F. Geoffrey N. Cloke

Lipophilic strontium and calcium alkyls, amides and phenoxides; X-ray structures of the crystalline square-planar [{trans-Sr(NR′2)2(µ-1,4-dioxane)}∞] and tetrahedral [CaR2(1,4-dioxane)2]; R′= SiMe3, R = CH(SiMe3)2]

Treatment of pyrophoric strontium powder in tetrahydrofuran with ArOH (Ar = C6H2But3-2,4,6) or HNR′2 at ambient temperature affords crystalline [Sr(OAr)2(THF)4] or [Sr(NR′2)2(THF)2]3, respectively, and 3 with 1,4-dioxane yields crystalline [{trans-Sr(NR′2)2(µ-1,4-dioxane)}∞]4; co-condensation of calcium vapour and RBr in THF at 77 K affords [CaR2(THF)3]5, which with 1,4-dioxane gives [CaR2(1,4-dioxane)2]6; X-ray structures reveal the alkaline earth metal environment to be square-planar for 4[Sr-N 2.449(7), Sr-O 2.533(9)A] but tetrahedral for 6[Ca-C 2.483(5), Ca-O 2.373(4)A] with dioxane as a bridging bidentate 4 or monodentate 6 ligand.

An improved synthesis of bis(1,3-di-N-tert-butylimidazol-2-ylidene)palladium(0) and its use in C–C and C–N coupling reactions

A new, improved synthesis of [Pd{CN(tBu)(CH)2N(tBu)}2] (1) and its use as a catalyst in coupling reactions, including aminations, is presented. An interesting side product formed in the synthesis of 1, [Pd(?3-C4H7){(CN(tBu)(CH) 2N(tBu)}Cl] (2), is also discussed.

Novel zirconium complexes derivedfrom C2-symmetric diamide ligands; the X-ray crystal structure of [Zr(η1-CH2Ph)(η2-CH2Ph){(C6H3)2-2,2′-(NCH2C6H4Ph-4)2-6, 6′-Me2}]

Abstract The novel alkene polymerisation cocatalysts [Zr(CH 2 Ph) 2 (ArDABP)] containing the biphenyl-ligands 2,2′-di-(N-benzyl)amino-6,6′ dimethylbiphenyl (ArDABP, Ar = CH 2 C 6 H 4 t Bu-4 or CH 2 C 6 H 4 -Ph) display averaged C 2 -symmetry in solution and an η 2 -benzyl coordination mode in the solid state.

Axial coordination of NHC ligands on dirhodium(II) complexes: Generation of a new family of catalysts

An efficient new methodology for the arylation of aldehydes is disclosed which uses dirhodium(II) catalysts and N-heterocyclic carbene (NHC) ligands. Complexes of Rh 2(OAc) 4 with one and two NHCs attached on the axial positions were successfully isolated, fully characterized, and used as catalysts in the reaction. The saturated monocomplex ((NHC 5)Rh 2(OAc) 4) 31 was shown to be the most active catalyst and was particularly efficient in the arylation of alkyl aldehydes. DFT calculations support participation of complexes with one axial NHC in the reaction as the catalysts active species and indicate that hydrogen bonds involving dirhodium unit, reactants, and solvent (alcohol) play an important role on the reaction mechanism.

Facile Conversion of CO/H2 into Methoxide at a Uranium(III) Center†

The reaction of [U(-C8H6{SiiPr3-1,4}2)(-Cp*)] in toluene with CO and H2 at sub to ambient temperature and pressure affords the methoxide complex [U(-C8H6{SiiPr3-1,4}2)(-Cp*)OMe]

The First Delocalized Phosphole Containing a Planar Tricoordinate Phosphorus Atom: 1-[Bis(trimethylsilyl)methyl]-3,5-bis(trimethylsilyl)-1,2,4-triphosphole

The sterically demanding groups on the tricoordinate phosphorus atom, the π-electron acceptors substituted on the ring, and the dicoordinate phosphorus atoms within the ring are the most significant factors contributing to the planarity and aromaticity of the 1,2,4-triphosphole ring in 1. The Bird aromaticity index for 1 shows that it has the most pronounced aromatic character of all known phospholes.

Titanium(IV) complexes incorporating the aminodiamide ligand [(SiMe3)N CH2CH2 N(SiMe3)]2−(L) ; the X-ray crystal structures of [TiMe2(L) ] and [TiClCH(SiMe3)(L)]

Abstract The reaction of the lithium salt of the aminodiamide ligand Lie[(SiMe 3) N(CH 2 CH 2 N(SiMe 3 ) 2 (Li 2 L) 1 with [TiCl 4 (THF) 2 ] (THF = tetrahydrofuran) forms [TiCl 2 (L)] 2 , from which Ti IV mono and dialkyl complexes are accessible. The treatment of 2 with Me 2 Mg, LiCH 2 (SiMe 3 ) or LiCH(SiMe 3 ) 2 results in the formation of [TiMe 2 (L) 3 , [Ti(CH 2 (SiMe 3 ) 2 (L)] 4 or [TiCI{CH(SiMe 3 ) 2 }(L)] ( 5 ) respectively, in which only partial coordination of the amino-nitrogen is observed in solution and the solid state. The X-ray crystal structures of 3 and 5, and an improved synthesis of 1, are described.

Trimethylsilyl derivatives of cyclooctatetraene

Abstract An improved, large scale synthesis of 5,8-bis(trimethylsilyl)cycloocta-1,3,6-triene is described. The compound may be deprotonated with n-butyllithium/THF or n-butyllithium/TMEDA to afford stable dilithium salts of the 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion, which may be oxidised with mercuric chloride to give free bis(trimethylsilyl)cyclooctatetraene as a mixture of the 1,4- and 1,6-isomers. Treatment of the bis(trimethylsilyl)cyclooctatetraenyl dianion with an excess of chlorotrimethylsilane gives 2,5,5,8-tetrakis(trimethylsilyl)cycloocta-1,3,6-triene.

Organometallic pentalene complexes

There has been a recent renaissance in the organometallic chemistry of pentalene, following the discovery of the first complexes incorporating pentalene η8-ligated to a single metal center. This short review outlines recent work in the authors laboratory on the preparation of silylated pentalene ligands and the subsequent synthesis of novel, monometallic, and bimetallic pentalene sandwich and half-sandwich complexes of the f- and d-block elements.

Zirconium complexes incorporating the new tridentate diamide ligand [(Me3 Si)N{CH2CH2N(SiMe3)}2]2–(L); the crystal structures of [Zr(BH4)2L] and [ZrCl{CH(SiMe3)2}L]

The lithium complex of the sterically demanding, polyfunctional amide ligand [(Me3Si)N-{CH2CH2N(SiMe3)}2]2–,Li2L reacted with [ZrCl4(thf)2](thf = tetrahydrofuran) to form dimeric [(ZrCl2L)2]2, in which the ligand is facially co-ordinated in a tridentate manner. Treatment of 2 with LiBH4 or Li[CH(SiMe3)2] generated [Zr(H3BH)L]3 and [ZrCl{CH(SiMe3)2}L]4, respectively. Variable-temperature NMR studies on 4 give evidence for restricted rotation of both the alkyl and amino SiMe3 groups. The crystal structures of 3 and 4 have been determined.