Tp ligand 4289193 179070005 2007-12-19T23:54:08Z GlassFET 3712038 /* Manganese */ remove "it is important to note" In [[organometallic chemistry]], the '''trispyrazolylborate [[ligand]]''', often known as '''Tp''', is a [[scorpionate ligand]]. By using different pyrazoles, a range of different ligands can be formed. The Tp ligands are usually synthesized by reacting [[pyrazole]] with [[alkali metal]] borohydrides, such as [[sodium borohydride]] NaBH<sub>4</sub>, under reflux. H<sub>2</sub> is evolved as the borohydride is sequentially converted first to pyrazolylborate [H<sub>3</sub>B(C<sub>3</sub>N<sub>2</sub>H<sub>3</sub>)], then to dipyrazolylborate [H<sub>2</sub>B(C<sub>3</sub>N<sub>2</sub>H<sub>3</sub>)<sub>2</sub>], and finally to tris(pyrazolyl)borate [HB(C<sub>3</sub>N<sub>2</sub>H<sub>3</sub>)<sub>3</sub>]. Bulky pyrazolyl borates can be prepared from 3,5-disubstituted pyrazoles, such as the dimethyl derivative. These bulky pyrazolyl borates have proven especially valuable in the preparation of catalysts and models for enzyme active sites. Utilizing scorpionate ligands in the syntheses of metal catalysts may allow simpler and more accurate methods to be developed. [[ligand]]s allow for good shielding of the bound metal while strong [[sigma bond]]s between the nitrogens and the metal stabilize the metal; these attributes help scorpionate compounds with creating highly symmetrical [[supramolecular chemistry|supramolecular]] silver complexes and [[olefin]] [[polymerization]] (with the compound hydrotris(pyrazolyl) borate Mn). == [[Manganese]] == As commented above, [MnBr(CO)<sub>5</sub>] reacts with KTp to form [MnTp(CO)<sub>3</sub>]. This is a compound which is interesting because examples of it with many of the scorpionates (Cp, Tp, Tm and the thia-crown) are known. These compounds are interesting because by using solution state [[IR]] spectrscopy that it is possible to use the [[carbonyl]] stretching frequencies as a measure of the [[electron]] [[density]] on the metal, the [[electron density]] in turn is controlled by the ligands. Solid state infra-red spectrscopy can be complicated by the existence of more than one crystal form (A good example being the [[ruthenium]] complex [RuHCl(CO)(PPh<sub>3</sub>)<sub>3</sub>] which has a [[pink]] and a [[yellow]] form which have different IR spectra). == [[Copper]] == While the first row [[transition metal]]s from [[chromium]] through to [[nickel]] form plenty of both [[homoleptic]] and mixed [[ligand]] [[carbonyl]] complexes (such as [[nickel carbonyl]], [[iron pentacarbonyl|iron carbonyl]] and [[chromium carbonyl]]), it is important to note that few copper carbonyls are known: If copper was to form a homoleptic carbonyl [[18VE]] it would be Cu<sub>2</sub>(CO)<sub>7</sub>. It is however possible by reacting a copper (I) salt with a Tp ligand and then with [[carbon monoxide]] to form a copper (I) carbonyl complexes. [CuTp(CO)] is an 18VE complex. For a recent example see. S. Imai, K. Fujisawa, T. Kobayashi, N. Shirasawa, H. Fujii, T. Yoshimura, N. Kitajima, and Y. Moro-oka, ''Inorganic Chemistry'', 1998, '''37''', 3066. == [[Gold]] == Gold complexes similar to the copper (I) Tp carbonyls have been reported, in addition an [[isocyanide]] complex has been reported. In this paper the normal Tp ligand was replaced with a fluorinated tris([[pyrazole|pyrazolyl]])borate ligand {hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate)}. H. V. Rasika Dias and W. Jin, ''Inorganic Chemistry''', 1996, '''35''', 3687. == [[Molybdenum]] == An example of a metal which has a wide range of Tp complexes is molybdenum, a great wealth of different complexes of this metal with Tp ligands are known. It is possible to react molybdenum hexa[[carbonyl]] with [[acetonitrile]] to form molybdenum triscarbonyl trisacetonitrile ([Mo(CO)<sub>3</sub>(MeCN)<sub>3</sub>]) with KTp to form the [[anion]]ic complex [MoTp(CO)<sub>3</sub>]<sup>-</sup>. This anion can be crystallised using a tetra[[alkyl]] [[ammonium]] [[cation]], or it can be reacted with a range of electrophilic reagents. [[image:TpMotriscarbonyl.jpg|center|300px]] Here is picture of the tetraethyl ammonium salt of [MoTp(CO)<sub>3</sub>]<sup>-</sup>. * [[Proton]], it is possible by reacting [MoTp(CO)<sub>3</sub>]<sup>-</sup> with a [[bronsted]] acid to form [MoTp(H)(CO)<sub>3</sub>]. This is a metal hydride. * [[Tin]] [[electrophile]]s, by reacting the [MoTp(CO)<sub>3</sub>]<sup>-</sup> anion with triphenyl tin [[chloride]] or trimethyl tin chloride compounds with molybdenum-tin bonds can be formed. In the case of the triphenyl tin compound this provides a method of forming an [[air]] stable [[crystaline]] compound which is an ''[[synthon]]'' for the [MoTp(CO)<sub>3</sub>]<sup>-</sup> anion. * If the [Mo(CO)<sub>3</sub>(MeCN)<sub>3</sub>] is reacted with 1 equiv of [[bromine]] or [[iodine]] then [MoX<sub>2</sub>(CO)<sub>3</sub>(MeCN)<sub>2</sub>] will be formed, this can be reacted with KTp to form [MoTp(X)(CO)<sub>3</sub>]. * If the [Mo(CO)<sub>3</sub>(MeCN)<sub>3</sub>] is reacted with allyl chloride before the addition of the KTp, then [MoTp(Allyl)(CO)<sub>2</sub>] will be formed.[http://www.efcats.org/pages/Summerschool/Ustron%202004/Posters/Kisala.pdf] * If the [MoTp(CO)<sub>3</sub>]<sup>-</sup> anion is treated with iso[[amyl nitrite]] (or another [[alkyl]] [[nitrite]] [[ester]]) then a [[nitrosyl]] complex ([[MoTp(CO)<sub>2</sub>(NO)]] is formed. This is one of many examples of molybdenum nitrosyls.[http://journals.tubitak.gov.tr/chem/issues/kim-05-29-3/kim-29-3-2-0409-10.pdf] [[image:MoTpCO2NO.jpg|center|300px]] Here is a picture of a typical mixed nitrosyl carbonyl complex. Note that the carbonly and nitrosyl ligands are [[disordered]] for clarity of expression: a randomly-chosen ligand has been designated as the [[nitrosyl]]. == [[Ruthenium]] == A range of ruthenium complexes of Tp are known, [http://www.u-bourgogne.fr/EuroH-2000/Jalon.pdf],[http://pubs.acs.org/cgi-bin/abstract.cgi/orgnd7/1999/18/i06/abs/om980752q.html],[http://www.webstracts.com/icomc2004/finals/10332.pdf]. [[Category:Coordination compounds]] [[Category:Inorganic chemistry]] [[Category:Organometallic chemistry]]