The first deprotonation of a borohydride anion was achieved by treatment of [BH(CN) ] with strong non-nucleophilic bases, which resulted in the formation of alkali-metal salts of the tricyanoborate dianion B(CN) in up to 97 % yield and 99.5 % purity. [BH(CN) ] is less acidic than (Me Si) NH but a stronger acid than iPr NH. Less sterically hindered, more nucleophilic bases such as PhLi and MeLi mostly attack a CN group under formation of imine dianions [RC(N)B(CN) ] , which can be hydrolyzed to ketones of the [RC(O)B(CN) ] type. The boron-centered nucleophile B(CN) reacts with CO and CN reagents to give salts of the [B(CN) CO ] dianion and the tetracyanoborate anion [B(CN) ] , respectively, in excellent yields.
Die Reaktionen von [BH(CN) 3 ] À mit starken nichtnucleophilen Basen sind die ersten Beispiele fürd ie Deprotonierung eines Hydridoborat-Anions.D iese liefern Alkalimetall-Salzem it dem Tricyanoborat-Dianion B(CN) 3 2À in bis zu 97 %A usbeute und 99.5 %R einheit. [BH(CN) 3 ] À ist weniger acide als (Me 3 Si) 2 NH, aber eine stärkere Säure als iPr 2 NH. Sterischw eniger gehinderte,s t ärker nucleophile Basen wie PhLi und MeLi greifen hauptsächlichd ie CN-Gruppen unter Bildung von Imino-Dianionen [RC(N)B(CN) 3 ] 2À an, die mit Wasser zu Ketonen vom Typ[RC(O)B(CN) 3 ] À reagieren. Das Bor-zentrierte Nucleophil B(CN) 3 2À reagiert mit CO 2 und CN + -Reagenzien in exzellenten Ausbeuten zu Salzen mit dem [B(CN) 3 CO 2 ] 2À -b zw.d em Tetracyanoborat-Anion [B-(CN) 4 ] À .
The reactivity of [Ni(iPr2Im)4(µ‐COD)] 1 (iPr2Im = 1,3‐diisopropyl‐imidazolin‐2‐ylidene, COD = 1,4‐cyclooctadiene) in Hiyama‐ and Negishi‐type cross‐coupling reactions as well as the synthesis of several novel nickel fluoroaryl alkyl complexes is reported. Hiyama coupling of 1.1 equiv. perfluoroaromatics and 1 equiv. PhSi(OR)3 (R = Me, Et) with 5 mol‐% of 1 as catalyst leads to the C–C coupling product ArF–Ph in good to fair yields. In presence of the additive NMe4F alkoxy transfer from PhSi(OR)3 to the perfluoroarene occurs to yield ArF–OR and PhSiF(OR)2. Negishi cross‐coupling between C6F6 or C7F8 (1 equiv.), diorganozinc reagents [ZnR2] (R = Me, Et) (2.1 equiv.) and 5 mol‐% 1 as the catalyst in toluene at 115 °C leads to ArF–R only in traces. However, NMR experiments revealed that nickel alkyl complexes are readily formed from the reaction of trans‐[Ni(iPr2Im)2(F)(ArF)] with [ZnR2] (R = Me, Et). In course of these investigations, a series of novel nickel alkyl complexes trans‐[Ni(iPr2Im)2(R)(ArF)] (R = Me, ArF = C6F5 2, C7F7 3, C12F9 4; R = Et, ArF = C6F5 5, C7F7 6, C12F9 7) have been synthesized in stoichiometric reactions starting from trans‐[Ni(iPr2Im)2(F)(ArF)] (ArF = C6F5, C7F7, C12F9) and [ZnR2] (R = Me, Et) in thf at –78 °C. As these nickel alkyl complexes 2–7 are stable at room temperature in solution for several days with respect to reductive elimination, their thermal stability was investigated. Heating trans‐[Ni(iPr2Im)2(Me)(C6F5)] 2 for 24 hours at 100 °C leads to 91 % unreacted complex 2 and only traces of reductive elimination product, i.e. C6F5Me, are formed. Furthermore, the nickel ethyl complex trans‐[Ni(iPr2Im)2(Et)(C6F5)] 5 is also very stable, even with respect to β‐hydride elimination. After heating this complex to 100 °C for 24 hours there is still 26 % unreacted 5 left.
A series of unprecedently air‐stable (tricyanoboryl)plumbate anions was obtained by the reaction of the boron‐centered nucleophile B(CN)32− with triorganyllead halides. Salts of the anions [R3PbB(CN)3]− (R=Ph, Et) were isolated and found to be stable in air at room temperature. In the case of Me3PbHal (Hal=Cl, Br), a mixture of the anions [Me4−nPb{B(CN)3}n]n− (n=1, 2) was obtained. The [Et3PbB(CN)3]− ion undergoes stepwise dismutation in aqueous solution to yield the plumbate anions [Et4−nPb{B(CN)3}n]n− (n=1–4) and PbEt4 as by‐product. The reaction rate increases with decreasing pH value of the aqueous solution or by bubbling O2 through the reaction mixture. Adjustment of the conditions allowed the selective formation and isolation of salts of all anions of the series [Et4−nPb{B(CN)3}n]n− (n=2–4) including the homoleptic tetraanion [Pb{B(CN)3}4]4−.
Eine Serie unerwartet luftstabiler Tricyanoborylplumbat‐Anionen wurde ausgehend vom Bor‐zentrierten Nukleophil B(CN)32− und Triorganylbleihalogeniden erhalten. Unterschiedliche an der Luft und bei Raumtemperatur stabile Salze mit den Anionen [R3PbB(CN)3]− (R=Ph, Et) wurden isoliert. Die Reaktionen ausgehend von Me3PbHal (Hal=Cl, Br) lieferten Mischungen der Anionen [Me4−nPb{B(CN)3}n]n− (n=1, 2). Das [Et3PbB(CN)3]−‐Ion dismutiert in wässriger Lösung stufenweise zu [Et4−nPb{B(CN)3}n]n− (n=2–4) mit PbEt4 als Nebenprodukt. Die Geschwindigkeit der Umsetzungen steigt mit abnehmendem pH‐Wert des wässrigen Reaktionsmediums oder beim Durchleiten von O2. Die selektive Synthese von Salzen mit den Anionen [Et4−nPb{B(CN)3}n]n− (n=1–4) einschließlich des homoleptischen Tetraanions [Pb{B(CN)3}4]4− wurde durch Anpassen der Reaktionsbedingungen erreicht.
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