The Os(CO)(PⁱPr₃)₂ Unit as a Support for the Transformation of Two Alkyne Molecules into New Organometallic Ligands

Abstract

In 2-propanol, the C−C triple bond of one of the two alkynyl ligands of the complex Os(C2Ph)2(CO)(PiPr3)2 (1) can be broken by water to give Os(CH2Ph)(C2Ph)(CO)2(PiPr3)2 (2). The reaction involves a metal-promoted, hydration−disproportionation of the transformed alkynyl ligand catalyzed by the solvent. Thus, the treatment of 1 with H2 18O yields Os(CH2Ph)(C2Ph)(C18O)(CO)(PiPr3)2 (2- 18 O ), and the reaction of 1 with water in the presence of deuterated 2-propanol (iPrOD-d 8) affords Os(CD2Ph)(C2Ph)(CO)2(PiPr3)2 (2- d 2 ). In methanol and in the presence of trifluoroacetic acid, complex 2 isomerizes into the osmaindene The structure of 3 has been determined by X-ray diffraction. The geometry around the osmium atom can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying two relative trans positions. The remaining perpendicular plane is formed by the carbonyl ligands mutually cis disposed and the metallacycle, which forms a planar five-membered ring with the osmium atom. In methanol-d 4, complex 2 reacts with CF3COOD to (3- d 1 ) and 3 in a 2.5:1 molar ratio. Complex 2 also reacts with HBF4. The reaction leads to a mixture of 3 and the π-allyl complex [Os{η3-CH(Ph)CHCHPh}(CO)2(PiPr3)2]BF4 (4), which is a result from the addition of the proton from the acid and the carbon−carbon coupling of the benzyl and alkynyl ligands of 2. Similar to 2, complex 2- d 2 reacts with HBF4 to give a mixture and [Os{η3-CD(Ph)CDCHPh}(CO)2(PiPr3)2] BF4 (4- d 2 ). On the basis of the isotope labeling experiments, the mechanisms of the above-mentioned transformations are discussed.

Reaction of an (Alkyl)(alkenyl)(alkynyl)iridium(III) Complex with HCl: Intramolecular C−C Bond Formation from Alkyl, Alkenyl, and Alkynyl Groups Coordinated to “Ir(CO)(PPh3)2”. H/D Exchange between CH3 and DCl

“…The position of the deuterium atom in 9 - d 1 suggests an electrophilic attack of D + at the β-carbon of the alkynyl ligand of 2 to give the iridium vinylidene ( A - d 1 ) (see Scheme ), as it is well-known that the proton attacks the β-carbon of an alkynyl ligand to give a metal vinylidene . The intermediate A - d 1 may undergo the CH 3 group migration to the α-carbon of the vinylidene group to give another intermediate B - d 1 , as previously observed for the alkyl (R) group migration of Re(CCH 2 )(R) to give Re(CRCH 2 ) 12h and the reaction of Os(CH 2 Ph)(C⋮CPh) with H + to give Os(C(CH 2 Ph)CHPh) . It is most likely that B - d 1 undergoes the β-hydrogen elimination to give the allene ( 9 - d 1 ) and 10 as shown in Scheme .…”

Isomerization of CH3C⋮CPh to Phenylallene Promoted by an Osmium Hydride Complex

“…5 A related reaction mechanism has been proposed for the reaction of Os(CD 2 Ph)(CtCPh)(CO) 2 -(P(i-Pr) 3 ) 2 with HBF 4 to give [Os(η 3 -PhCHCDCDPh)-(CO) 2 (P(i-Pr) 3 ) 2 ]BF 4 . 22 It should be noted that 1-metallacyclopropene rather than a η 1 -vinyl species is involved in the formation of [Cp*Re(CO) 2 (η 3 -CH 3 CHCHCH 2 )] + from protonation of Cp*Re(CO) 2 (MeCtCMe) 6 and in the formation of Cp*Re(CO) 2 (CH 2 dCdCMe) from acidcatalyzed isomerization of Cp*Re(CO) 2 (MeCtCMe). 10 In the latter case, the allene ligand is more likely formed by direct deprotonation of metallacyclopropene rather than -hydrogen elimination.…”

The Five-Coordinate Hydrido−Dihydrogen Complex [OsH(η2-H2)(CO)(PiPr3)2]BF4 Acting as a Template for the Carbon−Carbon Coupling between Methyl Propiolate and 1,1-Diphenyl-2-propyn-1-ol

“…In 2-propanol, the C⋮C triple bond of one of the two alkynyl ligands of this complex can be selectively broken by reaction with water to give Os(CH 2 Ph)(C 2 Ph)(CO) 2 (P i Pr 3 ) 2 . In methanol and in the presence of trifluoroacetic acid, the alkynyl-benzyl compound isomerizes into the osmaindene derivative In the presence of tetrafluoroboric acid, in addition to the isomerization, the π-allyl derivative [Os{η 3 -CH(Ph)CHCH(Ph)}(CO) 2 (P i Pr 3 ) 2 ]BF 4 is produced as a result of the addition of the proton from the acid and the carbon−carbon coupling of the benzyl and alkynyl fragments of Os(CH 2 Ph)(C 2 Ph)(CO) 2 (P i Pr 3 ) 2 …”