No abstract

Novel methyl complexes [Pd(Me)(N‐N‐N)]X (N‐N‐N = flexible or rigid terdentate nitrogen ligand, X = Cl, SO3CF3, BAr′4) have been synthesized and fully characterized. All complexes readily underwent insertion of carbon monoxide resulting in the quantitative formation of complexes [Pd{C(O)Me}(N‐N‐N)]X [X = Cl (1d–6d), BAr′4 (1e–6e)]. Subsequently, complexes 2e–6e underwent quantitative insertion of norbornadiene, resulting in complexes [Pd{C7H8C(O)Me}(N‐N‐N)]BAr′4 (2f–6f). Unexpectedly, these complexes, including even those containing rigid terdentate nitrogen ligands, possess a structure in which the nitrogen ligand is coordinated in a bidentate fashion. A kinetic study of the reaction of norbornadiene with complexes 1e–6e revealed that the reactivity of complexes 1e–6e toward norbornadiene increases with increasing rigidity of the terdentate ligand, i.e. with increasing strain in the PdN3 moiety, which indicates that insertion very likely occurs via a mechanism involving nitrogen dissociation. This is fully supported by ab initio MO calculations on CO and ethylene insertion into carbon–palladium bonds of cationic model systems containing a rigid terdentate nitrogen ligand, which showed that the lowest‐energy pathway for both insertion reactions consists of substitution of one of the distal nitrogen atoms of the rigid terdentate nitrogen ligand by the substrate, followed by a rate‐determining migratory insertion of the substrate into the carbon–palladium bond.

No abstract

The versatile carbene‐like chemistry of electrophilic phosphinidene complexes (R−P=MLn) with C=C, C≡C, C=X, and C≡X (X = N, O, S, Si, and P) bonds and aromatics is discussed.

No abstract

Double addition of the phosphinidene complex [PhPW(CO)5] to 2,5‐dimethyl‐2,4‐hexadiene led to the first bisphosphiranes. The s‐trans conformation of the intermediate vinylphosphiranes prevents rearrangements and epimerizations, but does not hamper a second addition (see scheme).

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.

No abstract