Tp*IrH2

Photochemical C-H activation has also been effected with a variety of Tp MLL complexes, often with surprising results. For instance, activation of diethyl ether by Tp " IrH(CH = CH2)(// -C2H4) (203) (UV irradiation), affords not a Fischer carbene, but rather a mixture of Tp IrH(CH2CH20Et)(// -C2H4) (214) and Tp IrH2( 7 -H2C = CH20Et) (215), products analogous to those obtained from the thermal activation of n-pentane. ... 

A significant series of studies have focussed on the iridium(III) complex Tp IrH2(COE) (207), which in the presence of P(OMe)3 photolytically... 

The photochemical activation of solvents has afforded several complexes of the type Tp M(Ar)X(L) (Table III). Thus, in the presence of P(OMe)3, Tp IrH2 ( -COE) (207) photolytically activates benzene to afford 321, the mechanism of which was explored at some length (Section III-B. 1 and III-B.2). The rhodium analogue of 321 (324) was obtained under comparable conditions, but from the rhodium(I) complex Tp Rh( " -1,3-COD) (171), " which also activates benzene in the presence of t rt-butylacrylate to afford 326. The bis(isonitrile) complex Tp Rh(CNCH2 Bu)2 (509) photolytically activates benzene to afford... 

The Ir(V) tetrahydride 322, Ir(II) carbonyl-dihydride 323 and their fully deuterated congeners have also been encountered as the result of photolytic degradation of methanol by Tp IrH2(f/ -COE) (207) and Tp Ir(f/ -1,5-COD) (179). The latter has also served as precursor to 207 under high-pressure hydrogenation (500 atm), while at lower pressure (200 atm) the related dihydride Tp IrH2(i/ -l,5-COD) (209) is instead obtained. 

Though observed with many complexes, C-H activation has been most widely studied for Tp Rh( -1,3-COD) (171), Tp IrH2( -COE) (207), Tp Rh(CO)2 (430) and Tp Rh(j -Ph-N=C = NR)(CNR) (395, R = CH2 Bu), which photochemi-cally activate a range of hydrocarbons. On this basis (detailed below) the generic mechanism has been determined to involve (i) initial photo-dissociation of a labile... 

C-H bond activation step (Scheme 71). A mechanism accounting for the formation of the dihydridocarbene [Tp =IrH2 =C(H)0CH2CH20Me ] 529 and the aromatic diether PhCH20CH2CH20Me has been proposed. 

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