117438-22-9Relevant academic research and scientific papers
Synthesis, structure, and reactions of rhenium aminocarbyne complexes formed from [ReCl2(CNR)3(PMePh2)2]+ (R = t-Bu or Me) cations under reductive coupling conditions
Warner, Steve,Lippard, Stephen J.
, p. 228 - 236 (2008/10/08)
The seven-coordinate [ReCl2(CNR)3(PMePh2)2]+ cations, R = Me or t-C4H9, react with Zn(s) or Al(s) in refluxing THF containing ～1% H2O to form (alkylamino)carbyne complexes [ReCl(CNH-t-Bu)(CN-t-Bu)2(PMePh2)2] (SbF6) (1) and [ReCl(CNHMe)(CNMe)2(PMePh2)2](SbF6) (2). The structure of 1, determined by X-ray diffraction, contains a chloride ligand, trans pairs of phosphine and isocyanide ligands, and a Re≡CNHR carbyne unit characterized by a Re-C bond length of 1.82 (1) ?, a C-N distance of 1.30 (1) ?, a Re-C-N angle of 175.7 (9)°, and a C-N-C bend angle of 127.6 (9)°, consistent with considerable Re=C=NHR character. Infrared and 1H, 31P, and 13C NMR spectroscopic data support the persistence of this structure for both 1 and 2 in solution. Multiple recrystallizations of 2 from THF led to the formation of [ReCl(CNMe)3(PMePh2)2] (3) through formal loss of HSbF6. Compound 3 was structurally characterized by X-ray diffraction. It contains two trans phosphine ligands and a meridionally disposed set of three isocyanide ligands, all of which have considerable Re=C=NR character, judging by C-N-C bend angles ranging from 144 (2) to 155 (2)°. Addition of excess zinc to 2 in acetonitrile leads to a similar electron-rich isonitrile complex, [Re(NCMe)(CNMe)3(PMePh2)2](SbF6) (5), in which an acetonitrile solvent molecule replaces the chloride ligand. The structure of 5 is similar to that of 3, but with less back-donation to the isocyanide ligands judging by the C-N-C angles of 160.4 (5)-178.4 (5)°, owing to the positive charge on the complex. Reaction of [ReBr2(CNMe)3(PMePh2)2]+ with Zn in refluxing aqueous THF gave only [ReBr(CNMe)3(PMePh2)2] (4), which was not protonated. Spectral studies of 3-5 established that the solution structures were analogous to those found in the solid state for 3 and 5. These results are consistent with the following reaction pathway for reductive coupling of isocyanide (and analogous CO) complexes: (Chemical Equation Presented) In the present instance, the {Re(CNHR)(CNR)}2+ unit is presumably too stable to form the reductively coupled {Re(RHNC≡CNHR)Cl}2+ moiety.
