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The Diversity of Difluoroacetylene Coordination Modes Obtained by Coupling Fluorocarbyne Ligands on Binuclear Manganese Carbonyl Sites
Author(s) -
Liu Xianmei,
Wang Chaoyang,
Li Qianshu,
Xie Yaoming,
King R. Bruce,
Schaefer Henry F.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802754
Subject(s) - ligand (biochemistry) , chemistry , manganese , crystallography , metal , bridging ligand , triple bond , acceptor , stereochemistry , crystal structure , double bond , polymer chemistry , organic chemistry , physics , biochemistry , receptor , condensed matter physics
Abstract One Mn or two? The fluorocarbyne manganese carbonyl complexes [Mn(CF)(CO) n ] ( n =3, 4) and [Mn 2 (CF) 2 (CO) n ] ( n =4–7; see picture) have been investigated by density functional theory. In mononuclear complexes the CF ligand behaves very much like the NO ligand in terms of π‐acceptor strength. In binuclear complexes the two CF ligands couple in many of the low‐energy structures to form a bridging C 2 F 2 ligand derived from difluoroacetylene.Recent work has shown that the fluorocarbyne ligand CF, isoelectronic with the NO ligand, can be generated by the defluorination of CF 3 metal complexes, as illustrated by the 2006 synthesis by Hughes et al. of [C 5 H 5 Mo(CF)(CO) 2 ] in good yield by the defluorination of [C 5 H 5 Mo(CF 3 )(CO) 3 ]. The fluorocarbyne ligand has now been investigated as a ligand in the manganese carbonyl complexes [Mn(CF)(CO) n ] ( n =3, 4) and [Mn 2 (CF) 2 (CO) n ] ( n =4–7) by using density functional theory. In mononuclear complexes, such as [Mn(CF)(CO) 4 ], the CF ligand behaves very much like the NO ligand in terms of π‐acceptor strength. However, in the binuclear complexes the two CF ligands couple in many of the low‐energy structures to form a bridging C 2 F 2 ligand derived, at least formally, from difluoroacetylene, FCCF. The geometries of such [Mn 2 (C 2 F 2 )(CO) n ] complexes suggest several different bonding modes of the bridging C 2 F 2 unit. These include bonding through the orthogonal π bonds of FCCF, similar to the well‐known [R 2 C 2 Co 2 (CO) 6 ] complexes, or bonding of the C 2 F 2 unit as a symmetrical or unsymmetrical biscarbene. This research suggests that fluorocarbyne metal chemistry can serve as a means for obtaining a variety of difluoroacetylene metal complexes, thereby avoiding the need for synthesizing and handling the very unstable difluoroacetylene.