Nickel , hydrido anion

The anion [Fe3Co(CO)12] has recently been reported to be prepared by Chini from the redox reaction of Fe3(CO)12 with Co(CO)infrared spectra indicate a Co4(CO)i2 structure with nickel in the basal plane (234). 

A more favorable synthesis of salts of the iron, cobalt and nickel carbonyl anions, which were initially prepared by disproportionation reactions of Fe(CO)5, Co2(CO)8, and Ni(CO)4 with pyridine and other amines, was found by treatment of the neutral carbonyls with alkali in aqueous or alcoholic solutions. Careful studies by Hieber revealed that Fe(CO)5 as well as Fe3(CO)12 reacted with exactly four equivalents of hydroxide ions to give the corresponding dianionic iron carbonylates (Scheme 4.4). These dianions are relatively strong bases and readily accept a proton from a water molecule to give the monoanionic hydrido carbonylates [I IFe(CO)4] and [HFe3(CO)n], respectively [36]. The related carbonylates of cobalt and manganese, [Co(CO)4] and [Mn(CO)5], were obtained by a similar way as [Fe(CO)4]2 [25]. With regard to the mechanism of Hieber s Basenreaktion , the most plausible explanation is based on an initial nucleophilic attack by the hydroxide ion at the carbon atom of a CO... 

The reaction of [Ni(ethene)3] with a hydride donor such as trialkyl(hydrido)-aluminate results in the formation of the dinuclear anionic complex [ Ni(eth-ene)2[2l 11 [22]. The nickel(O) centers in this complex are in a trigonal planar environment of two ethene molecules and a bridging hydride ion, with the ethene carbons in the plane of coordination. The two planes of coordination within the dinuclear complex are almost perpendicular to each other, and the Ni-H-Ni unit is significantly bent, with an angle of 125° and a Ni-Ni distance of 2.6 A [22],... 

When nickel(II) salts containing a coordinating anion (halide and pseudohalide) are reacted with NaBH4 in the presence of np3, trigonal bipyramidal nickel(I) complexes of the type [NiXnp3], in which the coordinating anion occupies die axial position, 39,340 are obtained. When nickel(II) salts with poorly coordinating anions are used, non-stoichiometric hydrido complexes of nickel(II) are obtained (equations 108 and 109). 

The hydrido complexes are diamagnetic, and are square planar or five-coordinate. Their stability, in general, increases with the number of coordinated phosphines. In the complex [Ni(BH4)(H)(PCy3)2] (153) the nickel atom is coordinated in the equatorial positions by two hydrogens of the borohydride and by one hydride anion. 

---