US EPA

4889088 

Journal Article 

MATRIX PHOTOCHEMISTRY OF TRANS-[CP-ASTERISK-FE(CO)](2)(MU-CO)(MU-CH2) - GENERATION OF THE CIS ISOMER AND OF A DOUBLE-CO-LOSS PHOTOPRODUCT 

Spooner, YH; Mitchell, EM; Bursten, BE 

1995 

1 

Organometallics
ISSN: 0276-7333
EISSN: 1520-6041 

14 

11 

5251-5257 

10.1021/om00011a048 

WOS:A1995TE43400048 

The photochemistry of [Cp*Fe(CO)](2)(mu-CO)(mu-CH2) (7*; Cp* = eta(5)-C(5)Me(5)) has been investigated in a matrix of 3-methylpentane at low temperatures. Compound 7* undergoes CO loss to form the triply bridged product [Cp*Fe](2)(mu-CO)(2)(mu-CH2) (8*), a species similar to the CO-loss product from [CpFe(CO)](2)(mu-CO)(2) (1). Compound 8* undergoes a subsequent photochemical CO loss to generate the double-CO-loss product Cp*Fe-2(2)(mu-eta(1):eta(2)-CO)(mu-CH2) (9*), which contains a semibridging CO ligand. Because of the preference for CH2 to serve as a bridging ligand, 9* is very different from the double-GO-loss product from I, i.e. [CpFe(CO)](2) (3), which has terminal CO ligands. Compound 9* thermally reacts with CO to reform 8*. Thermal ramping experiments demonstrate that 8* thermally reacts with CO to re-form 7*, with a preference for the formation of the thermodynamically unfavored cis isomer. The cis isomer of 7* converts to the trans isomer via a first-order process that is considerably slower than cis/trans isomerization for 1 or [Cp*Fe(CO)](2)(mu-CO)(2) (1*). A scheme is proposed to explain the formation of cis-7* in preference to trans-7*. The photochemistry of the Cp-containing, alkylidene-bridged compounds [CpFe(CO)](2)(mu-CO)(mu-CH2) (7) and [CpFe(CO)](2)(mu-CO)(mu-CHCH3) (7') is not as straightforward as that of 7*, owing to multiple isomers and low solubility.