Metal groups carbonylation

A variety of catalysts including copper, nickel, cobalt, and the platinum metals group have been used successfully in carbonyl reduction. Palladium, an excellent catalyst for hydrogenation of aromatic carbonyls is relatively ineffective for aliphatic carbonyls this latter group has a low strength of adsorption on palladium relative to other metals (72,91). Nonetheless, palladium can be used very well with aliphatic carbonyls with sufficient patience, as illustrated by the difficult-to-reduce vinylogous amide I to 2 (9). 

FlO. 1. Theoretical curves of OC—M—CO bond angle in M(CO)3 groups with approximate trigonal symmetry, with transition metal M enneacoyalent (u = 9) or octacovalent (< = 8), as functions of the bond number n from n = 1 (single bond from metal to carbonyl) to n = 2 (double bond). 

A particularly interesting case is that of the platinum metal group which, in addition to platinum (Pt), comprises ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), and palladium (Pd). These carbonyl halides are usually the most practical precursors for metal deposition because of their high volatility at low temperature. Indeed two of them, palladium and platinum, do not form carbonyls but only carbonyl halides. So does gold. 

Metallo-organics are compounds in which the atom of an element is bound to one or more carbon atoms of an organic hydrocarbon group. Many of the elements used in MOCVD are the metals of groups Ila, Ilb, Illb, IVb, Vb, and VIb, which are non-transitional. The metallo-organics thus complement the halides and carbonyls, which are the precursors for the deposition of transition metals (Groups IVa, Va, and Via) and their compounds. 

Ziegler-Natta catalyst for polymerization of alkenes. Considerable attention has been directed to double-bonded Fischer carbenes of Cr and W, the Schrock carbenes of Ta and Ti, and cyclic polyene ligands of Fe, Co, Cr, and U. Carbonyls of transition metals from groups 6 to 10 of the periodic table include both the monomeric compounds such as Cr(CO)g, Fe(CO)5, Ni(CO)4 and those with two metal groups such as Mn2(CO)io and Co2(CO)s, which is used industrially for hydroformylation. Although their source has not been identified, it has been shown that volatile compounds from landfills contain carbonyls of Mo and W (Feldmann and Cullen 1997). 

The earliest NLO studies involving metal pyridyl complexes were reported by Frazier et al. in 1986 who investigated the SHG properties of various group 6 metal pyridyl carbonyls.63 Although most of the complexes tested show little or no activity, (6) and (7) have respective SHG efficiencies of 0.2 and 1.0 times ADP using a 1,064 nm laser.63 Shortly after, Calabrese and Tam reported SHG from the Re1 complex (8).64 Subsequent studies by Eaton and Tam et al.65,66 describe the preparation of inclusion compounds of various metal complexes with thiourea or tris-ort/ o-thymotide. Unfortunately, none of the complexes [W(CO)5L] (L = pyridine, py, or a 4-substituted py) produce SHG-active materials.65,66... 

The use of hetero-metallic (MM )carbonyl complexes as precursors can lead to the preparation of supported catalysts having weU-defined bimetallic entities in which the intimate contact between M and M remains in the final catalyst and the atomic ratio M/M of the aggregates is that of the bimetallic carbonyl precursor used. This is illustrated in Figure 8.1, in which the definite interaction of the MjM (CO) complex with the functional group (F) of a surface (S) produces a new anchored surface species. This new surface species could evolve with an appropriate treatment producing tailored bimetallic particles. 

The lactone concept is not restricted to the simple model biaryl synthesis presented here. It has been successfully expanded to a broad series of structurally diverse biaryl substrates (e.g., lactones with additional stereocenters and functional groups, configurationally stable lactones, seven-membered lactones, and again configurationally unstable biaryl hydroxy aldehydes ), to different activation modes in the ring-opening step (e.g., use of metallated nucleophiles, carbonyl activation by Lewis acids, (Ti -complexation, etc.), and for various strategies of stereoselection (e.g., external vs. internal asymmetric induction). ... 

The unsaturated molecule Y may be carbon monoxide, an olefin, a conjugated diene, an acetylene, a carbonyl compound, various unsaturated carbon-nitrogen compounds, or probably any of several other unsaturated materials. The reactive part of the covalent metal compound is usually a metal-hydrogen, metal-carbon, metal-oxygen, metal-halogen, metal-nitrogen, or metal-metal group. This reaction... 

Although the ultimate fate of the nitrosyl ligands has not been established, a reasonable pathway for their removal can be postulated based on our IR data and recent literature results. Shriver et al. (42) have found that organoaluminum species will complex with the oxygen of metal-coordinated carbonyl groups. For example, the six-coordinate... 

Carbonyls, A group of compds of CO metals, having the general formula Mx(CO)y. They are usually prepd by interaction of CO with heated metals. Most carbonyls are highly toxic and dangerous when heated. Some compds are reported to be expl or very unstable ... 

These complexes readily insert carbon monoxide between the alkyl and metal groups giving acylmetal complexes. As in the preceding examples, these complexes undergo alcoholysis readily to form esters and a hydride. The reaction is then made catalytic in the metal by adding a base to convert the hydride back into the carbonyl anion ... 

It has been shown that calix[4]aryl esters 12 exhibit remarkably high selectivity toward Na+ [26-30], This is attributable to the inner size of the ionophoric cavity composed of four OCH2C=0 groups, which is comparable to the ion size of Na+ [18]. In the absence of guest metals the carbonyls are turned to the exoannulus direction to reduce electrostatic repulsion whereas in the presence of guest metals they rotate to the endo-annulus direction to coordinate with the... 

The normal reaction of tertiary phosphines is to replace metal-coordinated carbonyl groups (Section III,E,1) or, less commonly, to form adducts with P—>Si bonds (Section III,D). In special cases, however, cleavage of the Si-metal bond may occur directly (entries 63, 66, 66a, and 67) the manganese derivative is discussed further in Section... 

There is a patent claim for the preparation of [C6H6Ti(CO)4]+Br and [C6H6Ti(CO)3(NO)]+Br 47). Apart from this, there appear to be no examples of Group IV metal cationic carbonyls. 

Organometallic compounds with metal-carbon bonds are formed by nearly all metallic elements, but those of transition metals show a diversity without parallel in main groups. Carbonyl has cyanide ligands are not considered organic, although they may also be present in organometallic compounds along with... 

Short M—C Contacts between Group IB Metals and Carbonyl Ligands Bonded to Adjacent Metals... 

As has been described, the parent monocarbollide-metal carbonyl piano-stool species 2-(CO)n-closo-2,1 -MCB,0II n] are now known for all of the metals M = Mo (12), W (13), Re (14), Fe (11), Ru (6), Os (8), and Ni (18). Evidence also exists for a dicarbonyl-platinum analogue of compound 18,20 and as mentioned earlier, the manganese analogue of 14 has also briefly been reported.3a A notable absence from this list, however, is any representative of the Group 9 metals. The carbonyl nitrosyl-cobalt complex 21 is very closely related to the hitherto unknown dicarbonyl-cobalt dianion [2,2-(CO)2-< 7<9.v<9-2,1 -CoCB10H 11]2 and this species remains an attractive synthetic target. 

Although the principles of cluster bonding developed for main-group clusters carry over to transition-metal clusters of the group 8/9 metals with carbonyl ligands, we fully expect transition metals to exhibit variations on this cluster bonding theme as well as novel behavior not seen in main-group systems. In this section we introduce those aspects of cluster chemistry characteristic of transition-metal clusters. 

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