In the presence of catalysts, curable organosilicone compositions undergo hydrosilation, a reaction involving the addition of a siliocon-hydrogen bond across a pair of aliphatic carbon atoms linked by multiple bonds. Catalysts used for reactions of this type are metals, most notably platinum, rhodium, iridium, and palladium, and compounds thereof. Hydrosilation has found widespread use in the production of silicone materials and organosilanes. Compared with platinum, relatively little work has been done on rhodium- and iridium-containing hydrosilation catalysts. Various chloro-rhodium compounds, wherein the valence of rhodium (Rh) is 1, particularly [RhCl(CO).sub.2 ].sub.2 and RhCl(CO)[P(C.sub.6 H.sub.5).sub.3 ].sub.3 (A. J. Chalk, J. Organometal. Chem; 21, 207-213 (1970)), [RhCl(C.sub.2 H.sub.4).sub.2 ].sub.2 (U.S. Pat. No. 3,296,291), and RhCl[P(C.sub.6 H.sub.5).sub.3 ].sub.3 (U.S. Pat. No. 3,546,266), are disclosed in the literature to be hydrosilation catalysts. The mono- and bi-metallic pyrazine compounds, (pyrazine)Rh(CO).sub.2 Cl and (pyrazine)Rh.sub.2 (CO).sub.4 Cl.sub.2, have been disclosed (A. L. Balch et al., J. Organometal. Chem., 169, 97 (1979), but no use is specified. R. N. Haszeldine, R. V. Parish and D. J. Perry, J. Chem. Soc. (A), 683 (1969), found that [(C.sub.6 H.sub.5).sub.3 P].sub.2 Rh(CO)Cl was active as a hydrosilation catalyst but that the iridium analogue was inactive.