Carbonyl migration from phosphorus to the metal in binuclear phosphaketenyl metal carbonyl complexes to give bridging diphosphido complexes. (15th December 2014)

• Record Type: Journal Article
• Authors: Lü, Wenjun; Wang, Chaoyang; Luo, Qiong; Li, Qian-shu; Xie, Yaoming; King, R. Bruce; Schaefer III, Henry F.
• Is Part Of: New journal of chemistry. Volume 39:Number 2(2015:Feb.)
• Page Start: 1390
• Page End: 1403
• Publication Date: 2014-12-15
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c4nj01311e
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Carbonyl groups from bridging phosphaketenyl ligands in Mn2 (CO)8 (μ-PCO)2 are predicted to migrate from phosphorus to manganese upon decarbonylation, giving the diphosphido Mn2 (CO) n +2 (μ-P2 ) derivatives. Abstract : Alkali metal salts of the 2-phosphaethynolate anion PCO − synthesized from reactions of CO with NaPH2 or K3 P7 have recently become available in quantities for the synthesis of transition metal complexes of the potentially ambidentate PCO ligand ( Angew. Chem., Int. Ed., 2013, 38, 10064). This is exemplified by the recently reported rhenium carbonyl complex (triphos)Re(CO)2 (PCO) (triphos = MeP(CH2 PPh2 )3 ). Density functional theory studies on the related manganese carbonyl complexes Mn(CO) n (PCO) ( n = 5, 4, 3) and Mn2 (CO) n (PCO)2 ( n = 8, 7, 6, 5) are now reported. For the binuclear systems the low-energy Mn2 (CO)8 (PCO)2 structures are singlet spin state structures having two bridging P-bonded phosphaketenyl μ-PCO ligands without a direct Mn–Mn bond. Carbonyl loss from Mn2 (CO)8 (μ-PCO)2 is predicted to lead to migration of CO groups from phosphorus to manganese resulting in Mn2 (CO) n +2 (μ-P2 ) structures with bridging diphosphido groups as the lowest energy Mn2 (CO) n (PCO)2 isomers ( n = 7, 6, 5). Isomeric Mn2 (CO)6 (PCO)2 structures with dihapto bridging η 2 -μ-PCO ligands at ∼30 kcal mol −1 above the global minimum are also found representing intermediates in the migration of CO groups from phosphorus to manganese. For the mononuclear systems the P-bonded Mn(CO) n (PCO) ( n = 5, 4) phosphaketenyl structures are found to lie 20 to 28 kcal mol −1 in energy below the isomeric O-bonded Mn(CO) n (PCO) phosphaethynoxy isomers consistent with previously reported results by Grützmacher and coworkers on R3 E(PCO)–R3 E(OCP) systems (R = iPr, Ph; E = Si, Sn, Ge, Pb). The lowest energy structure for the tricarbonyl Mn(CO)3 (PCO) is a singlet structure with an unusual trihapto η 3 -PCO ligand. However, higher energy isomeric Mn(CO)3 (PCO) structures with P-bonded phosphaketenyl or O-bonded phosphaethynoxy ligands and tetrahedral Mn coordination are also found.