Cobalt,rhodium and iridium

In the reaction of the cobalt carbene complex 12 with 3-hexine at 25 °C, the r -vinylketene complex 13 was formed in 35% isolated yield (reaction 8.31) [62], 

In a slow dediazotation reaction of bis(trifluoromethyl)diazomethane with (Ph2PCH3)2lr(CO)Cl, the iridium carbene complex 14 was formed and isolated in 37% yield (reaction 8.32) [63]. 

The carbene transfer from bis(trifluoromethyl)diazomethane to octacarbonyl dicobalt gives at room temperature in 28 days the p -bis(trifluoromethyl)methylene complex IS that was isolated in 54% yield (reaction 8.33) [64,65]. 

The dediazotation reaction of various diazoalkanes (reaction 8.34) was successfully applied in the preparation of stable dinuclear cobalt carbene complexes (16) containing Tj -cydopentadienyl ligands [66-71]. 

By the reaction of Co2(CO)6(dppm) (dppm = bis-diphenylphosphanomethane, Ph2PCH2PPh2) with diazomethane or ethyl diazoacetate stable p-methylene complexes 17,18,19, and 20 were prepared (reactions 8.35-8.38). On the basis of NMR spectra obtained at different temperatures, an equilibrium transformation of p-methylene into terminal methylene in complex 17 (reaction 8.39) [72] was shown. 

Rh2(COD)2Cl2 with NaCgH and phosphines gives CpRh(PR2)2- New 

Cp RhH2(SiEt )2 CpCo(COT) (COT = cyclooctatetrene) has been used to catalyse the conversion of nitriles and acetylenes into pyridines. 

This has been interpreted as a concentration of electron density 

6 Cobalt, Rhodium and Iridium. - This group is justifiably recognised for its catalytic prowess and a number of papers each year are targeted at using Co, Rh or Ir carbonyls as catalysts for some reaction or other. Often, papers deal with the simple carbonyls themselves, such as that by Kurhinen and Pakkanen examining the temperature-programmed decomposition, oxidation, and reduc- 

Catalysis studies are also the goal in a paper by Bianchini and co-workers dealing with the in situ high-pressure NMR spectra of the hydroformyla- 

Moving to dinuclear species, the p-substituent effects on the redox chemistry 

Of the larger clusters, the 1,2,3-triphenylphosphirene derivatives of the iridium carbonyl clusters [HIr4(CO)9L( u-PPh2)] (L = CO, PPhs) resulting from substitution, insertion and hydrometallation processes are discussed by Hitchcock et 

Other clusters have been prepared from the metals in this group, but they are to be found mixed with metals from other groups and in a later section of this report. 

There have been a number of papers dealing with the synthesis and characterization of cluster complexes in this group. Estiu and Zerner have published a theoretical model dealing with CO bonding to Rh clusters and the formation of the same from metal particles is discussed by Takahashi et 

There has been a usefid study of die equilibrium between CH3COCo(CO)4 and CH3Co(CO)4. The endia tyassodatedwididiedecaiban ation  

Two new riiodium cluster compounds have been prepared by Heaton et a/ the 

Mononuclear iridium comfdexes have not been much studied in recent years, but Rahim et al have published a study on the synthesis, characterisation and reactivity of a number of trutns-lr(PR3)2(CO)(NHR ) complexes (R = Me, Et R = Ph, Bu). 

The chonistiy of the iridium complexes based on an [Ir(CO)2Cl] unit has been reported. The solution structures of some cobalt-rhodium complexes have been followed by NMR spectroscopy. PearsaU and Horvath have shown that Co2Rh2(CO) 2 changes, on heating, to Co3Rh3(CO)j5. This larger complex forms an equililnium system with CO which re-forms die Co2Rh2(CO)]2 and produces CoRh(CO)7. 

A number of yellow complexes frflBi -(PR 3)2CoR2, where R is an ortho-substituted phenyl ligand such as mesityl (mes), CeCls or 1 (2-methyl-naphthyl), have been described [47] (see Table 23). They are paramagnetic (jj, = 2-3-2-7 B.M.) in agreement with a square-planar configuration. The structure of the complex rraraj-(PEt2Ph)2Co(Mes)2, 7.13, has been deter- 

A number of six-co-ordinate rhodium alkyl complexes are known. From the reaction between (Me2S)3RhCl3 and MeMgl the red-brown tetra-methyl complex (Me2S)3Me4Rh2l2 is isolated the structure, 7.14a, is proposed [48i]. 

The cyanoalkyl py3RhCl2(CHMeCN) is formed by addition of pyridine and acrylonitrile to RhCh in ethanol [48c]. Possibly a Rh-hydride intermediate is involved in this reaction. The unusual methyl complexes (Ph3P)2MMeClI(MeI), where M = Rh or Ir, are of interest since they are thought to contain Mel acting as a ligand to the metal via the iodine [48d]. If it does then these are the first examples where an alkyl halide complexes with a transition metal. 

Several tertiary phosphine iridium-alkyl and -aryl complexes have been 

It is thought that the reaction with diazomethane giving the chloromethyl complex may proceed by a five co-ordinate carbene intermediate such as (Ph3P)2lrCOCl(=CH2) [48/]. 

Oxidative addition of mCaF to rhodium and iridium complexes takes place readily, and may be followed by loss of a labile group such as 

With 1,2-dibFomotetrafluoroethane, (66) gives the corresponding bromo-tetrailaoFoethyl bromide (67a) this is debrominated by zinc in dimethyl formamide to give the tetiafluoroethylene complex, from which the new a complex (67b) is produced by hydriodic acid. Unfortunately, attempts to 

Co Ktfen) + MeCo (acen) Co (acen) + MeCo (tfen) which have been established for the alkyl complexes. 

Perfluoro-(l-methylpropenyl)silver displaces iodine from(7r-CsH5)Co(CO)-(Rp)I (Rp = CjFj or n-CjF,) to give low yields of (72) compounds of this type [(t7-C5H5)Co(CO)R R ] are rare even when R = R . 

Fluoroacyl complexes (RFCO)Co(CX))a(PPh3) CRp = CHFj or CH F) are prepared in 30—40% yield by the reaction of the appropriate acid anhydride with Na[Co(CO)3PPhj] at -78 °C in THF, in a modification of the more usual route using the acyl halide, and at 55—60 °C in toluene give the corresponding fluoroalkyl compounds.  

Earlier reference has been made to vibrational studies on CoL2, where L = (2-thiophenyl)bis(pyrazolyl)methane, ° and Rh2(02CR)4, where R = H or Me, Rh2(02CH)4(H2O)2.  

Bands due to vCoCl were seen at 318 and 280 cm in the IR spectrum of (CoCl2)2(tpta), where tpta= l,4,8,ll-tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetrazacyclotetradecane. The complexes CoX2(L), where L = Ph2PCH2CHMe2CH2PPh2, show vCoX bands at 320 cm (Cl), 270 cm- (Br) and 224 cm- (I), i.e. terminal Co-X coordination. vCo-P bands lay in the range 210-350 cm-.  

TR data have been reported for the short-lived triplet (5a 7ia) excited state of Rh2(TMB)4, where TMB = 2,5-dimethyl-2,5-diisocyanohexane. vRhRh was found to be at 151 cm , compared to 50 cm in the ground state. The resonance Raman spectra of dinuclear Rh(II) phthalocyanines containing a Rh-Rh single bond contain a band due to vRhRh at 176 cm-.  

The multiple desilyation of silyated cydopentadienes is promoted by ionic ruthenium and rhodium halides. For example the reaction of ruthenium trichloride with 

Chiral cycltqtentadienyl and indenyl rhodium complexes of the type CpRh(l 2) and (q -C H7)Rh(L2), L2 = chiral phosphine have been prepared and characterised by NMR. The reaction of [Cp Ir(L-prolinate)Cl] with l,l-dimethylbut-3-yne results in the addition of the alkyne in a terminal a-bonding mode with chloride displacement. The reactivity and synthesis of the (CpCo)3(CO)2 cluster has been reviewed in a thesis report originating in 1991. The reaction of enantiommcally pure CpCo (PHj2NHC H(Me)Ph)(X), X = CF3, C3F7 with 

A series of Na(Co(CO)4.jj(Alkene)jj) (x = 1 and 2) complexes have been prepared from Na(Co(CO)4) which was thought to be resistant to substitution in this way Cobalt carbonyls have also been used in reactions with SO2 to make alkoxysuphinyl complexes 

The use of the cobalt triad carbonyls as catalysts continues to provide many papers for this report. Publications cover the silylformylation of 1-Hexyne catalyzed by diodium-cobalt carbonyl clusters the formation of hydroxycarbene cobalt carbonyl derivatives, the use of rhodium cluster carbonyls in the water-gas shift reaction Rh4(CO) 2 and Co3Rh(CO)] 2 catalysts for the hydrosilation of isoprene, cyclohexanone and cyclohexenone catalytic reduction of NO by CO and the carbonylation of unsaturated compounds The chemistry of iridium carbonyl cluster complexes has been extended by making use of capping reactions with HgCl2and Au(PPh3)Q 

Earlier reference has been made to a vibrational study of Co(acac)3.  

DFT calculations on Co2(CO)x, where x = 5-8, gave predicted vibrational wavenumbers. For Co2(CO)8, the vCo-Co values were in good agreement with experimental data. The resonance Raman spectrum of CpCo(COD) included bands assigned to vCo-COD at 470 cm and vCo-Cp at 354 cm  

Cobalt atoms reacted with CO/NO mixtures to produce a range of matrix-isolated species, including OCo(NCO), for which vCo-O is at 971 cm (933 cm for Temperature-dependent micro-Raman data were used to study 

The resonance Raman spectrum of Rh3 is dominated by the fundamental and overtones of the symmetric stretch vi (cOe 322.4(6) cm , eXe 0.49(10) cm ). Features due to the antisymmetric stretch (v2, 259 cm ) and the bend (V3, 248 cm ) were also seen. All of the data were consistent with C2V symmetry. The complex (18) gives an IR band due to vRhH at 2084 cm .  

A band assigned as vIrH was seen at 2123 cm in the IR spectrum of the complex Cp (PMe3)Ir(p-C6H4CH3)(H), with similar values in related species.  

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Table 26.1 Some properties of the elements cobalt, rhodium and iridium...

R. S. Dickson, Organometallic Chemistry of Rhodium and Iridium, Academic Press, New York, 1983, 432 pp. C. White, Organometallic Compounds of Cobalt, Rhodium and Iridium, Chapman Hall, London 1985, 296 pp. 

Interest in the synthesis and reactivity of coordinatively unsaturated low-valent metal complexes has led to the use of an o-carboranedithiolato ligand in the formation of metalladithiolene ring complexes. Recently, we69 70 and Wrackmeyer et al.1 72 have reported on the synthesis of the 16e cobalt, rhodium, and iridium... 

Of the three catalytic systems so far recognized as being capable of giving fast reaction rates for methanol carbonylation—namely, iodide-promoted cobalt, rhodium, and iridium—two are operated commercially on a large scale. The cobalt and rhodium processes manifest some marked differences in the reaction area (4) (see Table I). The lower reactivity of the cobalt system requires high reaction temperatures. Very high partial pressures of carbon monoxide are then required in the cobalt system to... 

Catalysts Prepared from Metal Carbonyls of Croup 9 Cobalt, Rhodium and Iridium... 

The Group 9 elements, cobalt, rhodium and iridium, have redox chemistry which in aqueous acidic solution can be summarized by Latimer diagrams ... 

As an appropriate concluding section in this wide-ranging review of oxygen activation by cobalt-, rhodium-, and iridium-containing systems, it has been reported (233) that molten sodium meta-phosphate (NaP03), at 850°C, reacts with dioxygen to produce the superoxide... 

Alcohols. Similarly to acids metals can also catalyze the transformation of alcohols to produce carboxylic acids. Cobalt, rhodium, and iridium were studied... 

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