Poly borates synthesis

Ion coupling of anionic and cationic living polymers is an interesting procedure for the synthesis of a well-defined block copolymer. Attempted coupling of the polystyrene anion with the poly-THF cation initiated by triethyloxonium tetrafluoro-borate yielded a block copolymer mixed with homopolymers394. The block ef-... 

During the time of the Olin reports, the first examples of oligomeric boron-bridged (l-pyrazolyl)borate systems appeared from the laboratory of Trofimenko at DuPont Chemicals 24 He reported the synthesis of poly(l-pyrazolyl)borates (6) (Fig. 5) from the reactions of alkali metal borohydrides with the pyrazole ligand. The (l-pyrazolyl)borate ligand was obtained from two pyrazole units when bridged by a BR2 unit on one side and by a metal or onium ion on the other. Even though reports... 

It is an axiom of modern organometallic chemistry that the pursuit of late transition metal complexes is ultimately driven by the need to formulate ever more efficient catalysts and reagents for chemical synthesis. In this respect, the field of poly(pyrazolyl)borate chemistry is no different from any other, albeit that in the case of the group 10 triad the breadth of study is perhaps more limited than for other metals and/or ligands. This section provides an overview of prominent results in respect of both catalysis and the C—H activation processes that underpin them. 

Probing C—H addition/elimination in Pt(ll)/Pt(IV) systems The importance of oxidative addition of aromatic and aliphatic C—H bonds to Pt(II) centers and its microscopic reverse, reductive elimination of C—H from Pt(IV) species, is ubiquitous in the context of both catalysis and synthesis. It is thus inevitable that the chemical, mechanistic, and kinetic facets of such reactions have become a prominent focus of group 10 poly(pyrazolyl)borate research, although this remains a relatively nascent area. 

Poly(pyrazolyl)borate complexes of Sn(II) and Pb(II) 92SL469. Synthesis, structure, and properties of vicinal hydroxy-, mercapto-, and hydroselenoaldimines of the pyrazole series 92MI22. 

The main method of preparation of the alkaline-earth poly(pyrazolyl) borates is by halide metathesis. Belderrain et al. have reported the synthesis of the Ca, Sr, and Ba poly(pyrazolyl)borates MTp by reaction of the metal iodides, MI2, with KTp (Tp = HB(3,5-Me2pz)3) in THF, similar to the method described for the metallocene compounds.111... 

Beeby, A., Burton-Rye, B.P., Faulkner, S., et al. (2002) Synthesis and near-lR luminescence properties of neodymium(III) and ytterbium(III) complexes with poly(pyrazolyl)borate ligands. Journal of the Chemical Society, Dalton Transactions, 1923. 

The tris(pyrazolyl)boratothallium(I) compounds are the most widely studied among thallium poly(pyrazolyl)borates. An excellent recent review article has appeared that covers the synthesis, structures, properties, and applications of tris(pyrazolyl)boratothallium(I). ... 

Since the first report of Trofimenko,1 many papers have appeared describing the synthesis and the application of poly(pyrazolyl)borates, or Trofimenko ligands, in an extraordinarily wide range of chemistry, from modeling the active site of metallo-enzymes, through analytical chemistry and organic synthesis, to catalysis and material science. 

In 1988 Lalor reported the synthesis and spectroscopic characterization of some new poly(benzo-triazolyl)borate salts (Scheme 8).180 The regiospecifity of the synthesis of I I B( Btz)4 differs from that of pyrazole/BH4 reaction in that B—N bond formation takes place in a manner that maximizes steric crowding at boron (i.e., at the triazole N(l) atoms). In 1989 Shiu describes some new metal carbonyls of HB(Btz)3.181 The synthesis and spectroscopic characterization of some first-row transition metal complexes was reported by Cecchi,182 whereas Hill described some new Rh183 and Ru184 carbonyl and isonitrile complexes. The formation of isonitrile derivatives was proposed to proceed through an associative mechanism involving an intermediate complex... 

The book Scorpionates The Coordination Chemistry of Polypyra-zolylb orate Ligands, organized according to the ligand type and to the coordinated metal, is the reference work for the papers published on poly(pyrazolyl)borates until April 1999.75 A review on this book by Templeton appeared in Journal of American Chemical Society in 2000.76 More recently, Trofimenko described also the most important features of poly(pyrazolyl)borates, from their synthesis and naming to their main applications.77... 

Insulin-like model complexes Synthesis, spectra characterization and crystal structure of two novel oxovanadium complexes with poly(pyrazolyl)borate ligands VO(HB(pz)3)(H2B(pz)2) and VO(B(pz)4)2... 

Synthesis of Poly[lsobutylene-co-(4-Methylstyrenyl, Triphenyl Phosphonium Tetraphenyl Borate)]... 

The first alkylidyne-metal complexes were prepared by Fischer et al. more than 30 years ago. Since this pioneering event, the chemistry of the transition metal-carbon triple bond present in such complexes has developed into a major field of research and though the poly(pyrazolyl)borate ligands were discovered 7 years prior to the synthesis of the first alkylidyne complexes, their importance and significance in this field has only more recently been truly appreciated. 

A typical synthesis of poly(pyrazolyl)borate alkylidyne complexes involves displacement of labile ligands from pre-existing alkylidynes prepared according to the classic oxide-abstraction Fischer preparation (Scheme 2), which has been developed by Mayr and co-workers into an efficient approach to Group 6 alkylidynes. 

Synthesis from pre-existing alkylidyne complexes L M( = CR) can also occur via the modification of the alkylidyne ligand, involving the elaboration of R or the replacement of R by R. These modifications typically involve alkylidyne complexes which already incorporate the poly(pyrazolyl)borate ligand, and consequently there is overlap between this section and Section IV, and such syntheses will be expanded upon therein. 

During the 40 years of poly(pyrazolyl)borate chemistry, complexes with group 9 metals have provided a particularly fertile area of research. Over 400 publications describe aspects ranging from the synthesis of homoleptic and heteroleptic coordination compounds to the application of complex organometallic molecules in catalysis, and the development of advanced specialist materials. 

This is particularly remarkable given the usual prevalence of metal hydrides as organometallic decomposition products, a context in which such species have seemingly never been encountered within the poly(pyrazolyl)borate chemistry of cobalt. The synthesis of 70 has been effected via several routes, including (i) reaction of Tp with hydride-donor reagents, (ii) treatment of... 

An exciting recent development has been the synthesis and preliminary investigation of the first members of a new generation of poly(pyrazolyl)borate ligand that bear a hydrocarbyl chain in place of the hydride, and are also bifunctionalised with a phosphine donor. The first such ligand, [H2C = CHCH2B (CH2PPh2)(pz)2] (herein abbreviated (u-allyl)(P)Bp) was prepared (Scheme 77) as... 

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