Syntheses, structures and spectroscopy of new heteroselenometalates

[PPh₄]₂[MoSe₄] and [PPh₄]₂[WSe₄] react with two equivalents of AuCN in CH₃CN to afford [PPh₄]₂[(NC)Au(μ-Se)₂-Mo(μ-Se)₂Au(CN)] · CH₃CN (bd1) and [PPh₄]₂[(NC)Au(μ-Se)₂Au(CN)] · CH₃CN (bd2), respectively. Compounds 1 and 2 are isostructural. Compound 1 crystallizes in the triclinic space group P1 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 F² led to a value of R₁=0.0562 for those 9075 data having F_o² . 2σ(F_o²). 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 [MoSe₄]^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 CH₃CH 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 PME₂Ph to the same solutions that produce 1 and 2 results in the formation of [PPh₄][(Me₂PhP)Au(μ-Se)₂MoSe₂] (3) and [PPh₄][(Me₂PhP)Au(μ-Se)₂WSe₂] (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 F² led to a value of R₁=0.0481 for those 6851 data having F_o² > 2σ(F_o²). Compound 4 crystallizes in the triclinic space group P1 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 F² led to a value of R₁=0.0414 for those 7825 data having F_o² > 2σ(F_o²). The [(Me₂]PhP)Au(μ-Se)₂MoSe₂]^- anion of 3 and the [(Me₂PhP)Au(μ-Se)₂WSe₂]^- anion of 4 comprise an [(Me₂PhP)Au]⁺ fragment ligated across an edge of a tetrahedral (MSe₄]^2- moiety. [PPh₄]₂[MoSe₄] and [PPh₄]₂[WSe₄] react with one equivalent of AuCN in CH₃CH to afford [PPh₄]₂[(NC)Au(μ-Se)₂MoSe₂] (5) and [PPh₄]₂[(NC)Au(μ-Se)₂WSe₂] (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 F² led to a value of R₁=0.0457 for those 4003 data having F_o² > 2σ(F_o²). The [(NC)Au(μ-Se)₂MoSe₂]^2- anion of 5, which has a crystallographically imposed twofold axis, comprises an AuCN fragment ligated across an edge of a tetrahedral [MoSe₄]^2- moiety. The reaction of [PPh₄]₂(NC)Cu(μ-Se)₂MoSe₂] with one equivalent of AuCN in CH₃CN produces a precipitate that is then redissolved through reaction with an excess of PMe₂Ph to afford [PPh₄][(Me₂PhP)₂Cu(μ-Se)₂MoSe₂] (7). Compound 7 crystallizes in the monoclonic space group P1₁/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 F² led to a value of R₁=0.0305 for those 5205 data having F_o² > 2σ(F_o²). The [(Me₂PhP)₂Cu(μ-Se)₂MoSe₂]^- anion of 7 comprises an [(Me₂PhP)₂Cu]⁺ fragment ligated across an edge of the [MoSe₄]^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.