The Allenylidene Complex [Ru(η⁵-C₅H₅)(CCCPh₂)(CO)(PⁱPr₃)]BF₄ as a Precursor of Novel Pyrido[1,2-a]pyrimidinyl and 1,3-Thiazinyl Complexes

Abstract

The allenylidene complex [Ru(η5-C5H5)(CCCPh2)(CO)(PiPr3)]BF4 (1) reacts with 2-aminopyridine to give a mixture of the complexes [Ru(η5-C5H5){2,2-diphenyl-2H-pyridinium[1,2-a]pyrimidin-4-yl}(CO)(PiPr3)]BF4 (2) and (3). The molar ratio of the isomers in the mixture depends on the reaction temperature. At temperatures lower than −30 °C, isomer 2 is the main reaction product, while at 0 °C an inverse relationship is observed. The structure of 2 has been determined by an X-ray investigation, revealing a Ru−C(bicycle) distance of 2.08(1) Å. Treatment of 2 with sodium methoxide results in the deprotonation of the NH group of the heterocycle to give the pyrido[1,2-a]pyrimidinyl derivative Ru(η5-C5H5){2,2-diphenyl-2H-pyrido[1,2-a]pyrimidin-4-yl}(CO)(PiPr3) (4), which has been also characterized by an X-ray diffraction analysis. In this case, the study reveals a Ru−C(bicycle) distance of 2.097(5) Å. The deprotonation of 2 is reversible. Thus, the addition of HBF4·OEt2 to dichloromethane solutions of 4 regenerates 2. Similarly, the treatment of 4 with methyl trifluoromethanesulfonate affords [Ru(η5-C5H5){1-methyl-2,2-diphenyl-2H-pyridinium[1,2-a]pyrimidin-4-yl}(CO)(PiPr3)]CF3SO3 (5). Complex 1 also reacts with thioisonicotinamide. The reaction yields [Ru(η5-C5H5){4,4-diphenyl-2-(p-pyridinyl)-4H-1,3-thiazinium-6−yl}(CO)(PiPr3)]BF4 (6), which in the presence of sodium methoxide affords Ru(η5-C5H5){4,4-diphenyl-2-(p-pyridinyl)-4H-1,3-thiazin-6-yl}(CO)(PiPr3) (7). The structure of 7 has been determined by an X-ray investigation, revealing a Ru−C(cycle) distance of 2.067(4) Å. The deprotonation of 6 is also reversible. Thus, the addition of HBF4·OEt2 to dichloromethane solutions of 7 regenerates 6. Similarly, treatment of 7 with methyl trifluoromethanesulfonate gives [Ru(η5-C5H5){3-methyl-4,4-diphenyl-2-(p-pyridinyl)-4H-1,3-thiazinium-6-yl}(CO)(PiPr3)]CF3SO3 (8).

Nucleophilic addition reactions to the allenylidene complex [Cp∗RuCCCPh2(CO)(PMeiPr2)]+: X-ray crystal structures of , , and

“…The addition of tertiary phosphines leads to allenylphosphonio derivatives ½Cp à RufCðPR 3 ÞC@CPh 2 ðCOÞðPMe i Pr 2 Þ ½BAr 0 4 , whereas the reaction with propanethiol yields the thiocarbene ½Cp à RufCðS n PrÞCH@CPh 2 ðCOÞ ðPMe i Pr 2 Þ½BAr 0 4 which is better considered as a thiabutadienyl complex as inferred from its X-ray crystal structure analysis. In summary, despite of the well-known differences between systems bearing Cp or Cp * ligands, in this particular case the reactivity of the complex [Cp * Ru‚C‚C‚CPh 2 (CO) (PMe i Pr 2 )] + towards nucleophiles parallels in general terms that of the related CpRu system [CpRu‚ C‚C‚CPh 2 (CO)(P i Pr 3 )] + [8][9][10][11][12][13][14][15][16][17]29].…”

“…The reactivity of allenylidene ligands attached to different cationic ruthenium fragments such as {[(g 5 -C 9 H 7 )Ru(PPh 3 ) 2 ] + } [5][6][7], {[(g 5 -C 9 H 7 )Ru(CO)(PPh 3 )] + } [5][6][7], {[CpRu-(CO)(P i Pr 3 )] + } [8][9][10][11][12][13][14][15][16][17] or {[(g 6 -arene)RuCl(PR 3 )] + } [18][19][20][21] has been studied by several research groups. Although the reactivity of cationic allenylidene complexes is governed by the electron deficiency of both the C a and C c atoms of the unsaturated chain, its is known that regioselective nucleophilic additions at C c take place when bulky, electron-rich metallic fragments are used, leading to r-alkynyl complexes [2,5].…”

Nucleophilic Addition Reactions to Allenylidene Complexes of Ruthenium Bearing Hemilabile P,N Ligands: Isolation of the Vinylcarbene Complex [Cp*Ru═CHCH═CPh2(iPr2PNHPy)][PF6]

“…The reactivity of cationic allenylidene complexes is governed by the electron deficiency of both the C α and C γ atoms of the unsaturated chain, and this is strongly dependent on the electron density at the metal center. Thus, addition to the C γ was observed in the case of the electron-rich systems [Cp*RuCCCRR′(P) 2 ] + ((P) 2 = dippe, (PEt 3 ) 2 ). − However, the introduction of a strong π-acceptor ligand such as CO modifies both the electronic and the steric properties of the metallic fragment, and in electron-poor systems of the type [(C 5 R 5 )RuCCCPh 2 (CO)(PR 3 )] + (R = H, PR 3 = P i Pr 3 ; R = Me, PR 3 = PMe i Pr 2 ) − products derived from the regioselective addition to C α of the allenylidene ligand have been isolated. The addition of electrophiles to C β of the allenylidene is less frequent and usually leads to dicationic vinylcarbyne derivatives such as [Cp*RuCCHCRR′(dippe)] 2+ (R = R′ = Ph; R = H, R′ = Ph) or [Cp*RuCCHCRR′(PEt 3 ) 2 ] 2+ (R = R′ = Ph; R = H, R′ = Ph) .…”

Transition Metal Complexes of Neutral eta1-Carbon Ligands

“…The structure of the products generated depends mainly on the number (6) with dinucleophiles possessing only one heteroatom-hydrogen bond, such as pyrazoles, leads to the heterocyclic alkenyl derivatives 95 (Fig. 19) [289,291,292]. Complexes 94 result formally from the addition of the nitrogen and oxygen atoms to C a and C g , respectively, and the transfer of two hydrogen atoms to the C b position.…”