Rhodium complexes cyclopentadiene

However, because the rhodium complexes of tetraphosphine ligand 4 behave differently than the rhodium complex of Josiphos ligand 3 for both substrates, we postulate that either a) different rhodium complexes are being formed (different binding modes as discussed above, see Fig. 2) by 3 and 4, or b) the substituents on the second cyclopentadiene (cp) ring influence the catalytically active site in the rhodium complexes of 4. 

The reaction of M3(CO)12 with both open-chain and cyclic poly-alkenes has attracted some attention, especially in the case of Ru3(CO)i2. In most of the examples reported, the organic fragment bonds to the metal framework in such a way as to interact with more than one of the three metal atoms (68-77). There are some exceptions to this general statement, however. One is the reaction of Ru3(CO)j 2 with cyclopentadiene, in which a mononuclear complex is obtained (78). In other cases, tetranuclear and hexanuclear compounds are obtained (79 81). Cluster breakdown has also been observed in the case of a rhodium complex upon reaction with ethylene (55) as shown in Fig. 3. 

Preparative Methods the ligand (3R,4R)-3,4-bis(di-phenylphosphino)-l-methylpyrrolidine (la) is prepared from L-tartaric acid via (3R,4R)-3,4-bis(diphenylphosphino)-1-benzylpyrrolidine (lb) as shown in eq 1. Tbe title cationic rhodium complex is made by mixing bis(l,5-cyclopentadiene)rhodium tetrafluoroborate and (la) in CH2CI2 under nitrogen. 

C5H5.1,3-Cyclopentadiene, chromium complex, 29 247,251, 252 chromium, molybdenum, and tungsten complexes, 26 343, 28 148,196,197 cobalt complex, 26 191-197,309 cobalt and rhodium complexes, 28 280, 281... 

The 4-I-2-cycloaddition of trimethylsilyl (TMS)-substituted cyclopentadiene with phosphorylated nitroso alkenes formed bicyclo 1,2-oxazines. However, as dienophiles, phosphorylated nitroso alkenes also react with cyclopentadiene and cyclohexadiene. The phosphoramidite-rhodium complex (84)-catalysed 4- -2-cycloaddition of a,fi-unsaturated imines with isocyanates produced pyrimidinones in good yields and with high enantioselectivities. ... 

The dichlororuthenium arene dimers are conveniently prepared by refluxing ethanolic ruthenium trichloride in the appropriate cyclohexadiene [19]. The di-chloro(pentamethylcyclopentadienyl) rhodium dimer is prepared by refluxing Dewar benzene and rhodium trichloride, whilst the dichloro(pentamethylcyclo-pentadienyl)iridium dimer is prepared by reaction of the cyclopentadiene with iridium trichloride [20]. Alternatively, the complexes can be purchased from most precious-metal suppliers. It should be noted that these ruthenium, rhodium and iridium arenes are all fine, dusty, solids and are potential respiratory sensitizers. Hence, the materials should be handled with great care, especially when weighing or charging operations are being carried out. Appropriate protective clothing and air extraction facilities should be used at all times. 

As mentioned earlier, ruthenium cymene, rhodium and iridium pentamethyl-cyclopentadiene are good metal complexes, to start with, in a screen. It is diffi-... 

The well-known rhodium (136) and iridium 137) peroxo complexes (PhgPlaRhCKOa) (40), [(PhgPlaRhCKOalJa (41), and (Ph3P)2(C0)IrCl(02) (42) have been investigated for their reactivity with acetylacetone, acacH 138). Only the former complex, 40, exhibited any reactivity (in the presence of two equivalents of triphenylphosphine), yielding the hydroperoxo complex (43), (see Scheme 8). Complex 43 reacts with PPhg to form triphenylphosphine oxide, but does not react with any active methylene compounds (methyl acetoacetate, diethyl malonate, or acetone) save for cyclopentadiene. In the last instance, a poorly characterized, unstable system tentatively formulated as 44 may have been formed. In refluxing benzene, 43 did react with excess acacH to form the bis(acac) complex 45. 

The hydrogen atom of the central cyclopentadiene ring can be displaced by potassium with t-BuOK to form the K(CgoMe5) complex in which the potassium atom can then be displaced to form iridium complexes such as Ir(ri5-C6oMe5)(CO)2 [Matsuo, Iwashita and Nakamura Organometallics 24 89 2005], and with rhodium to form Rh(ri5-C6oMe5)(CO)2 [Sawamuia, Kuninobu and Nakamura Chem Soc 122 12407 2000], structures which are supported by X-ray structure analyses. The same cyclopentadiene can complex with Fe and cyclopentadiene (Cp) to form a hybrid of buckyferrocene Fe(C6oMe5)Cp [Sawamura et al. J Am Chem Soc 124 9354 2002, Nakamura Pure Appl Chem 75 427 2003],... 

Buryak and Severin developed an array that detects amino acids using a rhodium-cyclopentadiene complex (24) and three UV indicators. Upon iniroduction of amino acids to these metal receptor-indicator complexes, a certain degree of indicator displacement could be measured for each amino acid. An important feature of this array arose from collecting optical data at various pH levels, which resulted in selectivity changes for the amino acids to the metal receptor. First, the authors tested the amino acids with one metal-indicator combination at pH 7. This led to a separation of the amino acids into two groups one... 

An intramolecular variant of the cyclopropene-alkyne [3+2] annulation reaction was studied (Scheme 2.98). Cyclopropenes with an alkynyl chain at the sp carbon furnished fused cyclopentadienes when treated with rhodium(I) complexes [152]. 

Phosphanylalkyl/aryl)tetramethylcyclopentadienyl complexes of rhodium 84 were obtained from lithiated 1,2,3,4-tetramethyl-5-(2-P,P-dialkyl/arylphosphinoethyl)cyclopentadiene and [Rh(/r-Cl)(CO)2]2. The electron-donating properties of these ligands were compared to the related (phosphanylalkyl/aryl)cyclopentadienyl complexes 85. The P-Rh bond is shown to be stable under methanol carbonylation reaction conditions. ... 

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