Nitrosyl clusters structures

Cluster Compounds.—The green nitrosyl cluster Os3(CO)jo(NO)2 has been reported in 13% yield from the reaction of NO with Os3(CO) 2 benzene. Its i.r. spectrum suggests bridging nitrosyl groups, which was confirmed from an X-ray analysis of the Ru analogue. I.r. studies show that the structure (23)... 

The preparation and X-ray crystal structure of [Ru5C(CO)i3(Ti -C4Ph4)], the first cluster to carry a cyclobutadiene ring, has been reported . The synthesis and X-ray crystal structure of the nitrosyl cluster [Ru6C(CO)i4(NO)( j,-ti3-C3H5)], which contains a fluxional allyl moiety has been reported i . 

Fig. 5.3 Structures of some well-known iron-sulfur cluster nitrosyls.

Several iron sulfide nitrosyl compounds are known. These have structures that in some cases are formally related to the FeS clusters by replacement of thiolate by NO. The compounds include the anions [Fe2S2(NO)4]2 and [Fe4S3(NO)7] (Roussin s red and black salts, respectively) and the neutral compounds [Fe C J and [Fe4S4(NO)4]. Roussin s black salt has found use as a NO releasing vasodilator. 

Table II summarizes the data for the structurally characterized clusters containing the nitrosyl ligand. Some general trends that are distinguishable...

Fe4N(CO)i2] and [Fe5N(CO)i4]" (90). After 1 hour at 130 C the tetranuclear cluster is isolated in 3.3% yield, while the pentanuclear species, which forms after longer reaction times (2 hours) at a slightly higher temperature (145 C), is produced in 66% yield. This anion could be protonated and the structure of HFesN(CO)i4 is shown in 22. It was noted that below 130°C a nitrosyl complex was formed. 

The reaction of the tetranuclear Ru and Os anionic clusters, [H3M4(CO)i2] , with NO has been reported to give both nitrosyl and nitrido clusters (22,38). With M = Ru only nitrido products are isolated in low yield [Eq. (47)]. The dodecacarbonyl cluster is similar in structure to... 

The cubane-like cluster [ Fe(/X3-S)(NO) 4] (68) is not formally an organometallic compound, but the structural changes observed when it is reduced, and the MO description of its bonding, are relevant to the cyclopentadienyl complexes described above. The nitrosyl complex contains 60 valence electrons, 8 less than [ Fe()U3-S)Cp 4], and is reduced in two consecutive one-electron steps to an isolable monoanion [68] , and to a dianion [68] . 

Nitrosyl complexes are of considerable structural and chemical interest. Direct syntheses from the corresponding carbonyls are reported here for two nitrosyl-carbonyl clusters containing double nitrosyl bridges. ( Caution. Considerable amounts of toxic nitric oxide are used in these reactions, which should therefore be carried out in an efficient hood.)... 

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