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The synthesis, spectroscopy, structures and chemical reactivity of platinum(II) diolefin complexes cis-[(∥∧∥)PtCl2], cis-[(∥∧∥)PtCl(R)] and cis-[(∥∧∥)Pt(R)2] [∥∧∥ = chelate diolefin ligand: 1,5-cyclooctadiene (COD), 1,5-dimethylocta-1,5-diene (Me2COD), norbornadiene (NBD), 1,5-hexadiene (HEX), 3-allyloxypropene (All2O, diallyl ether), diallylamine (All2NH); R = Me, Bn, C6F5, C6F4H-4 (or -5), or C≡C(4-Me)Ph] have been explored. The relative exchange rates of the cis-[(∥∧∥)PtCl2] complexes towards the diimine ligand diisopropyl-1,4-diazabutadiene (iPr-DAB) increased along the series COD < Me2COD < NBD < HEX < All2O by a factor of 4. The presumably dimeric complex [(All2NH)PtCl2]2 undergoes a unique rearrangement process in dimethyl sulfoxide (DMSO) solution to yield the dimeric piperazine complex [PtCl(dmso)(C6H10N)]2, which has been characterised by single-crystal XRD. For selected platinum complexes, cytotoxic effects in HT-29 colon carcinoma and MCF-7 breast cancer cell lines were evaluated. For comparison, the dicationic complexes [(COD)Pt(Bn)(L)][PF6]2 with the very labile coligands N-methyl-4,4′-bipyridinium (MQ+) and N-methyl-1,4-pyrazinium (Mpz+) were added to the study. Although the hexadiene complexes [(HEX)Pt(C6F4H-4)2] and [(HEX)Pt(C6F4H-5)2] show strong cytotoxicity, the introduction of labile diolefin ligands or the labile cationic MQ+ or Mpz+ coligands does not generally lead to markedly increased cytotoxicity.

The reaction of HSC6F4H-4 or KSC6F4H-4 with the palladium(II) complexes [(NN)PdCl2] [NN = 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)] leads to the mononuclear palladium complexes [(NN)Pd(SC6F4H-4)2] or [(NN)PdCl(SC6F4H-4)], whereas the reaction with [(COD)PdCl2] (COD = 1,5-cyclooctadiene) results in the loss of COD and the formation of the oligonuclear species [Pd(SC6F4H-4)2]m. For NN = phen, the compound [(phen)2K(μ-phen)2K(phen)2][(4-HC6F4S)2Pd(μ-SC6F4H-4)2Pd(SC6F4H-4)2] containing a homoleptic dimeric dianionic Pd complex was also obtained. The reaction of KSC6F4H-4 with PdCl2 yielded K2[Pd(SC6F4H-4)4]. The new compounds were analysed and characterised by single-crystal XRD, 1H and 19F NMR spectroscopy and IR spectroscopy. The UV/Vis absorption spectroscopy and electrochemistry of [(bpy)Pd(SC6F4H-4)2] have been investigated and are compared to those of the related Pt derivative [(bpy)Pt(SC6F5)2].

The 1:1 (arene)mercury complexes [HgR2(arene)] [R = C6F4-o-NO2, C6F4-m-NO2, C6F4-o-H, C6F5; arene = TMB (1,2,4,5-tetramethylbenzene), PMB (1,2,3,4,5-pentamethylbenzene)] are readily formed when mixtures of the mercurial and arene are crystallised from CH2Cl2 or CH2Cl2/hexane. Analogous 1:1 complexes are also formed from Hg(C6F5)(2) and PhMe, whereas novel 1:2 complexes [HgR2(arene)(2)] result from Hg(C6F4-o-NO2)(2) and PhMe or TMO (1,2,4-trimethoxybenzene) and from Hg(C6F5)(2) and TMO. In the crystalline state, the 1:1 [HgR2(arene)] complexes exist as canted columns of alternating planar HgR2 and arene layers linked by weak (Hg center dot center dot center dot C 3.2-3.5 angstrom) eta(1) or eta(2) pi-arene-mercury interactions. For the TMB (R = C6F4-o-NO2, C6F4-o-H, C6F5) and PhMe (R = C6F5) complexes, the packing of neighbouring columns shows aligned, alternating fluoroarene and arene ring planes resulting in a 2D brick-wall motif with potential supramolecular components (fluoroarene-fluoroarene and fluoroarene-arene stacking). For the TMB complex with R = C6F4-m-NO2 the 2D array is distorted into a herringbone motif by weak C-H center dot center dot center dot O interactions. The 1:2 complex [Hg(C6F4-o-NO2)(2)-(PhMe)(2)] has an analogous mercury environment to the 1:1 complexes, and the packing shows a distinct layer structure of alternating rows of PhMe and HgR2 with two PhMe units per HgR2 unit but with no inter-stack interactions. The TMO complexes have long Hg center dot center dot center dot O contacts (3.2 angstrom.) rather than Hg center dot center dot center dot C and similarly show a layered structure, but in this case, with a single column of alternating HgR2 and pairs of TMO. Theoretical calculations for the 1:2 [HgR2(TMB)(2)] Complexes (R = C6F4-o-NO2, C6F4-m-NO2) are consistent with the findings from the observed crystal structures.

Reaction of chloropropyl-substituted stanna-closo-dodecaborate [Cl(CH 2 ) 3 SnB 1 1 H 1 1 ] - with the nucleophile Li[CH 2 PPh 2 ] provided a straightforward synthesis of an anionic phosphane [Ph 2 PCH 2 SnB 1 1 H 1 1 ] - . Derivatization of the phosphane was carried out in reaction with sulfur and hydrochloric acid to give [Bu 3 MeN][Ph 2 P(S)CH 2 SnB 1 1 H 1 1 ] and the zwitterion [Ph 2 P(H)CH 2 SnB 1 1 H 1 1 ]. In reaction with various transition metal electrophiles, complexation reactions were accomplished resulting in the isolation of trans-substituted palladium and platinum complexes [Bu 3 MeN] 2 [trans-(Ph 2 PCH 2 SnB 1 1 H 1 1 ) 2 MCl 2 ] (M = Pd, Pt), a neutral silver adduct [(acetone)Ag(Ph 2 PCH 2 SnB 1 1 H 1 1 )], and a linearly coordinated bisphosphane of gold [Bu 3 MeN][Au(Ph 2 PCH 2 -SnB 1 1 H 1 1 ) 2 ]. The solid state structures of the ligand salt, the palladium and gold coordination compounds were determined and discussed.

Nucleophilic substitution at (γ-chloropropyl)stanna-closododecaborate [Cl(CH2)3SnB11H11]− with RLi [R = Ph, Me2NC6H4, ferrocenyl (Fc)] and RMgBr (R = vinyl, benzyl) affords the substitution products containing the anion [RSnB11H11]−. The reaction products have been characterized by elemental analysis, NMR spectroscopy and in the cases where R = Ph, Me2NC6H4, Fc and vinyl by X-ray structure analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)