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⋮CCHC(C6H4NO2-3)2}(η5-C9H7)(PPh3)2] and (EE)-[Ru{C⋮C(CHCH)2-C6H4NO2-4}(η5-C9H7)(PPh3)2]

σ-Alkynyl complexes [Ru(C⋮C−C 6 H 4 R-4)(η 5 -C 9 H 7 )L 2 ] (L = PPh 3, R = NO 2 ( 3a ), C⋮C−C 6 H 4 NO 2 -4 ( 4 ), N CH−C 6 H 4 NO 2 -4 ( 5 ); L 2 = 1,2-bis(diphenylphosphino)ethane (dppe), R = NO 2 ( 3b ); L 2 = bis(diphenylphosphino)methane (dppm), R = NO 2 ( 3c )) have been prepared by reaction of [RuCl(η 5 -C 9 H 7 )L 2 ] ( 1a − c ) with HC⋮C−C 6 H 4 R-4 and NaPF 6, via deprotonation of the corresponding intermediate vinylidene derivatives. The treatment of the alkynyl−phosphonio complex [Ru{C⋮CCH 2 (PPh 3 )}(η 5 -C 9 H 7 )(PPh 3 ) 2 ][PF 6 ] ( 6 ) with Li n Bu and the appropriate aldehyde or ketone yields, via Wittig type reactions, σ-enynyl complexes [Ru{C⋮CCH CR 1 (CH CH) n R 2 }(η 5 -C 9 H 7 )(PPh 3 ) 2 ] ( n = 0, R 1 = H, R 2 = C 6 H 4 NO 2 -4 ( 7a ), C 4 H 2 ONO 2 -3,4 ( 8a ), C 4 H 2 SNO 2 -3,4 ( 8b ), C 6 H 4 CN-4 ( 13 ), C 5 H 4 N-4 ( 16 ); n = 0, R 1 = R 2 = C 6 H 4 NO 2 -3 ( 9 ); n = 1, R 1 = H, R 2 = C 6 H 4 NO 2 -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 ( 13 C{ 1 H} NMR) show an extensive electronic delocalization between the donor fragment [Ru(η 5 -C 9 H 7 )(PPh 3 ) 2 ] and the acceptor nitroaryl group. In accordance with this, values of resonantly enhanced molecular quadratic hyperpolarizabilities (β) for these donor−acceptor derivatives (β 1064 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 [(η 5 -C 9 H 7 )(PPh 3 ) 2 Ru{(μ-C⋮N)ML 5 }][CF 3 SO 3 ] n ( n = 0, ML 5 = Cr(CO) 5 ( 11a ), W(CO) 5 ( 11b ); n = 3, ML 5 = Ru(NH 3 ) 5 ( 12 )), [(η 5 -C 9 H 7 )(PPh 3 ) 2 Ru{(μ-C⋮CCH CH−C 6 H 4 C⋮N-4)ML 5 }][CF 3 SO 3 ] n ( n = 0, ML 5 = Cr(CO) 5 [( E, Z )- 14a ], W(CO) 5 [( E, Z )- 14b ]; n = 3, ML 5 = Ru(NH 3 ) 5 [( E, Z )- 15 ] and [(η 5 -C 9 H 7 )(PPh 3 ) 2 Ru{(μ-C⋮CCH CH−C 5 H 4 N-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 (β o = 10−150 × 10 - 30 esu) surpass the largest reported to date for bimetallic compounds. The bimetallic σ-enynyl complex [Ru(C⋮CCH CH(η 5 -C 5 H 4 )Fe(η 5 -C 5 H 5 )(η 5 -C 9 H 7 )(PPh 3 ) 2 ] [( E )- 18 ] was obtained stereoselectively from the alkynyl−phosphonio complex 6, Li n Bu, and {η 5 -C 5 H 4 (CHO)}Fe(η 5 -C 5 H 5 ). Protonation of ( E )- 18 with HBF 4 yields the vinylidene derivative [Ru{=C C(H)CH CH(η 5 -C 5 H 4 )Fe(η 5 -C 5 H 5 )}(η 5 -C 9 H 7 )(PPh 3 ) 2 ][BF 4 ] ( 19 ). Quadratic hyperpolarizabilities for these ruthenium(II)−iron(II) bimetallic complexes are also reported.