Ir -complex

Rhodocene, [Rh()7 -C5H5)2], is also known but is unstable to oxidation and has a tendency to form dimeric species. Claims for the existence of iridocene probably refer to Ir " complexes. However, the yellow rhodicenium and iridice-nium cations are certainly known and are entirely analogous to the cobalticenium cation in their resistance to oxidation and susceptibility to nucleophilic attack. 

Unusual ir-complex compounds were obtained when reacting with Yb(fod)3 and Ag(fod) with 9-vinylcarbazole (83PJC1393). The NMR spectrum of 9-vinylcarbazole in the presence of Yb(fod)3 + Ag(fod) as the lanthanide shift... 

The activation of olefins through the formation of the ir-complex with the transition metal ion at polymerization was postulated as one of the stages of the propagation reaction in many works, beginning with those of Ludlum el at. 184) and Carrick (185) ... 

With the increase in electronegativity of the element M the degree of covalence of the bonds M —O and M—0 should increase, as a result of which an increase in electron density on the ion M can be expected. As in the formation of the ir-bond with olefin the ir-backbonding mechanism plays a large role, that should result in an increase in the ir-complex stability. 

Unsaturated alkyl halides react first by ir-complexation (141), followed by C-X oxidative addition, probably on matrix warm-up [but see the preceding point 3, and see ref. (81), which suggests that pyrolysis and radical production can occur on the crucible insulating material to cause reaction]. 

Very recently Page and coworkers have reported the D KR of sec-amines using a low catalyst loading of an Ir complex for the racemization, and Candida rugosa lipase for the enzymatic resolution [38]. 

TABLE 11.1 Relative Stabilities of Arenium Ions and ir Complexes and Relative Rates of Chlorination and Nitration ... 

A series of Rh and Ir complexes is also basic enough to add boron halides, although the metal-boron bonds are weak, e.g., dppe and PPh3-Rh complexes serve as electron-pair bases when they react with BF3 and BCI3 . Table 1 summarizes the results. 

The reactivity of the Cp (L)Ir=PMes (L=PPh3, CO) phosphinidene complexes is much less diverse than those with Zr. Only the formation of phosphaalkenes has been observed in the reaction with CH2I2 and CHI3 [102]. This reduced reactivity of the Ir complexes as compared to Zr complex 53 has been... 

Table 2 Results of the transfer hydrogenation of ketones with fluorinated (salen)Ir complexes under biphasic conditions ...

The Ir complexes 83 or [lr(lMes)Cl2Cp ], in the presence of NaOAc and excess of (Bcat), catalyse the diboration of styrene, at high conversions and selectivities for the diborated species, under mild conditions. Other terminal alkenes react similarly. The base is believed to assist the heterolytic cleavage of the (cat)B-B(cat) bond and the formation of Ir-B(cat) species, without the need of B-B oxidative addition [66]. 

The Rh and Ir complexes 85-88 (Fig. 2.14) have been tested for the intramolecular hydroamination/cyclisation of 4-pentyn-l-amine to 2-methyl-1-pyrroline (n = 1). The reactions were carried out at 60°C (1-1.5 mol%) in THF or CDCI3 The analogous rhodium systems were more active. Furthermore, the activity of 87 is higher than 85 under the same conditions, which was attributed to the hemilabihty of the P donor in the former complex, or to differences in the trans-eSects of the phosphine and NHC ligands, which may increase the lability of the coordinated CO in the pre-catalyst [75,76]. 

More success has been had with Ir complexes incorporating permelhylcyclopentadiene and NHC ligands. Complexes 18-20 (Fig. 4.7) were evalnated for norbomene polymerisation following activation with MAO [22]. Complex 19 was the most active, giving a TOF of 12 220 h over 10 min, followed by 18 (TOF = 3 220 h" ), while 20 was inactive, indicating that a hemilabile pendant group seems essential. Analysis (NMR) of the polymers formed with 18 and 19 shows that polymerisation proceeds via an addition (coordination-insertion) mechanism. 

Scheme 13.16 H/D exchange catalysed by monodentate and cyclometaUated Ir complexes...

Very recently Chin et al. reported Ir complex-catalyzed hydration as well as the first example of methanolysis of nitriles [75]. Hydration of RCN (R = Me, MeCH=CH, Ph) is catalyzed by [Cp Ir(Tl -CH2CHCHPh)(NCR)]OTf (R = Me,... 

The Ir complex (NH4)[Ir(NH3)Cl5] has been prepared by the oxidation of the Ir111 analogue with Cl2 at 330 °C, and its structure determined from powder diffraction studies.30... 

The binuclear Ir complex (93) is produced from the direct coupling reaction of the Ir-bound 5-chloro-phen ligand as shown in reaction Scheme 12.153 The nonplanar structure of the bridging ligand results in the electronic isolation of the two Ir centers. Hence both metal centers and ligands are oxidized and reduced, respectively, in two-electron processes. 

The crystal structure of (232) is reported. Ir complexes bound to the multidentate ligand as in (232) have proved successful in the enantioselective reduction of a,/3-unsaturated ketones to allylic alcohols.404... 

The binuclear complex [[ Ir(/ -pz)(NCBu )2j2], (283), oxidizes readily with [cp2Fe]+ to give the Ir11—Irn-bonded dication (284), which adds I yielding the neutral complex (285).469 Reaction of (283) with I2 gives (285) directly, which reacts with further I2 to yield the Ir complex (286). 

The orange-red, divalent Ir complex [Ir(C5H4PPh2)2CO]22+ was synthesized following the chemical oxidation of [Ir(C5H4PPh2)CO]2 by either [Fe(cp)2]BF4 or AgPF6.492 The Ir11 complex was characterized by IR (j/co) and NMR spectroscopy. 

Luminescent Ir complexes of diphosphine and diphosphinite calix[4]arene show emission maxima at 619 nm and 597 nm, respectively, at 77 K. The emission lifetimes are perturbed by addition of Li+, Na+, and U022+. 

The in vitro trypanocidal and antitumor activities of lfr(cot)L], cot = cyclotetraene, derivatives of dithiocarbamates and xanthates, have been investigated.700 The Ir complexes were characterized by IR spectroscopy, and MO calculations (Hiickel) were performed on the ligands. Similar studies were performed on [Ir(nbr)L], nbr = norbornadiene, L = derivatives of alquil and aryl xanthates 701 and also on [Ir2(cod)2L]X2, where L = 2-hydroxystilbamidine, X = C1, N03, C104, BPh4, and [Ir(cod)L2 ]X, where L = benznidazole, R0-2516, nifurtimox, niridazole. The complex [Ir2(cod)2(2-hydroxystilbami-dine)](BPh4)2 showed the highest activity, as studied by optical microscopy of rats kidneys. 

---