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The magnitude of the “kinetic indenyl effect” for the π-thiapentalenyl ligand, isoelectronic heteroanalogue of the indenyl ligand, has been tested using the reaction between complex, Rh(η5-th)(CO)2 3 (th = 2-ethyl-5-methyl-cyclopenta[b]thienyl or thiapentalenyl) and PPh3 as a model process. Only moderate “kinetic indenyl effect” of the thiapentalenyl ligand was observed. The rational for such behavior was also supported by DFT computational correlation of ground and transition states for the reaction of carbonyl group substitution by a phosphine in the corresponding indenyl and thiapentalenyl rhodium complexes. more...

The complex [IndCpMo(NCMe) 2 ][BF 4 ] 2 provides a suitable entry to the synthesis of IndCpMoBr 2 and IndCpMoMe 2 . The latter, also available from IndCpMoX 2 (X = Cl, Br) and MeMgCl, reacts with HCl to give IndCpMoCl(Me) which, in turn reacts with NaSPh to yield IndCpMo(SPh)(Me). Cyclic voltammetry shows that these three alkyl complexes undergo a 1e reversible oxidation to 17 e Mo V cations. IndCpMoCl(Me) is oxidized by [Cp 2 Fe]BF 4 to afford [IndCpMoCl(Me)]BF 4 in 95% yield. Reaction of [IndCpMo(NCMe) 2 ][BF 4 ] 2 with KBPz 4 in CH 2 Cl 2 /NMF leads to [IndCpMo(κ 2 -BPz 4 )]BF 4 . Taken together with previous reports these results show that the indenyl ring slows down substitutional chemistry at the Cp 2 ′ Mo ( IV ) fragment (Cp′ = Cp, Ind) by steric reasons, overshadowing any acceleration due to a possible indenyl effect. more...

The bis(indenyl) derivatives of Fe, Co, and Ni were studied by means of DFT calculations ( adf program). The calculated structures were compared with the experimental ones and a good agreement was observed. While bis(indenyl)iron is an 18-electron compound, exhibiting an almost perfect η 5 coordination of the indenyl ring, the cobalt complex is a paramagnetic species, owing to the presence of an extra electron and structural distortions start to be detected. More interesting is the nickel complex, where the ring exhibits a coordination between η 2 +η 3 and η 3 , and is definitely slipped and folded. On the other hand, nickelocene chooses a distorted η 5 coordination with long NiC bonds and two unpaired electrons. This different behavior is related to the tendency of the indenyl to slip, compared to cyclopentadienyl. The geometry of the indenyl ring in bis(indenyl)nickel is useful to compare with that of non-isolable intermediates and transition states. more...

Kinetic studies were performed for CO substitution reactions of (η 5 -C 5 H 5 )M(CO) 4 and (η 5 -C 9 H 7 )M(CO) 4 (where M=Nb, Ta) with phosphines and phosphites. Niobium derivatives were found to undergo ligand exchange at higher rates than tantalum, and indenyl derivatives exchanged faster than cyclopentadienyl derivatives. The cyclopentadienyl compounds were found to react by a dissociative or dissociative interchange mechanism as opposed to an associative mechanism as suggested by an earlier kinetic study. The indenyl compounds were found to predominantly react by an associative mechanism. Rate and thermodynamic data indicate that the indenyl effect is operative in these Group V compounds. The molecular structure of (η 5 -C 5 H 5 )Nb(CO) 3 [P(C 6 H 5 ) 3 ]·0.25CH 2 Cl 2 was determined: P 1, a =10.817(2), b =12.403(2), c =18.962(3) A, α =100.901(13), β =104.695(10), γ =103.52(2)°, V =2307.6(7) A 3 , Z =4, R F =3.36. more...

The triruthenium cluster with bridging ethanethiolato and indenyl ligands [( η 5 -C 9 H 7 )Ru( μ -SEt)] 3 ( 2 ) was synthesized by heating the mononuclear indenyl complex [( η 5 -C 9 H 7 )Ru(SEt)(PPh 3 ) 2 ] ( 1a ) in toluene. Cluster 2 reacted with MeI to afford the S-methylated cluster [( η 5 -C 9 H 7 ) 3 Ru 3 ( μ -SEt) 2 ( μ -SEtMe)]I·CH 2 Cl 2 ( 4a ) with high stereoselectivity through the attack of MeI on the axial SEt group from the equatorial side. The PF 6 − salt of the cationic cluster [( η 5 -C 9 H 7 ) 3 Ru 3 ( μ -SEt) 2 ( μ -SEtMe)][PF 6 ] was further converted into the cationic carbonyl complex [( η 5 -C 9 H 7 ) 2 Ru 2 ( μ -SEt)(CO) 4 ][PF 6 ] ( 5 ) by treatment with CO at 50°C. The crystal structures of 4a and 5 were determined by X-ray diffraction study. When a THF solution of 2 was allowed to contact with atmospheric pressure of CO at room temperature, the trinuclear carbonyl cluster [( η 5 -C 9 H 7 ) 3 Ru 3 ( μ -SEt) 3 ( μ -CO)(CO)] ( 6 ) and the dinuclear carbonyl complex [( η 5 -C 9 H 7 )Ru( μ -SEt)(CO)] 2 ( 7 ) were obtained. The structures of 6 and 7 were also crystallographically determined. Furthermore, cluster 2 was oxidized in refluxing CHCl 3 to give [( η 5 -C 9 H 7 )Ru(SEt)Cl] n ( 9 ). The Cp analogue of 2 , [CpRu( μ -SEt)] 3 , failed to react with CO and CHCl 3 , and the hapticity change of the indenyl ligand in 2 is considered to be crucial for the initial interaction of 2 with CO and CHCl 3 . These reactions provide rare examples of the indenyl ligand effect in a multinuclear complex. more...

The titanium methoxo complex Ti(η5-C9H7)Cl2OMe), prepared from the trichloro complex Ti(η5-C9H7)Cl3, was found to polymerize ϵ-caprolactone with ring opening significantly more efficiently than analogous cyclopentadienyl derivatives. The crystal structure of Ti(η5-C9H7)Cl2OMe) was determined and shows a Cs-symmetric piano-stool conformation with the strongly π-donating methoxo group trans to the six-membered ring. more...