Nickel thioether chemistry: synthesis, structures and electrochemistry of five-co-ordinate nickel( II ) complexes of [9]aneS ₃ . Crystal structures of [Ni([9]aneS ₃ )-(dppm)][PF ₆ ] 2′ , [Ni([9]aneS ₃ )(dcpe)][PF ₆ ] ₂ ·1.25MeCN and [Ni([9]aneS ₃ )(tdpme)][PF ₆ ] ₂ {[9]aneS ₃ = 1,4,7-Trithiacyclononane, dppm = Ph ₂ PCH ₂ PPh 2′ , dcpe =(C ₆ H ₁₁ ) ₂– PC ₂ H ₄ P(C ₆ H ₁₁ ) 2′ , tdpme = CH ₃ C(CH ₂ PPh ₂ ) ₃ }

Reaction of [Ni(L–L)Cl2]{L–L = Ph2PCH2PPh2(dppm), R2PCH2CH2PR2[R = Ph (dppe), C6H11(dcpe) or Me (dmpe)], cis-Ph2PCHCHPPh2(dppv), Ph2PCH2CH2CH2PPh2(dppp) or MeC(CH2PPh2)3(tdpme)} with 1 molar equivalent of 1,4,7-trithiacyclononane([9]aneS3) afforded the complex cations [Ni([9]aneS3)(L–L)]2+. The crystal structures of [Ni([9]aneS3)(dppm)][PF6]2, [Ni([9]aneS3)(dcpe)][PF6]2·;1.25MeCN and [Ni([9]aneS3)(tdpme)][PF6]2 showed five-co-ordinate complexes with distorted square-pyramidal geometries about the nickel(II) centres with the S-donors of [9]aneS3 occupying two basal and the apical position, Ni–Sapical 2.40–2.65 Å, Ni–Pbasal 2.17–2.22 Å. The complex [Ni([9]aneS3)(dppm)][PF6]2 crystallises in triclinic space group P, a= 10.9748(25), b= 13.9702(20), c= 15.7688(24)Å, α= 80.071(7), β= 70.817(8), γ= 76.441(8)°, Dc= 1.374 g cm–3, Z= 2; [Ni([9]aneS3)(dcpe)][PF6]2·;1.25MeCN crystallises in triclinic space group P, a= 12.432(8), b= 13.382(4), c= 15.070(6)Å, α= 86.83(2), β= 70.47(2), γ= 77.28(2)°, Dc= 1.445 g cm–3, Z= 2; [Ni([9]aneS3)(tdpme)][PF6]2 crystallises in monoclinic space group Cc, a= 10.7597(16), b= 37.399(5), c= 13.104(3)Å, β= 103.746(11)°, Dc= 1.491 g cm–3, Z= 4. Cyclic voltammetry of the complexes [Ni([9]aneS3)(L–L)][PF6]2 in MeCN (0.1 mol dm–3 NBu4PF6) at 293 K at platinum electrodes showed one chemically reversible and one quasi-reversible one-electron reduction at 1E1/2=–0.77 to –1.16 V, 1Ep= 61–92 mV, 2E1/2=–1.31 to –1.93 V vs. ferrocene–ferrocenium. On the basis of ESR and electronic spectroscopy, these reduction products are assigned as pyraidal d9 nickel(I)[Ni([9]aneS3)(L–L)]+ with binding of both P-donors retained, and tetrahedral d10 nickel(0)[Ni([9]aneS3)(L–L)]0 species respectively. The reaction of [Ni([9]aneS3)(L–L)]+ with CO in MeCN is discussed.