Hydridostannylene Derivatives of Magnesium and Calcium.

Reactions of a m-terphenylhydridostannylene with β-diketiminato magnesium and calcium hydrides provide bis-μ-hydrido species, the heterobimetallic constitutions of which are maintained after the addition of THF donor solvent. In both cases, reactions with hex-1-ene result in the formation of tetravalent organostannyl alkaline earth derivatives. Whereas the magnesium reagent undergoes facile twofold addition, the calcium-centered process is arrested after a single alkene reduction event.

Nucleophilic Triphenylgermanides of Magnesium and Calcium.

The dimeric calcium and magnesium hydrides, [(BDI)AeH] [BDI=HC{(Me)CNDipp}, Dipp=2,6-i-PrCH; Ae=Mg or Ca] do not react with PhGeH in non-coordinating solvent. Addition of THF, however, induces deprotonation and access to monomeric Ae-germanide complexes, [(BDI)Ae{GePh}(THF)], both of which have been structurally characterized. Although this process is facile when Ae=Ca, the analogous magnesium-based reaction requires heating to temperatures >100 °C, under which conditions germanide formation is complicated by THF ring opening and the generation of an alkaline earth germyl-C-terminated n-butoxide, [(BDI)Mg{μ-O(CH)GePh}].

Variable Ca-C Hapticity and its Consequences in Arylcalcium Dimers.

The dimeric β-diketiminato calcium hydride, [( BDI)CaH] ( BDI = HC{(Me)CN-2,6-i-Pr C H } ), reacts with ortho-, meta- or para-tolyl mercuric compounds to afford hydridoarylcalcium compounds, [( BDI) Ca (μ-H)(μ-o-,m-,p-tolyl)], in which dimer propagation occurs either via μ -η -η or μ -η -η bridging between the calcium centers. In each case, the orientation and hapticity of the aryl units is dependent upon the position of the methyl substituent. While wholly organometallic meta- and para-tolyl dimers, [( BDI)Ca(m-tolyl)] and [( BDI)Ca(p-tolyl)] , can be prepared and are stable, the ortho-tolyl isomer is prone to isomerization to a calcium benzyl analog.

Beryllium-centred C-H activation of benzene.

Reaction of BeCl with the dilithium diamide, [{SiN}Li] ({SiN} = {CHSiMeNDipp}), provides the dimeric chloroberyllate, [{SiNBeCl}Li], en route to the 2-coordinate beryllium amide, [SiNBe]. Lithium or sodium reduction of [SiNBe] in benzene, provides the relevant organoberyllate products, [{SiNBePh}M] (M = Li or Na), the presumed intermediacy of transient Be(I) radicals.

Synthesis of Molecular Phenylcalcium Derivatives: Application to the Formation of Biaryls.

Hydrocarbon-soluble β-diketiminato phenylcalcium derivatives, which display various modes of Ca-μ -Ph-Ca bridging, are accessible from reactions of Ph Hg and [(BDI)CaH] . Although the resultant compounds are inert toward the C-H bonds of benzene, they yield selective and uncatalyzed biaryl formation when reacted with readily available aryl bromides.

A Benzodiphosphaborolediide.

The first example of a diphosphaborolediide, the benzo-fused [C H P BPh] (1 ), is prepared from ortho-bis(phosphino)benzene (C H {PH }) and dichlorophenylborane, via a sequential lithiation approach. The dilithio-salt can be obtained as an oligomeric THF solvate or discrete TMEDA adduct, both of which are fully characterized, including by X-ray diffraction. Alongside NICS calculations, data strongly suggest some aromaticity within 1 , which is further supported by preliminary coordination studies that demonstrate η -coordination to a zerovalent molybdenum center, as observed crystallographically for the oligomeric [{Mo(CO) (η -1)}{μ-η -Mo(CO) (TMEDA)} ] ⋅ [μ-Li(THF)][μ-Li(TMEDA)].

Diphosphametacyclophanes: Structural and Electronic Influences of Substituent Variation within a Family of Bis(diketophosphanyl) Macrocycles.

The condensation of MeP(SiMe) with a series of 5-substituted isophthaloyl chlorides (5-R'CH-2,6-{C(O)Cl}) affords the diphosphametacyclophanes -{-C(O)-CH-5-R'-(C(O)PMe)} (R' = I, Me, Bu, Ph, and -NCCH); the analogues -{-C(O)-CHN-(C(O)PMe)} and -{-C(O)-CH-(C(O)PPh)} are similarly obtained in preference to higher oligomers, in contrast to precedent reports. The cyclophanes all adopt butterfly-like conformations in the solid state with the P-organyl substituents adopting mutually arrangements. Structural and computational data suggest the nature of the 5-R substituent is key in directing the inter-ring angle and the extent of LUMO stabilization about the diketophophanyl scaffold.

Phosphacycloalkyldiones: synthesis and coordinative behaviour of 6- and 7-member cyclic diketophosphanyls.

Glutaryl and adipoyl chlorides undergo facile condensation with the bis(silyl)phosphanes RP(SiMe) (R = Me, Bu, Bu, Ph, Mes) to afford exclusively the phosphacycloalkyldiones (CH)(C[double bond, length as m-dash]O)PR (n = 3, 4). Characterised spectroscopically and, for R = Ph, Mes (n = 3) crystallographically, the macrocycles are conformationally fluxional in solution and appreciably moisture sensitive. Though seemingly resistant to chemical oxidation at phosphorus, coordination is readily achieved, as illustrated by isolation of trans-[Pt(PEt){P(Ph)(CO)(CH)}Cl] and a series of tungsten pentacarbonyl complexes, which are characterised crystallographically and by infrared and NMR spectroscopy.

Controlled Reactivity of Terminal Cyaphide Complexes: Isolation of the 5-Coordinate [Ru(dppe)(C≡P)].

The novel cyaphide complex -[Ru(dppe)Me(C≡P)] is obtained in excellent yields and exhibits the first instance of controlled reactivity of any terminal cyaphide complex. Its treatment with ZnX/PPh effects selective metathesis of the methyl moiety to afford the unprecedented halocyaphide complexes -[Ru(dppe)(X)(C≡P)] (X = Cl, Br, I), which are structurally characterized (X = Cl, Br). Exemplified with the -bromide, these compounds are susceptible to substitution of the halides by nucleophilic reagents-illustrated with MeMg-and also readily undergo halide abstraction by TlOTf to afford the first hypocoordinate cyaphide complex, viz.

Exploring the Reactivity of Donor-Stabilized Phosphenium Cations: Lewis Acid-Catalyzed Reduction of Chlorophosphanes by Silanes.

Phosphane-stabilized phosphenium cations react with silanes to effect either reduction to primary or secondary phosphanes, or formation of P-P bonded species depending upon counteranion. This operates for in situ generated phosphenium cations, allowing catalytic reduction of P(III)-Cl bonds in the absence of strong reducing agents. Anion and substituent dependence studies have allowed insight into the competing mechanisms involved.