Ali A. Bahsoun

Reactivity of cyclopalladated complexes. Part 5. Insertion reactions of diphenylacetylene, 1-phenylprop-1-yne, and hexafluorobut-2-yne with cyclopalladated compounds. Crystal and molecular structure of chloro{3–4-η-4-[(2-dimethylaminomethyl)phenyl]-1,4-dimethyl-2,3-diphenylbuta-1,3-dienyl-C1N}palladium(II) and bromo{3–4-η-4-[(2-dimethylaminomethyl)phenyl]-2,4-dimethyl-1,3-diphenylbuta-1,3-dienyl-C1N}-palladium(II)

Reactions between disubstituted alkynes RC2R′(R = R′= Ph and R = Me, R′= Ph) and [{Pd(dmba)X}2](dmba =NN-dimethylbenzylamine, X = Cl or Br) afford bis-insertion products [Pd{(RCCR′)2C6H4CH2NMe2}X] in high yield. With MeC2Ph two isomers have been isolated, (1bα) and (1bβ). In order to establish their molecular structures, a single-crystal X-ray diffraction study has been made on the chloro-derivative of (1bβ) and the bromo-derivative of (1bα). Crystals of (1bα; X = Br) are monoclinic, space group P21/c, Z= 4, with a= 15.362(13), b= 12.368(5), c= 14.886(11)A, and β= 94.86(13)°. The structure has been refined to R 0.078 (R′ 0.105) for 2 529 independent reflections; the two acetylenes inserted into the Pd–C bond have a head-to-tail arrangement, the Pd being σ-bonded to a carbon bearing a phenyl group. Crystals of (1bβ; X = Cl) are monoclinic, space group P21, Z= 2, with a= 8.227(6), b= 16.059(33), c= 8.923(9)A, and β= 99.30(12)°. The structure has been refined to R 0.074 (R′ 0.065) for 2 077 independent reflections. The molecule shows a tail-to-tail arrangement for the two inserted acetylenes, the carbon σ-bonded to the palladium bearing a methyl group. The corresponding reaction with the 8-methylquinoline palladated dimer affords a benzenoid trimer via a bis-insertion analogue which was isolated for R = R′= Ph. Hexafluorobut-2-yne (hfb) reacts with the above palladated dimers and those formed from benzo[h]quinoline and NN-dimethyl-1-naphthylamine to give novel halide-bridged binuclear complexes with seven-membered rings. They are formed by formal insertion of one hfb unit into the Pd–C σ bond. With the naphthylamine dimer only an organic compound was isolated. The novel dimeric complexes easily afford monomeric derivatives by bridge-splitting reactions with pyridine or PPh3.

Synthetic and fluxional behaviour of M(1,5 cyclooctadiene)(tripod)+BF4− (M = Rh Ir; Tripod = HC(PPh2)3)

Abstract The complexes M(1,5 cyclooctadiene)(HC(PPh 2 ) 3 ) + BF 4 − (M = Rh, Ir) have been synthesized characterized. The 31 P 1 H NMR spectra show that in the ground-state structure the tripod ligand forms a bidentate chelate with the metal, the third phosphorus atom remaining uncoordinated. However, VTNMR studies show a rapid exchange process to be occurring at room temperature causing equilibration of all the phosphorus nuclei as well as the vinylic and methylenic protons of the diene ligand. An associative intramolecular exchange mechanism is proposed.

Rhodium (I) complexes of the dppn ligand, 3,6-bis (2′-pyridyl) pyridazine and X-ray structure of [Rh (CO) (dppn) (PPh 3 ) ] (PF 6 )

Abstract The reaction of the 3,6-bis (2′-pyridyl) pyridazine (dppn) ligand, with one and two equivalents of [Rh (CO) 2Sn] (PF6) , (s = THF) , yields respectively the mononuclear complex [Rh (CO) 2 (dppn) ] (PF6) 1 and the binuclear complex [Rh2 (CO) 4 (dppn) ] (PF6) 2 3. Furthermore, the reaction of 1 with PPh3 results in a substitution reaction to give [Rh (CO) (dppn) (PPh3) 2] (PF6) 2. The unsaturated complex 3 reacts with the monodentate phosphine PPh3 to yield a mixture of the known compound [Rh (CO) 2 (PPh3) 2] (PF6) and of the mononuclear [Rh (CO) (dppn) (PPh3) ] (PF6) 4, the crystal structure of which was established by X-ray diffraction. Moreover, 3 reacts with the bis (diphenylphosphino) methane (dppm) ligand in a 1 : 2 ratio to form the binuclear A-frame complex [Rh2 (CO) 2 (dppn) (μ-dppm) 2] (PF6) 2 5. However, the reaction of 3 with excess dppm (1 : 4 ratio) gives the known complex [Rh (CO) (dppm) 2] (PF6) 6.

Synthesis and structure of a triply-chloro-bridged dimer of a homobinuclear RhI complex: [{Rh2(CO)(HC(PPh2)3)}2(μ-Cl)3]+[Rh(CO)2Cl2]−

Abstract The tripod ligand HC(PPh2)3 reacts with Mo(CO)3(CH3CN)3 yielding Mo(CO)3(CH3CN)(HC(PPh2)3). Reaction of this Mo0 complex with [Rh(CO)2Cl]2 gives unexpectedly the tetranuclear species [Rh2(CO)(HC(PPh2)3)]2(μ-Cl)+3 (3) which crystallizes as the Rh(CO)2Cl−2 salt (3a). This complex crystallizes in the monoclinic space group P21/c with Z = 4, with all dimensions a = 19.685(3), b = 19.524(3), c = 22.657(4) A, and β = 96.96(2)°. A direct route to the PF−6 salt of 3 (3b) is also presented. The 31P NMR data show 3a and 3b to be identical and that the tetranuclear structure is retained in solution, i.e. two units of binuclear RhI species bridged by three chlorine atoms. In each binuclear unit, the tripod ligand spans two RhI which are linked directly by a metal-metal bond (RhRh = 2.696 A).

Oxidative electrochemistry of the cluster [Co4(CO)9{HC(PPh2)3}]. Reactivity with the nucleophiles PPh3 and P(OMe)3

The one-electron-oxidized cluster [Co4(CO)9{HC(PPh2)3}]˙+ reacts with PPh3 and P(OMe)3. The reaction mechanisms involve the substitution of CO by PR3. The P(OMe)3 substituted cluster is stable, whereas the PPh3 substituted cluster undergoes an intramolecular electron transfer which regenerates the initial cluster. A general reaction scheme is proposed for the one-electron-oxidized and the one-electron-reduced cluster.

Heterobimetallic synthesis using the tripod ligand, HC(PPh2)3: the X-ray structure of [(CO)5FeRh(tripod)]+

The tripod ligand, HC(PPh2)3, can be used to construct heterobimetallic complexes such as [(CO)5FeRh(tripod)]+, the X-ray structure of which shows the presence of a metal–metal bond.