Carbonyl sulfide metal complexes

Sulfur cycling is affected in a variety of ways, including UV photoinhibition of organisms such as bacterioplankton and zooplankton that affect sources and sinks of DMS and UV-initiated CDOM-sensitized photoreactions that oxidize DMS and produce carbonyl sulfide. Metal cycling also interacts in many ways with UVR via direct photoreactions of dissolved complexes and of metal oxides and indirect reactions that are mediated by photochemically-produced ROS. Photoreactions can affect the biological availability of essential trace nutrients such as iron and manganese, transforming the metals from complexes that are not readily assimilated into free metal ions or metal hydroxides that are available. Such photoreactions can enhance the toxicity of metals such as copper and can initiate metal redox reactions that transform non-reactive ROS such as superoxide into potent oxidants such as hydroxyl radicals. 

Ethers, sulfides, amines, carbonyl compounds, and imines are among the frequently encountered Lewis bases in the ylide formation from such metal carbene complex. The metal carbene in the ylide formation can be divided into stable Fisher carbene complex and unstable reactive metal carbene intermediates. The reaction of the former is thus stoichiometric and the latter is usually a transition metal complex-catalyzed reaction of a-diazocarbonyl compounds. The decomposition of a-diazocarbonyl compounds with catalytic transition metal complex has been the most widely used approach to generate reactive metal carbenes. For compressive reviews, see Refs 1,1a. 

The reaction of carbonyl sulfide with [M(02)(PPh3)2] (where M = Pd or Pt) has resulted in the first reported examples of transition metal complexes of the monothiocarbonate anion (47 R = O-). Bidentate S—O coordination was concluded from 3IP H NMR analyses of these compounds.184 A short structural review of metal complexes of monothiocarbamate ions (47 R = N(R )R") demonstrates their varied coordination chemistry.185 In complexes of the dialkyl forms the sulfur atom is seen to have considerable mercaptide character , whereas aromatic amine derivatives demonstrate C—S and M—S partial multiple bonding.185,251 A review on the coordination chemistry of these ligands has appeared.186 Additional detail is provided in Chapter 16.4 of this volume. 

The hydrogen sulfides (H2S, SH-, S2 and their metal complexes) are well known in restricted reducing regions of the world ocean such as anoxic basins (1), but they have traditionally been dismissed as unimportant for, or even nonexistent in, most oxic seawaters 12-41. Several lines of reasoning are now beginning to suggest that sulfides actually do exist in the surface ocean, and enter into a rich metal chemistiy there. Extensive measurements of carbonyl sulfide (OCS) in seawater (5.61 permit the quantification of a mixed layer source, the hydrolysis reactions f7-111... 

Among the carbonylative cycloaddition reactions, the Pauson-Khand (P-K) reaction, in which an alkyne, an alkene, and carbon monoxide are condensed in a formal [2+2+1] cycloaddition to form cyclopentenones, has attracted considerable attention [3]. Significant progress in this reaction has been made in this decade. In the past, a stoichiometric amount of Co2(CO)8 was used as the source of CO. Various additive promoters, such as amines, amine N-oxides, phosphanes, ethers, and sulfides, have been developed thus far for a stoichiometric P-K reaction to proceed under milder reaction conditions. Other transition-metal carbonyl complexes, such as Fe(CO)4(acetone), W(CO)5(tetrahydrofuran), W(CO)5F, Cp2Mo2(CO)4, where Cp is cyclopentadienyl, and Mo(CO)6, are also used as the source of CO in place of Co2(CO)8. There has been significant interest in developing catalytic variants of the P-K reaction. Rautenstrauch et al. [4] reported the first catalytic P-K reaction in which alkenes are limited to reactive alkenes, such as ethylene and norbornene. Since 1994 when Jeong et al. [5] reported the first catalytic intramolecular P-K reaction, most attention has been focused on the modification of the cobalt catalytic system [3]. Recently, other transition-metal complexes, such as Ti [6], Rh [7], and Ir complexes [8], have been found to be active for intramolecular P-K reactions. 

In oxides or sulfides of low-valent phosphorus with their cage-type stmctures, like P4O6 or P4S3, the phosphorus atoms have very significant donor character and consequently the molecules can be introduced as ligands into metal complexes. Classical examples are the 1 1 complexes with nickel carbonyls, (P406)Ni(C0)3 (57) or (P406)[Ni(C0)3]2, in which one or two P-donor sites are occupied by Ni(CO)3 acceptors. 

This route probably involves carbonyl insertion into a metal-carbene bond. Closely related compounds can also be prepared from M(CO)g (M = Cr, W)-a-lithiated sulfides-[Et3 0][Bp4] or by treatment of pentacarbonyl(thio)metal complexes,... 

The hydroformylation of alkenes is commonly run using soluble metal carbonyl complexes as catalysts but there are some reports of heterogeneously catalyzed reactions of olefins with hydrogen and carbon monoxide. Almost all of these are vapor phase reactions of ethylene or propylene with hydrogen and carbon monoxide catalyzed by rhodium, " 20 ruthenium,nickel, 22,123 cobalt, 23,124 and cobalt-molybdenum 23 catalysts as well as various sulfided metal catalysts. 23,125,126... 

Pandey KK (1995) Reactivities of carbonyl sulfide (COS), carbon disulfide (CS2) and carbon dioxide (CO2) with transition metal complexes. Coord Chem Rev 140 37-114... 

Sulfonium ylides generated through base-promoted deprotonation of sulfonium salt have been extensively studied. The reaction of sulfides with a diazo carbonyl compound in the presence of a transition metal catalyst is an alternative approach to obtain sulfonium ylides. Sulfonium ylides are more stable than the corresponding oxonium ylides. Stable sulfonium ylides generated by the reaction of an Rh(ii) carbene complex with thiophene have been reported (Figure 5). ... 

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