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P Le Floch

Publications and source records attributed to P Le Floch.

15 recordsLinked to original sources
PubMed2001

Di- and tetranuclear palladium complexes incorporating phospha- and diphosphaferrocenes as ligands.

Monophosphaferrocenes and 4 react with [Pd(COD)Cl2] (COD = cyclooctadiene) to afford cis- [Pd(1 or 4)2Cl2] complexes that slowly decompose in solution to give dimeric complexes 3 and 6 of general formula [[Pd(1 or 4)Cl]2]. In these dimers, which incorporate a Pd-Pd bond, phosphaferrocenes act as four electron donors through the phosphorus-atom lone pair (mu2-bonded) and through one orbital of appropriate symmetry at iron. These dimers can also be more conventionally prepared from the reaction of cis- [Pd(1 or 4) Cl2] complexes with [Pd(dba)2] (dba = dibenzylidene acetone). The reaction of octaethyldiphosphaferrocene (7) with [Pd(COD)Cl2] yields a dinuclear complex [Pd2(7)2Cl4] (8) in which the two ligands 7 are coordinated in a trans fashion through the phosphorus-atom lone pairs. Decomposition of 8 in solution yields a dimeric dicationic complex of general formula [[Pd2(7)2Cl]2]2+[FeCl4]2- (9a) incorporating four palladium atoms. In each ligand. one phospholyl ring behaves as a two-electron donor through the phosphorus-atom lone pair whereas the second binds two palladium centers in a mu2-fashion. A plausible mechanism that explains the formation of dimers 3, 6, and 9a involves the preliminary oxidation of the mono- or diphosphaferrocene ligand. Parallel experiments aimed at confirming this hypothesis have shown that complex 9a can be synthesized from the reaction of FeCl2 with complex 8. Also presented is another synthetic approach to the synthesis of the tetranuclear complex 9b (counterion is GaCl4-) from the reaction of the palladium(0) complex [Pd(7)2] (10) with [Pd(COD)Cl2] the presence of GaCl3 as chloride abstractor.

Journal Article↗
PubMed2001

Formation of a phosphorus-phosphorus bond by successive one-electron reductions of a two-phosphinines-containing macrocycle: crystal structures, EPR, and DFT investigations.

Chemical and electrochemical reductions of the macrocycle 1 lead to the formation of a radical monoanion anion [1](*)(-) whose structure has been studied by EPR in liquid and frozen solutions. In accord with experimental (31)P hyperfine tensors, DFT calculations indicate that, in this species, the unpaired electron is mainly localized in a bonding sigma P-P orbital. Clearly, a one-electron bond (2.763 A) was formed between two phosphorus atoms which, in the neutral molecule, were 3.256 A apart (crystal structure). A subsequent reduction of this radical anion gives rise to the dianion [1](2)(-) which could be crystallized by using, in the presence of cryptand, Na naphthalenide as a reductant agent. As shown by the crystal structure, in [1](2)(-), the two phosphinine moieties adopt a phosphacyclohexadienyl structure and are linked by a P-P bond whose length (2.305(2) A) is only slightly longer than a usual P-P bond. When the phosphinine moieties are not incorporated in a macrocycle, no formation of any one-electron P-P bond is observed: thus, one-electron reduction of 3 with Na naphthalenide leads to the EPR spectrum of the ion pair [3](*)(-) Na(+); however, at high concentration, these ion pairs dimerize, and, as shown by the crystal structure of [(3)(2)](2)(-)[(Na(THF)(2))(2)](2+) a P-P bond is formed (2.286(2) A) between two phosphinine rings which adopt a boat-type conformation, the whole edifice being stabilized by two carbon-sodium-phosphorus bridges.

Journal Article↗
PubMed2001

Preparation and characterization of ruthenium(II) monophosphaferrocene complexes. Reactivity, dynamic solution behavior, and X-ray structure of [RuH(2)(eta(2)-H(2))(PCy(3))2(2-phenyl-3,4-dimethylphosphaferrocene)].

The bis(dihydrogen) complex RuH(2)(H(2))(2)(PCy(3))(2) (1) reacts with 2-phenyl-3,4-dimethylphosphaferrocene (L(1)) to give RuH(2)(H(2))(PCy(3))(2)(L(1)) (2). This dihydride-dihydrogen complex has been characterized by X-ray crystallography and variable-temperature (1)H and (31)P NMR spectroscopy. The exchange between the dihydrogen ligand and the two hydrides is characterized by a DeltaG() of 46.2 kJ/mol at 263 K. H/D exchange is readily observed when heating a C(7)D(8) solution of 2 (J(H-D) = 30 Hz). The H(2) ligand in 2 can be displaced by ethylene or carbon monoxide leading to the corresponding ethylene or carbonyl complexes. The reaction of 1 with 2 equiv of 3,4-dimethylphosphaferrocene (L(2)) yields the dihydride complex RuH(2)(PCy(3))(2)(L(2))(2) (5).

Journal Article↗
PubMed1982

[Serous ischial bursa].

The ischial bursa (Bursa ischiatica) lies on the posterior aspect of the tuberosity of the ischium at the level of the origin of the hamstring muscles. Its relations with the inferior fibers of the musculus gluteus maximus vary with the degree of the hip's flexion. Its role in the sitting position explains the specific bursitis when medullar lesions disturb the normal physiology of this posture.

Hip Joint↗
PubMed1982

[Biometry of the cervical spine using tomodensitometry].

Biometry was performed on the computed tomographical cross-sections of one human cervical spine. The entire spine was removed with the head and neck from a fresh cadaver of an adult man. Horizontal cross-sections were performed with a C.T. scan from the base of the skull to the thoracic level. The measurements concerned the diameters of the vertebrae, spinal canal and spinal cord: the density of the posterior and anterior walls, and of the para-vertebral muscles. Clinical and fundamental applications are underlined.

Aged↗
PubMed1981

[The two columns of the lower end of the humerus].

The anatomical examination of the distal end of the human humerus brings new perspectives. The lower extremity of the humerus is considered as a structure with two diverging columns that prolong the diaphysis and flank the trochlear mass articulate with the ulna. Two series of dry humeruses, one of 100, and the other 20 permitted a study with measurements of the posterior width of the columns, their antero-posterior dimensions, the angle that they form with the posterior longitudinal axis of the diaphysis. Dry bones, radiographs, and direct tracing were used. The second series of bones was used for cross-sections in several planes, and for perforations of the fossae. Lastly, graded cuts of frozen elbows were done. These methods showed the two columns to be completely different. The outer column is thick, quadrangular, bulky, convex at the back, wide, almost vertical; in front it bears the condyle, while a lateral facet appears on its distal part; this column is articulated with the radius and extends itself to the thumb column. The inner column is fusiform, narrow, oval on cross-sections; it is a column which supports the trochlea and the muscles, two roles played also by the outer column.

Anthropometry↗
PubMed1981

[Anatomic conditions of sitting positions].

Sitting positions are anatomically defined. Three types are described: sitting on a chair, on the ground, and half-sitting position. The ischial support is always predominant in durable sitting; the others are subsidiary: trochanter, thigh, trunk or forelimb. The respect of the articular mobility of the hips and knees is important. Several orthopaedical and neurological diseases disturb the anatomical conditions of normal sitting.

Adult↗
PubMedDate not supplied

[Lymphatico-venous experimental anastomosis (author's transl)].

Since the pioneer work of Nielubowicz et Olszewski successful anastomoses have been caried out between lymphnodes and veins in experiments and in the clinic as well. The creation of patent anastomoses between lymphatic trunks and veins still present many problems, primarily due to the small size of the lymphatic vessels. The microsurgical technique permits the authors to overcome these difficulties. End-to-side anastomosis between lymphatic trunk and the superficial femoral vein was carried out - using stereo microscopic - on rabbits, with a modification of Cordeiro's and Degni's technique; a longitudinally divided plastic catheter was introduced into the vein and the lymphatic trunk was pulled into the lumen and fixed to the upper venous wall with one suture. End-to-end anastomosis was created between lymphatic trunk and the superficial femoral vein or one of it's branches with a technique using a small piece of plastic catheter, which was introduced into the lymphatic trunk on one side and to the vein on the other side in order to prevent the transfixation of the vessels wall. Interrupted 11/0 atraumatic sutures were used to create the anastomosis. With both of these methods patent anatomosis can be carried out between lymphatic trunks and veins.

Animals↗