Exceptionally facile CO addition to a saturated ruthenium complex.
Synthesis and characterization of Cp*Ru[eta3-HC(PPh2NPh)2], 1, reveals it to have a "piano stool" structure with the ligand bound to Ru(II) via two N and the unique, sp3 hybridized carbon. While the analogous (cymene) Ru[eta3-HC(PPh2NPh)2]+ does not react with CO, under the same conditions, 1 adds one CO rapidly (25 degrees C, 1 atm CO). Characterization, including an X-ray structure determination, shows that CO has displaced one chelate ligand nitrogen, which then hangs off the molecule, free of Ru. DFT calculations reveal a possible mechanism via a remarkably low energy (+9.3 kcal/mol) intermediate, pendant N, but with one phenyl on phosphorus stabilizing Ru via donation from a C(ipso)=C(ortho) bond. DFT calculations show that the electronic energy change for binding CO is over 20 kcal/mol less favorable for cymene than for C5Me5- as ligand; the reactivity difference is thus thermodynamic in origin.
Bibal
Christine
C
Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, USA.
Smurnyy
Yegor D
YD
Pink
Maren
M
Caulton
Kenneth G
KG
D002248:Carbon Monoxide / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D017975:Ruthenium Compounds / Q000138:chemical synthesis* / Q000737:chemistry
D009942:Organometallic Compounds; D017975:Ruthenium Compounds; D002248:Carbon Monoxide; D012428:Ruthenium