Metallacumulenylidene complexes in the cycloheptatrienyl molybdenum series [Mo{(C)n=CR2}L2(η-C7H 7)]+ (n = 0-2; L2 = P-Donor Ligand). X-ray crystal structures of [Mo{C=C(H)Ph}{P(OMe)3}2(η-C 7H7)][BF4]and [Mo(C=C=CPh2)(dppe) (η7-C...

Richard W. Grime, Madeleine Helliwell, Zaffar I. Hussain, Hannah N. Lancashire, Christopher R. Mason, Joseph J W McDouall, Christopher M. Mydlowski, Mark W. Whiteley

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Title full: Metallacumulenylidene complexes in the cycloheptatrienyl molybdenum series [Mo{(C)n=CR2}L2(η-C7H 7)]+ (n = 0-2; L2 = P-Donor Ligand). X-ray crystal structures of [Mo{C=C(H)Ph}{P(OMe)3}2(η-C 7H7)][BF4]and [Mo(C=C=CPh2)(dppe) (η7-C7H7)][PF6] and DFT investigation of cumulenylidene ligand orientations. A series of metallacumulenylidene complexes of the cycloheptatrienyl molybdenum auxiliary [Mo{(C)n=CR2}L2(η- C7H7)]+ (n = 0-2; L2 = P-donor ligand) have been synthesized by reaction of [MoXL2(η-C 7H7)] (X = Br, L2 = Ph2PCH 2CH2PPh2 (dppe); X -1, L2 = 2P(OMe)3) or [Mo(OCMe2)L2(η-C 7H7)]+ (L2 = dppe, Ph 2PCH2PPh2 (dppm)) with the terminal alkynes HC=CR; use of [MoBr(dppe)(ηC7H7)] as a precursor is facilitated by an improved, one-step synthesis from [MoBr(CO) 2(η-C7H7)]. Syntheses of the 2-oxacyclocarbene complexes [Mo(CCH2CH2(CH 2)xO)L2(η-C7H7)] + (x = 1, L2 = dppm (1), dppe (2); x = 2, L2 = dppm (3), L2 = dppe (4)), the vinylidenes [Mo{C=C(H)(CH 2)2CH2OH}(dppe)(η-C7H 7)][PF6] (5), [Mo{C=C(H)(CH2) xPh}(dppe)(η-C7H7)]+(x=2(6), 1 (7)), and [Mo(C=C(H)Ph) (P(OMe)3}2(η-C 7H7)]+ (8), and the first examples of monometallic molybdenum allenylidene complexes, [Mo(C=C=CRPh)-(dppe)(η- C7H7)]+ (R = Ph (9), Me (10)) are reported. X-ray structural studies on complexes 8 and 9 have determined Mo-C α distances as follows: 8, 1.929(3) Å 9, 1.994(3) Å. In 8, the vinylidene ligand substituents lie in the pseudo mirror plane of the MoL2(η-C7H7) auxiliary (vertical orientation) with the phenyl group located syn to the cycloheptatrienyl ring, whereas the allenylidene ligand substituents of 9 are perpendicular to the pseudo mirror plane (horizontal orientation). This series of atypical orientations of cumulenylidene ligand substituents, imposed by the cycloheptatrienyl molybdenum auxiliary, has been investigated further by variable-temperature NMR spectroscopy and quantum-chemical theoretical calculations. A DFT analysis of the complexes [Mo(C=CH2)(dppe)(η- C7H7)]+ (11), [Ru(C=CH2) (dppe)Cp]+ (12), and [Mo(C=C=CMePh)(dppe)(η-C7H 7)]+ (10) concurs with experimentally determined cumulenylidene ligand orientations. A separate analysis of the fragments [Mo(dppe)(η-C7H7)]+ and [Ru(dppe)Cp] + reveals that the HOMO of the [Mo(dppe)(η-C7H 7)]+ fragment includes a significant contribution from the metal dz2 orbital, whereas the HOMO of the [Ru(dppe)Cp]+ fragment is based on a metal dxy orbital, orthogonal- to the HOMO of the [Mo(dppe)(η-C7H 7)]+ unit. In cumulenylidene complexes of the Mo(dppe)(η-C7H7) auxiliary, interactions between the dz2-based HOMO of the metal fragment and the vacant LUMO of the cumulenylidene ligand dominate the control of ligand orientation and thus account for the observed structures. © 2008 American Chemical Society.
    Original languageEnglish
    Pages (from-to)857-871
    Number of pages14
    JournalOrganometallics
    Volume27
    Issue number5
    DOIs
    Publication statusPublished - 10 Mar 2008

    Keywords

    • Carbene complexes Role: PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (Group VIB element complexes, cumulenylidene
    • prepn. and structure of cycloheptatrienylmolybdenum oxacyclocarbenes, vinylidenes and allenylidenes via cycloheptatrienylmolybdenum complexes and terminal alkynes and DFT study of cumulenylidene orientations)
    • Carbene complexes
    • Metallocenes Role: PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (Group VIB element complexes
    • Group VIB element complexes Role: PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (carbene complexes, cumulenylidene
    • Group VIB element complexes Role: PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (carbene complexes
    • NMR (carbon-13
    • Sandwich compounds Role: PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (half-sandwich, cycloheptatrienylmolybdenum
    • Group VIB element complexes Role: PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (metallocenes
    • Crystal structure
    • Molecular structure (of cycloheptatrienyl molybdenum vinylidene and allenylidene complexes)
    • Molecular structure (optimized
    • of cycloheptatrienylmolybdenum and cyclopentadienylruthenium carbene, vinylidene and allenylidene complexes)
    • NMR (phosphorus-31
    • Conformation
    • HOMO
    • LUMO
    • NMR
    • Rotamers
    • Rotational barrier (prepn. and structure of cycloheptatrienylmolybdenum oxacyclocarbenes, vinylidenes and allenylidenes via cycloheptatrienylmolybdenum complexes and terminal alkynes and DFT study of cumulenylidene orientations)
    • Alkynes Role: RCT (Reactant), RACT (Reactant or reagent) (alpha -
    • bromodicarbonylcycloheptatrienylmolybdenum reaction dppe dppm terminal alkyne
    • cycloheptatrienyltoluenemolybdenum hexafluorophosphate reaction dppe dppm terminal alkyne cyclization
    • cycloheptatrienyliodomolybdenum bisphosphite reaction terminal alkyne
    • cycloheptatrienylmolybdenum oxacyclocarbene vinylidene allenylidene prepn
    • crystal mol structure cycloheptatrienylmolybdenum vinylidene allenylidene conformation prepn
    • mol structure optimized cycloheptatrienylmolybdenum cyclopentadienylruthenium carbene cumulenylidene MO conformation

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