The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: synthesis and redox chemistry of some phosphine- and phosphite-substituted halide and acetonitrile derivatives

Carbonyl(cycloheptatrienyl)iodo(phosphorus donor)tungstens ([wI(C7H7)(CO)L]; L = P(OMe),, la; L = P[O(i-Pr)],, lb; L = PPh,, lc) were prepared from dicarbonyl(cycloheptatrieny1)iodotungsten ([wI(C,H,)(CO),]) via a carbonyl-substitution process. Similarly, bromocarbonyl(phosphorus donor)( 1,2,4,6-tetramethylcycloheptatrieny1)tungstens ([wBr(Me4C7H3),, 6b; L = PPh,, 6c) were obtained from the reaction of bromodicarbonyl( 1,2,4,6-tetramethylcycloheptatrienyl)tungsten ([wBr(Me4C7H3)(CO)2]; 4) with L. The reduction of la-, 4, and 6a,b with sodiumdihydridobis(2-methoxyethoxy)aluminium in toluene led to. Complexes 2a and 7b were characterized by X-ray structure analyses.Introduction. -In recent papers, we have reported about the activating influence of NO ligands on M-H bonds [14]. In order to further test the hypothesis that hydride complexes with odd-electron ligands and the odd electron in an antibonding orbital can achieve enhanced reactivity of the transition-metal-hydrogen bond, we focussed on the synthesis of (cycloheptatrieny1)hydridotungsten complexes. Among related systems with VIb transition metal centers, Green and coworkers reported the [MoH(C,H,)(dppe)] compound (dppe = ethane-1,2-diylbis[diphenylphosphanel) [ 51, which appeared quite stable at room temperature. Because of that observation, it seemed appropriate to attempt syntheses of heavy-element hydride derivatives preferably with phosphorusdonor substitution in which stable M-H bonds could be expected.

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“…Chromatography: silica gel 60 (Merck). [7] were prepared as described in the literature. IR spectra (cm-'): Biorad FTS 45.…”

Section: Experimental Partmentioning

confidence: 99%

“…-Our goal of finding access to (cycloheptatrieny1)-or (1,2,4,6-tetramethylcycloheptatrienyl)hydridotungsten compounds with either CO or phosphorus donors in the ancillary ligand sphere was pursued by utilizing bromo or iodo derivatives as key intermediates, as shown in Scheme 1. In the cycloheptatrienyl series, we [7].…”

mentioning

confidence: 99%

(Cycloheptatrienyl)hydridotungsten Complexes

Schwed

Hund

Bosch

et al. 1991

Helvetica Chimica Acta

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“…The chemistry of the W(dppe)(h-C 7 H 7 ) system was initiated more than a decade ago, 15 but our investigations were impeded by the poor accessibility of precursor complexes of the type [WX(dppe)(h-C 7 H 7 )]; the synthetic challenges involved have been well documented. 15,16 Recently however, we have developed a direct synthesis 9 of [MoBr(dppe)(h-C 7 H 7 )] from the dicarbonyl precursor [MoBr(CO) 2 (h-C 7 H 7 )] and this led to a re-evaluation of the analogous tungsten chemistry. Most known complexes of the cycloheptatrienyl tungsten system are derived from [WX(CO) 2 (h-C 7 H 7 )] (X = halide) which is obtained in a four step synthesis from W(CO) 6 in relatively low overall yield (Scheme 1).…”

Section: Synthesis Of [Wbr(dppe)(g-c 7 H 7 )]mentioning

confidence: 99%

Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(CCHR)(dppe)(η-C₇H₇)]⁺and [W(CCR)(dppe)(η-C₇H₇)]ⁿ⁺(n = 0 or 1)

et al. 2011

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The first examples of vinylidene complexes of the cycloheptatrienyl tungsten system [W(C=CHR)(dppe)(η-C₇H₇)](+) (dppe = Ph₂PCH₂CH₂PPh₂; R = H, 3; Ph, 4; C₆H₄-4-Me, 5) have been synthesised by reaction of [WBr(dppe)(η-C₇H₇)], 1, with terminal alkynes HC≡CR; a one-pot synthesis of 1 from [WBr(CO)₂(η-C₇H₇)] facilitates its use as a precursor. The X-ray structure of 4[PF₆] reveals that the vinylidene ligand substituents lie in the pseudo mirror plane of the W(dppe)(η-C₇H₇) auxiliary (vertical orientation) with the phenyl group located syn to the cycloheptatrienyl ring. Variable temperature ¹H NMR investigations on [W(C=CH₂)(dppe)(η-C₇H₇)][PF₆], 3, estimate the energy barrier to rotation about the W=C(α) bond as 62.5 ± 2 kJ mol⁻¹; approximately 10 kJ mol⁻¹ greater than for the molybdenum analogue. Deprotonation of 4 and 5 with KOBu(t) yields the alkynyls [W(C≡CR)(dppe)(η-C₇H₇)] (R = Ph, 6; C₆H₄-4-Me, 7) which undergo a reversible one-electron oxidation at a glassy carbon electrode in CH₂Cl₂ with E(½) values approximately 0.12 V negative of Mo analogues. The 17-electron radicals [6](+) and [7](+) have been investigated by spectroelectrochemical IR, UV-visible and EPR methods. The electronic structures of representative vinylidene (3) and alkynyl (6) complexes have been investigated at the B3LYP/Def2-SVP level. In both cases, electronic structure is characterised by a frontier orbital with significant metal d(z²)character and this dominates the structural and spectroscopic properties of the system.

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“…Cyclic voltammetric studies on [WI(CO)(PPh 3 )(t| 7 -C 7 H 7 )] in CH 2 C1 2 disclose a reversible one-electron oxidation process (E° = +0.49 V vs. saturated calomel electrode) and the chemically generated radical has been observed by IR and ESR spectroscopy. 345 The unusual hydride species [WH(CO)(L)(r| 7 …”

Section: [Mx(l) 2 (T) 7 -C 7 H 7 )] (X = Halide L = Co or Phosphorusmentioning

confidence: 99%

The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: synthesis and redox chemistry of some phosphine- and phosphite-substituted halide and acetonitrile derivatives

Cited by 25 publications

References 15 publications

(Cycloheptatrienyl)hydridotungsten Complexes

(Cycloheptatrienyl)hydridotungsten Complexes

Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(CCHR)(dppe)(η-C₇H₇)]⁺and [W(CCR)(dppe)(η-C₇H₇)]ⁿ⁺(n = 0 or 1)

π-Complexes of Chromium, Molybdenum and Tungsten, Excluding those of Cyclopentadienyls and Arenes

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The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: synthesis and redox chemistry of some phosphine- and phosphite-substituted halide and acetonitrile derivatives

Cited by 25 publications

References 15 publications

(Cycloheptatrienyl)hydridotungsten Complexes

(Cycloheptatrienyl)hydridotungsten Complexes

Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(CCHR)(dppe)(η-C7H7)]+and [W(CCR)(dppe)(η-C7H7)]n+(n = 0 or 1)

π-Complexes of Chromium, Molybdenum and Tungsten, Excluding those of Cyclopentadienyls and Arenes

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Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(CCHR)(dppe)(η-C₇H₇)]⁺and [W(CCR)(dppe)(η-C₇H₇)]ⁿ⁺(n = 0 or 1)