The Organometallic Chemistry of Halocarbonyl Complexes of Molybdenum(II) and Tungsten(II)

Synthesis and Structure of [{Mo(CO)4}2(cis-μ-F2SbF4)3]x[Sb2F11]x: An Ionic Coordination Polymer

“…We report here the synthesis and the molecular structure of a new type of predominantly σ-bonded metal carbonyl derivative, polymeric [{Mo(CO) 4 } 2 ( cis -μ-F 2 SbF 4 ) 3 ] x [Sb 2 F 11 ] x (see Figure ), which has no precedent among known CO-containing organometallic cations 7,8 or coordination compounds of molybdenum 9-12 on three accounts: (i) all known homoleptic metal carbonyl cations and their derivatives 3 are mononuclear or occasionally like [Pd 2 (μ-CO) 2 ] 2+ binuclear . Likewise, previously reported molybdenum(II) carbonyl derivatives are either monomers or ligand-bridged di-, tri-, or tetramers. − (ii) The existence range of predominantly σ-bonded cationic metal carbonyl derivatives is now extended to group 6. The range of coordination geometries and d-electron configurations includes in addition to d 10 (linear), d 8 (square planar), and d 6 (octahedral), also d 4 with a seven-coordinate geometry for the metal ion.…”

“…Important bond parameters for the cation as well as for [Sb 2 F 11 ] - are summarized in Table , together with vibrational wavenumbers (ν̄CO) for the Mo II (CO) 4 moiety. As can be seen both molybdenum ions are seven-coordinate, which is rather common for Mo(II) complexes. − The coordination polyhedron is best described as a square antiprism or 4:3 geometry, where a trigonal MoF 3 and an approximately square Mo(CO) 4 pyramid share a common apex. For the latter, observed bond angle alternation and coincidence of ν̄CO in the IR and Raman spectra (see Table ) suggest the local symmetry of the Mo(CO 4 ) moiety to be approximately C 2 v .…”

Molybdenum η3-Allyl Dicarbonyl Complexes as a New Class of Precursors for Highly Reactive Epoxidation Catalysts with tert-Butyl Hydroperoxide

“…The availability of suitable starting materials has always been of considerable importance to the synthetic chemist. η 3 -Allyl dicarbonyl complexes of Mo and W play an important role in both coordination chemistry − and catalytic organic transformations, and their reactivity depends on the nature of the ligands completing the coordination sphere. − Since the discovery of pseudooctahedral molybdenum(II) complexes of the type [Mo(η 3 -allyl)X(CO) 2 (CH 3 CN) 2 ] (X = halide) in 1968, a series of derivatives containing the {Mo(η 3 -allyl)(CO) 2 } + moiety has been easily prepared by substitution of the labile nitrile ligands and/or the anion X. ,,,,− In particular, compounds of the type [Mo(η 3 -allyl)X(CO) 2 (N−N)], where N−N = 2,2‘- bipyridine or 1,10-phenanthroline, were found to possess some air and water tolerance. , These compounds have been successfully used as catalyst precursors for imine aziridination, oxidation of triphenylphosphine with molecular oxygen, or as catalysts for allylic alkylations. − Recent studies have revealed that complexes [Mo(η 3 -C 3 H 5 )X(CO) 2 (CH 3 CN) 2 ] act as single component initiators for ring-opening metathesis polymerization of norbornene and polymerization of terminal acetylenes and catalyze the oligomerization of Ph(C⋮C) n Ph ( n = 1, 2) …”

Halocarbonyltungsten(II) Complexes Containing Tripodal Tris(pyrazolyl)borate Ligands

“…Since then, halo carbonyl complexes have been extensively studied and have underpinned many advances in organometallic chemistry . In the late 1960s, important halo carbonyl complexes of Mo(II) and W(II), including the versatile starting materials M 2 X 4 (CO) 8 (M = Mo, W; X = Cl, Br, I), were prepared by Colton and co-workers; , these spawned a wealth of halocarbonyl−Mo and −W chemistry . Around the same time, Trofimenko reported the first organometallic poly(pyrazolyl)borate complexes, viz., [(HB(pz) 3 )M(CO) 3 ] - and [LM(CO) 3 ] - [M = Cr, Mo, W; HB(pz) 3 = hydrotris(pyrazolyl)borate; L = hydrotris(3,5-dimethylpyrazol-1-yl)borate ]; this heralded the beginning of another extensive area of organometallic chemistry …”