TY - JOUR
T1 - Synthesis of 2,6-bis(2-oxazolinyl)phenylplatinum(II) NCN pincer complexes by direct cyclometalation. Catalysts for carbon-carbon bond formation
AU - Fossey, John S.
AU - Richards, CJ
PY - 2004/2/2
Y1 - 2004/2/2
N2 - 1,3-Bis(4',4'-dimethyl-2'-oxazolinyl)benzene (5a) and 5-nitro-1,3-bis(4',4'-dimethyl-2'-oxazolinyl)benzene (5b) were heated in dry acetic acid with K2PtCl4 to give the corresponding 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenylplatinum(II) chloride complexes 6a and 6b in 49 and 11% yield, respectively. The X-ray structure of 6b is reported. The main side product observed in the platination of 5a was identified as di(2-methyl-2-N-acetyl)propyl isoplithalate. In contrast, use of Pd(OAc)(2) with 5a in this protocol, followed by addition of LiBr, gave 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenylpalladium(II) bromide in only 3% yield. Treatment of 6a with AgOTf and AgSbF6 in acetone gave quantitatively the corresponding cationic 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenyl(aquo)platinum(II) complexes 15a and 15b. Similarly treatment of 6b with AgOTf in acetone gave 4-nitro-2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenyl(aquo)platinum(II) trifluoromethanesulfonate (15c) (72%). Complexes 15a-c, together with 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenylaquopalladium(II) triflate (15d), were applied as catalysts for the Michael reaction between methyl vinyl ketone and ethyl cyanoacetate and the Diels-Alder reaction between acrylonitrile and cyclopentadiene. In both cases platinum complex 15a was found to be the most active, with the 4-nitro group of 15c resulting in decreased catalytic activity.
AB - 1,3-Bis(4',4'-dimethyl-2'-oxazolinyl)benzene (5a) and 5-nitro-1,3-bis(4',4'-dimethyl-2'-oxazolinyl)benzene (5b) were heated in dry acetic acid with K2PtCl4 to give the corresponding 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenylplatinum(II) chloride complexes 6a and 6b in 49 and 11% yield, respectively. The X-ray structure of 6b is reported. The main side product observed in the platination of 5a was identified as di(2-methyl-2-N-acetyl)propyl isoplithalate. In contrast, use of Pd(OAc)(2) with 5a in this protocol, followed by addition of LiBr, gave 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenylpalladium(II) bromide in only 3% yield. Treatment of 6a with AgOTf and AgSbF6 in acetone gave quantitatively the corresponding cationic 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenyl(aquo)platinum(II) complexes 15a and 15b. Similarly treatment of 6b with AgOTf in acetone gave 4-nitro-2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenyl(aquo)platinum(II) trifluoromethanesulfonate (15c) (72%). Complexes 15a-c, together with 2,6-bis(4',4'-dimethyl-2'-oxazolinyl)phenylaquopalladium(II) triflate (15d), were applied as catalysts for the Michael reaction between methyl vinyl ketone and ethyl cyanoacetate and the Diels-Alder reaction between acrylonitrile and cyclopentadiene. In both cases platinum complex 15a was found to be the most active, with the 4-nitro group of 15c resulting in decreased catalytic activity.
U2 - 10.1021/om0305162
DO - 10.1021/om0305162
M3 - Article
VL - 23
SP - 367
EP - 373
JO - Organometallics
JF - Organometallics
IS - 3
ER -