Alkyne complexes of the group 8 metals: Reactivity of the M(CO)4(eta(2)-alkyne) (M = iron, osmium) compounds | | Posted on:2004-03-20 | Degree:Ph.D | Type:Dissertation | | University:University of Alberta (Canada) | Candidate:Major, Quinn Dean | Full Text:PDF | | GTID:1461390011975251 | Subject:Chemistry | | Abstract/Summary: | | | The reactivity of M(CO)4(η2-alkyne) (M=Fe, Os) compounds toward two electron donor ligands has been investigated. These compounds were found to undergo both ligand substitution and reactions that involve coupling of the alkyne and selected unsaturated organic ligands.; Reaction of Fe(CO)4(η2-C2(CF 3)2) with two or more equivalents of bulky phosphine ligands (PtBu2Me, PiPr3, PCy 3) proceeded with the substitution of two carbonyl ligands. The structure of the products Fe(CO)2(PR2R′) 2(η2-C2(CF3)2) is trigonal bipyramidal with the phosphine ligands occupying mutually trans axial coordination sites. Reaction of Fe(CO)4(η 2-C2(CF3)2) with one equivalent of bulky phosphine ligand (PtBu2Me, PiPr 3, PCy3, PtBu3) yielded isolable Fe(CO)2(PR2R′)(η2-C 2(CF3)2) compounds. The geometry around the iron atom is best described as distorted tetrahedral or square pyramidal. The 13C NMR chemical shift of the alkyne carbons and the Fe-Calkyne separations are indicative of a four electron donor alkyne ligand. Therefore, stabilization of these coordinatively unsaturated compounds stems from additional electron donation from the π⊥ orbital of the alkyne ligand. Reaction of OS(CO)4(η2-C 2(CF3)2) with one equivalent of either cyclohexylisocyanide or trans-cyclooctene proceeded by single carbonyl substitution and yielded Os(CO)3(CNCy)(η2-C2(CF 3)2) or Os(CO)3(η2- trans-cyclooctene)(η2-C2(CF3) 2), respectively. Ligand substitution in M(CO)4(η 2-alkyne) (M=Fe, Os) compounds is not limited to carbonyl ligands. Reaction between M(CO)4(η2-C2H 2) and the pseudo-alkyne complex (η5-C5H 5)(CO)2W≡CC6H5 proceeds by loss of the alkyne ligand and formation of the carbyne bridged heterobimetallic complex FeW(μ-CC6H5)(CO)6(η 5-C5H5).; Both Fe(CO)2(PR2R′)(η 2-C2(CF3)2) and Os(CO)4(η 2-C2(CF3)2) compounds were found to promote coupling of coordinated F3CC≡CCF3 and selected unsaturated organic ligands. Reaction of Fe(CO)2(PR 2R′)(η2-C2(CF 3)2) with allenes yielded Fe(CO)2(PR2R ′)(η1,η3-(F3C)C=C(CF 3)C(CH2)CR″2) (R″ =H, Me), which contained a chelating 2-vinylallyl ligand. This ligand resulted from the coupling of the alkyne and allene ligands via C-C bond formation between a ligating carbon of the alkyne and the central carbon of the allene. The products exist as geometric isomers and were characterized by both NMR spectroscopy and X-ray structure determination. The reaction of Os(CO)4(η2-C2(CF3) 2) with excess | | Keywords/Search Tags: | &eta, Alkyne, Compounds, Ligands, Reaction | | Related items |
| |
|
