Diastereoselective Synthesis of the Indenylruthenium(II) Complexes [Ru(n5-C9H7){k3(P,C,C)-Ph2P(CH2CR=CH2))(PPh3)][PF6](R = H, Me): Enantiofacial Coordination, Hemilabile Properties, and Diastereoselective Nucelophilic Additions to k3 (P,C,C)-Allylphosphin

The mixed-phosphine complexes [Ru(è5-C9H7)Cl{k1(P)-Ph2P(CH2CRdCH2)}(PPh3)] (R ) H (1a), Me (1b)) are prepared by phosphine exchange reactions (1:1 molar ratio) of [Ru(eta-5- C9H7)Cl(PPh3)2] with the corresponding allylphosphines Ph2P(CH2CRdCH2) in refluxing THF. The reaction of 1a with sodium methoxide in methanol yields the hydride derivative [Ru- (eta-5-C9H7)H{k1(P)-Ph2P(CH2CHdCH2)}(PPh3)] (1c). The treatment of complexes 1a and 1b with NaPF6 in methanol diastereoselectively affords the cationic complexes [Ru(eta-5-C9H7)- {k3(P,C,C)-Ph2P(CH2CRdCH2)}(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){k1(P)-Ph2P(CH2CHdCH2)}(PPh3)][PF6] (R) Me (3a), Bz (3b)). Similarly, the neutral complexes [Ru(è5-C9H7)(N3){k1(P)-Ph2P(CH2CRdCH2)}(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 Câ atom of the coordinated allylic group, affording the ruthenacyclopentane complexes [Ru- (eta-5-C9H7){k2(P,C)-Ph2P{CH2C(R)(R¢)CH2}}(PPh3)] (R ) H) Me (5a), nBu (5b); R ) Me, R¢ ) Me (6a), nBu (6b)) in 80-95% yield. Similarly, the complexes [Ru(eta-5-C9H7){k2(P,C)- Ph2P{CH2CH(R)CH2}}(PPh3)] (R ) H (5c), Me (6c)) are formed by the reaction of equimolar mixtures of complexes 2a,b with Li[B(C2H5)3H]. 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.