Reaction of the cationic η 2 -alkyne iron complex, [Fp(η 2 -Ph-CtCPh)]BF 4 (1) [Fp ) (η 5 -C 5 H 5 )-Fe(CO) 2 ], with various O-, N-, and C-nucleophiles afforded products containing the Ph-Cd C-Ph linkage. i.e., cis-(3) and trans-alkenyl complexes (4), Fp-C(Ph)dC(Ph)-Nu, and metallacycles, Cp(CO)Fe-C(Ph)dC(Ph)-C(dO)-Nu [coordinated at dO (5) or Nu (6)]. Crystallographic determination of the configuration of the CdC moiety in 3 and 4 and analysis of the product distribution revealed that basic nucleophiles bearing alkyl substituents produced the cis-alkenyl complex (3) and/or the metallacycles (5, 6), whereas less basic nucleophiles bearing aryl substituents afforded the trans-alkenyl complex (4). Correlation between the product distribution and pK b values of the nucleophiles leads to the conclusions that (1) products 3, 5, and 6 arise from acyl intermediates formed by initial nucleophilic addition of basic nucleophiles at the CO ligand, (2) trans-alkenyl complexes 4 result from addition of less basic nucleophiles to the η 2 -alkyne ligand from the exo-side, and (3) the equilibrium of the CO addition governed by the basicity of the nucleophile is the key step of the diversity of the stereochemistry of the alkenyl products. Reactions of 2-hexyne complex, [Fp(η 2 -Et-CtC-Et)]BF 4 (2), were also examined.

Treatment of the triruthenium pentahydrido complex {Cp*Ru(μ-H)}3(μ3-H)2 (1; Cp* = η5-C 5Me5) with cycloalkene resulted in exclusive formation of the μ3-cycloalkyne complex {Cp*Ru(μ-H)}3(μ3-η2:η2(⊥)-C n H2 n - 4) (2a; n = 5, 2b; n = 6) as a result of vinylic C−H bond cleavage. VT NMR studies revealed fluxional behavior of the perpendicularly coordinated cycloalkyne ligand. Reaction of 2b with carbon monoxide afforded the 48-electron complex (Cp*Ru)3(μ-CO)(μ3-CO)(μ-H)(μ3-η2(∥)-C6H8) (3b) with a parallel-coordinated alkyne ligand.

The ruthenium hydrido bis(dihydrogen) complex [Cn*RuH(H2)2][PF6] (2-PF 6 ; Cn* = 1,4,7-trimethyl-1,4,7-triazacyclononane) was synthesized by treatment of Cn*RuCl3 with NaBH4. Complex 2-PF 6 undergoes a H/D exchange between its hydrido ligands and CD3OD, D2, or THF-d 8. Treatment of 2-PF 6 with Cp*IrH4 or Cp*OsH5 (Cp* = C5Me5) affords the heterometallic dinuclear polyhydrido complexes [Cn*Ru(μ-H)3IrCp*][PF6] (3-PF 6 ) and [Cn*Ru(μ-H)3OsHCp*][PF6] (4-PF 6 ), respectively. Treatment of 3-PF 6 with triphenylphosphine affords the complex [Ru(PPh3)(μ-η3:η1-Cn*CH2)(μ-H)2IrCp*][PF6] (5-PF 6 ), in which the triphenylphosphine is coordinated to the Ru atom as a terminal ligand and the C−H bond of the methyl group in the Cn* ligand is cleaved by the Ir atom. Reaction of 3-PF 6 with acetylene gives a bis(μ-vinyl) complex, [Cn*Ru(μ-σ,π-CHCH2)IrH(μ-σ,π-CHCH2)Cp*][PF6] (6-PF 6 ), in which one vinyl ligand is σ-bonded to the Ru atom and the other is σ-bonded to the Ir atom. The molecular structures of 2-PF 6 , [Cn*Ru(μ-H)3Ir(C5Me4Et)][BPh4] (3′-BPh 4 ), 4-BPh 4 , 5-BPh 4 , and 6-PF 6 were confirmed by X-ray analyses, and the coordination modes of the hydrido ligands in 2-PF 6 were confirmed by density functional theory calculations.

A ruthenium bis(η 2 -dihydrogen)-hydrido complex with 1,4,7-triazacyclononane (Cn), [CnRuH(H 2 ) 2 ]-(BPh 4 ) (2a-BPh 4 ), was prepared. The infrared spectra, longitudinal relaxation time (T 1 ) measurements, and density functional theory calculations reveal that the electron density at the metal center of complex 2a is higher than that of the 1,4,7-trimethyl-1,4,7-triazacyclononane (Cn*) analogue [Cn*RuH(H 2 ) 2 ] þ (2b). Complex 2a-BF 4 is converted into the tetranuclear octahydrido cluster complex [(CnRu) 4 (μ-H) 6 -(μ 3 -H) 2 ](BF 4 ) 4 (3-BF 4 ) via spontaneous dehydrogenation, whereas the dehydrogenation of 2b-PF 6 exclusively affords the diruthenium trihydrido complex [(Cn*Ru) 2 (μ-H) 3 ](PF 6 ) 2 (4-PF 6 ).

Treatment of a coordinatively saturated cationic y2-alkyne iron complex [(y5-C5H5)Fe(C0),(Ph-C=C-Ph)]BF4 with various nucleophiles (Nu: 0-, Sand N-nucleophiles) does not afford a trans-alkenyl complex but alkenic products with cis-structure, i.e. a cis-alkenyl complex, cis-(y5-C5H5)(C0),Fe-C(Ph)=C(Ph)-Nu and/or a metallacycle, (y5-C5H5) (OC) ke-[C( P h )=C( P h)-C(=d)-N ul or (q5C5H5) (OC) ie-[ C( P h )=C( P h )-CI=O)-N u] .