Synthesis and Second-Order Nonlinear Optical Properties of Donor−Acceptor σ-Alkynyl and σ-Enynyl Indenylruthenium(II) Complexes. X-ray Crystal Structures of [Ru{C⋮CCHC(C6H4NO2-3)2}(η5-C9H7)(PPh3)2] and (EE)-[Ru{C⋮C(CHCH)2-C6H4NO2-4}(η5-C9H7)(PPh3)2]

σ-Alkynyl complexes [Ru(C⋮C−C6H4R-4)(η5-C9H7)L2] (L = PPh3, R = NO2 (3a), C⋮C−C6H4NO2-4 (4), NCH−C6H4NO2-4 (5); L2 = 1,2-bis(diphenylphosphino)ethane (dppe), R = NO2 (3b); L2 = bis(diphenylphosphino)methane (dppm), R = NO2 (3c)) have been prepared by reaction of [RuCl(η5-C9H7)L2] (1a − c) with HC⋮C−C6H4R-4 and NaPF6, via deprotonation of the corresponding intermediate vinylidene derivatives. The treatment of the alkynyl−phosphonio complex [Ru{C⋮CCH2(PPh3)}(η5-C9H7)(PPh3)2][PF6] (6) with LinBu and the appropriate aldehyde or ketone yields, via Wittig type reactions, σ-enynyl complexes [Ru{C⋮CCHCR1(CHCH) n R2}(η5-C9H7)(PPh3)2] (n = 0, R1 = H, R2 = C6H4NO2-4 (7a), C4H2ONO2-3,4 (8a), C4H2SNO2-3,4 (8b), C6H4CN-4 (13), C5H4N-4 (16); n = 0, R1 = R2 = C6H4NO2-3 (9); n = 1, R1 = H, R2 = C6H4NO2-4 (7b)) isolated as mixtures of the corresponding E and Z stereoisomers. The structures of complexes 7b and 9 have been confirmed by X-ray diffraction. Structural data in the solid state as well as in solution (13C{1H} NMR) show an extensive electronic delocalization between the donor fragment [Ru(η5-C9H7)(PPh3)2] and the acceptor nitroaryl group. In accordance with this, values of resonantly enhanced molecular quadratic hyperpolarizabilities (β) for these donor−acceptor derivatives (β1064 nm= 100−1320 × 10-30 esu), determined by the hyper-Rayleigh scattering technique (HRS) at 1064 nm which are dependent on the molecular design of the bridged enynyl chain, are significantly larger than those of their analogous organic chromophores. Mixed-valence bimetallic donor−acceptor derivatives [(η5-C9H7)(PPh3)2Ru{(μ-C⋮N)ML5}][CF3SO3] n (n = 0, ML5 = Cr(CO)5 (11a), W(CO)5 (11b); n = 3, ML5 = Ru(NH3)5 (12)), [(η5-C9H7)(PPh3)2Ru{(μ-C⋮CCHCH−C6H4C⋮N-4)ML5}][CF3SO3]n (n = 0, ML5 = Cr(CO)5 [(E, Z)-14a], W(CO)5 [(E, Z)-14b]; n = 3, ML5 = Ru(NH3)5 [(E, Z)-15] and [(η5-C9H7)(PPh3)2Ru{(μ-C⋮CCHCH−C5H4N-4)M(CO)5}] (M = Cr [(E)-17a], W [(E)-17b]) have also been prepared in high yields. Static quadratic hyperpolarizabilities values of these derivatives (βo = 10−150 × 10-30 esu) surpass the largest reported to date for bimetallic compounds. The bimetallic σ-enynyl complex [Ru(C⋮CCHCH(η5-C5H4)Fe(η5-C5H5)(η5-C9H7)(PPh3)2] [(E)-18] was obtained stereoselectively from the alkynyl−phosphonio complex 6, LinBu, and {η5-C5H4(CHO)}Fe(η5-C5H5). Protonation of (E)-18 with HBF4 yields the vinylidene derivative [Ru{=CC(H)CHCH(η5-C5H4)Fe(η5-C5H5)}(η5-C9H7)(PPh3)2][BF4] (19). Quadratic hyperpolarizabilities