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Note Added in Proof. While the series of substituted diphenylacetylenes reported in this paper exhibit centrosymmetric crystal phases (from acetonitrile solution) and are essentially SHG inactive, we31 and others35 have recently shown that highly SHG active (efficiencies up to 200 times urea) derivatives, e.g., NH2, C02CH3, CH3S, and N02, of diphenylacetylenes can be prepared.

Ru4H4(CO)i2 and Os3H2(CO)iq are obtained in high yield and purity by reaction of H2 at atmospheric pressure at 120°in hydrocarbon solutions of Ru3(CO)i2 and Os3(CO)u, respectively. Further treatment of Os3Fl2(CO)io with H2 leads to Os4H4(CO)i2. Ru4D4(CO)i2 is obtained from Ru3(CO)i2 and D2 in hydrocarbon solvent; however, extensive hydrogen exchange with solvent is observed in the osmium system. Ru4H2D2(CO)i2 is obtained in the reaction of D2 with Ru4H2(CO)i3 and the new mixed metal complex FeRu3H4(CO)i2 is obtained from FeRu3H2(CO)i3 and H2. Substances are characterized by ir, NMR, Raman, and mass spectrometry.We report here our studies of the treatment of metal carbonyls with H2 (or D2) at atmospheric pressure and elevated temperature giving a convenient synthesis2 of a number of hydrido (or deuterio) carbonyl metal clusters. We were led to this reaction through earlier observations in the chemistry of Re4H4(CO)i2.3 This complex is readily transformed into higher carbonyls in contact with CO at atmospheric pressure as indicated in reaction sequence (1); at Re4H4(CO)P + SCO -Re3H3(CO)12 + ReH(CO)r, |h2 + |Re2(CO)10 slightly elevated temperatures, H2 evolution was observed. This suggested to us that the reverse of this transformation might be possible and indeed when H2 at atmospheric pressure is bubbled through a hydrocarbon solution of Re2(CO)io at 150°, the lower carbonyl cluster compounds are obtained, first Re3H3(CO)i2 subsequently replaced by Re4H4(CO)i2.2 We subjected a number of other carbonyls to this treatment and found several hydrido-metal carbonyl cluster complexes of ruthenium, osmium, and a mixed ironruthenium cluster can be obtained through this route. RutheniumTreatment of Ru3(CO)j2 with H2 gives Ru4H4(CO)i2 conveniently in high yield and purity. Excellent analytical data were obtained for our product which displays five maxima in the carbonyl stretching region of the ir (see Table I) consistent with that independently obtained by Piacenti and coworkers4 in an autoclave reaction of Ru3(CO)i2 with H2 at 110°and 150 atm, but in contrast to earlier reports5 of two isomers a and ß of the same formulation each with different and more complex carbonyl ir absorptions. Both we and the Italian group have shown that the spectrum reported for the "a isomer" is derived from a mixture of Ru4H4(CO)i2 and Ru3(CO)]2 which can easily be separated by column chromatography. Indeed single crystals suitable for structure determination of Ru3(CO)i26 were obtained from a solution containing "a-Ru4H4(CO)i2". Regarding the "ß isomer", we have not been able to observe any evidence for its existence either in the direct reaction of Ru3(CO),2 with H2 or in attempts to repeat the earlier

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