135228-51-2Relevant academic research and scientific papers
Synthesis and reactivity of a series of analogous rhenium tris(imido), bis(imido) alkyne, and imido bis(alkyne) complexes
Williams, Darryl S.,Schrock, Richard R.
, p. 1148 - 1160 (2008/10/08)
A reaction between Re2O7, ArNH2 (Ar = 2,6-C6H3-i-Pr2), NEt3, and Me3SiCl yields Re(NAr)3Cl. Reduction of Re(NAr)3Cl in THF by 1 equiv of sodium amalgam gives Hg[Re(NAr)3]2 in ca. 50% yield. An X-ray study showed Hg[Re(NAr)3]2 to be composed of molecular units of (ArN)3Re-Hg-Re(NAr)3 having a linear Re-Hg-Re bond and nearly trigonal planar staggered Re(NAr)3 units. Reduction of either Hg[Re(NAr)3]2 or Re(NAr)3Cl by 2 equiv of sodium amalgam in THF affords Na(THF)2Re(NAr)3 in high yield. An X-ray structure of [N(PPh3)2][Re(NAr)3] showed that the [Re(NAr)3]- ion is a trigonal planar species in which the Re-N-C angles all are essentially linear. Compounds that contain the [Re(NAr)3]- ion can be alkylated to give compounds of the type Re(NAr)3R and protonated to give Re(NAr)3H. Reactions between Re(NAr)3H and π-acceptor ligands yield pseudotetrahedral compounds of the type Re(NAr)2-(NHAr)(η2-L) [L = C2H2, C2Me2, OCHCMe3, C2H4, or norbornene]. Addition of 2 equiv of pyHCl to Re(NAr)3Cl yields Re(NAr)2Cl3(py). Reduction of Re(NAr)2Cl3(py) with sodium amalgam in THF in the presence of MeC≡CMe or NpC≡CNp (Np = neopentyl) yields complexes of the type Re(NAr)2(η2-C2R2)Cl. Reduction of Re(NAr)2(η2-C2Np2)Cl by 1 equiv of sodium amalgam yields Hg[Re(NAr)2(η2-C2Np2)] 2, while reduction by 2 equiv of sodium amalgam yields pentane-soluble Na(THF)2Re(NAr)2(η2-C2Np 2). Na(THF)2Re(NAr)2(η2-C2Np 2) reacts with MeI or ClCH2-2,4,6-C6H2Me3 to yield Re(NAr)2(η2-C2Np2)R or with [Et2NH2][OTf] in THF to give Re(NAr)2(η2-C2Np2)H. Addition of excess PMe2Ph to Re(NAr)2(η2-C2Np2)H yields Re(NAr)2(PMe2Ph)2H. Addition of 4 equiv of pyridinium chloride in a 1:5 mixture of THF and pyridine to Na(THF)2Re(NAr)3 affords Re(NAr)Cl3(py)2 in high yield. Re(NAr)Cl3(py)2 is reduced by excess Zn dust in the presence of 2 equiv of dineopentylacetylene in refluxing THF to afford Re(NAr)(η2-C2Np2)2Cl. Reduction of Re(NAr)(η2-C2Np2)2Cl by 1 or 2 equiv of sodium amalgam in THF yields Hg[Re(NAr)(η2-C2Np2)2] 2 or Na(THF)2Re(NAr)(η2-C2Np2) 2, respectively. The molecular structure of Na(THF)2Re(NAr)(η2-C2Np2) 2 shows that [Na(THF)2]+ is bound to the imido nitrogen atom (2.464(9) A?), not to rhenium (Re-Na = 3.17 A?), and the coordination about the rhenium center is distorted from the pseudotrigonal planar geometry expected for [Re(NAr)(η2-C2Np2)2] -. Na(THF)2Re(NAr)(η2-C2Np2) 2 is alkylated smoothly by MeI or ClCH2-2,4,6-C6H2Me3 to afford Re(NAr)(η2-C2Np2)2R, while addition of [Et2NH2][OTf] yields pale yellow Re(NAr)(η2-C2Np2)2H. Cyclic voltammograms (200 mV s-1) were obtained for the chloride derivatives and sodium salts of the tris-, bis-, and mono(imido) complexes in a solution of 0.5 M[NBu4][PF6] in THF. Extended Hu?ckel calculations on [Re(NH)3]-, [Re(NH)2(C2H2)]-, and Re(NH)(C2H2)2]- all clearly show that a 20-electron count on the metal is avoided by filling a ligand-centered nonbonding orbital.
