Fluoride abstraction from different types of transition metal fluoride complexes [LnMF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C2F5)3PF2 to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C2F5)3PF3]−) is reported. (C2F5)3PF2 reacted with trans‐[Ni(iPr2Im)2(ArF)F] (iPr2Im=1,3‐diisopropylimidazolin‐2‐ylidene; ArF=C6F5, 1 a; 4‐CF3‐C6F4, 1 b; 4‐C6F5‐C6F4, 1 c) through fluoride transfer to form the complex salts trans‐[Ni(iPr2Im)2(solv)(ArF)]FAP (2 a‐c[solv]; solv=Et2O, CH2Cl2, THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh3, solvent coordination was suppressed and the complexes trans‐[Ni(iPr2Im)2(PPh3)(C6F5)]FAP (trans‐2 a[PPh3]) and cis‐[Ni(iPr2Im)2(Dipp2Im)(C6F5)]FAP (cis‐2 a[Dipp2Im]) (Dipp2Im=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) were isolated. Fluoride abstraction from [(Dipp2Im)CuF] (3) in CH2Cl2 or 1,2‐difluorobenzene led to the isolation of [{(Dipp2Im)Cu}2]2+2 FAP− (4). Subsequent reaction of 4 with PPh3 and different carbenes resulted in the complexes [(Dipp2Im)Cu(LB)]FAP (5 a–e, LB=Lewis base). In the presence of C6Me6, fluoride transfer afforded [(Dipp2Im)Cu(C6Me6)]FAP (5 f), which serves as a source of [(Dipp2Im)Cu)]+. Fluoride abstraction of [Cp2TiF2] (7) resulted in the formation of dinuclear [FCp2Ti(μ‐F)TiCp2F]FAP (8) (Cp=η5‐C5H5) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand.

The regioselective syntheses of 1,2-azaborinines is achieved using an unsymmetrical iminoborane through both catalytic and stepwise modular routes. The 1,2-azaborinine ring can be selectively functionalized in the 4- and/or 6-position through control of the stepwise reaction sequence, allowing access to vinyl-functionalized and redox-active, luminescent, donor-functionalized 1,2-azaborinines. The electrochemistry and photochemistry of a tetraarylamine-substituted 1,2-azaborinine are studied. Cyclic voltammetry of this compound, relative to a non-B,N-substituted reference molecule, showed an additional oxidation wave assigned to the oxidation of the azaborinine ring, while emission spectroscopy indicated that the azaborinine was significantly more fluorescent than the reference.

The reaction of 1,3-diisopropylimidazolin-2-ylidene (iPr 2 Im) with diphenyldichlorostannane and dimethyldichlorostannane, respectively, leads to the formation of the adducts (iPr 2 Im)·SnPh 2 Cl 2 (1) and (iPr 2 Im)·SnMe 2 Cl 2 (2). These compounds are stable in solution to temperatures up to 80°C for several days and rearrangement to backbonetethered bis(imidazolium) salts or ring expansion reaction to six mem-* Prof. Dr. U. Radius 1282 bered heterocyclic rings was not observed. The reaction of iPr 2 Im with triphenylstannane Ph 3 SnH leads to reductive dehydrocoupling of the stannane to yield distannane Sn 2 Ph 6 and iPr 2 ImH 2 . Thus, the reactivity of these tin compounds is completely different compared to those of the lighter congener silicon, for which rearrangement (chlorides) and NHC ring expansion (hydrides) was reported earlier.

A study on the reactivity of the N‐heterocyclic silylene Dipp2NHSi (1,3‐bis(diisopropylphenyl)‐1,3‐diaza‐2‐silacyclopent‐4‐en‐2‐yliden) with the transition metal complexes [Ni(CO)4], [M(CO)6] (M=Cr, Mo, W), [Mn(CO)5(Br)] and [(η5‐C5H5)Fe(CO)2(I)] is reported. We demonstrate that N‐heterocyclic silylenes, the higher homologues of the now ubiquitous NHC ligands, show a remarkably different behavior in coordination chemistry compared to NHC ligands. Calculations on the electronic features of these ligands revealed significant differences in the frontier orbital region which lead to some peculiarities of the coordination chemistry of silylenes, as demonstrated by the synthesis of the dinuclear, NHSi‐bridged complex [{Ni(CO)2(μ‐Dipp2NHSi)}2] (2), complexes [M(CO)5(Dipp2NHSi)] (M=Cr 3, Mo 4, W 5), [Mn(CO)3(Dipp2NHSi)2(Br)] (9) and [(η5‐C5H5)Fe(CO)2(Dipp2NHSi‐I)] (10). DFT calculations on several model systems [Ni(L)], [Ni(CO)3(L)], and [W(CO)5(L)] (L=NHC, NHSi) reveal that carbenes are typically the much better donor ligands with a larger intrinsic strength of the metal–ligand bond. The decrease going from the carbene to the silylene ligand is mainly caused by favorable electrostatic contributions for the NHC ligand to the total bond strength, whereas the orbital interactions were often found to be higher for the silylene complexes. Furthermore, we have demonstrated that the contribution of σ‐ and π‐interaction depends significantly on the system under investigation. The σ‐interaction is often much weaker for the NHSi ligand compared to NHC but, interestingly, the π‐interaction prevails for many NHSi complexes. For the carbonyl complexes, the NHSi ligand is the better σ‐donor ligand, and contributions of π‐symmetry play only a minor role for the NHC and NHSi co‐ligands.

The reaction of one and two equivalents of the N‐heterocyclic carbene IMes [IMes = 1,3‐bis(2,4,6‐trimethyl‐phenyl)imidazolin‐2‐ylidene] or the cyclic (alkyl)(amino)carbene cAACMe [cAACMe = 1‐(2,6‐diisopropyl‐phenyl)‐3,3,5,5‐tetra‐methylpyrrolidin‐2‐ylidene] with [TiCl4] in n‐hexane results in the formation of mono‐ and bis‐carbene complexes [TiCl4(IMes)] 1, [TiCl4(IMes)2] 2, [TiCl4(cAACMe)] 3, and [TiCl4(cAACMe)2] 4, respectively. For comparison, the titanium(IV) NHC complex [TiCl4(IiPrMe)] 5 (IiPrMe = 1,3‐diisopropyl‐4,5‐dimethyl‐imidazolin‐2‐ylidene) has been synthesized and structurally characterized. The reaction of [TiCl4(IMes)] 1 with PMe3 affords the mixed substituted complex [TiCl4(IMes)(PMe3)] 6. The reactions of [TiCl3(THF)3] with two equivalents of the carbenes IMes and cAACMe in n‐hexane lead to the clean formation of the titanium(III) complexes [TiCl3(IMes)2] 7 and [TiCl3(cAACMe)2] 8. Compounds 1–8 have been completely characterized by elemental analysis, IR and multinuclear NMR spectroscopy and for 2–5, 7 and 8 by X‐ray diffraction. Magnetometry in solution, EPR and UV/Vis spectroscopy and DFT calculations performed on 7 and 8 are indicative of a predominantly metal‐centered d1‐radical in both cases.