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Syntheses, Structures, and Stabilities of [PPh 4 ][WS 3 (SR)] (R = i Bu, i Pr, t Bu, Benzyl, Allyl) and [PPh 4 ][MoS 3 (S t Bu)]

2001; American Chemical Society; Volume: 40; Issue: 13 Linguagem: Inglês

10.1021/ic000970n

1520-510X

Naomi L. Kruhlak, Meiping Wang, P. Michael Boorman, Masood Parvez, Robert McDonald,

Metal complexes synthesis and properties

Intermediates in the condensation process of [MS4]2- (M = Mo, W) to polythiometalates, in the presence of alkyl halides, had not been reported prior to our communication of [PPh4][WS3(SEt)] (Boorman, P. M.; Wang, M.; Parvez, M. J. Chem. Soc., Chem. Commun. 1995, 999−1000). We now report the isolation of a range of related compounds, with 1°, 2°, and 3° alkyl thiolate ligands, including one Mo example. [PPh4][WS3(SR)] (R = iBu (1), iPr (2), tBu (3), benzyl (5), allyl (6)) and [PPh4][MoS3(StBu)] (4) have been isolated in fair to good yields from the reaction of [PPh4]2[MS4] with the appropriate alkyl halide in acetonitrile and subjected to analysis by X-ray crystallography. Crystal data are as follows: for 1, triclinic space group P1̄ (No. 2), a = 11.0377(6) Å, b = 11.1307(5) Å, c = 13.6286(7) Å, α = 82.941(1)°, β = 84.877(1)°, γ = 60.826(1)°, Z = 2; for 2, monoclinic space group P21/c (No. 14), a = 9.499(6) Å, b = 15.913(5) Å, c = 18.582(6) Å, β = 99.29(4)°, Z = 4; for 3, monoclinic space group P21/n (No. 14), a = 10.667(2) Å, b = 17.578(2) Å, c = 16.117(3) Å, β = 101.67(1)°, Z = 4; for 4, monoclinic space group P21/n (No. 14), a = 10.558(3) Å, b = 17.477(3) Å, c = 15.954(3) Å, β = 101.18(2)°, Z = 4; for 5, monoclinic space group P21/n (No. 14), a = 16.2111(9) Å, b = 11.0080(6) Å, c = 18.1339(10) Å, β = 111.722(1)°, Z = 4; for 6, triclinic space group P1̄ (No. 2), a = 9.4716(9) Å, b = 10.4336(10) Å, c = 14.4186(14) Å, α = 100.183(2)°, β = 90.457(2)°, γ = 91.747(2)°, Z = 2. Structures 3 and 4 are isomorphous, and 1 exhibits disorder about the tertiary carbon. 6 has been shown to exhibit fluxionality in solution by variable-temperature 1H NMR studies, and an allyl migration mechanism is implicated in this process. The kinetics for the reaction of [WS4]2- and EtBr were measured and suggest an associative nucleophilic substitution (SN2) mechanism. The decomposition of the [WS3(SEt)]- ion is shown to be second order with respect to this ion, suggesting the formation of a transient binuclear intermediate. M−S bond cleavage is the predominant step in decomposition of 1−6 to yield alkyl sulfides, alkyl thiols, and polythiometalates such as [PPh4]2[M3S9]. In contrast, reactions of [PPh4]2[WOxS4-x] (x = 1, 2) with tBuBr result in the additional decomposition product of isobutene, presumably by C−S bond cleavage and β-hydrogen transfer. Interestingly, the reaction of [PPh4]2[WOS3] with BzCl yields 5 as the only isolable W thiolate species.