or Me resonances.(2) Irradiation of HB results in large enhancement of the HA resonance and lesser enhancement of the Cp and phenyl resonances. (3) Irradiation of the Me resonance resulted in enhancement of the HA, Cp, and part of the phenyl multiplet. (4) Irradiation of the Cp resonance resulted in enhancements of the HB, Me, and o-phenyl resonances but in a negative NOE for the HA resonance.(5) Irradiation of the o-phenyl multiplet resulted in enhancements of the HA, HB, and Cp resonances, but not in the Me resonance.In a spin system such as that under consideration here, all nuclei can in principle experience dipolar relaxation by (and hence gain NOE from irradiation of) all other nuclei, the relative effects being inversely proportional to the sixth power of the distance between pairs of nuclei.10"13 The fact that the two «-hydrogen atoms gain almost as much total enhancement from irradiation of the Cp, Me, and phenyl resonances as they do from irradiation of their geminal partner demonstrates this fact. It is also to be expected that the Cp and PPh3 ligands may well be undergoing rotational motions which are rapid relative to the various dipolar relaxation rates, and it becomes clear that a comprehensive description of the NOED experiments in terms of molecular geometry is a far from trivial task.However, if one assumes that the rapidly rotating Cp (16) The alternate "eclipsed" structure, involving eclipsing of the other methylene hydrogen atom with L, can be ruled out on the basis of both anticipated steric effects and the NOED data.

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The reaction C O~( C O )~ + 2BH3.THF -2(CO),CoBH2.THF (I) + H2 has been demonstrated to occur cleanly at -15 "C in THF. I has been characterized by low-temperature I'B NMR and infrared spectroscopies as well as classical chemical analysis. The formation of I bears a remarkable similarity to that of (CO),CoSiR,. Displacement of the bound THF of I occurs with Lewis bases, and the Lewis acidity of I relative to that of BH3.THF for SMe, has been estimated. Displacement of [Co(CO),]-from I occurs easily; e.g., reaction with PhMgBr yields PhBH,. I readily accepts hydride from [HFe2(CO)B]-, losing [Co(CO)J but reduces the CO ligands of hydride-free metal carbonylate anions. I is a very active reducing agent and above 10 "C cleaves THF and condenses with hydrocarbyl and metal fragments to yield a mixture of clusters including an unusual tailed cluster (CO)&o3C(CH2),OH ( n = 4,5) (11). A deuterium labeling experiment showed that four of the n carbons in the hydrocarbyl chain of I1 arise from THF. The results of an X-ray diffraction study suggest association of I1 in the solid state. [Crystals of I1 (the ratio of I1 with n = 5 / n = 4 is 4) form in the space group R3 with unit cell parameters a = 34.409 (15) A, 6 = 34.398 (21) A, c = 8.575 (5) A; a = 0 = 90°, y = 120°, V = 8789.8 A', and Z = 18. Solution was by direct methods, and all atoms were refined to R, = 0.077 and R2 = 0.096 for 1443 independent reflections (F, > 3u(FO)). Because of the disorder caused by the cwrystallization of species with different chain lengths, the last two atoms at the OH end of the chain could not be fully defined.] Association of I1 in solution is shown by a IH NMR study, thereby demonstrating that I1 behaves as an ambiphilic cluster.

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Simulants for the HartfordWaste Vitrification Plant _) feed containingthe major non-radioactive componentsAI, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO32-, NO3-, and NO2-were usedasmediatoevaluatethestabilityof formicacidtowards hydrogen evolutionby thereactionHCO2H_ H2 + CO2 catalyzedbythi_noblemetalsRu,Rh, and/or Pd found in significant quantifiesin uranium fLssi0nproducts. Small scale experiments using40-50 mLof feedsimulant in closedglassreactors (250-550mLtotal volume)at 80-100°(3wereused tostudy theeffectof nitriteandnitrateiononthecatalytic activitiesof thenoblemetalsforformicaciddecomposition.Reactions weremonitored usinggaschromatography to analyzethe CO2,H2, NO, andN20 in thegasphaseasa functionof time. Rhodium, whichwasintroduced as solubleRhCI3.3H20,wasfoundto bethemostactivecatalyst forhydrogen generation from formic acidabove~80°Cin the presence of nitrite ion in accord withearlierobservations.The inherent homogeneous natureof the nitrite-promoted Rh-catalyzed formicaciddecomposition issuggested bythe approximate pseudo first-orderdependence of the hydrogen production rate on Rh concentration. Titration of the typicalfeed simulants containing carbonateandnitritewith formic acid in the presence of rhodiumat the reaction temperature(,-x)0°C) indicatesthatthe nitrite-promoted Rh-catalyzeddecomposition of formic acid occurs only afterformicacid has reacted with all of the c_bonate and nitrite present to form CO2 and NO/N20, respectively. The catalytic activities of Ru and Pcl towards hydrogen generation from formic acid are quite different than those of Rh in that they are inhibited rather than promoted by the presence of nitrite ion. Palladium is also an active catalyst for the reductions of nitrate and NO to N20 in feed simulant media.