Bis l-pyrazolyl methane

A solution of 15.0 g (0.221 mole) of pyrazole and 2.0 g (5.9 mmole) of tet-rabutylammonium hydrogen sulfate in 250 mL of methylene chloride is 

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Other cationic Ir(I) complexes containing the bidentate ligands, such as bis(l-pyrazolyl)methane (BPM) and bis(3,5-dimethyl-l-pyrazolyl)methane (dmBPM), that is [Ir(BPM)(CO)2] [BPli4p and [Ir(dmBPM)(CO)2] BPh4]T were also reported to be effective catalysts for the alcoholysis of binary and tertiary silanes [77]. 

Benzylic N-protection (entry 1) is often unsatisfactory since competitive reaction at the exocyclic methylene can occur [84JCS(PI)481 85S302]. As with bis(l-pyrazolyl)methane (Section I1,C,1)(83T4133), the nature of the isolated product is determined by the type of electrophile used, with benzyl halides and, to a certain extent, iodomethane reacting at the A-benzyl carbon atom, whereas most other electrophiles give rise to the normal C-2 alkylated products (90JHC673). This result was interpreted in terms of steric rather than thermodynamic factors, since the two species that reacted at the benzylic carbon required a bulkier pentacoordinate transition state, whereas all of the others were able to react via a lower coordinate species (90JHC673). 

Bis(l-pyrazolyl)methane (bpm) can be prepared by the method of Elguero and co-workers, or by the procedure reported more recently by Jameson and Castellano. Solid bpm is added (2.96 g, 20 mmol) to a stirred solution of [Ni (0H2)6](N03)2 (2.91 g, 10 mmol) dissolved in 100 mL of water. Total dissolution of the bpm occurs after 15 min, resulting in a deep blue solution. Slow evaporation of the solution over several days gives blue crystals of the product. The crystals are filtered, washed with a small amount of water and diethyl ether, and dried in air. Yield 4.3 g, 84%. 

C7H704Rh, Rhodium(I), dicarbonyl(2,4-pentanedionato)-, 34 128 C7HgN4, Bis(l-pyrazolyl)methane, bpm, complex with nickel(ll), 34 139 CgH5FeKN20, Ferrate(ll), carbonyldicyano-(cyclopentadienyl)-, potassium, 34 172 CgH23Ns, Tetraethylenepentamine, tetren, complex with nickel(ll), 34 147, 148 CgH24B2N4, Diborane(4), tetrakis(dimethyl-amino)-, 34 1... 

Ci4H2oNioNiOg, Nickel(ll), diaquabis(bis(l-pyrazolyl)methane)-, nitrate, 34 139 C14H20NO6V, Vanadate(l-), hexacarbonyl-, tetraethylammonium, 34 98 C14H22RU, Ruthenium, bis(7) -2,4-dimethylpen-tadienyl)-, 34 61... 

NioNiOgCi4H2o, Nickel(II), diaquabis(bis-(l-pyrazolyl)methane)-, nitrate,... 

The recent report of a chiral bis(l-pyrazolyl)methane provides the first example of L not based on pyrazole or 3,5-dimethylpyrazole.13-14 The substituted bis(pyrazolyl)methane was prepared by Method A, which gave... 

The non-classical silane complex (64) gave characteristic 111 and 13C NMR spectra.333 The 3H and 13C NMR spectra of (65) show that it has a very symmetrical structure.334 The 3H NMR spectra of [Rh(COD)(L)]+, where L = tris[2-(l- pyrazolyl)methyl]amine or tris[(3,5-dimethyl-l-pyrazolyl)methyl]amine, show that each exists as two isomers in solution (involving k2- and K3-coordi-nation).335 The ll NOESY and l9F lI HOESY spectra for [M(N-N) (CO)2]+X , where M = Rh, Ir, N-N = bis(l-methylimidazol-2-yl)methane or bis(l-pyrazolyl)methane, gave evidence for strong interionic contacts.336 11 1, 13C... 

Scheme 16 Rh(I) mono- and bimetallic catalysts containing the bis(l-pyrazolyl)methane ligand used for the intramolecular dihydroalkoxylation reaction...

Fig. 3 Conformational flexibility of bimetallic complexes containing the bis(l-pyrazolyl) methane ligand donor...

Ho JHH, WaglerJ, WiUis AC, Messerle BA. Synthesis and stmctures of homo-and het-erobimetaUic rhodium(l) and/or iridium(l) complexes of binucleating bis(l-pyrazolyl) methane ligands. Dalton Trans. 2011 40 11031-11042. 

The synthesis of spiroacetals was improved by using new simple and readily accessible Rh(COD)2 complexes that allowed excellent conversions and an overall reduction of reaction times [33]. Moreover, very recently a dual metal catalytic system (Rh(l) and lr(I)) was successfully utilized for these reactions on alkynediols, and in some cases it works more efficiently than the single metal catalyst [34]. The combination of the two metal complexes ([Rh(bpm)(CO)2]BAr4 and [Ir (bpm)(CO)2]BAr4 (bpm = bis(l-pyrazolyl)methane, BAt4 = tetrakis[3,5-bis (trifluoromethyl)phenyl]borate) acted cooperatively to promote an efficient dual activation pathway for both the 5-exo and 6-endo cyclization in which the Rh(I) preferentially promotes the 6-membered ring formation, while the Ir(I) in preference promotes the 5-membered cyclization of alkynediols. 

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