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A high-nuclearity {Ni 18 } complex (1) with a unique 'flying saucer' motif has been prepared from the organic chelate, α-methyl-2-pyridine-methanol (mpmH), in conjunction with bridging azido (N 3 - ) and peroxido (O 2 2- ) ligands. Magnetic susceptibility measurements revealed the presence of both ferro- and antiferromagnetic exchange interactions between the metal centres in 1, and the stabilization of spin states with appreciable S values at two different temperature regimes. The end-on bridging azido and alkoxido groups are in all likelihood the ferromagnetic mediators, while the η 3 :η 3 :μ 6 -bridging peroxides most likely promote the antiparallel alignment of the metals' spin vectors, yielding an overall non-zero spin ground state for the centrosymmetric compound 1. Furthermore, the {Ni 18 } nanosized cluster behaves as a single-molecule magnet, exhibiting magnetic hysteresis at low temperatures and two relaxation processes at 15 K and 1.3 K, a very rare phenomenon in polynuclear magnetic 3d-metal clusters., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

The germylone dimNHCGe (5, dimNHC=diimino N-heterocyclic carbene) undergoes a [2+2] cycloaddition with isocyanates RNCO (R=4-tolyl or 3,5-xylyl) to furnish novel alkyl carboxamido germylenes 7 (R=4-tolyl) and 8 (R=3,5-xylyl), featuring a C-C bond between the former carbene carbon and the isocyanate moiety. Heating a mixture of 8 with 4-tolyl isocyanate to 100 °C results in isocyanate metathesis, demonstrating reversible C-C bond formation on the reduced germanium compound. DFT calculations suggest that this process occurs via the reductive dissociation of isocyanate from 8 that regenerates the parent Ge(0) compound 5., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The germylone dimNHCGe (dimNHC=diimino N-heterocyclic carbene) reacts with azides N 3 R (R=SiMe 3 or p-tolyl) to furnish the first examples of germanium π-complexes, i. e. guanidine-ligated compounds (dimNHI-SiMe 3 )Ge (NHI=N-heterocyclic imine, R=SiMe 3 ) and (dimNHI-Tol)Ge (R=p-tolyl). DFT calculations suggest that these species are formed by a Staudinger type replacement of dinitrogen in the azide by a nucleophilic germylone, leading to a transient carbene adduct of iminogermylidene. Heating a solution of compound (dimNHI-SiMe 3 )Ge to 70 °C results in extrusion of the iminogermylidene that further aggregates to produce the known [Me 3 SiNGe] 4 tetramer, whereas the imidazolylidene fragment transforms into an unusual heptatriene species that can be considered as a product of carbene insertion into the C-C bond of a pendant Ar substituent at the imidazolylidene nitrogen of the dimNHC. Reaction of (dimNHI-SiMe 3 )Ge with tetrachloro-o-benzoquinone results in the net transfer of a germanium atom and formation of the free diimino-guanidine ligand. This ligand also forms when (dimNHI-SiMe 3 )Ge is treated with azide N 3 (p-Tol), with the germanium product being [(p-Tol)NGe] n ., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Diimino-carbene-supported germylone dimNHCGe does not react with BPh 3 and does not activate dihydrogen in the FLP mode in the combination with this borane. However, it reacts with B(C 6 F 5 ) 3 to give the zwitterionic borate dimNHCGe-(C 6 F 4 )BF(C 6 F 5 ) 2 . This compound can be converted into the hydroborate dimNHCGe-(C 6 F 4 )BH(C 6 F 5 ) 2 (8) and further into [dimNHCGe-(C 6 F 4 )B(C 6 F 5 ) 2 ] + (4). Compound 4 is a Ge/B analogue of Stephan's FLP parent P/B compound (C 6 H 2 Me 3 ) 2 P-C 6 F 4 -B(C 6 F 5 ) 2 but unlike the latter cannot split dihydrogen. Moreover, attempts to prepare a Ge/B analogue of the zwitterion (C 6 H 2 Me 3 ) 2 HP-C 6 F 4 -BH(C 6 F 5 ) 2 by protonation of borate 8 resulted in immediate elimination of H 2., (© 2023 The Authors. Chemistry - An Asian Journal published by Wiley-VCH GmbH.)

Oxidation of a base-stabilized phosphinidene (κ 2 -NNP)P (12, NNP=phosphinoamidinate) with N 2 O afforded a labile phosphinidene oxide (κ 2 -NNP)P=O (16) which was characterized by NMR spectroscopy. Further oxidation of 16 by N 2 O or reaction of 12 with two equivalents of pyridine oxide afforded the isolable dioxide (κ 2 -NNP)PO 2 which was characterized by NMR and SC XRD. Trapping of 16 with tolyl isocyanate resulted in P=O/N=C metathesis, eventually affording a urea-ligated phosphine (κ 1 -NNP)P(NTol) 2 C=O (17) The mechanism of this reaction was elucidated by DFT calculations. Reactions of phosphinidene 12 with azides generated transient imines (NNP)P=NR, which in the case of R=Tol underwent cycloaddition with tolyl Isocyanate to afford the urea product 17, and in the case of R=SiMe 3 reacts with N 3 SiMe 3 via the addition of N-Si across the P=N bond affording, after the extrusion of dinitrogen, a P,N-heterocyclic compound. Both products of the reactions with azides have been fully characterized, both in solution and the solid-state. Finally, reaction of phosphinidene 12 with one equivalent of sulfur resulted in the isolation of the base-stabilized phosphinidene sulfide (κ 2 -NNP)P=S that has also been fully characterized., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Reduction of (NP)PCl 2 (NP=phosphinoamidinate [PhC(NAr)(=NPPr i 2 )] - ) with KC 8 affords the phosphinoamidinato-supported phosphinidene (NP)P (9). Reaction of 9 with a N-heterocyclic carbene (MeC(NMe)) 2 C: results in the NHC-adduct NHC→P-P(Pr i 2 )=NC(Ph)=NAr featuring an iminophosphinyl group. Reactions of 9 with HBpin and H 3 SiPh led to the metathesis products (NP)Bpin and (NP)SiH 2 Ph, respectively, whereas with HPPh 2 a base-stabilized phosphido-phosphinidene, the product of N-P and H-P bond metathesis, was obtained. Reaction of 9 with tetrachlorobenzaquinone results in oxidation of P(I) to P(III), accompanied by oxidation of the amidophosphine ligand into P(V). Addition of benzaldehyde to 9 results in a phospha-Wittig reaction affording a product of P=P and C=O bond metathesis. Related reaction with phenylisocyanate results in a product of N-P(=O)Pr i 2 addition to the C=N bond of an intermediate iminophosphaalkene to produce a phosphinidene intramolecularly stabilized by a diaminocarbene., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Reactions of silicon and germanium dichlorides L⋅ECl 2 (E=Si, L=IPr; E=Ge, L=dioxane) with the phosphinoamidinato-supported disilylene ({κ 2 (N,P)-NNP}Si) 2 resulted in formal tetrylene insertions into the Si-Si bond. In the case of the reaction with silylene, two products were isolated. The first product ({κ 2 (N,P)-NNP}Si) 2 SiCl 2 , is the formal product of direct SiCl 2 insertion into the Si-Si bond of ({κ 2 (N,P)-NNP}Si) 2 and thus features two separated silylamido silylene centers. Over time, migration of the SiCl 2 group to a lateral position afforded the second product, the disilylene {κ 2 (Si,P)-SiCl 2 NNP}Si-Si{κ 2 (N,P)-NNP}. In contrast, insertion of GeCl 2 resulted only in the isolation of the germanium analogue of {κ 2 (Si,P)-SiCl 2 NNP}Si-Si{κ 2 (N,P)-NNP}, containing a Ge atom in the central position namely, compound {κ 2 (Si,P)-SiCl 2 NNP}Ge-Si{κ 2 (N,P)-NNP}, which is a rare example of a silylene-germylene. Finally, reaction of disilylene ({κ 2 (N,P)-NNP}Si) 2 with SiCl 4 and SiHCl 3 led to the formation of the new bis(silyl)silylene, ({NNP}SiCl 2 ) 2 Si:. All four new products from these insertion reactions have been characterized by multinuclear NMR and single-crystal X-ray diffraction studies., (© 2022 Wiley-VCH GmbH.)

Reaction of the Ga(I) compound NacNacGa (9) with the diazo compound N 2 CHSiMe 3 affords the nitrilimine compound NacNacGa(N-NCSiMe 3 )(CH 2 SiMe 3 ) (10). Carrying out this reaction in the presence of pyridine does not lead to C-H activation on the transient alkylidene NacNacGa=CHSiMe 3 but generates a metallated diazo species NacNacGa(NHN=CHSiMe 3 )(CN 2 SiMe 3 ) (13) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe 3 )(N(NC)SiMe 3 ) (15). Reactions of 10 with the silane H 3 SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ER n )NCSiMe 3 }(CH 2 SiMe 3 ), whereas reaction with the diborane B 2 cat 2 gave the product of formal nitrene insertion into the B-B bond. DFT calculations suggest that the interaction of 9 with N 2 CHSiMe 3 proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N 2 CHSiMe 3 . Insertion into the B-B bond likely proceeds through an initial 1,3-addition of the diborane, followed by boryl migration to the former nitrene center., (© 2021 Wiley-VCH GmbH.)

The Al I compound NacNacAl (1, NacNac = [ArNC(Me)CHC(Me)NAr] - , Ar = 2,6-iPr 2 C 6 H 3 ) serves as a template for the chemoselective coupling between carbonyls (benzophenone, fenchone, isophorone, p-tolyl benzoate, N,N-dimethylbenzamide, (1-phenylethylidene)aniline) and pyridine. With the CH-acidic ketone (1R)-(+) camphor, the reaction affords a hydrido alkoxide compound of Al, formed as the result of enolization, whereas an enolizable imine, (1-phenylethylidene)aniline, and the bulky ketone isophorone, still chemoselectively couple with pyridine. In contrast, reaction with the ester p-tolyl benzoate results in cleavage of the ester bond together with replacement of the alkoxy group by a hydrogen atom of the pyridine moiety. This study demonstrates that for carbonyl substrates featuring phenyl substituents, the reaction proceeds via intermediate formation of η 2 (C,X)-coordinated (X = O, N) carbonyl adducts, whereas the reaction of 1 with (R)-(-)-fenchone in the absence of pyridine leads to CH activation in the pendant isopropyl group of the Ar substituent of the NacNac ligand., (© 2021 Wiley-VCH GmbH.)

The aluminum(I) compound NacNacAl (NacNac=[ArNC(Me)CHC(Me)NAr] - , Ar=2,6-iPr 2 C 6 H 3 , 1) shows diverse and substrate-controlled reactivity in reactions with N-heterocycles. 4-Dimethylaminopyridine (DMAP), a basic substrate in which the 4-position is blocked, induces rearrangement of NacNacAl by shifting a hydrogen atom from the methyl group of the NacNac backbone to the aluminum center. In contrast, C-H activation of the methyl group of 4-picoline takes place to produce a species with a reactive terminal methylene. Reaction of 1 with 3,5-lutidine results in the first example of an uncatalyzed, room-temperature cleavage of an sp 2 C-H bond (in the 4-position) by an Al I species. Another reactivity mode was observed for quinoline, which undergoes 2,2'-coupling. Finally, the reaction of 1 with phthalazine produces the product of N-N bond cleavage., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An unsymmetrical guanidine-cyclopropenimine proton sponge DAGUN and the related BF 2 -chelate DAGBO are reported. Insight into the structural, electronic, bonding and photophysical properties of these two molecules are presented. Joint experimental and theoretical studies reveal the protonated form of DAGUN possesses an intramolecular N⋅⋅⋅H-N hydrogen bond which affords a high experimental pK BH+ of 26.6 (computed=26.3). Photophysical studies show that in solution DAGUN displays a green emission at 534 nm, with a large Stokes shift of 235 nm (14,718 cm -1 ). In contrast, the conjugate acid DAGUN-H + is only weakly emissive due to attenuated intramolecular charge transfer. X-ray diffraction studies reveal that DAGBO contains a stable tetracoordinate boronium cation, reminiscent of the well-established BODIPY family of dyes. In solution, DAGBO exhibits a strong blue emission at 450 nm coupled with a large Stokes shift (Δλ=158 nm, Δν=11,957 cm -1 ) and quantum yield of 62 %, upon excitation at 293 nm. DAGBO sets the stage as the first entry into a new class of boron-difluoride diaminonaphthalenes (BOFDANs) that represent highly fluorescent and tunable next-generation dyes with future promise for biosensing and bioimaging applications., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In situ oxidation of the Ga I compound NacNacGa by either N 2 O or pyridine oxide results in the generation of a labile monomeric oxide, NacNacGa(O), which can easily cleave the C-H bonds of aliphatic and aromatic substrates featuring good donor sites. The products of this reaction are gallium organyl hydroxides. DFT calculations show that these reactions start with the formation of NacNac-Ga(O)(L) adducts, the oxo ligand of which can easily abstract protons from nearby C-H bonds, even for sp 2 -hybridized carbon centers. Aliphatic amines do not enter this reaction for kinetic reasons, presumably because of the unfavorable sterics., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new tetrathiafulvalene (TTF) donor covalently appended with a 1,5-diisopropylverdazyl radical through a cross-conjugated pyridyl linker (3) has been prepared and characterised. Reaction of 3 with tetracyanoquinonedimethane (TCNQ) afforded the 2:1 charge-transfer complex (3) 2 ⋅TCNQ (4), in which the IR and structural data are consistent with 0.25 e - charge transfer from the TTF donor (D) to the TCNQ acceptor (A). The TTF and TCNQ molecules adopt a mixed-stack D⋅⋅⋅D⋅⋅⋅A arrangement that does not facilitate conduction. A solution EPR spectrum of 4 comprises a broad featureless singlet, which is consistent with the presence of a TCNQ radical anion. Theoretical studies were performed to probe the exchange interactions within selected fragments of 4 with and without charge transfer. In the absence of charge transfer, DFT calculations reveal weak antiferromagnetic exchange between verdazyl radicals within the (3) 2 monoradical unit. However, partial oxidation of the dimer (3) 2 to the diradical cation leads to an S= 1 / 2 ground state, in which the verdazyl radical spins are now aligned co-parallel as a consequence of antiferromagnetic exchange to the additional delocalised TTF-based spin containing unit. The magnetic properties of 4 are consistent with a net S= 1 / 2 spin state per formula unit with dominant antiferromagnetic interactions between spin-bearing building blocks., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)