Syntheses, structures and spectroscopy of new heteroselenometalates

Abstract

[PPh 4] 2[MoSe 4] and [PPh 4] 2[WSe 4] react with two equivalents of AuCN in CH 3CN to afford [PPh 4] 2[(NC)Au(μ-Se) 2-Mo(μ-Se) 2Au(CN)] · CH 3CN (bd1) and [PPh 4] 2[(NC)Au(μ-Se) 2Au(CN)] · CH 3CN (bd2), respectively. Compounds 1 and 2 are isostructural. Compound 1 crystallizes in the triclinic space group P 1 with two formula units in a cell dimensions a=13.181(4), b=14.239(4), c=14.684(4) A ̊ , α=73.00(3), β=73.66(2), γ=79.06(2)° at 113 K. Full anisotropic refinement of the structure of 1 on F 2 led to a value of R 1=0.0562 for those 9075 data having F o 2 . 2 σ( F o 2). The [(NC)Au(μ-Se) 2Mo(μ-Se) 2Au(CN)] 2− anion of 1 comprises two AuCN fragments ligating the opposite edges of a tetrahedral [MoSe 4] 2− moiety. Compounds 1 and 2 exhibit an IR band at 2250 cm −1 that may be assigned to a CN stretching mode of the CH 3CH solvate; such a solvate molecule was found in the crystal structure of 1. The 77Se NMR spectra show a resonance at 1104 ppm for 1 and 832 ppm for 2. Addition of excess PME 2Ph to the same solutions that produce 1 and 2 results in the formation of [PPh 4][(Me 2PhP)Au(μ-Se) 2MoSe 2] ( 3) and [PPh 4][(Me 2PhP)Au(μ-Se) 2WSe 2] ( 4), respectively. Compounds 3 and 4 are not isostructural. Compound 3 crystallizes in the monoclinic space gorup Cc with four formula units in a cell of dimensions a=21.912(4), b=9.809(2), c=15.959(3) A ̊ , β=100.79(3) at 113 K. Full anisotropic refinement of the structure of 1 on F 2 led to a value of R 1=0.0481 for those 6851 data having F o 2 > 2 σ( F o 2). Compound 4 crystallizes in the triclinic space group P 1 with two formula units in a cell of dimensions a=11.315(2), b=13.053(3), c=14.173(3) A ̊ , α=103.59(3), β=103.55(3), γ=114.75(3)δ at 113 K. Full anisotropic refinement of the structure of 4 on F 2 led to a value of R 1=0.0414 for those 7825 data having F o 2 > 2 σ( F o 2). The [(Me 2]PhP)Au(μ-Se) 2MoSe 2] − anion of 3 and the [(Me 2PhP)Au(μ-Se) 2WSe 2] − anion of 4 comprise an [(Me 2PhP)Au] + fragment ligated across an edge of a tetrahedral (MSe 4] 2− moiety. [PPh 4] 2[MoSe 4] and [PPh 4] 2[WSe 4] react with one equivalent of AuCN in CH 3CH to afford [PPh 4] 2[(NC)Au(μ-Se) 2MoSe 2] ( 5) and [PPh 4] 2[(NC)Au(μ-Se) 2WSe 2] ( 6), respectively. Compounds 5 and 6 are isostructural. Compounds 5 crystallizes in the monoclinic space group C2/ c with four formula units in a cell of dimensions a=11.234(15), b=20.329(28), c=20.046(28) A ̊ , β=91.81(5)° at 113 K. Full anisotropic refinement of the structure of 5 on F 2 led to a value of R 1=0.0457 for those 4003 data having F o 2 > 2 σ( F o 2). The [(NC)Au(μ-Se) 2MoSe 2] 2− anion of 5, which has a crystallographically imposed twofold axis, comprises an AuCN fragment ligated across an edge of a tetrahedral [MoSe 4] 2− moiety. The reaction of [PPh 4] 2(NC)Cu(μ-Se) 2MoSe 2] with one equivalent of AuCN in CH 3CN produces a precipitate that is then redissolved through reaction with an excess of PMe 2Ph to afford [PPh 4][(Me 2PhP) 2Cu(μ-Se) 2MoSe 2] ( 7). Compound 7 crystallizes in the monoclonic space group P1 1/ c with four formula units in a cell of dimensions a=9.975(1), b=30.391(7), c=14.541(6) A ̊ , β=109.66(3) at 113 K. Full anisotropic refinement of the structure of 7 on F 2 led to a value of R 1=0.0305 for those 5205 data having F o 2 > 2 σ( F o 2). The [(Me 2PhP) 2Cu(μ-Se) 2MoSe 2] − anion of 7 comprises an [(Me 2PhP) 2Cu] + fragment ligated across an edge of the [MoSe 4] 2− moiety to provide a tetrahedral geometry about the Cu atom. The NMR, IR and UV-Vis spectroscopic data for these compounds are consistent with their solid-state structures.