14740-77-3Relevant articles and documents
Connor, Joseph A.,Day, J. Philip,Turner, Robert M.
, (1976)
Chemoselective stepwise demetalation of unusually stable fischer biscarbene complexes by domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline to 1-alkynyl Fischer carbene complexes of chromium and tungsten
Chen, Jinzhu,Yu, Zhengkun,Zheng, Zhaoyan,Gu, Kaichun,Wu, Sizhong,Zeng, Fanlong,Tan, Weiqiang,Wu, Xiaowei,Xiao, Wenjing
, p. 302 - 308 (2008/10/09)
Domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline 2 to 1-alkynyl Fischer carbene complexes (CO)5M=C(OEt)C=CPh 1 (a, M = Cr; b, W) in a 1:2 molar ratio afforded unusually stable biscarbene complexes 3a and 3b containing a novel four-, five-, and six-membered tricyclic core in 99.6% and 45.2% yields, respectively. Chain-opening β-aminoalkenyl monocarbene complex 4b and β-amidoalkenyl monocarbene complex 5b of tungsten were also isolated from the cycloaddition upon treatment of the reaction mixture of 1b and 2 on silica gel. Partial and full oxidation of 3a,b with pyridine N-oxide underwent efficient chemoselective stepwise demetalation to afford the corresponding monocarbene complexes 6a,b and organic diester 7, respectively, under mild conditions. The X-ray crystallographic study revealed the presence of a four-, five-, and six-membered tricyclic core in compounds 3,6, and 7, and the methyl and oxazolindinyl groups derived from oxazoline 2 are positioned syn with respect to the azabicyclo[4.2.0]octadiene bicyclic moiety, which is oriented in the opposite direction. X-ray crystal structural data are reported for the bis- and monocarbene complexes 3a, 5b, and 6b as well as for diester 7.
Photochemistry of (η6-2,6-X2C5H3 N)Cr(CO)3 (X = H, CH3, (CH3)3Si). First example of a photoinduced ring-slip at an (η6-arene)M(CO)3 center.
Breheny, Ciara J.,Draper, Sylvia M.,Grevels, Friedrich-W.,Klotzbücher, Werner E.,Long, Conor,Pryce, Mary T.,Russell, Graham
, p. 3679 - 3687 (2008/10/08)
The photochemistry of (η6-2,6-X2C5H3N)Cr(CO) 3 was investigated both in low-temperature matrices (X = H or (CH3)3Si) and in room-temperature solution (X = H, CH3, or (CH3)3 Si), Room-temperature photolysis (λexc > 410 nm) in CO-saturated methanol or acetonitrile produced (η1-2,6-X2C5H3N)Cr(CCO) 5 which subsequently formed Cr(CO)6 in a secondary photochemical process (X = H or CH3), The efficiency of pentacarbonyl formation is lower in CO-saturated cyclohexane and follows the order X = H > X = CH3, Photolysis in low-temperature matrices resulted in an η6 to η1 pyridine ring-slippage (λexc = 460 nm; X = H). Visible irradiation in a CO-doped methane matrix produced (η1-C5H5N)Cr(CO)5, while in an N2 matrix fac-(η1-C5H5N)N2 2Cr(CO)3 is formed. Irradiation with λexc = 308 nm produced both the ring-slippage product and also the CO-loss product (η6-C5H5)Cr(CO)2, which in a N2 matrix is trapped as (η6- C5H5N)Cr(CO)2(N2). Time-resolved infrared spectroscopy in cyclohexane revealed only the CO-loss product (λexc = 308 nm; X = H). The apparent difference in room-temperature and low-temperature photochemistry is explained by a rapid regeneration of (η6- C5H5N)Cr(CO)3 from the η1-intermediate. This explanation was supported by laser flash photolysis experiments (λexc = 355 nm) in CO-saturated cyclohexane (Sol), where the recovery of the (η6- C5H5N)Cr(CO)3 absorption follows a biphasic time profile, whereby the faster process was assigned to the η1 to η6 transformation and the slower to the reaction Of (η6- C5H5N)Cr(CO)2(Sol) with CO. Crystals of (η6-2,6-(CH3)2C5H 3N)Cr(CO)3 and (η6-2,6-((CH3)3Si)2C 5H3N)Cr(CO)3 were characterized by X-ray diffraction.
