Isoprene complexes with ruthenium

The trinuclear pentahydride complex [Cp Ru]3(/w-H)3(/x3-H)2 (105) in Scheme 26 consists of ruthenium centers tightly bound by bridging hydrides. Treatment of the pentahydride complex with excess butadiene in THF results in a trinuclear 1-methyl-1,3-dimetalloallyl complex [Cp"Ru]3(H)4[/x3- ] -C(Me)CHCH] (106). This interaction shows the cooperation of all three ruthenium centers as either coordination sites or activation sites. Similar results are found by treating (105) with isoprene. Treatment of (105) with five equivalents of cyclopentadiene results in bond cleavage of the cyclopentadiene to form a dark purple crystalline solid [Cp Ru(/u.-H)]3[/x3- j4-C(Me)=CHCH=CH] (107). In this complex, two of the ruthenium centers act as a coordination site, while the third is an activation... 

Iron and ruthenium also form compounds of the type [M(allyl)cp(CO)] and [Fe(allyl) cp(PPh3)]. Ruthenium furnishes the typical derivative [Ru(allyl)2(COD)], [Ru(allyl)2(PR3)2, and [Ru2Cl2(allyl)2(COD)2]. The reaction of ruthenium trichloride with butadiene gives [RuCl2(Ci2Hi8)], while the reaction of RuCla with isoprene affords the dinuclear complex with the structure (7.70). 

The 1,5 cyclooctadiene complex [Cp Ru(jj rf--C Yiu) (CO)]OTf was isolated upon treatment of Cp Ru(j)" -butadiene)X (X = Cl, Br) with butadiene, AgOTf, and CO. A similar [4-1-4] cycloaddition (a thermally forbidden reaction see Woodward-Hoffmann Rules)) is observed when Cp Ru(isoprene)Cl is treated with iso-prene, AgOTf, and CO. Likewise, the reaction of 1,3-pentadiene with Cp Ru( ) -l,3-pentadiene)Cl results in linear dimerization to form [Cp Ru(4-methyl-(l,3-jj 6-8-j) )-nonadienediyl)]OTf. These types of dimerization occur with both stoichiometric and catalytic amounts of the ruthenium complex. ... 

A series of easily prepared and exceptionally active ruthenium catalysts for ringopening metathesis polymerization (ROMP) have been reported. As mentioned previously, the reaction of isoprene with RuCh gave a bis(jt-allyl)ruthenium(IV) complex of [RuC1(m-C1)( -CioHi6)]2, which was converted into cationic bis(jt-allyl)-ruthenium(IV) complexes by treatment with silver tetrafluoroborate. All of these complexes are stable in air and in solution for several hours. Although alone they... 

Ruthenium-catalyzed hydroacylation of 1,3-dienes with aromatic and heteroaromatic aldehydes occurs in relatively good yields to afford the corresponding fi, /-unsaturated ketones . Isoprene and benzaldehyde were treated with 4 mol% Ru(COD)(COT) (COD = 1,5-cyclooctadiene, COT = 1,3,5-cyclooctatriene) and 4 mol% PPhs under argon for 40 hours to give 54% 80 (equation 41). The key intermediate is an acyl- ) -(allyl)ruthenium complex which undergoes reductive elimination to give the corresponding... 

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