Marius Schakel

The Electrophilic Phosphinidene Complex i Pr 2 N–P Fe(CO) 4 Trapped by Alkynes

Abstract The in-situ formation at −30°C of the electrophilic phosphinidene complex iPr2NPFe(CO)4, resulting from reaction of dichlorophosphine iPr2NPCl2 with Na2Fe(CO)4 (Collmans reagent), was demonstrated by trapping reactions with various alkynes. The resulting phosphirenes were obtained in good yields. The reactivity of iPr2NPFe(CO)4 is less than that of PhPW(CO)5, which is, however, generated at much higher temperatures. The stabilization of iPr2NPFe(CO)4 in the reaction medium is discussed.

Olefin cycloadditions of the electrophilic phosphinidene complex iPr2N-P=Fe(CO)4

Highly strained methylenephosphiranes are formed in the reaction of the new electrophilic phosphinidene complex [iPr(2)N-P=Fe(CO)(4)] with allenes. Remarkably, reaction with diallenes at 0 degrees C also leads to a phosphirane, which rearranges upon warming to room temperature to a bis-isopropylidenephospholene (see scheme).

IN SEARCH OF STABLE LITHIUM PENTAORGANYLSILICATES; SPECIAL ROLE OF FIVE PHENYL LIGANDS AND OF LIGANDS CONTAINING THE 1,4-(1,3-BUTADIENEDIYL) UNIT

Abstract Among several tetraorganylsilanes tested, only 4–6, containing the 1,4-(1,3-butadienediyl) unit, have been found to form, by addition of a σ-organolithium, lithium pentaorganylsilicates identifiable by characteristic 29Si-NMR chemical shifts. Lithium silicates formed from 4 are of particular stability (and correspondingly low reactivity) and appear to have trigonal-bipyramidal structures that undergo stereomutation with ΔH≠ ca. 50 kJ/mol, ΔS≠ ca. −20 J/kmol. So far, lithium pentaphenylsilicate (3) is the only other lithium pentaorganylsilicate that could be identified by 29Si-NMR.

N-heterocyclic carbene-functionalized ruthenium phosphinidenes: what a difference a twist makes

Catalyst tuning by changing ligands is a well-established protocol in transition-metal chemistry. N-Heterocyclic carbenes (NHCs) and tertiary phosphines (R(3)P) are the ubiquitous ligand actors. Here we demonstrate that the relative sigma-donor/pi-acceptor ability of the NHC ligand itself can be influenced by a simple substituent-controlled conformational change, thereby directly impacting the reactivity of the transition-metal complex.

Addition of a phosphinidene complex to C=N bonds: P-ylides, azaphosphiridines, and 1,3-dipolar cycloadditions.

The terminal phosphinidene complex PhPW(CO)5 adds to the imine bond of PhHC=N-Ph to give 3-membered ring azaphosphiridines, which undergo ring-expansion with an additional imine to yield a set of four isomeric five-membered ring diazaphospholanes. Treatment with the diimines PhHC=N-(CH2)n-N=CHPh (n=2,3,4) results instead-in all three cases-in only a single isomer of the (CH2)n bridged diazaphospholane. For n=2 or 3, this aminal group is easily hydrolyzed to afford new 6- and 7-membered ring heterocycles. No intermediate azaphosphiridine complex is observed during the addition reaction to the diimines. B3LYP/6-31G* calculations on an unsubstituted, uncomplexed system suggest that the initially formed P,N-ylide of the H2C=N-(CH)2-N=CH2 diimine both kinetically and thermodynamically favors an intramolecular 1,3-dipolar cycloaddition over an imine insertion into the CPN ring of an intermediate azaphosphiridine. Single-crystal X-ray structures for the (CH2)2-bridged azaphospholane complex and the HCl adduct of the 7-membered hydrolysis product are presented.

REACTIONS OF THE BUTYLLITHIUMS WITH TERTIARY OLIGOETHYLENEPOLYAMINES

Abstract Complexes of t-BuLi monomer with 1,4,7-trimethyl-1,4,7-triazacyclononane (TMTAN, 3-CH 3 ) and tris(N,N-dimethyl-2-aminoethyl)amine ( 4-CH 3 ) were identified by 13 C-NMR. Rapid elimination of LiN(CH 2 CH 2 NMe 2 ) 2 takes place from the free CH 2 CH 2 NMe 2 group of t-BuLi· 4-CH 3 . BuLi complexes of hexamethyltriethylenetetramine ( 5-CH 3 ) and octamethylpentaethylenehexamine ( 6 ) behave similarly, as does 4-CH 2 Li . Complexes of BuLi oligomers are lithiated at free N-CH 3 .

Iridium phosphinidene complexes: a comparison with iridium imido complexes in their reaction with isocyanides

18-Electron nucleophilic, Schrock-type phosphinidene complexes 3 [Cp*(Xy-N[triple bond]C)Ir=PAr] (Ar = Mes*, Dmp, Mes) are capable of unprecedented [1 + 2]-cycloadditions with 1 equiv of isocyanide RNC (R = Xy, Ph) to give novel iridaphosphirane complexes [Cp*(Xy-N[triple bond]C) IrPAr C=NR]. Their structures were ascertained by X-ray diffraction. Density functional theory investigations on model structures revealed that the iridaphosphirane complexes are formed from the addition of the isocyanide to 16-electron species [Cp*Ir=PAr] forming first complex 3 that subsequently reacts with another isocyanide to give the products following a different pathway than its nitrogen analogue [Cp*Ir[triple bond]Nt-Bu] 1.

Spiro ketone synthesis via lithium—iodine exchange of α-(ω-iodoalkyl) esters

The title reaction (2 eq. of t-BuLi, –100°C) provides a new route to five- and six-membered ring ketones and has permitted the synthesis of two spiro ketones that were inaccessible by conventional methods.

Mixed tetramers of sec-butyllithium and 3-methoxypropyllithium ; degree of intracluster etheration and reactivity of sec-butyllithium towards ethylene

Abstract In benzene, neither sec -butyllithium ( 1 ) nor 3-methoxypropyllithium ( 2 ) react with ethylene, while in solutions containing 1 plus 2 3-methylpenty- llithium ( 3 ) is produced by ethylenation of 1 . Clusters 1 n 2 4−n (n: 0 – 4) are indicated by NMR and 1 2 2 2 is deduced to be the most reactive species. At [ 2 ]:[ 1 ] = 2, the reaction order in 1 is 0.74, signifying reversible formation of a pre-reaction complex 1 2 2 2 ·ethylene.

Reaction of a complexed phosphinidene with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene.

The terminal phosphinidene complex PhPW(CO)5 reacts with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene to give two unexpected multicyclic organophosphorus compounds. One of them results from an initial 1,2-addition, followed by an intramolecular rearrangement. B3LYP/6-31G* calculations on simplified parent systems suggest that the reaction follows a unique concerted reaction pathway. The second, and major, product is a tetraphosphaquadricyclane derivative, which presumably results from an intramolecular [2+2] cycloaddition of an intermediate tetraphosphanorbornadiene complex. Single-crystal X-ray structures are presented for both products.