Diastereoselective synthesis of the indenylruthenium(II) complexes [Ru(η-C9H7){κ3(P,C,C)-Ph2P(CH2CR=CH2)}(PPh3)][PF6](R = H, Me):: Enantiofacial coordination, hemilabile properties, and diastereoselective nucleophilic additions to κ3(P,C,C)-allylphosphine ligands

The mixed-phosphine complexes [Ru(eta(5)-C9H7)Cl{K-1(P)-Ph2P(CH2CR=CH2)}(PPh3)] (R = H (1a), Me (1b)) are prepared by phosphine exchange reactions (1:1 molar ratio) of [Ru(eta(5-)C(9)H(7))Cl(PPh3)(2)] with the corresponding allylphosphines Ph2P(CH2CR=CH2) in refluxing THF. The reaction of la with sodium methoxide in methanol yields the hydride derivative [Ru-(eta(5)-C9H7)H{(1)(K)(P)-Ph2P(CH2CH=CH2)}(PPh3)] (1c). The treatment of complexes la and 1b with NaPF6 in methanol diastereoselectively affords the cationic complexes [Ru(eta(5)-C9H7)- {(3)(K)(p,C,C)-Ph2P(CH2CR=CH2)}(PPh3)][PF6] (R = H (2a), Me (2b)) in good yield. An X-ray crystal structure determination of complex 2a shows that the si enantiofacial coordination of the olefin group accompanies the R relative configuration of the metal center. No epimerization process has been observed. Olefin exchange substitution reactions of complex 2a with MeCN and BzCN (1:1.5 molar ratio) in refluxing CH2Cl2 yield the cationic complexes [Ru(eta(5)-C9H7)(NCR){(1)(K)(P)-Ph2P(CH2CH=CH2)}(PPh3)] [PF6] (R = Me (3a), Bz (3b)). Similarly, the neutral complexes [Ru(eta(5)-C9H7)(N-3){(1)(K)(P)-Ph2P(CH2CR=CH2)}(PPh3)] (R = H (4a), Me (4b)) are obtained by the treatment of complexes 2a,b with sodium azide in THF/MeOH at room temperature. The addition of lithium carbanions LiR' (R' = Me, nBu) to solutions of complexes 2a,b in tetrahydrofuran results in regio- and stereoselective exo addition at the C-beta atom of the coordinated allylic group, affording the ruthenacyclopentane complexes [Ru(eta(5)-C9H7){(2)(K) (P,C)-Ph2P{CH2C(R)(R')CH2}}Ph-3)] (R = H, R'= Me (5a), nBu (5b); R = Me, R' = Me (6a), nBu (6b)) in 80-95% yield. Similarly, the complexes [Ru(eta(5)-C9H7){(2)(k)(P,C)- Ph2P{CH2CH(R)CH2}}Ph-3)] (R = H (5c), Me (6c)) are formed by the reaction of equimolar mixtures of complexes 2a,b with Li[B(C2H5)(3)H]. The molecular structure and relative configurations RRuS/SRUR of the new stereogenic atoms of complex 5b have been determined by X-ray diffraction. Kinetic studies on the substitution reaction of complex 2a with CD3CN in CDCl3 indicate that the olefin exchange occurs via parallel first-order (dissociative) and second-order (associative) pathways and highlight the intermediacy of a transient coordinatively unsaturated species, formed by olefin dissociation before attack of the nitrile.