Metal carbonyls, mononuclear preparation

Many of the methods used for the preparation of mononuclear hydrides may be applied to the polynuclear systems. Base attack on metal carbonyls, which furnished one of the first methods for the production of carbonyl hydride species, is applicable to a wide range of carbonyls. Borohydride reduction leads to a variety of products, depending upon the reaction conditions, Os3(CO)12 reacting with NaBH in di-oxane under reflux to give, after 4 hours, a mixture of the anions [H30s4(C0)12] and [H2Os4(CO)i2]2 (79). The related reaction in tetra-hydrofuran for 1 hour yields the anion [HOs3(CO)n]- as the main product with minor amounts of the two tetranuclear anions. 

Oligo- and polymethylene-bridged complexes can be prepared by reaction of metal carbonyl anions with w.w -dihaloalkanes. This method proved to be a simple entry to the iron series /j,-(CH2)j.][(t75-C5H5) Fe(CO)2]2 (x s 3) (283), but yielded quite different products in the case of Na[(T 5-C5H5)Mo(CO)3] (283) and Na[Mn(CO)s] (284). An alternative two-step synthesis of the iron compounds involves the preparation of the mononuclear w-haloalkyls LXM—(CH2)X—X, and a subsequent... 

A limitation of supported metal nanoclusters prepared from molecular metal carbonyl clusters is that, so far, clusters of only several metals (Ru, Rh, Ir, and Os) have been made in high yields (80 to 90%, with the likely impurity species being mononuclear metal complexes). However, this disadvantage is offset by the advantage of the characterizations, which show that some clusters are stable even during catalysis, at least under mild conditions. 

Molecularly or ionically dispersed metal carbonyl clusters on metal oxides have been prepared in high yields by reaction of metal carbonyl clusters with support surfaces or by syntheses on support surfaces from mononuclear precursors (Gates and Lamb, 1989 Iwasawa, 1993 Ichikawa, 1992 Gates, 1994). Synthesis of supported metal carbonyl clusters has been reviewed recently (Gates, 1995,1998), and only a few examples are included here. 

Few successful reactions are known by which an organometallic nitrosyl product has been formed from the condensation of mononuclear metal nitrosyl complexes. The unique cluster (Tj -C5H5)3Mn3(NO)4 (39), which contains the only i3-NO known (7) (40), is prepared using photochemical or thermal (41) decarbonylation of (Tj -C5H5)2Mn2(CO)2(NO)2 [Eq. (25)]. The use of the redox condensation of a nitrosyl carbonylmetallate with a neutral metal carbonyl cluster to produce a nitrosyl cluster has... 

Mononuclear allenylidene complexes have been prepared by either (i) reaction of a deprotonated propargyl alcohol with a binary metal carbonyl or (ii) dehydration of the acetylenic alcohol HC=CCR20H with an appro-... 

Metal carbonyl clusters on supports are important to the subject reviewed here because they are the best known precursors of structurally simple supported metal clusters, which are formed by decarbonylation of the precursors. The routes for preparation of molecularly or ionically dispersed metal carbonyl clusters on zeolite and metal oxide supports include syntheses from mononuclear precursors on the support surface [5,9]. Ship-in-a-bottle syntheses of this type take place when the clusters formed in zeolite cages are trapped there because they are too large to fit through the apertures. Syntheses in the nearly neutral NaY zeolite are similar to those occurring on the nearly neutral y-Al203 and in nearly neutral solutions. Examples are the syntheses of [Ir4(CO)i2] [8] and of [Ir6(CO)i6] [10] from [Ir(CO)2(acac)] in the presence of CO. Syntheses in the more basic NaX zeolite are similar to those occurring in basic solutions and on the basic surface of MgO, e g., those of [HIr4(CO)ii]-and [Ir6(CO)i5]2- [11]... 

In general, the preparation of sodium derivatives of metal carbonyls by reduction with sodium metal either in ethereal solvents or in liquid ammonia produces mononuclear anions. In certain cases it is possible to prepare... 

Flaving the d s configuration, the elements of this triad are able to conform with the 18-electron rule by forming mononuclear carbonyls of the type M(C0)5. These are volatile liquids which can be prepared by the direct action of CO on the powdered metal (Fe and Ru) or by the action of... 

Again starting from the decacarbonyl dimetalate(-I) anions, besides the mononuclear [M(CO)sX] anions, we were the first to prepare the dinuclear [M2(CO)toX] species (M = Cr, Mo, W) with the respective metal having the oxidation state 0. These anions can be formally derived from the unknown dinuclear carbonyls M2(CO)n by substituting a CO ligand by X" (X = CN, I, NCS, SH, SMe, SEt, SPh). 

The synthesis of pentacarbonyl rhenium(I) halides, Re(CO)5X, succeeded from simple and complex rhenium halides below 200 atm of CO at 200° C. The compounds are extraordinarily stable and form easily, often quantitatively, from carbon monoxide and rhenium metal in the presence of other heavy metal halides or halogen sources such as CC14. Later we prepared the corresponding carbonyl halides of manganese (67) and technetium (68) from their respective carbonyls. It was found that the corresponding binuclear tetracarbonyl halides [M(CO)4X]2 (M = Mn, Re) could be made by heating the mononuclear M(CO)5X complexes (15, 69), as well as by other methods. 

The heterobinuclear complexes [MCo(/u,-FiCC2CF3)2(CO)3Cp] have been prepared by addition of octacarbonyldicobalt to the mononuclear alkyne complexes [M(F3CC2CF3)2(Cl)Cp] (M = Mo or W)24 demonstrating that cobalt-carbonyl fragments can coordinate to an alkyne already bound to another metal-ligand fragment see Eq. (5). 

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