Nickel dihydride

The nickel dihydride dimer 398 inserts into the C-S bond of thioxanthene, rapidly producing a thiametallacycle and paving the way toward a facile catalytic hydrodesulfurization process (Equation 105) <1999JA7606>. 

Cobalt(III) sepulchrate (l)8 and tetrazamacrocyclic complexes of cobalt(II) (2)9 and nickel(II) (3) (6)9-11 catalyze the electroreduction of water to dihydrogen, at potentials ranging from - 0.7 V (complex (1)) to — 1.5 V (complexes (4)-(6)) vs. SCE in aqueous electrolytes, with current efficiencies as high as 95% for complex (4).9 It is noteworthy that the binuclear nickel biscyclam complex (6) is 10 times more active (at pH 7) than the mononuclear nickel cyclam complex (5). This behavior tends to indicate that some cooperativity between the two metal centers occurs in complex (6), as depicted in the possible reaction (Scheme 3) involving a dihydride intermediate.11... 

A useful method for the preparation of diorganogermanium dihydrides employs a nickel-the catalytic hydrogenation of germylenes (Equations (88)114 115 and (89)).113... 

Magnesium hydride, 4463 Magnesium-nickel hydride, 4464 Plutonium(III) hydride, 4509 Poly (germanium dihydride), 4415 Poly (germanium monohydride), 4413 Potassium hydride, 4427 Rubidium hydride, 4450 Sodium hydride, 4444 f Stibine, 4510 Thorium dihydride, 4489 Thorium hydride, 4540 Titanium dihydride, 4490 Titanium-zirconium hydride, 4491 Trigermane, 4421 Uranium(III) hydride, 4511 Uranium(TV) hydride, 4541... 

We now turn to the formation of some of these hydride structures. The majority of them are based on a fee array of metal atoms, as shown by the open circles in Figure 2. The dihydride structure comes from filling the tetrahedral interstice (large solid circles) in the lattice with hydrogens and gives the well known CaF2 or calcite structure. Similarly, if one fills the octahedral interstice (small solid circles), one gets the NaCl or rocksalt structure found in nickel hydride and palladium hydride, which we will discuss near the end of this chapter. 

REDUCTION, REAGENTS Aluminum amalgam. Borane-Dimethyl sulfide. Borane-Tetrahydrofurane. t-Butylaminoborane. /-Butyl-9-borabicyclo[3.3.1]nonane. Cobalt boride— f-Butylamineborane. Diisobutylaluminum hydride. Diisopropylamine-Borane. Diphenylamine-Borane. Diphenyltin dihydride. NB-Enantrane. NB-Enantride. Erbium chloride. Hydrazine, lodotrimethylsilane. Lithium-Ammonia. Lithium aluminum hydride. Lithium borohydride. Lithium bronze. Lithium n-butylborohydride. Lithium 9,9-di-n-butyl-9-borabicyclo[3.3.11nonate. Lithium diisobutyl-f-butylaluminum hydride. Lithium tris[(3-ethyl-3pentylK>xy)aluminum hydride. Nickel-Graphite. Potassium tri-sec-butylborohydride. Samarium(II) iodide. Sodium-Ammonia. Sodium bis(2-mcthoxyethoxy)aluminum hydride. 

Magnesium—nickel hydride, 4458 Plutonium(III) hydride, 4504 Poly(germanium dihydride), 4409 Poly(germanium monohydride), 4407 Potassium hydride, 4421 Rubidium hydride, 4444 Sodium hydride, 4438 f Stibine, 4505 Thorium dihydride, 4483 Thorium hydride, 4535 Titanium dihydride, 4484 Titanium—zirconium hydride, 4485 Trigermane, 4415 Uranium(III) hydride, 4506 Uranium(IV) hydride, 4536 Zinc hydride, 4486 Zirconium hydride , 4487 See COMPLEX HYDRIDES, PYROPHORIC MATERIALS See entry LANTHANIDE—TRANSITION METAL ALLOY HYDRIDES... 

Multimetallic complexes, molybdenocene dihydrides, 5, 570 Multimetallic nickel-alkynes, synthesis and reactivity, 8, 145 Multinuclear chromium(II) complexes, with halides, alkyls,... 

Magnesium dihydride is a white, granular solid which decomposes at 310° to magnesium metal and hydrogen.11 It is stable indefinitely at room temperature when protected from moisture and oxygen. It is pyrophoric in air and reacts violently with water. The infrared spectrum of magnesium dihydride shows two broad envelopes. One is at 1400-800 cm-1, the other at 800-400 cm-1. The x-ray powder diffraction (nickel-filtered CuKa) pattern shows lines at 3.17 A (s) 2.50 A (m) 2.25 A (m) 1.67 A (w). 

The acidification of H2 may also be involved in hydrogenase action, where H2 is beheved to bind to an Fe(II) center. Isotope exchange between H2 and D2O is catalyzed by the enzyme see Nickel Enzymes Cofactors Nickel Models of Protein Active Sites Iron-Sulfur Proteins). Similar isotope exchange can also occur in H2 complexes. Oxidative addition to give a classical dihydride is also a common reaction. [W(H2)(CO)3(PCy3)2] is in equilibrium with about 20% of the dihydride in solution. This can lead to subsequent hydrogenolysis of M-C bonds as in the case of a cyclometallated phenylpyridine complex of Ir(III). ... 

The nature of platinum zerovalent derivatives was questioned by Chopoorian et al. (55) who considered them platinum(II) dihydrides. A new careful investigation (47, 133)j however, has confirmed that they are certainly zerovalent compounds. The nickel(0) derivatives with tertiary monophosphines can be obtained as well from NiBr2L2 and sodium tetrahydridoborate or ethanolic potassium hydroxide in the presence of an excess of the ligand 185) j while those with phosphites were prepared using potassium graphite 110) (CsK) as the reducing agent. By reduction with alkylmetals 199), zerovalent tetrasubstituted nickel (0) compounds with tertiary phosphine, arsines, and stibines have been obtained. 

METHYL HYDRATE (67-56-1) CH O CH3OH Flammable liquid. Forms explosive mixture with air [explosion limits in air (vol %) 6.0 to 36.5 flash point 52 F/11 C autoignition temp 725°F/385°C 867°F/464°C " Fire Rating 3]. Violent reaction (possible fire and/or explosion) with strong oxidizers strong mineral acids (e.g., nitric, sulfuric, perchloric) acetyl bromide alkyl aluminum salts beryllium dihydride bromine, chromic acid l-chloro-3,3-difluoro-2-methoxycyclopropene, cyanuric chloride diethylzinc, isophthaloyl chloride potassium-ferf-butoxide phosphorus trioxide platinum-black catalyst (ignition) potassium sulfur diimide Raney-nickel catalysts 2,4,6-trichlorotriazine, triethylaluminum, 1,3,3 -trifluor o-2 -... 

Ni(CO)4 Nickel tetracarbonyl [Co(CO)4]2 Dicobalt octacarbonyl CoNO(CO)3 Cobalt nitrosyl tricarbonyl H2Fe(CO)4 Iron tetracarbonyl dihydride... 

The analogous iridium formate complex was synthesized by Kaska and coworkers by reacting CO2 with a Ir(lll) dihydride complex. However, in this case, the formate complex proved to be unstable, undergoing disproportionation to form the hydrogen carbonate complex and the carbonyl dihydride, overall corresponding to the reverse water gas shift reaction CO2 -H H2 - CO-P H20[45j. Reduction of CO2 to the methanol level has since been effected using an aromatic nickel pincer complex and a cascade reaction involving a ruthenium pincer complex in one step [46]. 

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