The chemistry of polynuclear compounds. Part 30. Some reactions of dodecacarbonyltetrahydridotetraosmium: the molecular and crystal structure of trihydrido-µ2-iodo-cyclo-tetrakis(tricarbonylosmium)-(4Os–Os)
Abstract
Dodecacarbonyltriosmium reacts with H2 under pressure to produce [Os4(CO)12H4] almost quantitatively. Methanolic K[OH] converts this into [Os4(CO)12H3]– which gives the title compound [Os4(CO)12H3l] with l2. Crystals of [Os4(CO)12H3l] are monoclinic, with a= 17.307(8), b= 8.040(3), c= 17.760(9)Å, β= 119.80(2)°, space group C2/c, and Z= 4. The final residuals for 2 724 unique observed reflections are R 0.036 and R′ 0.039. The four Os atoms are in a ‘butterfly’ configuration: one edge has been extended and a bridging iodine inserted [Os-l 2.749(4)Å]. A crystallographic two-fold axis passes through the iodine atom and bisects the opposite Os–Os bond. The Os–Os distances are 2.876(1)(two), 2.927(3), and 3.052(1)Å(two): the crystallographic symmetry, 1H n.m.r. spectrum, and geometrical arrangements of the carbonyls indicate that the three longest Os–Os bonds are hydride-bridged. Methanolic Na(OMe) converts [Os4(CO)12H4] into [Os4(CO)11(CO2Me)H4]–, isolated as the [N(PPh3)2]+ salt.
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