134152-89-9Relevant academic research and scientific papers
Rhenium(VII) monoimido alkylidene complexes: Synthesis, structure, and Lewis-acid-cocatalyzed olefin metathesis
Schofield, Mark H.,Schrock, Richard R.,Park, Lee Y.
, p. 1844 - 1851 (1991)
Five-coordinate alkylidene complexes of the general type Re(CH-t-Bu)(NAr)(OAr′)3 (NAr = N-2,6-C6H3-i-Pr2; OAr′ = OC6F5 (1a), O-2,6-C6H3Cl2 (1b), OC6Cl6 (1c)) can be prepared in high yield by treating [Re(C-t-Bu)(NHAr)Cl3]2 with 6 equiv of potassium phenoxide. Re(CH-t-Bu)(NAr)(O-2,6-C6H3Cl2)3 (P21/c, a = 11.461 (3) ?, b = 32.86 (1) ?, c = 11.680 (2) ?, β = 103.31 (2)°) is essentially a square pyramid in which the alkylidene ligand occupies the apical position. Re(CH-t-Bu)(NAr)(OC6F5)3(THF) (2) is prepared in high yield from Re(C-t-Bu) (NHAr)Cl3(THF) and 3 equiv of KOC6F5. Re(CH-t-Bu)(NAr)(OC6F5)3(THF) (P1, a = 11.037 (7) ?, b = 17.66 (1) ?, c = 10.981 (6) ?, α = 90.28 (6)°, γ = 93.94 (6)°, γ = 94.15 (5)°) is pseudooctahedral with THF bound at the coordination site trans to the alkylidene ligand. Re(CH-t-Bu)(NAr)(OAr′)3 complexes do not react with terminal, internal, or strained cyclic olefins, possibly because an olefin can bind only to the site trans to the alkylidene ligand. Re(CH-t-Bu)(NAr)(OAr′)3 complexes react with pyridine to form alkylidyne complexes of the type Re(C-t-Bu)(NAr)(OAr′)2(py) (OAr′ = O-2,6-C6H3Cl2 (3a), OC6Cl5 (3b)). Alkylidene complexes of the type Re(CH-t-Bu)(NAr)(OAr′)Cl2 (OAr′ = O-2,6-C6H3Cl2 (4a), O-2,6-C6H3Me2 (4b), OAr (O-2,6-C6H3-i-Pr2), (4c), O-2,6-C6H3(OMe)2 (4d)) can be prepared in high yield by treating Re(C-t-Bu)(NAr)Cl2(DME) with 1 equiv of Ar′OH. NMR data suggest that Re(CH-t-Bu)(NAr)(OAr′)Cl2 complexes are isostructural with Re(CH-t-Bu)(NAr)(OAr′)3 complexes. Re(CH-t-Bu)(NAr)(OAr′)Cl2 complexes also do not readily react with terminal, internal, or strained cyclic olefins. However, addition of GaBr3 to Re(CH-t-Bu)(NAr)(OAr′)Cl2 (OAr′ = O-2,6-C6H3Cl2, O-2,6-C6H3Me2, OAr) yields highly active catalysts that metathesize trans-3-heptene at a rate of ～1000 turnover min-1. In some cases propagating alkylidene species can be observed by NMR spectroscopy. Re(CH-t-Bu)-(NAr)(OAr′)Cl2 complexes react with pyridine to produce complexes of the type Re(C-t-Bu)(NAr)Cl2(py)2.
