Nickel complexes borates

Bis(phosphoranimine) ligands, chromium complexes, 5, 359 Bis(pinacolato)diboranes activated alkene additions, 10, 731—732 for alkyl group functionalization, 10, 110 alkyne additions, 10, 728 allene additions, 10, 730 carbenoid additions, 10, 733 diazoalkane additions, 10, 733 imine additions, 10, 733 methylenecyclopropane additions, 10, 733 Bisporphyrins, in organometallic synthesis, 1, 71 Bis(pyrazol-l-yl)borane acetyl complexes, with iron, 6, 88 Bis(pyrazolyl)borates, in platinum(II) complexes, 8, 503 Bispyrazolyl-methane rhodium complex, preparation, 7, 185 Bis(pyrazolyl)methanes, in platinum(II) complexes, 8, 503 Bis(3-pyrazolyl)nickel complexes, preparation, 8, 80-81 Bis(2-pyridyl)amines... 

Hydrothermal methods, for molecuarlar precursor transformation to materials, 12, 47 Hydrotris(3,5-diisopropylpyrazolyl)borate-containing acetylide, in iron complex, 6, 108 Hydrotris(3,5-dimethylpyrazolyl)borate groups, in rhodium Cp complexes, 7, 151 Hydrotris(pyrazolyl)borates in cobalt(II) complexes, 7, 16 for cobalt(II) complexes, 7, 16 in rhodium Cp complexes, 7, 151 Hydrovinylation, with transition metal catalysts, 10, 318 Hydroxides, info nickel complexes, 8, 59-60 Hydroxo complexes, with bis-Cp Ti(IV), 4, 586 Hydroxyalkenyl complexes, mononuclear Ru and Os compounds, 6, 404-405 a-Hydroxyalkylstannanes, preparation, 3, 822 y-Hydroxyalkynecarboxylate, isomerization, 10, 98 Hydroxyalkynes, in hexaruthenium carbido clusters, 6, 1015 a-Hydroxyallenes... 

Cyclooctane-l,5-diyl-bis(pyrazol-l-yl)borate (L) with cobalt(II), nickel(II), and zinc(II) nitrates gives [(j -L)M] (M = Co, Ni, Zn) strongly stabilized by the C—H M agostic interactions, which justifies their inclusion in the class of organometallic complexes [89AGE205, 91ICA(183)203, 92IC974]. 

The family of poly(pyrazol-l-yl)borates has been widely used as supporting ligands in nickel coordination chemistry.556,557 Complex (191) is an example, where unusual cysteine coordination is achieved at a tris(pyrazolylborate)nickel(II) template.601 (191) undergoes rapid reaction with molecular oxygen to presumably form a sulfinate. 

Properties of nickel poly(pyrazol-l-yl)borate complexes such as solubility, coordination geometry, etc., can be controlled by appropriate substituent groups on the pyrazol rings, in particular in the 3- and 5-positions. Typical complexes are those of octahedral C symmetry (192)°02-604 and tetrahedral species (193). In the former case, two different tris(pyrazolyl)borate ligands may be involved to give heteroleptic compounds.602,603 Substituents in the 5-position mainly provide protection of the BH group. Only few representative examples are discussed here. 

This complex is not the actual catalyst for the hydrovinylation, but needs to be activated in the presence of a suitable co-catalyst. The role of this additive is to abstract the chloride ion from the nickel centre to generate a cationic allyl complex that further converts to the catalytically active nickel hydride species. In conventional solvents this is typically achieved using strong Lewis acids such as Et2AlCl. Alternatively, sodium or lithium salts of non-coordinating anions such as tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate (BARF) can be used to activate hydrovinylation... 

Reduction of NilvL2+ in aqueous media by two-electron reductants such as 1,2- or 1,4-dihydroxybenzene proceeds by consecutive two-electron transfer with formation of nickel(II) intermediates.3124,3125 Nickel(III) complexes with (415) and (416) of formula Nim(HL)(C104)2 and Nim(HT)(C104)2 have been obtained by oxidation with (NIL Og in borate buffer and alkaline solution respectively of nickel(II) complexes or by exposure of the nickel(IV) complexes to moist air.3031 The g values of the nickel(III) species are gii = 2.03-2.05, g = 2.15-2.16.3039,3104... 

Finally of note is the l,5-cyclooctanediylbis(pyrazolyl)borate complex BBN(pz)2 2Ni (7, BBN = borabicyclononane), which, as previously observed of its cobalt analogue,8 9 exhibits significant agostic bonding between nickel and the bridgehead protons located above and below the N4 plane. While this situation was confirmed crystallographically for the cobalt system, interactions in 7 were implied solely on the basis... 

Like many late transition metals, nickel has featured, albeit briefly, in the pursuit of poly(pyrazolyl)borate-metal-carbollide complexes. Thus, [c/oso-3-(r 2-Ph2Bp)-3,l,2-NiC2B9H11] (90 ) has been obtained as the tet-ramethylammonium salt,39 via the reaction of [Me4N][Ph2Bp] with the neutral bisphosphine nickel dicarbollide [doso-3,3-(PhEt2P)2-3,l,2-... 

In contrast to nickel, simple homoleptic Tpx or Bpx, and heteroleptic pyrazolylborate-halide complexes of palladium and platinum are largely unexplored. Indeed, while for 3d metals these are "standard" targets for each successive generation of poly(pyrazolyl)borate ligand, for the... 

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