TY - JOUR
T1 - tert-Butylazapentadienyl‒Iridium‒Phosphine Chemistry
AU - Bleeke, John R.
AU - Luaders, Scott T.
AU - Robinson, Kerry D.
PY - 1994/5/1
Y1 - 1994/5/1
N2 - Potassium tert-butylazapentadienide reacts with (Cl)Ir(PMe3)3 to produce (syn-(1,2,3-η)-5- tert-butyl-5-azapentadienyl)Ir(PMe3)3 (1a). Treatment of la with acetone leads to attack at the central allylic carbon of the azapentadienyl ligand (C2) and production of a novel iridacyclobutane complex, 2. The X-ray crystal structure of 2 (monoclinic, C2/c, a = 31.117(6) Å, b = 11.104(2) Å, c = 18.457(5) Å, β = 119.26(2)°, V = 5563(2) Å3, Z = 8, R = 0.033, Rw = 0.042) shows the expected trans orientation of the imine and acetone substituents on the four-membered ring. When 1a is stirred in pentane solution, it gradually converts to the thermodynamically favored onti-η3-azapentadienyl isomer, 1b. The structure of 1b has been confirmed by X-ray crystallography (monoclinic, P21/n, a = 15.709(14) Å, b = 26.154(10) Å, c = 18.915(7) Å, β = 108.97(3)°, V = 7351(3) Å3, Z = 12, R = 0.053, Rw = 0.069). The relatively short C3‒C4 bond distance (1.449(26) Å) in the azapentadienyl ligand of 1b may reflect some contribution by an η4-butadiene resonance structure. Treatment of 1b with triflic acid results in clean protonation of the nitrogen center and production of [(η4-(tert-butylamino)butadiene)Ir(PMe3)3]+O3SCF3− (3). Addition of a secondequivalent of triflic acid results in a second protonation at nitrogen, generating the dicationic species 5. Treatment of 1a with 1 or 2 equiv of triflic acid also leads primarily to formation of 3 and 5, respectively. However, a side reaction (~20%) involving protonation at iridium also occurs, generating (syn-η3-tert-butylazapentadienyl)Ir(PMe3)3(H)2+(O3SCF3−) (4) and [formula omited] (6), respectively. Compounds 1a. 1b and 3 are fluxional in solution, due to facile rotation of the π ligands with respect to the IRPMesls fragment. NMR line-shape analysis has yielded rotational barriers (ΔG‡) of 11.5(4), 11.1(4), and 16.4(4) kcal/mol, respectively.
AB - Potassium tert-butylazapentadienide reacts with (Cl)Ir(PMe3)3 to produce (syn-(1,2,3-η)-5- tert-butyl-5-azapentadienyl)Ir(PMe3)3 (1a). Treatment of la with acetone leads to attack at the central allylic carbon of the azapentadienyl ligand (C2) and production of a novel iridacyclobutane complex, 2. The X-ray crystal structure of 2 (monoclinic, C2/c, a = 31.117(6) Å, b = 11.104(2) Å, c = 18.457(5) Å, β = 119.26(2)°, V = 5563(2) Å3, Z = 8, R = 0.033, Rw = 0.042) shows the expected trans orientation of the imine and acetone substituents on the four-membered ring. When 1a is stirred in pentane solution, it gradually converts to the thermodynamically favored onti-η3-azapentadienyl isomer, 1b. The structure of 1b has been confirmed by X-ray crystallography (monoclinic, P21/n, a = 15.709(14) Å, b = 26.154(10) Å, c = 18.915(7) Å, β = 108.97(3)°, V = 7351(3) Å3, Z = 12, R = 0.053, Rw = 0.069). The relatively short C3‒C4 bond distance (1.449(26) Å) in the azapentadienyl ligand of 1b may reflect some contribution by an η4-butadiene resonance structure. Treatment of 1b with triflic acid results in clean protonation of the nitrogen center and production of [(η4-(tert-butylamino)butadiene)Ir(PMe3)3]+O3SCF3− (3). Addition of a secondequivalent of triflic acid results in a second protonation at nitrogen, generating the dicationic species 5. Treatment of 1a with 1 or 2 equiv of triflic acid also leads primarily to formation of 3 and 5, respectively. However, a side reaction (~20%) involving protonation at iridium also occurs, generating (syn-η3-tert-butylazapentadienyl)Ir(PMe3)3(H)2+(O3SCF3−) (4) and [formula omited] (6), respectively. Compounds 1a. 1b and 3 are fluxional in solution, due to facile rotation of the π ligands with respect to the IRPMesls fragment. NMR line-shape analysis has yielded rotational barriers (ΔG‡) of 11.5(4), 11.1(4), and 16.4(4) kcal/mol, respectively.
UR - https://www.scopus.com/pages/publications/0001129470
U2 - 10.1021/om00017a016
DO - 10.1021/om00017a016
M3 - Article
AN - SCOPUS:0001129470
SN - 0276-7333
VL - 13
SP - 1592
EP - 1600
JO - Organometallics
JF - Organometallics
IS - 5
ER -