A homoleptic tris(diphosphacyclobutadiene) tripledecker sandwich complex.

The synthesis and characterisation of [Co2(η4-P2C2tBu2)2(µ:η4:η4-P2C2tBu2)] (1) is described, featuring two cobalt atoms and three diphosphacyclobutadiene ligands. This compound is the first triple-decker sandwich complex which exclusively contains cyclobutadiene ligands.

Direct catalytic transformation of white phosphorus into arylphosphines and phosphonium salts.

Phosphorus compounds are ubiquitous in the chemical sciences, finding applications throughout industry and academia. Of particular interest to synthetic chemists are organophosphorus compounds, which contain P-C bonds. However, state-of-the-art processes for the synthesis of these important materials rely on an inefficient, stepwise methodology involving initial oxidation of white phosphorus (P4) with hazardous chlorine gas and the subsequent displacement of chloride ions. Catalytic P4 organofunctionalisation reactions have remained elusive, as they require multiple P-P bond breaking and P-C bond formation events to break down the P4 core, all of which must occur in a controlled manner. Herein, we describe an efficient transition metal-catalyzed process capable of forming P-C bonds from P4. Using blue light photocatalysis, this method directly affords valuable triarylphosphines and tetraarylphosphonium salts in a single reaction step.

Flexidentate Coordination Behavior and Chemical Non-Innocence of a Bis(1,3-Diphosphacyclobutadiene) Sandwich Anion.

The homoleptic 1,3-diphosphacyclobutadiene sandwich complex [Co(η4 -1,3-P2 C2 tBu2 )2 ]- behaved as a versatile and highly flexible metalloligand toward Ni2+ , Ru2+ , Rh+ , and Pd2+ cations, forming a range of unusual oligonuclear compounds. The reaction of [K(thf)2 {Co(η4 -1,3-P2 C2 tBu2 )2 }] with [Ni2 Cp3 ]BF4 initially afforded the σ-complex [CpNi{Co(η4 -1,3-P2 C2 tBu2 )2 }(thf)] (2), which converted into [Co(η4 -CpNi{1,3-P2 C2 tBu2 -κP,κC})(η4 -1,3-P2 C2 tBu2 )] (3) below room temperature. The structure of 3 contains an unprecedented 1,4-diphospha-2-nickelacyclopentadiene moiety formed by an oxidative addition of a ligand P-C bond onto nickel. At elevated temperatures, 3 isomerized to [Co(η4 -CpNi{1,4-P2 C2 tBu2 -κ2 P,P})(η4 -1,3-P2 C2 tBu2 )] (4), which features a 1,3-diphospha-2-nickelacyclopentadiene unit. Transmetalation of [K(thf)2 {Co(η4 -1,3-P2 C2 tBu2 )2 }] with [Cp*RuCl]4 (Cp*=C5 Me5 ) afforded tetranuclear [(Cp*Ru)3 (µ-Cl)2 {Co(η4 -1,3-P2 C2 tBu2 )2 }] (5), in which the [Co(η4 -1,3-P2 C2 tBu2 ]- anion acts as a chelate ligand toward Ru2+ . The diphosphido complex [(Cp*Ru)2 (µ,η2 -P2 )(µ,η2 -C2 tBu2 )] (6) was formed as a byproduct. Pure compound 6 was isolated after prolonged heating of the reaction mixture. The reaction of [K(thf)2 {Co(η4 -1,3-P2 C2 R2 )2 }] (R=tBu; adamantyl, Ad) with [RhCl(cod)]2 (cod=1,5-cyclooctadiene) afforded unprecedented π-complexes [Rh(cod){Co(η4 -1,3-P2 C2 R2 )2 }] (7: R=tBu; 8: R=Ad), in which one µ:η4 :η4 -P2 C2 R2 ligand bridges two metal atoms. The pentanuclear complex [Pd3 (PPh3 )2 {Co(η4 -1,3-P2 C2 tBu2 )2 }2 ] (10), featuring a Pd3 chain and a rare 1,4-diphospha-2-butene ligand, was synthesized by reacting [K(thf)2 {Co(η4 -1,3-P2 C2 tBu2 )2 }] with cis-PdCl2 (PPh3 )2 . The redox properties of selected compounds were analyzed by cyclic voltammetry, whereas DFT calculations gave additional insight into the electronic structures. The results of this study revealed several remarkable and previously unrecognized properties of the [Co(P2 C2 tBu2 )2 ]- anion.

1,3-Diphosphacyclobutene Cobalt Complexes.

The synthesis and characterization of rare 1,3-diphosphacyclobutene transition-metal complexes is described. Reactions of the cobalt-hydride complex [Co(P2 C2 tBu2 )2 H] (G) with nBuLi, tBuLi, or PhLi afforded [Li(solv)x {Co(η3 -P2 C2 tBu2 HR)(η4 -P2 C2 tBu2 )}] (1: R=nBu, (solv)x =(Et2 O)2 ; 2: R=tBu, (solv)x =(thf)2 ; 3: R=Ph, (solv)x =(Et2 O)(thf)2 ), with an η3 -coordinated 1,3-diphosphacyclobutene ligand as a result of organyl-anion attack at one of the phosphorus atoms of the bis(1,3-diphosphacyclobutadiene) backbone. In contrast to the reactions with PhLi, the aryl-magnesium compounds p-tolyl magnesium chloride and p-fluorophenyl magnesium bromide deprotonate [Co(P2 C2 tBu2 )2 H] to give the magnesium salt [Mg(MeCN)6 ][Co(η4 -P2 C2 tBu2 )2 ]2 (4), which contains a bis(1,3-diphosphacyclobutadiene)-cobaltate anion. The [Co(η4 -P2 C2 tBu2 )2 ]- anions are well separated from the octahedral [Mg(MeCN)6 ]2+ cation in the molecular structure of 4. Compound 1 reacts with Me3 SiCl to give neutral [Co(η3 -P2 C2 tBu2 HnBu)(η4 -P2 C2 tBu2 SiMe3 )] (5, 52 % yield) with an SiMe3 group attached to one of the P atoms of the previously unfunctionalized backbone.

Synthesis of a Cyclic Co2Sn2 Cluster Using a Co- Synthon.

[Ar'SnCo]2 (1, Ar' = C6H3-2,6{C6H3-2,6- iPr2}2), a rare metal-metal bonded cobalt-tin cluster with low-coordinate tin atoms, was prepared by the reaction of [K(thf)0.2][Co(1,5-cod)2] (cod = 1,5-cyclooctadiene) with [Ar'Sn(µ-Cl)]2. This reaction illustrates a promising synthetic strategy to access uncommon metal clusters. The structure of 1 features a rhomboidal Co2Sn2 core with strong metal-metal bonds between tin and cobalt and a weaker tin-tin interaction. Reaction of 1 with white phosphorus afforded [Ar'2Sn2Co2P4] (2), the first molecular cluster compound containing phosphorus, cobalt and tin.

Synthesis, electronic structure and redox properties of the diruthenium sandwich complexes [Cp*Ru(µ-C10H8)RuCp*]x (x = 0, 1+; Cp* = C5Me5; C10H8 = naphthalene).

The dinuclear ruthenium complex [Cp*Ru(µ-C10H8)RuCp*] (1; Cp* = η5-C5Me5) was prepared by reduction of the cationic precursor [Cp*Ru(η6-C10H8)]PF6 with KC8. Diamagnetic 1 has a symmetric molecular structure with an anti-facial configuration of the Cp*Ru moieties coordinating to naphthalene. Density Functional Theory (DFT) studies showed an electronic structure similar to that of the analogous diiron complex [Cp*Fe(µ-C10H8)FeCp*]. Cyclic voltammetry and UV-vis spectroelectrochemistry showed that 1 can be reversibly oxidized to 1+ and 12+. Chemical oxidation with [Cp2Fe]BArF4 afforded the paramagnetic compound [1]BArF4, which was investigated by EPR, single-crystal X-ray diffractometry and DFT calculations. Reaction of 1 with Brookhart's acid gave the hydride complex [3]BArF4, which was characterized spectroscopically and crystallographically. Cyclic voltammetry showed that [3]+ is converted back to 1 upon reduction and oxidation.

Oxidative P-P Bond Addition to Cobalt(-I): Formation of a Low-Spin Cobalt(III) Phosphanido Complex.

The first homoleptic cobalt phosphanido complex [K(thf)4 ][Co{1,2-(PtBu2 )2 C2 B10 H12 }2 ] (1) was prepared by an unprecedented oxidative P-P bond addition of an ortho-carborane-substituted 1,2-diphosphetane to cobalt(-I) in [K(thf)0.2 ][Co(η4 -cod)2 )] (cod=1,5-cycloctadiene). Compound 1 is a rare distorted tetrahedral 3d6 complex with a low-spin ground state configuration. Magnetic measurements revealed that the complex is diamagnetic between 2 to 270 K in the solid state and at 298 K in [D8 ]THF solution. Based on DFT calculations, the unusual singlet ground state is caused by the strong σ-donor and moderate π-donor properties of the bis(phosphanido) ligand.