Complex carbonyl

Several rhodixom complexes containing bridging pyrazolato-cinions have been isolated Including [Rh(y-pz)(CO)2 2  

Examples include those witji various 6-diketonates, N-o-tolylsalicylaldiminato, 

The nature of the products from reactions between [Rh(CO)2Cl]2 and N,N-bis(diphenylphosphino)alkyl- and -arylamines depend on temperature, solvent and reactant ratios. Complexes isolated include the cationic chelates [Rh (Ph2P) 2 HRh (CO) 2CI2I aJid [Rh(CO) (Ph2P)2NR 2l(Rh(00)2012 f the A-frame canplexes (Rh2(Vi-C0) u-(Ph2P)2NR 2X2l and [Rh2 (CO) 2 (p-CO) (p-Cl) y-(Ph2P) 2NR 2 -[Rh(CO),C1,1, (R = Me, Et, Ph, or -tol X = halide or 

The very air-sensitive anion [Rh(C0) ] is generated in THF solution by sodium amalgam reduction of [Rh(CO)2Cl]2 or [Rh(CO)Cl(PPhj)2] in the presence of carbon monoxide. Such solutions may be used to produce other tetrahedral Rh(-l) anions of 

Carbonylation of the A-frame complexes [Rh2(CO)2(y 0R)(y-dppm)2I[ClO l (R = H, Me, or Et) gives the 4E-electron cluster [Rh (CO) (y-CO) (y-dppm)2][CIO ] whose structure resembles that of an A-frame complex with a bridging 

Three of the rhodium(I) carbonyl complexes are particularly important and are selected for special study. 

Reduction of hydrated RhCl3 with CO at 100°C (best results are with CO saturated with methanol or ethanol) yields volatile red crystals of the dimer 

The Rh-Rh distance is 3.12 A, long compared with Rh—Rh single bonds (2.624 A in Rh2(MeCN) J, 2.73 A in Rh4(CO)i2) there is a weaker (3.31 A) intermolecular attraction. Dipole moment and IR studies indicate that the structure is retained in solution and is, therefore, a consequence of electronic rather than solid-state packing effects. Furthermore, it is found for some other (but not all) [RhCl(alkene)2]2 and [RhCl(CO)(PR3)]2 systems. SCF MO calculations indicate that bending favours a Rh-Cl bonding interaction which also includes a contribution from Rh-Rh bonding [56b]. 

This process has been used commercially at the 100 kilo tonne per year level running at around 100°C/20atm. 

The mercapto complex Rh(SH)(CO)(PPh3)2 can be made by an unusual route [60] involving COS, where an intermediate with CS bound COS has been suggested. 

Attempted synthesis of RhY(CO)(PPh3)2 in undried solvents (Y = a weakly coordinating anion, e.g. BF4, C104, S03CF3) leads to 

Rhci PPhyHCHO RljQ(co)(pph3)2 EtOH reflux  

Almost all of the transition metals form compounds in which carbon monoxide acts as a ligand. There are three points of interest with respect to these compounds 11) Carbon monoxide is not ordinarily considered a very strong Lewis base and yet it forms strong bonds to the metals in these complexes (2) the metals are always in a low oxidation state, most often formally in an oxidation state of zero, but sometimes also in a low positive or negative oxidation state and (3) as already discussed, the 18-electron rule is obeyed by these complexes with remarkable frequency, perhaps 99% of the time. 

The molecular structures adopted by simple carbonyl complexes are generally compatible with predictions based on valence shell electron pair repulsion theory. Three representative examples from the first transition series are shown in Fig. 15.2. 

Stable carbonyl complexes of the lirst-row transition melols 

Preparation and Some carbonyl complexes can be made by direct interaction of the finely divided  

Ntckel tetracarbonyl is a highly toxic volatile colorless liquid that is shipped in cylinders pressurized with carbon monoxide.8 Its vapor is about six times as dense as air. Purification of nickel by the Mond process is based on the decomposition of Nt(CO)4, the reverse of Eq. 15.3. The yellow-red iron pentacarbonyl slowly decomposes in air and is sensitive to light and heat. In fact, Fe CO), an orange solid, is prepared by photolysis of Fe(CO)5. 

15l2 Structures of the siiii ile caibonyl camiilexes of ckromium. iron, and nicfceL 

The IR spectrum of CO adsorbed on pure Zr02 included a vCO band at 2185 cm. The high-resolution FTIR spectrum of jet-cooled V(CO)6 showed three features in the region of ve (vCO), at 1972, 1989 and 2008 cm. These were consistent with a dynamic Jahn-Teller effect.  

Time-resolved IR spectroscopy (vCO) was used to investigate the photochemical reactions of CpM(CO)4 and (indenyl)M(CO)4, where M = Nb or Ta, with H2 in -heptane or liquid xenon solutions, or in low-temperature polyethylene matrices, and with CO and N2 in n-heptane solutions. Fast time-resolved IR data included characteristic vCO wavenumbers for CpM(CO)3(Xe), where M = Nb (1986,1885 cm ) or Ta (1983,1879 and 1873 cm ).  

Adsorption of CO at 175 K on Cr20s (0001) produced a surface carbonyl with vCO at 2178 cm. IR spectroscopy (vCO) was used to follow the electrochemical oxidation of Cr(CO)4(tmp) to the monocation (tmp = 3,4,7,8-tet-ramethyl-l,10-phenanthroline). Matrix-IR data (vCO) were used to monitor the photochemical reactions of chromium aminocarbene complexes such as (OC)5Cr[C(NMc2)R], where R = H or Me.  

Adsorption of CO on Si02-supported molybdenum leads to the appearance of two vCO IR bands, at 1990 and 2170 cm. The latter is believed to be due to a high-oxidation state molybdenum atom also bound to two oxygen atoms. Rapid time-resolved IR spectroscopy was used to follow the photochemistry of [CpMo(CO)3]2 and [Cp Fe(CO)2]2 in supercritical carbon dioxide. IR spectra (vCO) were used to characterise the photolysis products of (NBD)Mo(CO)4 in polyethylene matrices.  

Time-resolved IR spectroscopy was used to monitor the reactions of the transient species W(CO)5(cyclohexane) with cycl0-C4H.nO (where n = 4, 6 or 8) and with substituted furans or tetrahydrofurans.  

Bilhou, R. Mutin, M. Leconte, and J. M. Basset, Reel. Trav. Chim. Pays-Bas, 

Tsonis and Farona found Re(CO)sCl/EtAlCl2 active at 110°C for homo-polymerization of cyclic compounds containing 5-, 6-, 7-, and 8-membered rings to low-molecular-weight totally saturated materials (ring systems preserved). The initial active form of the catalyst is [(CO)4Re=CHEt ], the same as for the metathesis of internal and terminal olefins.  

Hussein, and C. L. Arora, Inorg. Chim. Acta, 1978, 29, L215. 

Lithium 2-methylmercaptobenzo-l-thiolate and dilithium benzene-1,2-dithiolate react with [CpFe(CO)2Cl] to give [CpFe(CO)2(SCeH4SMe)] and [ CpFe(CO)2)2-(S2C6H4)], respectively, The novel seleninato-complex [CpFe(C0)2 Se(0)2-Me ] may be prepared from the reactions of either [CpFe(CO)aMe] with SeOg or [CpFe(CO)2Cl] with NaiOaSeMe].  

Displacement of the allyl group from [( -C3H5)Co(CO)3] on reaction with [CpCo(CO)(PHMe2)] produces the metal-metal bonded complex [Cp(CO)Co-0 -PMe2)Co(CO)3]. However, reaction of [( -C3H6)Co(CO)s] with Mc2PH 

In the standard Lewis structures (4), (5) and (6), we have used a lone-pair of carbon or nitrogen electrons to form a o-single bond with the metal M. 

Carbonyl, dinitrogen and cyanide complexes of transition metals are generally not stable unless the metal has lone-pair electrons occupying atomic orbitals that overlap with Ugand n orbitals. In structures (4)-(6), we have indicated two sets of lone-pair electrons. If we assume that these electrons occupy metal and 

The tetracarbonyls NiCCO), Co(CO)4 and FeCCO) are isoelectronic and tetrahedral in shape. In Table 18-1, we have reported C-0 stretching frequencies Vco(cm ), and calculated and (in parentheses) experimental C-0 and M-C bond orders and bond-numbers n o and n j, . The C-0 stretching frequencies show that the strengths of the C-0 bonds decrease in the order CO Ni(CO), Co(CO) Fe(CO).  

The electronic configurations of isoelectronic Ni, Co and Fe are (3d) (4s), from which we can obtain the low-spin valence-state configuration of (9) 

To remove formal charge from the metal and the oxygen atoms, we delocalize metal electrons into antibonding C-0 orbitals. For Ni and Cb , we can delocalize four and five 3d electrons, to generate increased-valence structures (11) and (12). 

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Conjugated dienes, upon complexation with metal carbonyl complexes, are activated for Friedel-Crafts acylation reaction at the akyhc position. Such reactions are increasingly being used in the stereoselective synthesis of acylated dienes. Friedel-Crafts acetylation of... 

Substituted Nickel Carbonyl Complexes. The reaction of trimethyl phosphite and nickel carbonyl yields the monosubstituted colorless oil, (CO)2NiP(OCH )2 [17099-58-0] the disubstituted colorless oil, (CO)2Ni[P(OCH )2]2 [16787-28-3] and the trisubstituted white crystalline soHd,... 

Organometallic Compounds. The predominant oxidation states of indium in organometalUcs are +1 and +3. Iridium forms mononuclear and polynuclear carbonyl complexes including [IrCl(P(C3H3)3)2(CO)2] [14871-41-1], [Ir2014(00)2] [12703-90-1], [Ir4(CO)22] [18827-81 -1], and the conducting, polymeric [IrCl(CO)3] [32594-40-4]. Isonitnle and carbene complexes are also known. 

Representative icosahedral metaUacarborane carbonyl complexes are prepared as shown (193). 

Structure. The CO molecule coordinates in the ways shown diagrammaticaHy in Figure 1. Terminal carbonyls are the most common. Bridging carbonyls are common in most polynuclear metal carbonyls. As depicted, metal—metal bonds also play an important role in polynuclear metal carbonyls. The metal atoms in carbonyl complexes show a strong tendency to use ak their valence orbitals in forming bonds. These include the n + 1)5 and the n + l)p orbitals. As a result, use of the 18-electron rule is successflil in predicting the stmcture of most metal carbonyls. 

Because transition metals even in a finely-divided state do not readily combine with CO, various metal salts have been used to synthesize metal carbonyls. Metal salts almost always contain the metal in a higher oxidation state than the resulting carbonyl complex. Therefore, most metal carbonyls result from the reduction of the metal in the starting material. Such a process has been referred to as reductive carbonylation. Although detailed mechanistic studies ate lacking, the process probably proceeds through stepwise reduction of the metal with simultaneous coordination of CO (90). 

Positionalisomeri tion occurs most often duting partial hydrogenation of unsaturated fatty acids it also occurs ia strongly basic or acidic solution and by catalysis with metal hydrides or organometaUic carbonyl complexes. Concentrated sulfuric or 70% perchloric acid treatment of oleic acid at 85°C produces y-stearolactone from a series of double-bond isomerizations, hydration, and dehydration steps (57). 

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

C-C bonds can be formed by reaction with alkyl iodides or more usefully by reaction with metal carbonyls to give aldehydes and ketones e.g. Ni(CO)4 reacts with LiR to form an unstable acyl nickel carbonyl complex which can be attacked by electrophiles such as H+ or R Br to give aldehydes or ketones by solvent-induced reductive elimination ... 

The nature of the bonding, particularly in CO, has excited much attention because of the unusual coordination number (1) and oxidation state (-f2) of carbon it is discussed on p. 926 in connection with the formation of metal-carbonyl complexes. 

By contrast, reaction of XeFi with the iridium carbonyl complex cation [Ir(CO)3(PEt3)2] in CH2CI2 results in addition across one of the Ir-CO bonds to give the first example of a metal fluoroacyl complex ... 

Similarly many other ij -allyl carbonyl complexes convert to ij -allyl complexes with loss of I CO. 

Conjugated dienes sucb as butadiene and its open-chain analogues can act as 17 ligands the complexes are u.sunlly prepared from melal carbonyl complexes by direct replacement of 2CO by the diene. Isomerization or rearrangement of the diene may occur a.s indicated schematically below ... 

Synthesis and structures of carbonyl complexes with Si-heterocyclic rr-ligands 97JOM(536/537)31. 

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