Mehrfachbindungen zwischen Übergangsmetallen und “nackten” Hauptgruppenelementen: Brücken zwischen der anorganischen Festkörperchemie und der Organometallchemie

s-Block Multiple Bonds: Isolation of a Beryllium Imido Complex

A common feature of d- and p-block elements is that they participate in multiple bonding. In contrast, the synthesis of compounds containing homo- or hetero-nuclear multiple bonds involving s-block elements is extremely rare. Herein, we report the synthesis, molecular structure, and computational analysis of a beryllium imido (Be=N) complex (2), which was prepared via oxidation of a molecular Be⁰ precursor (1) with trimethylsilyl azide Me₃ SiN₃ (TMS-N₃ ). Notably, compound 2 features the shortest known Be=N bond (1.464 Å) to date. This represents the first compound with an s-block metal-nitrogen multiple bond. All compounds were characterized experimentally with multi-nuclear NMR spectroscopy (¹ H, ¹³ C, ⁹ Be) and single-crystal X-ray diffraction studies. The bonding situation was analyzed with density functional theory (DFT) calculations, which supports the existence of π-bonding between beryllium and nitrogen.

Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3- (A=As, Sb, Bi) Complexes

Heteronuclear transition-metal-main-group-element carbonyl complexes of AsFe(CO)₃^- , SbFe(CO)₃^- , and BiFe(CO)₃^- were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass-selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C_3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)₃^- . Chemical bonding analyses on the whole series of AFe(CO)₃^- (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp-p) type of transition-metal-main-group-element multiple bonding. The σ-type three-orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)₃^- (A=As, Sb, Bi) complexes.

Trigonal-bipyramidal and square-pyramidal chromium-manganese chalcogenide clusters, [E2CrMn2(CO)n](2-) (E=S, Se, Te; n=9, 10): synthesis, electrochemistry, UV/Vis absorption, and computational studies

The reactions of E powder (E=S, Se) with a mixture of Cr(CO)6 and Mn2(CO)10 in concentrated solutions of KOH/MeOH produced two new mixed Cr-Mn-carbonyl clusters, [E2CrMn2(CO)9](2-) (E=S, 1; Se, 2). Clusters 1 and 2 were isostructural with one another and each displayed a trigonal-bipyramidal structure, with the CrMn2 triangle axially capped by two μ3-E atoms. The analogous telluride cluster, [Te2CrMn2(CO)9](2-) (3), was obtained from the ring-closure of Te2Mn2 ring complex [Te2Mn2Cr2(CO)18](2-) (4). Upon bubbling with CO, clusters 2 and 3 were readily converted into square-pyramidal clusters, [E2CrMn2(CO)10](2-) (E=Se, 5; Te, 6), accompanied with the cleavage of one Cr-Mn bond. According to SQUID analysis, cluster 6 was paramagnetic, with S=1 at room temperature; however, the Se analogue (5) was spectroscopically proposed to be diamagnetic, as verified by TD-DFT calculations. Cluster 6 could be further carbonylated, with cleavage of the Mn-Mn bond to produce a new arachno-cluster, [Te2CrMn2(CO)11](2-) (7). The formation and structural isomers, as well as electrochemistry and UV/Vis absorption, of these clusters were also elucidated by DFT calculations.

Tellurium-bridged manganese carbonyl clusters: synthesis and structural transformations of [Te4Mn3(CO10]-, [Te2Mn3(CO)9]2-, [Te2Mn3(CO)9]-, and [Te2Mn4(CO)12]2-

The reactions of appropriate ratios of K2TeO3 and [Mn2(CO)10)] in superheated methanol solutions lead to a series of novel cluster anions [Te4Mn3(CO)10] (1), [Te2Mn3(CO)9]2- (2), [Te2Mn3(CO)9]- (3), and [Te2Mn4(CO)12]2- (4). When cluster 1 is treated with [Mn2(CO)10]/KOH in methanol, paramagnetic cluster 2 is formed in moderate yield. Cluster 2 is oxidized by [Cu(MeCN)4]BF4 to give the closo-cluster [Te2Mn3(CO)9]- (3), while treatment of 2 with [Mn2(CO)10]/KOH affords the closo-cluster 4. IR spectroscopy showed that cluster 1 reacted with [Mn2(CO)10] to give cluster 4 via cluster 2. Clusters 1-4 were structurally characterized by spectroscopic methods or/and X-ray analyses. The core structure of 1 can be described as two [Mn(CO)3] groups doubly bridged by two Te2 fragments in a mu2-eta2 fashion. Both [Mn(CO)3] groups are further coordinated to one [Mn(CO)4] moiety. Cluster 2 is a 49 e- species with a square-pyramidal core geometry. While cluster 3 displays a trigonal-bipyramidal metal core, cluster 4 possesses an octahedral core geometry.