No abstract

The β-diketiminato magnesium hydride, [(BDI)MgH]]2, reacts with alkenes and catalyses their hydrosilylation with PhSiH3.

The β-diketiminato aluminum dihydrides, [HC­{(Me)­CNAr}2AlH2] [4: Ar = 2,6-di-isopropylphenyl (Dipp), 5: 2,4,6-trimethyl­phenyl (Mes)] react directly with N-aryl-substituted N-heterocyclic carbenes (NHCs) by C–N bond activation to afford aluminum amido-alkyl derivatives of the form [HC­{(Me)­CNAr}2AlCH2(N­(Ar′)­CH)2]. The more sterically congested alane (4), bearing N-Dipp substitution, does not react with either 1,3-bis­(2,6-di-isopropylphenyl)­imidazol-2-ylidene (IPr) or 1,3-bis­(2,4,6-trimethyl­phenyl)­imidazol-2-ylidene (IMes), even under forcing conditions. In contrast, in situ generation of 1,3-bis­(phenyl)­imidazol-2-ylidene through deprotonation of the corresponding imidazolium tetrafluoroborate by KN­(SiMe3)2 in the presence of compound 4 provides facile ring opening of the NHC at room temperature to yield [HC­{(Me)­CNDipp}2AlCH2(N­(Ph)­CH)2]. Although compound 5 also does not react with IPr, relaxation of the steric demands of the supporting β-diketiminate ligand to N-mesityl substitution enables analogous ring opening of IMes, with the formation of [HC­{(Me)­CNMes}2AlCH2(N­(Mes)­CH)2] (7), when the reaction is heated to 80 °C. DFT calculations performed on model systems suggest that in comparison to the parent alane (AlH3) the enhanced propensity of these systems to induce NHC ring cleavage is a consequence of the relative stability of the initially formed five- and four-coordinate adducts as well as the augmented hydridic character of the Al–H bonds within the β-diketiminate-supported molecules.

Reactions of dimeric β-diketiminato (BDI) magnesium and calcium hydrides with [(BDI)Mg] + [Al{OC(CF 3 ) 3 } 4 ] − provide ionic multimetallic hydride derivatives, which have been characterized by single-crystal X-ray diffraction analysis. The exclusively magnesium centered species comprises a cation in which two [(BDI)Mg] + units are connected by a single μ 2 -bridging hydride. In contrast, the greater lability of the calcium-containing system is underscored by the isolation of a cyclic heterotrimetallic species in which a CaH 2 moiety is coordinated by a molecule of benzene and an aryl substituent of a [{(BDI)Mg} 2 H] + cation. The homometallic dimagnesium species displays a greater facility toward reaction with diphenylacetylene than neutral [(BDI)MgH] 2 , although the resultant crystallographically characterized vinyldimagnesium cation equilibrates into a complex mixture of neutral and ionic species in solution. An initial assessment of both systems for the hydrosilylation of 1-hexene and diphenylacetylene evidences an inferior catalytic performance of [(BDI)MgH] 2 in isolation.

A new protocol that enables the immobilization of DNA probes on aminated micro-titer plates activated with aldehyde-dextran via an amino group artificially introduced in the 3' end of the oligonucleotide probe is reported in this work. The method is based on the use of hetero-functional-dextran as a long and multifunctional spacer arm covalently attached to an aminated surface capable of immobilizing DNA oligonucleotides. The immobilization occurred only via the amino introduced in the 3' end of the probe, with no implication of the DNA bases in the immobilization, ensuring that the full length of the probe is available for hybridization. These plates having immobilized oligonucleotide probes are able to hybridize complementary DNA target molecules. The tailor-made hetero-functional aldehyde-aspartic-dextran together with the chemical blocking of the remaining primary amino groups on the support using acetic anhydride avoid the nonspecific adsorption of DNA on the surface of the plates. Using these activated plates, (studying the effect of the probe concentration, temperature, and time of the plate activation on the achieved signal), thus, the covalent immobilization of the aminated DNA probe was optimized, and the sensitivity obtained was similar to that achieved using commercial biotin-streptavidin systems. The new DNA plates are stable under very drastic experimental conditions (90% formamide, at 100 degrees C for 30 min or in 100 mM NaOH).

A Fischer carbene complex within the N‐heterocyclic carbene skeleton is present in MnI/AuI heterometallic compounds that were synthesized from an acyclic diaminocarbene complex, through a translocation process of metallic ions under basic conditions and subsequent alkylation with methyl triflate (see scheme; bipy=bipyridyl, [Mn]=[Mn(CO)2(bipy)]).

The reactivity of the mixed-ligand carbonyl–isocyanide complexes fac-[Mn(CNR)(CO)3(bipy)]+ (1a, R = Ph; 1b, R = xylyl; 1c, R = Me; 1d, R = CH2Ph; 1e, R = tBu) with the primary amines NH2Me and NH2CH2CH2CH2Br has been studied. Nucleophilic addition of the amine to a carbonyl ligand or to the isocyanide ligand may take place, depending on the nature of the amine, the substituent in the isocyanide ligand, and the reaction conditions; even replacement of a carbonyl ligand may occur. Thus, a variety of carbamoyl (2a–e), diaminocarbene (3a–d, 5a–d), N,O-heterocyclic carbene (6b), and amine (4b,c) complexes of manganese(I) has been obtained and characterized by spectroscopic and/or X-ray diffraction methods.

A new protocol for the synthesis of protic bis(N-heterocyclic carbene) complexes of Au(I) by a stepwise metal-controlled coupling of isocyanide and propargylamine is described. They are used as tectons for the construction of supramolecular architectures through metalation and self-assembly. Notably a unique polymeric chain of Cu(I) with alternate Au(I) /bis(imidazolate) bridging scaffolds and strong unsupported Cu(I) -Cu(I) interactions has been generated, as well as a 28-metal-atoms cluster containing a nanopiece of Cu2 O trapped by peripheral Au(I) /bis(imidazolate) moieties.