Osmium analogs

The osmium analog of 27 reacts with methylamine to give mixtures of cis-, bis-, and mer-triscarbene complexes (59). 

The osmium analog was obtained in moderate yield by pyrolysis of Os CO) or Os3(CO),2 (20). Both the ruthenium (29) and osmium clusters (31) are isostructural with the original iron analog, 1 (2), the metal atoms describing a square pyramid, each vertex bearing three terminal carbonyls. The carbon atom lies fractionally below the center of the basal plane of the cluster, protruding 0.11 A below the Ru4 plane in 10 and 0.12 A below the Os4 plane in 11 [cf. a value of 0.08 A for Fe5C(CO)15 (2)] (see Fig. 11). 

No osmium analogs to the octahedral RugC clusters have been reported. 

Whereas the monoolefin derivatives of 77-cyclopentadienylruthenium tricarbonyl cation are known (99), the unsubstituted carbonyl has only recently been prepared (24). The osmium analog has not been reported. 

Table 18 Interatomic distances (A) in BaMg2RuDg and osmium analog...

The ruthenium and osmium analogs have less tendency to fragment, presumably because of the stronger metal metal bonds. 

Homoleptic hepta-, octa-, and nonamthenium carbido clusters remain unknown. Two structurally similar decaruthenium clusters [RuioC(CO)24] and [HRuioC(CO)24] (33) were synthesized by treatment of (1) with mesitylene. They are isostructural with the osmium analogs. The dicarbido cluster, [Ruio(C)2(CO)24] (34), was formed by thermolysis of [Ru6(CO)i8] in refluxing diglyme. Synthesis of (34) was also accomplished by treatment of (1) with an excess of CaC2. 

Ruthenium and osmium analogs of the /r-oxo bound cluster are known. For example, (/r-H)Ru3(CO)io(/r-OSiEt3) and (/u.-H)Os3(CO)io(/r-OSiEt3) have been prepared, and the (/n-oxo)-bound triruthenium and the triosmium clusters can be selectively prepared on the surface of silica and alumina/ ... 

Tricarbonyls with D h symmetry (see Table 9) occur commonly in complexes of the type Fe(CO)3(L)2 (and their ruthenium and osmium analogs). There are two v(CO) modes, an a[ symmetric stretch, which is inactive in the IR, and an e stretch. These two absorptions are sufficient to determine the two force constants. 

The reactions of nitric oxide with metal cluster compounds themselves are complicated by the possibility of metal—metal bond cleavage. In the next example, the tri-iron compound shows very different reactivity from its ruthenium and osmium analogs (26-28) ... 

Coordination at the carbonyl oxygen causes a lengthening of the bridging carbonyl C—O bond by 0.1 A when compared to the anion, and the C—O—Me angle of 118° shows approximate sp2 hybridization of the oxygen. Alkylation has also been successfully performed on both the ruthenium and osmium analogs of the triiron cluster (89-91). A number of other alkylated species have been isolated and their spectroscopic data are presented in Table VI (J, 88-92). 

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