Photocarbonylation of Alkanes and Arenes

Eisenberg [16] noted that benzene can be carbonylated via eq. 17 on prolonged photolysis with either IrH3(CO)dppe (6) or IrH(CO)2dppe (7). Complex 6 can in principle photoextrude H2 and 7 can photoextrude CO to give the same intermediate IrH(CO)dppe (8), which has never been isolated and is presumably a highly reactive species. Species 8 was therefore 

Goldman [13b] has shown that aromatic ketones, such as Ph2CO, known to abstract H atoms from alkanes on irradiation, can give alkane carbonylation if a suitable metal carbonyl, such as IrCl(CO)2(PMe3)2 or Ru(CO)3(dmpe) (dmpe = Mc2PCH2CH2PMe2), is present to trap the resulting alkyl radical. The sequence proposed is shown in eq. 20-24. 

A related process, photodecarbonylation of RCHO to give CO and RH, has been found for [Rh( j.-Cl)(CO)(PMe3)]2. Oxidative addition of the aldehydic 

CH bond to an excited state of Rh2 is proposed as the C-H bond breaking step [13c]. 

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