Reactions of Ph₃Sb═S with Copper(I) Complexes Supported by N-Donor Ligands: Formation of Stable Adducts and S-Transfer Reactivity

Abstract

In the exploration of sulfur-delivery reagents useful for synthesizing models of the tetracoppersulfide cluster of nitrous oxide reductase, reactions of Ph 3 Sb=S with Cu(I) complexes of N,N,N', and 1,4,7-trialkyltriazacyclononanes (R 3 tacn; R = Me, Et, iPr) were studied. Treatment of [(R 3 tacn)Cu(NCCH 3 )]SbF 6 (R = Me, Et, or iPr) with one equivalent of S=SbPh 3 in CH 2 Cl 2 yielded adducts [(R 3 tacn)Cu(S=SbPh 3 )]SbF 6 (1-3), which were fully characterized, including by X-ray crystallography. The adducts slowly decayed to [(R 3 tacn) 2 Cu 2 (µ-η 2 : η 2 -S 2 )] 2+ species (4-6) and SbPh 3 , or more quickly in the presence of additional [(R 3 tacn)Cu(NCCH 3 )]SbF 6 to 4-6 and [(R 3 tacn)Cu(SbPh 3 )]SbF 6 (7-9). The results of mechanistic studies of the latter process were consistent with rapid intermolecular exchange of S=SbPh 3 between 1-3 and added [(R 3 tacn)Cu(NCCH 3 )]SbF 6 , followed by conversion to product via a dicopper intermediate formed in a rapid pre-equilibrium step. Key evidence supporting this step came from the observation of saturation behavior in a plot of the initial rate of loss of 1 versus the initial concentration of [(Me 3 tacn)Cu(NCCH 3 )]SbF 6 . Also, treatment of [(TMCHD)Cu(CH 3 CN)]PF 6 with S=SbPh 3 led to the known tricopper cluster [(TMCHD) 3 Cu 3 (µ 3 -S) 2 ](PF 6 ) 3 in good yield (79%), a synthetic procedure superior to that previously reported (Brown, E. C.; York, J. T.; Antholine, W. E.; Ruiz, E.; Alvarez, S.; Tolman, W. B.

X-ray Absorption Spectroscopic and Computational Investigation of a Possible S···S Interaction in the [Cu3S2]3+ Core

“…18 Because 1 is extremely air sensitive, sample manipulation and loading into the XAS cells were performed in an inert atmosphere glove box. Samples were prepared for both solution (5 mM in CH 2 Cl 2 ) and polycrystalline Cu K-edge XAS measurements.…”

Covalently bonded compounds of heavy group 15/16 elements – Synthesis, structure and potential application in material sciences

“…The Sb-S bond length of Et 3 SbS (2.381(7) Å), which is in between the calculated values for a Sb-S single bond (∑ cov (Sb,S) = 2.43 Å) [59] and a Sb=S double-bond (∑ cov (Sb,S) = 2.27 Å), [117] is significantly longer than that observed in Ph 3 Sb=S (2.244(1) Å). [30,31] Moreover, (Me 3 SbS) 2 Me 2 SnCl 2 (2.230(3 Å) [110] as well as three recently structurally characterized copper complexes of Ph 3 SbS (2.2735(9), 2.2812(7), 2.2832(7) Å) [111] show significantly shorter Sb-S bonds.…”

“…[30,31,32] In addition, transition metal and main group metal compounds of R 3 SbS were reported. [110,111] In contrast, solid state structures of selenostiboranes R 3 SbSe remained unknown, except for a single report, that describes their capability to serve as ligand in coordination chemistry. [112] Ph 3 SbS (2.244(1) Å) exhibits a short Sb-S bond, [113] which was described by Pebler as partial double bond due to dπ-pπ interaction.…”

Copper

“…The sulfur transfer reagent, [SQSbPh 3 ], was reacted with copper(I) complexes in an attempt to synthesize model compounds for this enzyme. 61 It was found that initially formed adducts underwent slow decay in solution to form dinuclear dications containing the (m-Z 2 : Z 2 -S 2 ) ligand. Nitrosobenzene, PhNO, is an isoelectronic analogue of singlet oxygen used as a probe in copper(I) models of mononuclear monooxygenase enzymes.…”