The present paper deals with the synthesis and full characterization of a series of pyridine-functionalized phosphine complexes of Ru(II), namely, RuCl 2 (L nx )(PPh 3 ) (L nx ) R 2 PCH 2 (C 5 H 2 R′R′′N)), differing in the nature of the substituents on the phosphorus (superscript label n in L nx defined as n ) 1 for R ) Ph, n ) 2 for R ) Cy) and/or on the pyridyl group (superscript label x in L nx defined as x ) a for picolyl, noted pic, and x ) b for quinolyl, noted quin) and discloses new aspects of their reactivity with respect to catalysis. The ligands 2-[(diphenylphosphino)methyl]-6-methylpyridine, L 1a , 2-[(diphenylphosphino) methyl]quinoline, L 1b , 2-[(dicyclohexylphosphino)methyl]-6-methylpyridine, L 2a , and 2-[(dicyclohexylphosphino)methyl]quinoline, L 2b , were prepared and respectively reacted with RuCl 2 (PPh 3 ) 3 under optimized experimental conditions. In a preliminary test, the reaction of RuCl 2 (PPh 3 ) 3 with L 1a using a stoichiometric 1/1 metal/ligand ratio gave three complexes, namely, [RuCl 2 (PPh 3 ) 2 ] 2 (1), [(PPh 3 ) 2 ClRu(µ-Cl) 3 Ru(L 1a )(PPh 3 )] (2 1a ), and RuCl 2 (L 1a ) 2 (3 1a ). These were isolated by fractional crystallization and, at that stage, identified only by single-crystal X-ray diffraction. The formation of 1 and 2 1a reflects the existence of the elusive 14 efragment "RuCl 2 (PPh 3 ) 2 ", which tends to relieve its unsaturation by intermolecular association. By contrast, controlled addition of 2-(phosphinomethyl)pyridine type ligands L nx to RuCl 2 (PPh 3 ) 2 leads selectively to the desired 16 especies RuCl 2 (L nx )(PPh 3 ) (4 nx ). For example, with L 1b , the green complex RuCl 2 (L 1b )(PPh 3 ) (4 1b -trans-Cl) was identified as the kinetic product of ligand addition. It slowly and irreversibly converts into the more stable isomer RuCl 2 (L 1b )(PPh 3 ) (4 1bcis-Cl), representing the thermodynamic product. Both isomers were fully characterized by NMR spectroscopy and X-ray diffraction. Similar transformations, taking place at different rates, were observed within the ligand series examined here. All isomeric forms of type 4 na complexes react cleanly with a terminal alkyne-like phenylacetylene to give a new complex identified by NMR spectroscopy as the vinylidene species RuCl 2 (L)(CCHPh)(PPh 3 ) (5 na ). The reaction of 4 nb -cis-Cl with an excess of ethyl diazoacetate at -60 °C gives the novel complex RuCl 2 (L na ){cis-EtO(O)C(H)CdC(H)C(O)OEt} (6 na ) with concomitant elimination of the phosphonium ylide, Ph 3 PdC(H)C(O)OEt. Whereas 1 equiv of diazoalkane thus serves as phosphine scavenger, the uptake of two more carbene units by the remaining 14 efragment "RuCl 2 (L 1a )" results in their coupling, providing diethyl maleate, intercepted in 6 na as a coordinated ligand. Preliminary catalytic tests indicate that the complexes 4 nx act as catalyst precursors for the ROMP of norbornene in the presence of trimethylsilyldiazomethane as the carbene source. The same compounds 4 nx are also used as catalyst precursors in the transfer hydrogenation of a series of...

The non-heteroatom-substituted alkynyl carbene Cp′(CO) 2 MndC(Tol)CtCPh (1, Cp′ ≡ (η 5 -MeC 5 H 4 )) is first shown to react at low temperature with lithium diorganophosphide LiPR 2 (R ) Ph, Cy) to form an anionic species. Subsequent treatment with CF 3 SO 3 H affords the η 4 -vinylketene complex Cp′(CO) 2 Mn[η 4 -{R 2 P(Ph)CdCHC(Tol)dCdO}] (2; 2a: R ) Ph (70% yield), 2b: R ) Cy (55% yield)) as the major compound, along with trace amounts of the η 2 -allene complex syn-Cp′(CO) 2 Mn[η 2 -{Ph 2 P(Tol)-CdCdC(Ph)H}] (syn-3a) for R ) Ph, or along with the η 2 -allene complex Cp′(CO) 2 Mn[η 2 -{H(Tol)-CdCdC(Ph)PCy 2 }] (4b, 26% yield, 1:2 mixture of syn/anti isomers) for R ) Cy. On the other hand, subsequent treatment with NH 4 Cl aq affords only η 2 -allene complexes, obtained either as a ca. 1:9 mixture of syn-3a and Cp′(CO) 2 Mn[η 2 -{H(Tol)CdCdC(Ph)PPh 2 }] (4a) (75% yield) for R ) Ph or as a 1:2 mixture of syn-and anti-4b for R ) Cy (74% yield). Combined NMR and single-crystal X-ray diffraction studies (for 2a, anti-4b, and syn-4b) revealed that both type 2 and type 4 species result from a nucleophilic attack of the diorganophosphide onto the remote alkynyl carbon atom in 1 (C γ ), whereas type 3 species results from a nucleophilic attack of the carbene carbon atom (C R ). Complexes 3a and 4a,b are prone to undergo a thermal rearrangement to give the η 1 -phosphinoallene complexes Cp′(CO) 2 Mn[η 1 -{Ph 2 P(Tol)CdCdC(Ph)H}] (5a) and Cp′(CO) 2 Mn[η 1 -{R 2 P(Ph)CdCdC(Tol)H}] (6; 6a: R ) Ph, 6b: R ) Cy), respectively. Reaction of 1 with p-toluenethiol in the presence of NEt 3 (20%) affords a 1.8:1 mixture of Cp′(CO) 2 Mn[η 2 -{TolS(Tol)CdCdC(Ph)H}] (syn-11), resulting from a nucleophilic attack at C R in 1, and Cp′(CO) 2 Mn[η 2 -{H(Tol)CdCdC(Ph)STol}] (12), resulting from a nucleophilic attack at C γ , whereas treatment of 1 with lithium p-toluenethiolate at -80 °C followed by protonation with NH 4 Cl aq gave the same syn-11 and 12 complexes now in a 1:2.3 ratio. Finally, 1 was found to react with cyclohexanone lithium enolate to afford, upon protonation, the η 2 -allene complex Cp′(CO) 2 Mn[η 2 -{H(Tol)CdCdC(Ph)CH(CH 2 ) 4 C(O)}] (syn-13), resulting from a nucleophilic attack at C γ in 1. The solidstate structures of syn-11 and syn-13 are also reported.

An uncommon synergism in the concerted action of OH- and PR3 toward the simple Ru(II) complex Ru(CO)3Cl2(thf) allows a highly efficient reduction of the metal in ethanol or acetonitrile solution at 0 degrees C, with selective production of the corresponding Roper's-type Ru(0) complexes Ru(CO)2(PR3)3 in high yields within 10 min.