst precursor was resistant to possible sulfur poisons [108]. 

The 0/7/fo-alkylation of aromatic ketones with olefins can also be achieved by using the rhodium bis-olefin complex [C5Me5Rh(C2H3SiMe3)2] 2, as shown in Equation (9).7 This reaction is applied to a series of olefins (allyltrimethyl-silane, 1-pentene, norbornene, 2,2 -dimethyl-3-butene, cyclopentene, and vinyl ethyl ether) and aromatic ketones (benzophenone, 4,4 -dimethoxybenzophenone, 3,3 -bis(trifluoromethyl)benzophenone, dibenzosuberone, acetophenone, />-chloroacetophenone, and />-(trifluoromethyl)acetophenone). 

Di-/i-chloro-bis(7)4-1,5-cyclooctadiene)dirhodium(l), [RhCl(l,5-C8Hi2)]2, has been prepared in 60% yield by reducing rhodium trichloride hydrate in the presence of excess olefin in aqueous ethanol.1 In the present preparation the yield has been greatly increased (to 94%). Two related complexes, [RhCl(l,5-C6Hio)]22 and [RhCl(C6H12)2]2, are similarly prepared in high yield from 1,5-hexadiene and 2,3-dimethyl-2-butene, respectively. 

The new 2,3-dimethyl-2-butene complex, [RhCl(C6H12)2]2, is prepared by a similar method, in which the solution is left at 20° for 30 days instead of being refluxed. A trace of metallic rhodium is deposited. This is removed by recrystallization from dichloromethane-diethyl ether to give an analytically pure product yield 75%. 

Important early work by Consiglio and Pino and Consiglio et al. on the asymmetric hydroformylation of butenes was published as early as 1982. In this work, the hydroformylation of 1-butene and ( ) and (Z)-2-butene was carried out under different conditions using different chiral complexes of rhodium and platinum. The highest enantiomeric excess of 47% was actually achieved using the platinum complex [((—)-DIOP)Pt(SnCl3)Cl] (DIOP = 2,2-dimethyl-4,5-bis(diphenylphosphinomethyl)-l,3-dioxolane) ... 

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