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A broad study on [4 + 1]- and [4 + 2]-cycloaddition reactions of a thiazole-2-thione-based 1,4-diphosphinine (1) is reported, with a special focus on reversible reactions. Reactions of 1 with group 13 carbenoids DippNacNacM (M = Al and Ga) afford [4 + 1] adducts that can be classified as Al and Ga phosphides or as 7-metalla-1,4-norbornadienes. Reactions of 1 with alkynes and alkenes result in [4 + 2]-cycloaddition, affording 1,4-diphosphabarrelenes. The effect of different dienophiles on the formation of 1,4-diphosphabarrelenes and their thermal [4 + 2]-cycloreversion reactions is studied from an experimental as well as theoretical point of view, opening the door for protection/deprotection strategies in this chemistry. [ABSTRACT FROM AUTHOR]

Reaction of complex [(ArN)Mo(H)(Cl)([PMe.sub.3]).sub.3] (1) with [BPh.sub.3] and silane [H.sub.3]SiPh affords a new silyl complex [(ArN)Mo([SiH.sub.2]Ph)(Cl)([PMe.sub.3]).sub.2] (3) that catalyses facile H-H/Si-H exchange. EXSY experiments suggest that this exchange does not involve the classical pathways such as oxidative addition of hydrogen or silane to the complex or [sigma]-bond metathesis. It is suggested that the exchange may occur in an FLP cage comprised by the complex and the silane. Key words: hydrogen, silane, imido, molybdenum, EXSY. La reaction du complexe [(ArN)Mo(H)(Cl)([PMe.sub.3]).sub.3] (1) avec le [BPH.sub.3] et le silane [H.sub.3]SiPh permet d'obtenir un nouveau complexe silyle, le [(ArN)Mo([SiH.sub.2]Ph)(Cl)([PMe.sub.3]).sub.2] (3), qui catalyse en douceur l'echange H-H/Si-H. Des experiences EXSY laissent supposer que cet echange ne procederait pas par les voies classiques comme l'addition oxydante d'hydrogene ou de silane au complexe ou la metathese de la liaison [sigma]. Nous posons l'hypothese selon laquelle l'echange s'effectuerait dans une cage dite de <>(PLF) formee par le complexe et le silane. [Traduit par la Redaction] Mots-cles: hydrogene, silane, imido, molybdene, EXSY., Introduction Dihydrogen is the simplest and yet one of the most important molecules, being the integral part of industrial hydrogenation reactions. (1) Activation of its strong and nonpolar H-H bond [...]

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. [ABSTRACT FROM AUTHOR]

Reaction of NacNacGa with phenylisocyante generates a transient species amenable to unusual 1,3-C–H bond addition of unactivated sp3 C–H and sp2 C–H bonds of substrates featuring a hard donor atom. This reaction proceeds for pyridine oxide, dimethylsulfoxide, and dimethylacetamide, but not for pyridine, cyclohexanone, and ethyl acetate. C–H activation was also not observed for reactions with triethylphosphine oxide but, interestingly, in the presence of this compound isocyanate undergoes self-coupling on Ga(I) with a regioselectivity that is different when carried out in the absence of Et3PO. [ABSTRACT FROM AUTHOR]

Diimino−carbene‐supported germylone dimNHCGe does not react with BPh3 and does not activate dihydrogen in the FLP mode in the combination with this borane. However, it reacts with B(C6F5)3 to give the zwitterionic borate dimNHCGe−(C6F4)BF(C6F5)2. This compound can be converted into the hydroborate dimNHCGe−(C6F4)BH(C6F5)2 (8) and further into [dimNHCGe−(C6F4)B(C6F5)2]+ (4). Compound 4 is a Ge/B analogue of Stephan's FLP parent P/B compound (C6H2Me3)2P−C6F4−B(C6F5)2 but unlike the latter cannot split dihydrogen. Moreover, attempts to prepare a Ge/B analogue of the zwitterion (C6H2Me3)2HP−C6F4−BH(C6F5)2 by protonation of borate 8 resulted in immediate elimination of H2. [ABSTRACT FROM AUTHOR]

Reduction of (NP)PCl2 (NP=phosphinoamidinate [PhC(NAr)(=NPPri2)]−) with KC8 affords the phosphinoamidinato‐supported phosphinidene (NP)P (9). Reaction of 9 with a N‐heterocyclic carbene (MeC(NMe))2C: results in the NHC‐adduct NHC→P−P(Pri2)=NC(Ph)=NAr featuring an iminophosphinyl group. Reactions of 9 with HBpin and H3SiPh led to the metathesis products (NP)Bpin and (NP)SiH2Ph, respectively, whereas with HPPh2 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)Pri2 addition to the C=N bond of an intermediate iminophosphaalkene to produce a phosphinidene intramolecularly stabilized by a diaminocarbene. [ABSTRACT FROM AUTHOR]

Reactions of silicon and germanium dichlorides L⋅ECl2 (E=Si, L=IPr; E=Ge, L=dioxane) with the phosphinoamidinato‐supported disilylene ({κ2(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 ({κ2(N,P)‐NNP}Si)2SiCl2, is the formal product of direct SiCl2 insertion into the Si−Si bond of ({κ2(N,P)‐NNP}Si)2 and thus features two separated silylamido silylene centers. Over time, migration of the SiCl2 group to a lateral position afforded the second product, the disilylene {κ2(Si,P)−SiCl2NNP}Si−Si{κ2(N,P)‐NNP}. In contrast, insertion of GeCl2 resulted only in the isolation of the germanium analogue of {κ2(Si,P)−SiCl2NNP}Si−Si{κ2(N,P)‐NNP}, containing a Ge atom in the central position namely, compound {κ2(Si,P)−SiCl2NNP}Ge−Si{κ2(N,P)‐NNP}, which is a rare example of a silylene‐germylene. Finally, reaction of disilylene ({κ2(N,P)−NNP}Si)2 with SiCl4 and SiHCl3 led to the formation of the new bis(silyl)silylene, ({NNP}SiCl2)2Si:. All four new products from these insertion reactions have been characterized by multinuclear NMR and single‐crystal X‐ray diffraction studies. [ABSTRACT FROM AUTHOR]

The syntheses and systematic X-ray investigations of complexes [Cp.sub.2]Nb(SiY[Me.sub.2])(H)(SiX[Me.sub.2]) and the neutron diffraction (ND) studies of complexes [Cp.sub.2]Nb-(SiH[Me.sub.2](H)(SiCl[Me.sub.2]) and [Cp.sub.2]Nb(SiH[Me.sub.2])(H)(SiBr[Me.sub.2]) is reported. The complexes show the largest structural distortions for the silyl groups substituted by heavy halogen atoms.

Reaction of the Ga(I) compound NacNacGa (9) with the diazo compound N2CHSiMe3 affords the nitrilimine compound NacNacGa(N‐NCSiMe3)(CH2SiMe3) (10). Carrying out this reaction in the presence of pyridine does not lead to C−H activation on the transient alkylidene NacNacGa=CHSiMe3 but generates a metallated diazo species NacNacGa(NHN=CHSiMe3)(CN2SiMe3) (13) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe3)(N(NC)SiMe3) (15). Reactions of 10 with the silane H3SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ERn)NCSiMe3}(CH2SiMe3), whereas reaction with the diborane B2cat2 gave the product of formal nitrene insertion into the B−B bond. DFT calculations suggest that the interaction of 9 with N2CHSiMe3 proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N2CHSiMe3. 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. [ABSTRACT FROM AUTHOR]

Research was conducted to study the metal-hydride and hydride-hydride distances from measurements of selective and nonselective 1H T1 relaxation of hydride ligands. The detailed 1H NMR relaxation study was focused on Cp2NbH3 since this classical trihydride and its derivatives usually demonstrate proton-proton exchange couplings. Results demonstrate that Nb-H dipole-dipole interactions are very critical for the hydride relaxation in Cp2NbHx(sub 2)(H(super A)) due to the shortened hydride T1 times of the hydride ligands.

The synthesis and X-ray structure characterization of zirconium tetraaza macrocycle-supported bis(amido) complexes from ((Me4taa)ZrX2), where X could either be a Cl or CH2SiMe3, were carried out. The reaction of bis(amido)-(mu-imido) dizirconium complexes with Me4taaH2 to yield the asymmetrically substituted complex represent the first successful preparation of a tetraaza macrocycle-supported imido complexes.

The AlI compound NacNacAl (1, NacNac = [ArNC(Me)CHC(Me)NAr]−, Ar = 2,6‐iPr2C6H3) 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 η2(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. [ABSTRACT FROM AUTHOR]

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Reaction of NacNacAl (NacNac=[DippNC(Me)CHC(Me)NDipp]−) with one equivalent of benzophenone affords a ketylate species NacNacAl(η2(C,O)‐OCPh2) that undergoes easy cyclization reactions with unsaturated substrates. The scope of substrates included benzophenone, aldimine (PhNC(Ph)H), quinoline, phenyl nitrile, trimethylsilyl azide, and a saturated cyclic thiourea. The latter substrate reacted by an unusual C−N cleavage that left the C=S functionality intact. The new products were characterized by NMR spectroscopy and X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]