Solid-gas reactions involving unsaturated transition metal clusters

3 Solid-gas reactions involving unsaturated transition metal clusters 

All three structural forms contain one terminal and one bridging hydride and ten terminal carbonyl ligands. The entering ligand occupies an equatorial site (la) when L is a phosphine or a phosphite whereas it coordinates axially (Ib or Ic) when L contains a nitrogen as the donor atom (nitriles, amines). The occurrenee of transformation (1) is accompanied by a net color change from the intense violet of (//-H)20s3(CO)io to the pale yellow of the saturated adducts. 

The first set of solid-gas reactions involving ( -H)20s3(CO)io we investigated were those with CO, NH3 and 

The reaction with CO proceeds smoothly at 80 °C under a pressure of 1 atm to afford a yellow material identified as H( -H)Os3(CO)ii by IR and solid state H NMR spectroscopy with magic angle spinning (MAS). The tatter technique was applicable because the H nuclei in H(/r-H)Os3(CO)n (Fig. 1) are sufficiently intramolecularly dilute to result in reduced dipole-dipole interactions. In fact, by rotating the sample at high speeds ( 8 kHz) two relatively sharp signals have been observed at -20.1 and -10.5 ppm. These values are very similar to the H chemical shifts found in solution for H(/i-H)Os3(CO)u. 

The reaction of solid (//-H)20s3(CO)io with NH3 affords the adduct H(//-H)Os3(CO)io(NH3), an interesting model for the chemisorption of ammonia on a metal surface. The reaction occurs in 2 h at room temperature in the presence of 1 atm NH3 gas. This compound has also been characterized by solid-state IR (carbonyl pattern similar to that of H(/z-H)Os3(CO)h and presence of stretching 

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