75102-51-1Relevant academic research and scientific papers
Activation of CO2-like molecules: Synthetic and structural studies on a η2-C,N metal-bonded carbodiimide and its conversion into a η2-C,N metal-bonded amidinyl ligand
Pasquali, Marco,Gambarotta, Sandro,Floriani, Carlo,Chiesi-Villa, Angiola,Guastini, Carlo
, p. 165 - 171 (2008/10/08)
Vanadocene reacts with p-tolylcarbodiimide (p-TCD) producing a metallaazacyctopropane-like complex Cp2V(RN-C=NR) (I) (R = p-CH3C6H4; Cp = η5-C5H5; vCN(Nujol) 1645 cm-1; μeff = 1.76 μB at 293.5 K). The X-ray analysis performed on complex I shows that vanadium is η5 bonded to the two Cp rings, which are in a bent arrangement, making a cavity in the equatorial plane for the CN2 unit. The C-N bond distances agree with the presence of a single C-N bond interacting with the metal and a free C=N double bond. Complex I reacts with both O2 and I2, releasing p-TCD. Coordinated p-TCD is converted in a η2-C,N metal-bonded trialkylamidinyl ligand by the action of CH3I on complex I. The reaction with CH3I, followed by the addition of I2, allowed isolation of [Cp2V(R(CH3)NC=NR)]I3 (II) (R = p-CH3C6H4; vCN(Nujol) 1680 cm-1; μeff = 1.78 μB at 293 K). The X-ray analysis showed an overall structure of the cation similar to that of I, with the amidinyl ligand acting as a three-electron-donor ligand and displaying a bonding mode similar to that observed for η2-C,O acyls and η2-C,N iminoacyls. The two C-N bond distances within the CN2 unit have a high double-bond character (1.26 (2) and 1.33 (2) A?), indicating a significant electronic delocalization all over the VCN2 unit with a carbenoid character for the carbon bonded to the vanadium atom. In both complexes, V-C bond distances (about 2.0 A?) fall in the expected range for a V-C (sp2) bond. Crystallographic details for complex I: space group Pna21 (orthorhombic); a = 14.446 (3) A?, b = 14.186 (2) A?, c = 20.903 (4) A?, V= 4283.7 A?3; Z = 8; Dcalcd = 1.251 g cm-3. The final R factor was 8.4% for 1439 observed reflections. Crystallographic details for complex II: space group P21/c (monoclinic); a = 14.260 (6) A?, b = 19.176 (5) A?, c = 10.628 (4) A?; β = 106.92 (5)°; V = 2780.4 A?3; Z = 4; Dcalcd = 1.910 g cm-3. The final R factor was 6.3% for 2283 observed reflections.
