Binuclear chromium carbonyl complexes of the highly basic small bite bidentate diphosphine bis(dimethylphosphino)methane. (14th December 2017)

• Record Type: Journal Article
• Authors: Zhang, Yujia; Miao, Huijuan; Liu, Ling; Zhang, Xiuhui; King, R. Bruce
• Is Part Of: Polyhedron. Volume 138(2017)
• Page Start: 194
• Page End: 205
• Publication Date: 2017-12-14
• Subjects: Chromium -- Small bite bidentate phosphines -- Binuclear metal carbonyls -- Four-electron donor bridging carbonyl groups -- Density functional theory; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2017.08.027
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: The structure and thermochemistry of the triads of binuclear chromium carbonyl complexes [(Me2 P)2 CH2 ]Cr2 (CO) n ( n = 10, 9, 8), [(Me2 P)2 CH2 ]2 Cr2 (CO) n ( n = 8, 7, 6) and [(Me2 P)2 CH2 ]3 Cr2 (CO) n ( n = 6, 5, 4) have been investigated using density functional theory. Examples of structures with Cr–Cr single and double bonds, four-electron donor η 2 -µ-CO groups, and split bridging Me2 P + Me2 PCH2 ligands are found. Abstract: The structure and thermochemistry of the triads of binuclear chromium carbonyl complexes [(Me2 P)2 CH2 ]Cr2 (CO) n ( n = 10, 9, 8), [(Me2 P)2 CH2 ]2 Cr2 (CO) n ( n = 8, 7, 6) and [(Me2 P)2 CH2 ]3 Cr2 (CO) n ( n = 6, 5, 4) have been investigated using density functional theory. The lowest-energy structures of the carbonyl-richest triad members [(Me2 P)2 CH2 ]Cr2 (CO)10, [(Me2 P)2 CH2 ]2 Cr2 (CO)8, and [(Me2 P)2 CH2 ]3 Cr2 (CO)6 have long Cr⋯Cr distances indicating the absence of direct chromium bonds. The lowest energy structures of the intermediate triad members [(Me2 P)2 CH2 ]2 Cr2 (CO)7 and [(Me2 P)2 CH2 ]3 Cr2 (CO)5 systems have Cr–Cr single bonds of lengths of 3.13 and 3.39 Å, respectively, and intact diphosphine ligands. However, in the lowest energy [(Me2 P)2 CH2 ]Cr2 (CO)9 structure, one of the terminal CO groups is converted into a four-electron donor bridging η 2 -μ-CO group, retaining a long non-bonding Cr⋯Cr distance of 4.80 Å. The lowest energy structure of the carbonyl-poorest [(Me2 P)2 CH2 ]Cr2 (CO)8, [(Me2 P)2 CH2 ]2 Cr2 (CO)6, and [(Me2 P)2 CH2 ]3 Cr2 (CO)4 members of each triad show different features. In the lowest energy [(Me2 P)2 CH2 ]Cr2 (CO)8 structure the ligand splits into separate Me2 P and Me2 PCH2 units, both of which bridge a Cr–Cr bond of length 3.06 Å. The lowest energy [(Me2 P)2 CH2 ]2 Cr2 (CO)6 structure has a four-electron donor bridging η 2 -μ-CO group and a Cr–Cr single bond of length 2.91 Å. The lowest energy [(Me2 P)2 CH2 ]3 Cr2 (CO)4 structure is a triplet structure with a Cr–Cr single bond of length 3.03 Å.