Indenylruthenium(II) Aminoallenylidenes: New Building Blocks for the Synthesis of Highly Unsaturated Alkynyl and Allenylidene Complexes

Abstract

The allenylidene complexes [Ru(CCCRPh)(η5-C9H7)(PPh3)2][PF6] (R = Ph (1); R = H (2)) react with the ynamines R‘CCNEt2 (R‘ = Me, SiMe3), yielding the aminoallenylidenes [Ru{CCC(NEt2)[C(R‘)C(R)Ph]}(η5-C9H7)(PPh3)2][PF6] (R = Ph, R‘ = Me (3); R = H, R‘ = Me (4); R = Ph, R‘ = SiMe3 (5)). The reactions proceed regio- and stereoselectively, the insertion of the ynamine taking place exclusively at the CβCγ bond of the unsaturated chain. The analogous allenylidene complex 6 (R‘ = H, R = Ph) is obtained by desylilation of complex 5 with KF. The treatment of complex 3 with HBF4 leads to the formation of the dicationic vinylidene [Ru{CC(H)C(NEt2)[C(Me)CPh2]}(η5-C9H7)(PPh3)2]2+ (7). The aminoallenylidene complex 3 undergoes regioselective nucleophilic additions of acetylides and other carbanions at the Cγ atom, yielding (i) the disubstituted alkynylalkenylallenylidenes [Ru{CCC(CCR)[C(Me)CPh2]}(η5-C9H7)(PPh3)2][BF4] (R = Ph (8), SiMe3 (9)) from the addition of acetylides LiCCR, (ii) the 3-alkenyl-3,4,5-hexatrien-1-ynyl derivatives [Ru{CCC(CCCRR‘)[C(Me)CPh2]}(η5-C9H7)(PPh3)2] (R = R‘ = Me (10); R = Ph, R‘ = H (11)) from the reaction with LiCCCHRR‘, and (iii) the 3-alkenyl-3-buten-1-ynyl species [Ru{CCC(CHR)[C(Me)CPh2]}(η5-C9H7)(PPh3)2] (R = H (12), R = n-Pr (13)) and the 3-alkenyl-3,5-hexadien-1-ynyl complex [Ru{CCC(CHCHCH2)[C(Me)CPh2]}(η5-C9H7)(PPh3)2] (14) from the treatment with LiCH2R (R = H, n-Pr) and BrMgCH2CHCH2, respectively. The secondary allenylidenes [Ru{CCC(H)[C(R)CPh2]}(η5-C9H7)(PPh3)2][PF6] (R = Me (16), R = H (17)) are obtained in a one-pot synthesis from the reactions of aminoallenylidenes 3 and 6 with LiBHEt3 and subsequent treatment with silica, respectively. Highly unsaturated alkenylaminoallenylidenes of the general formula [Ru{CCC(NEt2)[(CRCH)nC(Me)CPh2]}(η5-C9H7)(PPh3)2][PF6] (n = 1, R = Me (18), R = SiMe3 (19); n = 2, R = Me (22)) have been synthesized by regio- and stereoselective sequential insertion of one or two ynamines RCCNEt2 (R = Me, SiMe3) into the CβCγ bond of the cumulene group of complexes [Ru{CCC(H)[C(Me)CPh2]}(η5-C9H7)(PPh3)2][PF6] (16) and [Ru{CCC(H)[(CMeCH)C(Me)CPh2]}(η5-C9H7)(PPh3)2][PF6] (21), respectively. Structures of complexes 3 and 18 have been confirmed by X-ray crystallography.