Alkyne and Nitrile as η²(3e) Ligands in [Tris(pyrazolyl)borato]niobium(I) Complexes. Synthesis, Structure, and Coupling Reaction

Abstract

Treatment of the 4e-alkyne complex [Tp*Nb(CO)2(PhCCMe)] with the nitrile RCN (R = Ph, Me, Et) yields the first mixed 3e-alkyne−η2(3e)-nitrile complexes, [Tp*Nb(CO)(PhCCMe)(RCN)], which have been spectroscopically and structurally characterized. Upon addition of HBF4, the protonated coupling product [Tp*Nb(F)(CPhCMeCPhNH)] (R = Ph) is formed.

Unusual Nitrile–Nitrile and Nitrile–Alkyne Coupling of FcCN and FcCCCN

“…The compounds [Cp* 2 Zr(h 2 -Me 3 SiC 2 SiMe 3 )], [19] [Cp* 2 Ti(h 2 -Me 3 SiC 2 SiMe 3 )] [21] and FcÀCN [27] were synthesized as previously described in literature. The following instruments were used: NMR spectra: Bruker AV300 and AV400 ( 1 H and 13 Electrochemical measurements were conducted at 25 8C under argon on 1.0 mmol L À1 solutions in dry, air-free tetrahydrofuran solutions containing 0.1 mol l À1 of [N(nBu) 4 ][B(C 6 F 5 ) 4 ] as supporting electrolyte by using a Voltalap PGZ 100 radiometer electrochemical workstation interfaced with a personal computer. A three-electrode cell using a Pt auxiliary electrode, a glassy carbon working electrode (surface area 0.031 cm 2 ), and an Ag/Ag + (0.01 mol l À1 [AgNO 3 ]) reference electrode, mounted on a Luggin capillary, was used.…”

“…The origin of this proton can be an additional proton source or ligand L itself. [13] The other possible and comparable products of alkyne-nitrile coupling are B2 and B3 (Scheme 2). Compounds of type B2 were established in the reaction of bimetallic complexes, which consist either of a titanium and a boron or a zirconium and an aluminum center, with nitriles.…”

“…Subsequently, an additional ligand L (e.g., nitrile, phosphine) coordinates and a hydrogen atom is bonded to the nitrogen atom. The origin of this proton can be an additional proton source or ligand L itself 13…”

“…The thermal ellipsoids correspond to 30 % probability. Selected bond lengths [] and angles [deg]: Zr1ÀN1 2.1256(12), C5ÀZr1 2.4445(15), C3ÀN1 1.273(2), C3ÀC4 1.506(2), C4ÀC5 1.370(2), C6ÀN2 1.1611(19), C3-N1-Zr1 125.08(10), C4-C5-Zr1 114.02(10), N1-C3-C4 118.91(13), C5-C4-C3 111.30(13).…”

Phase Transitions in Tris(3,5-dimethylpyrazol-1-yl)methane. The Structure of the High-Temperature Phase from X-ray Powder Diffraction

“…One example showing the variability of the conformation angle can be seen in the hydridotris(3,5-dimethylpyrazol-1-yl)borate anion (Lorente, Etienne & Donnadieu, 1996). The corresponding values for the three molecules of the BBB isomer are 42 (1), 45 (2) and 47 (2) °.…”