Major Difference between the Isoelectronic Fluoroborylene and Carbonyl Ligands: Triply Bridging Fluoroborylene Ligands in Fe₃(BF)₃(CO)₉ Isoelectronic with Fe₃(CO)₁₂

Abstract

The structure of Fe(3)(BF)(3)(CO)(9) is predicted to be very different than that of any of the isoelectronic homoleptic M(3)(CO)(12) derivatives (M = Fe, Ru, Os). Thus the lowest energy Fe(3)(BF)(3)(CO)(9) structure by approximately 19 kcal/mol has mu(3)-BF groups bridging the top and bottom of the Fe(3) triangle with a third edge-bridging BF group in addition to nine terminal carbonyl groups. No analogous M(3)(CO)(12) structures are found with mu(3)-CO groups bridging the M(3) triangle. Higher energy Fe(3)(BF)(3)(CO)(9) structures with two edge-bridging mu-BF groups and one terminal BF group are also found, analogous to the experimentally known Fe(3)(CO)(12) structure. However, these structures are transition states leading to local minima with one unsymmetrical face-bridging mu(3)-BF group, one edge-bridging mu-BF group, and one terminal BF group. No Fe(3)(BF)(3)(CO)(9) structures are found with exclusively terminal BF and CO groups analogous to the known structures of M(3)(CO)(12) (M = Ru, Os). These studies suggest that the BF group has a significantly greater tendency than the CO group to bridge two or three metal atoms, probably owing to the reluctance of the fluorine of the BF ligands to be a part of a formal double or triple bond.

Application of Density Functional Theory in Coordination Chemistry: A Case Study of Group 13 Monohalide as a Ligand

“…Both methods have already been synthesised, and could be used to shield reactive boron centres: either by shielding with (NH 2 groups) BNR 2 or by incorporating haloborylene as a bridge between two metal sites [8][9][10][11][12][13][14][15][16][17]. In 2010, it was predicted that BF would adopt bridging modes of coordination (μ2 or μ3) in ruthenium bimetallic systems [45,46]. Timms et al synthesised and characterised a thermally unstable volatile complex [(F 3 P) 4 Fe(BF)] using IR and 19 F NMR spectroscopy [39].…”

“…Fischer et al described the chemical [(CO) 4 Fe-Al(η 5 -C 5 Me 5 )], which was synthesised from an AlCp* unit that was bonded to a metal via a terminal non-bridging bond. When compared to dialkyl fragment ER 2 [43][44][45], single-source precursors of M-M bonds with ER fragments were significant in attaining the molecular force of the thin film stoichiometry [104][105][106][107][108][109][110]. The metal complexes (CO) n ME[(X)L 2 ] of Cr, Mo, W, and Fe with the monohalides of aluminium and gallium ligands were explored in depth.…”

Coordination chemistry of group 13 monohalides

“…7,8 With the latter solution in mind, the increased propensity of BF (over valence isoelectronic group 4 ligands) to adopt bridging (m 2 or m 3 ) modes of coordination in multimetallic systems has recently been predicted. 34,35 The first experimental report of a transition metal complex of BF comes from the early work of Timms, in a brief description of a thermally unstable volatile compound formulated as [(F 3 P) 4 Fe(BF)], formed via the condensation of iron vapour with B 2 F 4 and PF 3 . 26 More recently a combination of infrared spectroscopy (Fig.…”

Stabilities, Electronic Structures, and Bonding Properties of Iron Complexes (E1E2)Fe(CO)2(CNArTripp2)2(E1E2=BF, CO, N2, CN−, or NO+)**

“…By using reactions of laser‐ablated metal atoms with BF 3 , Wang, Andrews, and co‐workers synthesized terminal fluoroborylene complexes FBMF 2 (M=transition metal) in the gas phase [15–17] . Fluoroborylene iron carbonyls and homoleptic fluoroborylenes complexes have also been proposed theoretically by Hoffmann and Schaefer and King [18–24] …”

“…[15][16][17] Fluoroborylene iron carbonyls and homoleptic fluoroborylenes complexes have also been proposed theoretically by Hoffmann and Schaefer and King. [18][19][20][21][22][23][24] Very recently, Figueroa et al successfully realized the isolation of the iron complex (BF)Fe(CO) 2 (CNAr Tripp2 ) 2 [Ar Tripp2 = 2,6-(2,4,6-(iso-propyl) 3 C 6 H 2 ) 2 C 6 H 3 ] with a terminal BF ligand, along with the isoelectronic dinitrogen and CO complexes (N 2 ) Fe(CO) 2 (CNAr Tripp2 ) 2 and Fe(CO) 3 (CNAr Tripp2 ) 2 . [25] Further singlecrystal x-ray diffraction, spectroscopic, and electron-density topology calculation studies demonstrated that the terminal BF ligand possesses particularly strong σ-donor and π-acceptor properties.…”