Abstract:Three m-terphenyl ligands 2,6-Ar 2 C 6 H 3 -[Ar = 2,6-Me 2 C 6 H 3 (2,6-Xyl); 3,5-Me 2 C 6 H 3 (3,5-Xyl); 2,3,4,5,6-Me 5 C 6 (Pmp)] have been used to stabilise three series of two-coordinate Group 12 diaryl complexes; (2,6-Ar 2 C 6 H 3 ) 2 M [M = Zn, Cd, Hg; Ar = 2,6-Xyl 1-3; 3,5-Xyl 4-6; Pmp 7-9], where differing steric demands on the metal centres are imparted. These are the first homoleptic d-block complexes featuring any of these ligands. Complexes 1-9 have been characterised in solution and the solid state; the analysis of structural changes produced by differences in ligand properties is reported. In particular, complexes 4-6 show smaller C-M-C bond angles and contain secondary ligand interactions that are not seen in the analogous complexes 1-3 and 7-9. † Electronic supplementary information (ESI) available: Crystallographic data for complexes 1-9, molecular structures and crystallographic data for iodides 2,6-Ar 2 C 6 H 3 I (Ar = 2,6-Xyl, 3,5-Xyl, Pmp) and [2,

Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln') or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 degrees C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln'/Ae)(2)(Odpp)(3)](+) cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)(4)] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr(Odpp)(4)] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba(2)(Odpp)(4)] with [Mg(Odpp)(2)(thf)(2)] in toluene afforded [Ba(2)(Odpp)(3)][Mg(Odpp)(3)(thf)]. Analogous solution-based syntheses were not possible for [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive pi-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

The synthesis and characterization of a set of redox-active iron and ruthenium alkynyl complexes of general formula [[M]Cl (1-p) {C≡CC 6 H 5-m (C≡CFlu) m } (1+p) ][PF 6 ] n are reported (n = 0-1; m = 1-2; [M] = [Fe(η 5-C 5 Me 5)(κ 2-dppe)] and p = 1 or [M] = [trans-Ru(κ 2-dppe) 2 ] and p = 0-1). The linear and third-order nonlinear optical properties of these new organometallic complexes featuring phenylalkynyl ligands functionalized by 2-fluorenyl (Flu) groups were studied in their stable redox states. Their first electronic transitions are assigned with the help of DFT calculations. We show here that these compounds possess significant third-order NLO responses in the near-IR range for molecules of their size. In particular, the remarkably large 2PA activities of the new Ru(II) compounds in the 600-800 nm range (Z-scan) make them attractive nonlinear chromophores. Structure-property studies emphasize the importance of para-vs. meta-connection of the 2-fluorenylethynyl units on the phenylalkynyl core, and also reveal that upon progressing from mono-to bis-alkynyl complexes, a further increase of the 2PA cross-section can be obtained while maintaining linear transparency in the visible range.

Carbazole-carborane linear dyads and di(carbazole)-carborane V-shaped dyads with phenyleneethynylene-based bridges have been synthesized. The V-shaped dyads display the expected red-shifts in the location of their UV-Vis absorption maxima on bridge-lengthening, but show unusual blue-shifts in charge-transfer (CT) emission on the same π-system lengthening. These blue-shifts can be attributed to the 2n + 3 electron count within the carborane cluster in the excited state. The linear dyads luminesce via a combination of local excited (LE) and CT emission, with a red-shift in LE emission and a blue-shift in CT emission accompanying π-bridge elongation. A quantum efficiency as high as 86% in the solution state is achieved from the hybrid LE/CT emission. Time-dependent density functional theory (TD-DFT) calculations at the excited state of these compounds have clarified the photoluminescence blue-shift and suggested a typical cluster C-C bond elongation in the V-shaped dyads. Calculations on the elongated linear dyads have suggested that the electron density is localized at the phenyleneethynylene-containing bridge.

Redox transmetallation ligand exchange reactions involving a rare earth metal, 2,4,6-trimethylphenol (HOmes), and a diarylmercurial afford rare earth aryloxo complexes, which are structurally characterized. Both the lanthanoid contraction and the identity of the reaction solvent are found to influence the outcome of the reactions. Using THF in the reaction affords a dinuclear species [Ln2(Omes)6(thf)4].2THF (Ln=La 1, Nd 2) for the lighter rare earth metals, while a mononuclear species [Ln(Omes)3(thf)3] (Ln=Sm 3, Tb 5, Er 6, Yb 7, Y 8) is obtained for the heavier rare earth elements. Surprisingly, there is no change in metal coordination number between the two structural motifs. A divalent trinuclear linear complex [Eu3(Omes)6(thf)6] 4 is obtained for Eu, and features solely bridging aryloxide ligands. Using DME as the reaction solvent affords [La(Omes)3(dme)2] 9 from the reaction mixture, and [Ln2(Omes)6(dme)2].PhMe (La 10, Nd 11) and [Y(Omes)3(dme)2] 14 following crystallization of the crude product from toluene. The dinuclear species [Eu2(Omes)4(dme)4] 12 contains two unidentate and two chelating DME ligands, and contrasts the linear structure of 4. Treatment of HOmes and HgPh2 with Yb metal in DME affords the mixed valent Yb(II/III) complex [Yb2(Omes)5(dme)2] 13, which is stabilized by an intramolecular pi-Ph-Yb interaction, and is a rare example of a mixed valent rare earth aryloxide. Treatment of Er metal with HOmes at elevated temperature (solvent free) affords the homoleptic [Er4(Omes)12] 15, which consists of a tetranuclear array of Er atoms arranged in a 'herringbone' fashion; the structure is stabilized by intramolecular pi-Ph-Er interactions. Reaction of La metal with HOmes under similar conditions yields toluene insoluble "La(Omes)3", which affords 1 following extraction with THF.

Reaction between N,N′-bis(aryl)amidines and di-n-butylmagnesium affords magnesium amidinates, where the steric bulk of the ligand influences both the solid state and solution behaviour of these complexes.

Cobalt(II) diaryl complexes react with CO to afford Co(2)(CO)(8) and sterically encumbered ketones whose structure varies depending on the nature of the aryl ligands.

Treatment of an alkaline earth metal (Ca, Sr, Ba) with 2,4,6-trimethylphenol (HOmes) at elevated temperatures in the presence of mercury under solvent-free conditions, followed by extraction of the reaction mixture with 1,2-dimethoxyethane (dme), afforded dinuclear alkaline earth aryloxo complexes [Ae2(Omes)4(dme)4] (Ae = Ca 1, Sr 3, Ba 6). Extraction of the Ca metal and HOmes reaction mixture with thf afforded [Ca3(Omes)6(thf)] 2. In contrast, redox transmetallation ligand exchange reactions between an alkaline earth metal, diphenylmercury and HOmes in dme yielded solely 1 for Ca metal, a mixture of 3 and the methoxide bridged cage [Sr5(Omes)5(OMe)5(dme)4] x 2dme 4 for Sr metal, and solely [Ba5(Omes)5(OMe)5(dme)4] x dme 7 for Ba metal. The methoxide ligands originate from the C-O activation of the dme solvent. Treatment of liquid ammonia activated Sr or Ba metal with HOmes in thf afforded the linear species [Ae3(Omes)6(thf)6] (Ae = Sr 5, Ba 8), and 8 was also obtained from barium metal and HOmes in refluxing thf. The structures of 1 and 3, determined by X-ray crystallography, consist of two six coordinate Ae metal atoms, to each of which is bound a terminal aryloxide ligand, two bridging aryloxide ligands, and chelating and unidentate dme ligands. The structures of 4 and 7 contain five Ae metal atoms arranged on the vertices of a distorted square based pyramid. The Ae atoms are linked by four mu3-OMe ligands and a mu4-OMe ligand. Four bridging aryloxide ligands and four chelating dme ligands complete the coordination spheres of the four seven coordinate Ae atoms at the base of the pyramid, and a terminal aryloxide ligand is bound to the five coordinate apical Ae atom. The structures of 5 and 8 consist of a trinuclear linear array of Ae metal atoms, and contain solely bridging aryloxide ligands. Three thf ligands are bound to each terminal Ae atom, giving all Ae atoms a coordination number of six.