Ternary B₂X₂H₂(X = O and S) rhombic clusters and their potential use as inorganic ligands in sandwich-type (B₂X₂H₂)₂Ni complexes

Abstract

Based upon global searches and electronic structure calculations at the B3LYP and CCSD(T) levels, we present the global-minimum structures of two ternary B-O-H and B-S-H rhombic clusters: D2h B2O2H2 (1, (1)Ag) and C2v B2S2H2 (2, (1)A1). Both species feature a B2X2 (X = O or S) four-membered ring as the core, with two H atoms attached terminally. The former cluster is perfectly planar, whereas the latter undergoes a slight butterfly distortion. Bonding analyses reveal a four-center four-electron (4c-4e) o-bond in these clusters, which are 4π systems in a nonbonding/bonding combination, in contrast to an antibonding/bonding combination in a classical 4π antiaromatic hydrocarbon such as cyclobutadiene (C4H4). Clusters 1 and 2 are considered to be aromatic. The present results also help elucidate the bonding nature in the relevant heteroatomic ring B2N2H4 system and suggest that it is not appropriate to consider B2N2H4 as an inorganic cyclobutadiene, a conception that has been in existence in the literature for over 40 years. The electronic properties of the global-minimum clusters 1 and 2 are predicted. It is shown that B2O2H2 (1) and B2S2H2 (2) may serve as effective inorganic ligands to form sandwich-type transition metal complexes, such as D2d [B2O2H2]2Ni (3) and D2d [B2S2H2]2Ni (4).

Binary B4S4 Rhombic Clusters as Promising Inorganic Ligands for ­Triple‐Decker Sandwich Complexes

“…The similar bonding pattern named o-bond was described recently in the boron oxide clusters, [14,18] boron hydride oxide, and boron hydride sulfide clusters. [19] The global bonding elements are also obvious in the AdNDP pattern. As presented in Figure 3, B 4 S 4 (1) possesses 36 valence electrons, among which eight are for the four 1c-2e S 3p lone pairs, eight are for four 2c-2e B-S single bonds within the B 2 S 2 ring, four are responsible for two 2c-2e B-B single bonds, four are responsible for two 2c-2e B-S σ bonds, and eight responsible for four 2c-2e B-S π bonds.…”

“…From the calculated bond lengths at the B3LYP/aug-cc-pVTZ level (listed in Figure 1), it is seen that both of the terminal BS bonds in the rhombic structures (1 and 2) are typical B≡S bonds, with short distances (1.607 and 1.640 Å). On the other hand, neutral structures 1 can be obtained from the nearest isomeric structures of B 2 S 2 H 2 [19] by isovalent BS/H substitution. Moreover, either the global minimum of B 4 S 4 (1, 1 A 1 ) or the reported B 2 S 2 H 2 possesses a distorted rhombic B 2 S 2 core.…”

“…It appears that the global minima for both the neutral cluster and anion are well-defined: C 2v B 4 S 4 (1, -are rather similar except for the distortion of the rhombic B 2 S 2 ring in 1 (Figure 1). Furthermore, 1 and 2 can be formulated as B 2 S 2 (BS) 2 and feature B 2 S 2 four-membered rings as the core, with two -BS terminal groups attached terminally, closely resembling B 2 S 2 H 2 with a rhombic B 2 S 2 [19] and obtainable from the latter by isovalent BS/H substitution. From the calculated bond lengths at the B3LYP/aug-cc-pVTZ level (listed in Figure 1), it is seen that both of the terminal BS bonds in the rhombic structures (1 and 2) are typical B≡S bonds, with short distances (1.607 and 1.640 Å).…”

“…Notably, both D 3h B 6 O 6 and D 2h B 2 O 2 H 2 can be used as inorganic ligands to form transitional-metal complexes, such as the sandwich-type D 3d (B 6 O 6 )Cr, [17] D 3d (B 6 O 6 )V, [20] and D 2d [B 2 O 2 H 2 ] 2 Ni. [19] Given the close similarity between S and O in valence electron configurations, a BS/H isolobal analogy may exist and the boron sulfide clusters may possess similar geometries and electronic structures with their corresponding boron oxides. However, in comparison with boron oxides, boron sulfide clusters bination, in contrast to the antibonding/bonding combination in a classical 4π antiaromatic hydrocarbon such as cyclobutadiene (C 4 H 4 ).…”

“…The B 6 O 6 cluster features a boroxol B 3 O 3 ring as the structural core with three boronyl (BO) groups attached terminally, closely resembling boroxine and obtainable from the latter by isovalent BO/H substitution. Interestingly, D 2h B 4 O 4 with a B 2 O 2 core and two terminal boronyl (BO) groups [18] can be obtained from D 2h B 2 O 2 H 2 [19] by isovalent BO/H substitution. Notably, both D 3h B 6 O 6 and D 2h B 2 O 2 H 2 can be used as inorganic ligands to form transitional-metal complexes, such as the sandwich-type D 3d (B 6 O 6 )Cr, [17] D 3d (B 6 O 6 )V, [20] and D 2d [B 2 O 2 H 2 ] 2 Ni.…”