Amy L. Gillon

Synthetic crystallography: synthon mimicry and tecton elaboration in metallate anion salts

The use of molecular tectons (building blocks) able to form cyano-based hydrogen bonded synthons (NH⋯NC) to synthesise a diverse range of crystal structures is described. Square planar dianionic metal complexes with 4 terminal cyano groups are shown to form salts with the dications [4,4′-H2bipy]2+ and [4,4′-H2bipip]2+ in which hydrogen bond networks of varying dimensionality are formed. The structures of new salts of these cations with [M(CN)4]2−, [M(SCN)4]2−, and [M(mnt)2]2− (M = Pt, and in one case Pd) are reported and compared with those of analogous [MCl4]2− and [M(dtox)2]2− salts. The consequences of the stereochemical preference of the cyano group for linear CN⋯H hydrogen bonding and the prospects for the elaboration of cyano-functionalised tectons to afford chemical and structural diversity in the structures synthesised are discussed.

Towards polymorphism control in coordination networks and metallo-organic salts

[{(4,4′-bipy)ZnCl2}n] (4) is known in three different polymorphs, in the space groups C2/c (4a), Pnma (4b) and Pban (4c). Solution synthesis produces a mixture of 4a and 4b, but solid-state synthesis, either by grinding together 4,4′-bipy and ZnCl2 or by heating [4,4′-H2bipy][ZnCl4] 3 to thermally eliminate HCl, generates only the 4b form, demonstrating that solid-state synthesis can exert control over polymorph formation; other solid-state preparations of 4 such as reaction of basic zinc carbonate with [4,4′-H2bipy]Cl2 or reaction of [4,4′-H2bipy][ZnCl4] 3 with KOH also increase the amount of 4b generated relative to the solution synthesis. It is also possible to form the mixed-metal phases [{(4,4′-bipy)Co1−xZnxCl2}n] 4x as effectively homogeneous solid-solutions by the same techniques, and when x 0.5, the amount of this polymorph is still greater than would be expected for a predominantly zinc-containing phase.

Biarylphosphonites: a class of monodentate phosphorus(III) ligands that outperform their chelating analogues in asymmetric hydrogenation catalysis

Rhodium(I) complexes of monodentate phosphonites derived from 2,2′-binaphthol and 9,9′-biphenanthrol are compared with diphosphonite chelate analogues as catalysts for asymmetric hydrogenation; the high ee’s (up to 92%) obtained with the monodentate systems and the observation that they are sometimes superior to the chelate analogues are discussed.

Homologous families of chloride-rich 4,4′-bipyridinium salt structures

New layer and three-dimensional 4,4′-bipyridinium salts of Cl−, [MCl6]2− (M = Os, Pt) and [FeCl5]2− contain NH⋯(Cl)2⋯HN interactions which form hydrogen bonded ribbons which in turn give one-, two-, or three-dimensional periodic networks; two related families of homologous motifs are present in these salts together with those of square planar, polymeric and tetrahedral [MCl4]2− (M = Pt, Pd, Mn, Cd, Pb, Co, Zn, Hg), planar [Cu2Cl6]2− and square pyramidal [SbCl5]2− dianions.

Synthesis and reactivity of μ-butadienyl diruthenium cations

Abstract Propargyl alcohols HCCCR 2 OH (R=H, Me or Ph) react with [Ru 2 (CO)(MeCN)(μ-CO)(μ-CH 2 )(η-C 5 H 5 ) 2 ] ( 2 ) to form the allylidene complexes [Ru 2 (CO)(μ-CO){μ-η 1 ,η 3 -C(CR 2 OH)CHCH 2 }(η-C 5 H 5 ) 2 ] ( 4a , R=H; 4b , R=Me; 4c , R=Ph). Treatment of complexes 4a – c with HBF 4 removes the hydroxide group as water, giving the 2-butadienyl complexes [Ru 2 (CO)(μ-CO)(μ-η 2 ,η 3 -CR 2 CCHCH 2 )(η-C 5 H 5 ) 2 ][BF 4 ] ( 5a , R=H; 5b , R=Me; 5c , R=Ph). The reactivity of 5a – c towards nucleophiles and bases is described. With hydride, 5a – c undergo nucleophilic attack at the C(R 2 ) carbon to give the allylidene complexes [Ru 2 (CO)(μ-CO){μ-η 1 ,η 3 -C(CR 2 H)CHCH 2 }(η-C 5 H 5 ) 2 ] ( 6a , R=H; 7 , R=Me; 11 , R=Ph) and, in the case of 5c , the butadiene complex [Ru 2 (CO) 2 (μ-η 2 ,η 2 -CPh 2 CHCHCH 2 )(η-C 5 H 5 ) 2 ] ( 12 ) and the allene complex [Ru 2 (CO) 2 (μ-η 2 ,η 2 -CPh 2 CCHMe)(η-C 5 H 5 ) 2 ] ( 13 ), formally due to attack at the μ-C and CH 2 carbons, respectively. The complexes 5a – c react with methyl lithium to undergo nucleophilic attack predominantly at the C(R 2 ) carbon, giving methylated allylidene complexes [Ru 2 (CO)(μ-CO){μ-η 1 ,η 3 -C(CR 2 Me)CHCH 2 }(η-C 5 H 5 ) 2 ] ( 6b , R=Me; 9 , R=Me; 14 , R=Ph). With 5b and 5c methyl lithium also acts as a base, abstracting protons to give the novel divinylcarbene complex [Ru 2 (CO)(μ-CO){μ-η 1 ,η 3 -C(CMeCH 2 )CHCH 2 }(η-C 5 H 5 ) 2 ] ( 8 ) and the μ-butatriene complex [Ru 2 (CO) 2 (μ-η 2 ,η 2 -CPh 2 CCCH 2 )(η-C 5 H 5 ) 2 ] ( 15 ), respectively. Complexes 8 and 15 are formed exclusively by treating 5b and 5c , respectively, with diazabicyclo[5.4.0]undec-7-ene (DBU). Complexes 8 and 9 were also prepared in good yield by reaction of complex 2 with 2-methyl-1-buten-3-yne {CH 2 C(Me)CCH} and t-butylacetylene, respectively. Treatment of complex 8 with HBF 4 resulted in protonation at each of the methylene groups, affording 5b and isomeric [Ru 2 (CO)(μ-CO){μ-η 2 ,η 3 -CH(Me)CC(Me)CH 2 }(η-C 5 H 5 ) 2 ][BF 4 ] ( 10 ). The structures of 5b , 5c and 8 were established by X-ray diffraction.

Steric activation of chelate catalysts: efficient polyketone catalysts based on four-membered palladium(II) diphosphine chelates

Palladium(II) complexes of ligands of the type Ar2PCH2- PAr2 and Ar2PN(Me)PAr2 (Ar = ortho-substituted phenyl group) are very efficient catalysts for copolymerisation of CO and C2H4.

Cation-controlled formation of [{MCl4}n]2n– chains in [4,4′-H2bipy][MCl4] (M = Mn, Cd): an alternative to the A2MCl4 layer perovskite structure†

The cis-MCl2‥HN+ chelated hydrogen bond synthon has been exploited in preparation of crystalline [4,4′- H2bipy][MCl4] (M = Mn 2 and Cd 3), which shows a one-dimensional substructure of the form [{MCl4}n]2n– consisting of a kinked chain of doubly edge sharing MCl6 octahedra. These chains are cross-linked by hydrogen bonding to the [4,4′-H2bipy]2+ ions.

Rationally designed improvement of the bis(phospholano)ethane ligand for asymmetric hydrogenation leads to a reappraisal of the factors governing the enantioselectivity of duphos catalysts

Enhancement of enantioselectivity in hydrogenations catalysed by δ vs. λ rhodium chelate complexes of trans-1,2-bis(phospholano)cyclopentanes cannot be rationalised using the current quadrant model for Duphos ligands and therefore a new consistent model is suggested.