Hydridotris borate

Complex [VO(Cl)L(Hpz )]-2AN, where L is hydridotris (3,5-dimethylpyra-zdyl)borate, reacted with the product rfinteraction of triediylamine and ferroceno-carboxylic acid to give the N2-coordinated [(Hpz )LV0(/i--rj -C5H4C02)Fe(ri -Cp)] [97JCS(D)1201]. 

HPA = (4-pyridylthio)aceticacid 2-fur = 2-furoate a-fur = a-furoate = ([Pg.116]

Hydridotris(pyrazolyl)borate (N,N,N)-containing ruthenium(ll) complexes activate benzene in stoichiometric amounts to give the isolable complex B. A catalytic hydroarylation of ethylene led to ethylbenzene and a ca. 1 1 mixture of branched and linear alkylbenzenes was obtained when employing propylene (Equation (62)).63,63a... 

The C-C bond-forming coupling of solvent molecules via sp2- and r/ -C-H bond functionalizations can be achieved using an iridium complex based on the TpMe2 ligand (hydridotris(3,5-dimethylpyrazolyl)borate) (Equation (64)).65... 

The hydroarylation of olefins is also achieved by using a ruthenium catalyst, TpRu(CO)(NCMe)(Ph) (Tp = hydridotris(pyrazolyl)borate) (Equation (34)).39 The reaction of benzene with ethene is catalyzed by the ruthenium complex to give ethylbenzene (TN = 51, TOF = 3.5 x 10 3mol 1 s-1 at 90 °G for 4h). The ruthenium-catalyzed reaction of benzene with propene gives the hydroarylation products with a 1.6 1.0 ratio of -propyl to isopropylbenzene, with 14 catalytic turnovers after 19 h. 

The analogous coordination behavior of hydridotris(pyrazolyl)borate and tetrakis(pyrazolyl)-borate has been demonstrated by numerous reactions. Reduction of the rhenium(VII) complex [Re03 B(pz)4] with PPh3 in THF gives a reactive dimeric intermediate which reacted with monodentate and bidentate protic substrates to yield products with tridentate B(pz)4 ligands... 

Hydridotris(pyrazolyl)borates, as cobalt complex ligands, 44 274-278 Hydroboration, 16 230-234 chain lenghtening, 16 231-232 role in sythesis, 16 231, 232 Hydrocarbons clusters, 18 57-59... 

Hydridotris(3,5-dimethyl-l-pyrazolyl)borate]molybdenum-(i72-acyl) complexes, such as 1, are deprotonated by butyllithium or potassium hydride to generate enolate species, such as 488.8> jjie overa]] structure of these chiral complexes is similar to that of the iron and rhenium complexes discussed earlier the hydridotris(3,5-dimethyl-l-pyrazolyl)borate ligand is iso valent to the cyclopentadienyl ligand, occupying three metal coordination sites. However, several important differences must be taken into account when a detailed examination of the stereochemical outcome of deprotonation-alkylation processes is undertaken. 

Alkylation of enolates, such as 4, produces products that are consistent with the preferred approach of the electrophile from either the least hindered face of an T -cnolate of conformation C or the least hindered face of a Z-enolate of conformation D88. Steric factors influencing approach of the electrophile appear to be similar in both of these models since the steric bulk of the hydridotris(3,5-dimethyl-l-pyrazolyl)borate ligand and the phosphite are both considerable any stereoelectronic and dipolar factors due to interaction of the enolate ligand with the carbon monoxide ligand would likely be similar for both geometries. The is-enolate geometry C appears to benefit from reduced steric interactions between the R substituent and the metal ligands. 

The hydridotris(pyrazolyl)borate (Tp) ligand has become well known and well established as a formal analogue of the cyclopentadienyl (Cp) ligand (43). Unlike Cp, however, when appropriately substituted, Tp can become what has been described (44, 45) as a tetrahedral enforcer ligand, producing complexes that are constrained to be tetrahedral even when other factors might allow octahedral coordination. 

In this reaction, four isomers should have been produced. However, the hydridotris(3-methyl-5-iso-propylpyrazolyl)borate isomer either was not produced in the reaction, or was formed in amounts too small to be detected. This isomer would be expected to be the most sterically hindered, at boron, of the four possibilities. 

Scheme 2.5 Ligands used to synthesize structural and/or functional models for iron enzymes containing a 2-His-l-carboxylate facial triad (a) R3TACN (TACN = 1,4,7-triazacyclononane) [25] (b) TpR,R [differently substituted hydridotris(pyrazol-l-yl)borates] [27] (c) differently substituted bis(pyrazol-l-yl)acetates [29] (d) differently substituted 3,3-bis(1 -alkylimidazol-2-yl)propionates [30],...

Tp" = hydridotris(3-isopropyl-5-methylpyrazolyl)borate Tp"-2H = generated by abstraction of 2H from Tp". First-order rate constant in s 1. 

Holmes, S. and CJ. Carrano. 1991. Models for the binding site in bromoperoxidase Mononuclear vanadium(V) phenolate complexes of the hydridotris(3,5-dimethylpyra-zolyl)borate ligand. Inorg. Chem. 30 1231-1235. 

An interesting approach to the substituted oxepine 102 has been described involving thermolysis of the bicyclic system 101, obtained from the rhenium complex 100 (Melm = N-methylimidazole Tp = hydridotris(pyrazolyl)borate) [02JA7395],... 

The establishment of electron-transfer equilibria is allowed by the unique stabilizations inherent in the organometallic anion TpMo(CO)3 [where Tp = hydridotris(3,5-dimethylpyrazolyl)borate] (85), in which the 17-electron radical (m20 is persistent (56). Since other members of the group VIB metals, namely, TpW(CO)3 and TpCr(CO)3-, are also available (87), this triad of anions enables the structural effects to be systematically examined,... 

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