Sandwich Compounds of Transition Metals with Cyclopolyenes and Isolobal Boron Analogues

Abstract

A series of sandwich compounds of transition metals (M=Ni, Fe, Cr) with cyclic hydrocarbon (M(CH)(n)) and borane (M(BH(2))(n)), ligands (including mixed hydrocarbon/borane sandwiches) has been studied using density functional theory (B3LYP/6-311+G(df,p)). Multicenter bonding between the central metal atom and basal cycloborane rings provides stabilization to planar cycloborane species. Large negative NICS values allude to aromatic character in the cycloboranes similar to the analogous cyclic hydrocarbons. The ability of cycloborane sandwiches to stabilize attached carbocations, radicals and carbanions is also assessed.

Ferrocene analogues of sandwich M(CrB6H6)2: a theoretical investigation

“…The ferrocene analogues [(η 5 -E 5 ) 2 M] (E = P, N, As, Sb, and Bi) have found important applications in both fundamental research and materials science. 1,[43][44][45][46][47][48][49] Besides, planar aromatic [Al 4 ] 2− , [50][51][52][53][54] [N 5 ] − , 49 [(P 5 ) 2 Ti] 2− , 55 borane, 56,57 CO, 58 PH 3 , 58 and boron clusters [59][60][61][62][63] can also be utilized as ligands to coordinate transition metals and form similar…”

A theoretical study on the stability difference of the borane BnHn2− and carborane C2Bn−2Hn(5 ≤ n ≤ 7) clusters

“…There are also many borane derivatives, such as metallaborane, macropolyhedral borane, and carborane. The metallaborane can be obtained by replacing the B atom of a simple borane with transitional metal atom, and some metallaboranes satisfy the 18‐electron rule . The condensation of two or more simple borane units by sharing one to four vertexes forms the macropolyhedral borane .…”

Ferrocene analogues of sandwich B12·Cr·B12: A theoretical study

“…Similarly, for Cr(C 6 H 6 ) 2 , a benzene molecule (C 6 H 6 ) contributes six π electrons as π -bonding ligand and the Cr (3d 4 4s 2 ) atom contributes six electrons, which also meets the 18-electron principle. With more studies on sandwich compounds, the ligands are various and include not only hydrocarbons, e.g., borane, 28,29 CO, 30 PH 3 ,30 boron clusters, [31][32][33][34][35] etc. The spectroscopic and theoretical studies have shown that boron clusters have planar geometries and exhibit aromatic and antiaromatic electronic properties analogous to hydrocarbons, 36 so they are predicted to be promising molecules for coordination chemistry as potential new ligands and for materials science as new building blocks.…”