Binuclear chromium carbonyl complexes of methylaminobis(difluorophosphine): metal–metal bonds versus four-electron donor bridging carbonyl groups. (7th March 2017)

• Record Type: Journal Article
• Authors: Miao, Huijuan; Zhang, Xiuhui; Bai, Yang; Li, Qian-shu; King, R. Bruce
• Is Part Of: New journal of chemistry. Volume 41:Number 7(2017)
• Page Start: 2625
• Page End: 2635
• Publication Date: 2017-03-07
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c7nj00295e
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : [MeN(PF2 )2 ] m Cr2 (CO) n ( m = 1, n = 10, 9, 8; m = 2, n = 8, 7, 6; m = 3, n = 6, 5, 4) have been studied theoretically. Low-energy structures with four-electron donor groups and split ligands are found. Abstract : Binuclear chromium carbonyl complexes of the general type [MeN(PF2 )2 ] m Cr2 (CO) n, including the experimentally known [MeN(PF2 )2 ]3 Cr2 (CO) n ( n = 6, 5) species, have been studied by density functional theory (DFT) methods. The lowest energy structures for the three series of [MeN(PF2 )2 ] m Cr2 (CO) n ( m = 1, 2, 3) structures can be grouped into three triads, namely [MeN(PF2 )2 ]Cr2 (CO) n ( n = 10, 9, 8), [MeN(PF2 )2 ]2 Cr2 (CO) n ( n = 8, 7, 6), and [MeN(PF2 )2 ]3 Cr2 (CO) n ( n = 6, 5, 4). The carbonyl richest structures of each triad, namely [MeN(PF2 )2 ]Cr2 (CO)10, [MeN(PF2 )2 ]2 Cr2 (CO)8, and [MeN(PF2 )2 ]3 Cr2 (CO)6 have all terminal carbonyl groups, no chromium–chromium bond, and the MeN(PF2 )2 ligands bridging the pair of chromium atoms. However, for [MeN(PF2 )2 ]3 Cr2 (CO)6 a structure with two of the three MeN(PF2 )2 ligands chelating to single chromium atoms are energetically competitive. Low-energy singlet spin state structures for the intermediate and carbonyl poorest members of each triad can incorporate a variety of features such as chromium–chromium single and double bonds, MeN(PF2 )2 ligands split into bridging MeNPF2 + PF2 groups, and four-electron donor bridging η 2 -μ-CO groups as required to give each chromium atom the favored 18-electron configuration. Such four-electron donor bridging η 2 -μ-CO groups are not found in low-energy structures of related binuclear carbonyl complexes [MeN(PF2 )2 ] m M2 (CO) n (M = Fe, Ni; m = 1, 2) of the later transition metals iron and nickel.