Osmium , hydrido anion

The osmium hydrido-catbonyl H2Os3(CO)]0 has featured in an interesting stucty by Aime et al where its reactions wito sitn(de ligands (CO, NH3 and H2S) were examined. Osmiiim carbotiyl-hydride anions (eg. [H30s4(C0) 2r) 1> l>cen (uepared on silica firom [Os(CO)3Cl2]2 in toe presence of K2CO3 and toe reactions of... 

Hydroxide induced disproportionation has been applied to osmium clusters whose stability again prevents total decomposition. In most cases one osmium atom is removed leaving behind an anionic cluster (176, 177). Thus, Osg(CO)22 converts into Os CO), Os7(CO)2l goes to Os6(CO) g, and Os6(CO),8 changes into Os5(CO)jj. All these species can be protonated to the corresponding hydrido clusters. 

The role of protonic acids in the stepwise oxidative addition of five-coordinate complexes is well illustrated by reactions of acids with the osmium(O) complex (XXXV). Hexafluorophosphonic and tetrafluoroboric acids form stable adducts (XXXVla) and (XXXVIb) which have been characterized as 1 1 electrolytes (39, 103). Similar cationic adducts (XXXVIc) have been formed by reaction of Os(CO)3(PPh3)2 with dry HCl and HBr gas [103). The osmium(II) hydrido cation (XXXVI) possesses trans CO groups (marked with an asterisk) which are mutually labilized through the trans effect. In the presence of a nucleophilic conjugate anion such as bromide one of these CO groups is replaced to yield a neutral adduct... 

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