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Structure and Dynamic Behavior of (η 3 ‐Allyl)bromodicarbonylmolybdenum(II) Complexes Containing Polydentate 2‐Pyridylphosphanes or Their Oxides as Chelating Ligands: Occurrence of Three Fluxional Processes
Author(s) -
Espinet Pablo,
Hernando Rosa,
Iturbe Gonzalo,
Villafañe Fernando,
Orpen A. Guy,
Pascual Isabel
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200005)2000:5<1031::aid-ejic1031>3.0.co;2-d
Subject(s) - chemistry , chelation , denticity , racemization , ligand (biochemistry) , octahedron , intramolecular force , stereochemistry , medicinal chemistry , crystallography , crystal structure , inorganic chemistry , receptor , biochemistry
The pseudo‐octahedral complexes [Mo(η 3 ‐allyl)Br(CO) 2 (PPy n Ph 3– n ‐ P,N )] (Py = 2‐pyridyl; n = 2, 3) and [Mo(η 3 ‐allyl)Br(CO) 2 (OPPy m Ph 3– m ‐ O,N )] ( m = 1, 2, 3) undergo three different dynamic processes in solution, depending on the chelating ligand. The complexes containing PPhPy 2 and PPy 3 as chelating P,N ‐donors undergo a novel “pivoted double switch” mechanism which scrambles two equatorial coordination sites with racemization, while maintaining the identity of the phosphorus atom trans to the allyl ligand. The complexes containing 2‐pyridylphosphane oxides as chelating O,N ‐donors undergo a nondissociative intramolecular trigonal‐twist (or turnstile) rearrangement which maintains the identity of the phosphane oxide oxygen atom coordinated in an equatorial position. All the complexes containing uncoordinated pyridyls undergo a slow dissociative exchange of pyridyls without coordination site scrambling. The structure of the complex [Mo(η 3 ‐allyl)Br(CO) 2 (OPPy 3 ‐ O,N )] has been determined by X‐ray diffraction.