Reaction of tungsten-phosphinidene and -arsinidene complexes with carbodiimides and alkyl azides: a straightforward way to four-membered heterocycles.

The reaction of the phosphinidene and arsinidene complexes [Cp*E{W(CO)5 }2 ] (E=P (1 a), As (1 b); Cp*=C5 Me5 ) with carbodiimides leads to the new four-membered heterocycles of the type [Cp*C(NR)2 E{W(CO)5 }2 ] (E=P: R=iPr (2 a), Cy (3 a); E=As: R=iPr (2 b), Cy (3 b)). The reaction of phosphinidene complex 1 a with alkyl azides yields the triazaphosphete derivatives [Cp*P{W(CO)5 }N(R)NN{W(CO)5 }] (R=Hex, Cy) (4). These unprecedented N3 P four-membered triazaphosphete complexes can be regarded as stabilized intermediates of the Staudinger reaction, which have not been previously isolated. All of the isolated products were characterized by NMR, IR spectroscopy, mass spectrometry, and by single-crystal X-ray diffraction analysis.

The complexed 1,3-diphospha-2-arsaallyl radical and its cationic and anionic derivatives.

Photolysis of [Cp*As{W(CO)(5)}(2)] (1a) in the presence of Mes*P=PMes* (Mes*=2,4,6-tri-tert-butylphenyl) leads to the novel 1,3-diphospha-2-arsaallyl radical [(CO)(5)W(mu,eta(2):eta(1)-P(2)AsMes*(2))W(CO)(4)] (2a). The frontier orbitals of the radical 2a are indicative of a stable pi-allylic system that is only marginally influenced by the d orbitals of the two tungsten atoms. The SOMO and the corresponding spin density distribution of the radical 2a show that the unpaired electron is preferentially located at the two equivalent terminal phosphorus atoms, which has been confirmed by EPR spectroscopy. The protonated derivative of 2a, the complex [(CO)(5)W(mu,eta(2):eta(1)-P(2)As(H)Mes*(2))W(CO)(4)] (6a) is formed during chromatographic workup, whereas the additional products [Mes*P=PMes*{W(CO)(5)}] as the Z-isomer (3) and the E-isomer (4), and [As(2){W(CO)(5)}(3)] (5) are produced as a result of a decomposition reaction of radical 2a. Reduction of radical 2a yields the stable anion [(CO)(5)W(mu,eta(2):eta(1)-P(2)AsMes*(2))W(CO)(4)](-) in 7a, whereas upon oxidation the corresponding cationic complex [(CO)(5)W(mu,eta(2):eta(1)-P(2)AsMes*(2))W(CO)(4)][SbF(6)] (8a) is formed, which is only stable at low temperatures in solution. Compounds 2a, 7a, and 8a represent the hitherto elusive complexed redox congeners of the diphospha-arsa-allyl system. The analogous oxidation of the triphosphaallyl radical [(CO)(5)W(mu,eta(2):eta(1)- P(3)Mes*(2))W(CO)(4)] (2b) also leads to an allyl cation, which decomposes under CH activation to the phosphine derivative [(CO)(5)W{mu,eta(2):eta(1)-P(3)(Mes*)(C(5)H(2)tBu(2)C(CH(3))(2)CH(2))}W(CO)(4)] (9), in which a CH bond of a methyl group of the Mes* substituent has been activated. All new products have been characterized by NMR spectrometry and IR spectroscopy, and compounds 2a, 3, 6a, 7a, and 9 by X-ray diffraction analysis.

1,2,3-triphosphole derivatives as reactive intermediates.

The complexes [Cp*E{W(CO)5}2] (E=P, As; Cp*=C5Me5) react with 1,2-diphosphinobenzene to give 1,2,3-triphosphole and 2-arsa-1,3-diphosphole derivatives as reactive intermediates that dimerise to polycyclic phosphorous and arsenic containing cage compounds.

The complexed triphosphaallyl radical, cation, and anion family.

Radically complex: The photolytic reaction of [Cp*P{W(CO)(5)}(2)] (Cp* = C(5)Me(5)) with a diphosphene produces, via a radical intermediate, an air-stable complexed triphosphaallyl radical, in which the unpaired electron is evenly distributed over both terminal P atoms. Oxidation of the radical leads to a triphosphaallyl cation, which is only stable at low temperatures in solution, whereas the stable triphosphaallyl anion is formed by reduction (see picture, Mes* = 2,4,6-tri-tert-butylphenyl).

CT and endoscopic ultrasound in comparison to endoluminal MRI: preliminary results in staging gastric carcinoma.

PURPOSE: To prospectively compare diagnostic parameters of a newly developed endoluminal MRI (endo-MRI) concept with endoscopic ultrasound (EUS) and hydro-computer tomography (Hydro-CT) in T-staging of gastric carcinoma on one patient collective. MATERIAL AND METHODS: 28 consecutive patients (11 females, 17 males, age range 46-87 years, median 67 years) referred for surgery due to a gastric malignancy were included. Preoperative staging by EUS was performed in 14 cases and by Hydro-CT in 14 cases within a time frame of 2 weeks. Ex vivo endo-MRI examination of gastric specimens was performed directly after gastrectomy within a time interval of 2-3h. EUS data were acquired from the clinical setting whereas Hydro-CT and endo-MRI data were evaluated in blinded fashion by two experienced radiologists and one surgeon well experienced in EUS on gastric carcinomas. RESULTS: Histopathology resulted in 4 pT1, 17 pT2, 3 pT3 and 2 pT4 carcinomas with 2 gastric lymphomas which were excluded. Overall accuracy for endo-MRI was 75% for T-Staging of the 26 carcinomas. EUS achieved 42.9% accuracy; endo-MRI in this subgroup was accurate in 71.4%. Hydro-CT was correct in 28.6%, accuracy for endo-MRI in this subgroup was 71.4%. CONCLUSION: The direct comparison of all three modalities on one patient collective shows that endo-MRI is able to achieve adequate staging results in comparison with clinically accepted methods like EUS and Hydro-CT in classifying the extent of tumor invasion into the gastric wall. However the comparison is limited as we compared in vivo routine clinical data with experimental ex vivo data. Future investigations need to show if the potential of endo-MRI can be transferred into a clinical in vivo setting.

Reactivity of transition metal-phosphorus triple bonds towards triply bonded [{CpMo(CO)2}2]: formation of heteronuclear cluster compounds.

Thermolysis of [Cp*P{W(CO)5}2] (1) in the presence of [{CpMo(CO)2}2] leads to the novel complexes [{(CO)2Cp*W}{CpMo(CO)2}(micro,eta2:eta1:eta1-P2{W(CO)5}2)] (6; Cp=eta5-C5H5, Cp*=eta5-C5Me5), [{(micro-O)(CpMoWCp*)W(CO)4}{micro3-PW(CO)5}2] (7), [{CpMo(CO)2}2{Cp*W(CO)2}{micro3-PW(CO)5}] (8) and [{CpMo(CO)2}2{Cp*W(CO)2}(micro3-P)] (9). The structural framework of the main products 8 and 9 can be described as a tetrahedral Mo2WP unit that is formed by a cyclisation reaction of [{CpMo(CO)2}2] with an [Cp*(CO)2W[triple chemical bond]P-->W(CO)5] intermediate containing a W--P triple bond and subsequent metal-metal and metal-phosphorus bond formation. Photolysis of 1 in the presence of [{CpMo(CO)2}2] gives 8, 9 and phosphinidene complex [(micro3-PW(CO)5){CpMo(CO)2W(CO)5}] (10), in which the P atom is in a nearly trigonal-planar coordination environment formed by one {CpMo(CO)2} and two {W(CO)5} units. Comprehensive structural and spectroscopic data are given for the products. The reaction pathways are discussed for both activation procedures, and DFT calculations reveal the structures with minimum energy along the stepwise Cp* migration process under formation of the intermediate [Cp*(CO)2W[triple chemical bond]P-->W(CO)5].

Magnetic resonance imaging for local staging of gastric carcinoma: results of an in vitro study.

OBJECTIVE: Preoperative staging of gastric carcinoma is limited by the fact that available imaging modalities do not enable accurate evaluation of the depth of infiltration of the gastric wall. The aim of this study was to evaluate the efficiency of conventional magnetic resonance imaging (MRI) in local staging of gastric carcinoma. METHODS: Sixty-five specimens of patients with proven gastric carcinoma were examined immediately after gastrectomy. Examination was performed with a 1-T MRI and included T1-weighted, T2-weighted, and opposed phase images. Images were analyzed for the number of visible wall layers and their signal intensity characteristics, for tumor localization and depth of infiltration. T-stage was classified according to the TNM system. Finally, the staging by MRI was compared with the histopathological staging of the specimens. RESULTS: The mucosal, submucosal, and proper muscle layers could be differentiated by the typical signal intensities. Depiction of the subserosa or serosa was not possible. In 65 specimens, 67 carcinomas were found by the pathologist. Sixty-four of 67 (96%) histologically proven carcinomas were correctly localized by MRI; T-staging accuracy was 50% only, mainly because of overstaging pT2 tumors as T3. CONCLUSIONS: MRI enables differentiation of gastric wall layers and, therefore, technically allows the evaluation of the local tumor stage of gastric carcinomas. However, infiltration of the subserosal and serosal layer cannot be proved accurately. Overstaging pT2 tumors is one of the most predominant problems. Yet further technical developments in high-resolution imaging of the gastric wall may improve T-staging in the near future and overcome today's staging limitations.

New coil concept for endoluminal MR imaging: initial results in staging of gastric carcinoma in correlation with histopathology.

Our aim was to conduct a prospective study to evaluate staging accuracy of a new coil concept for endoluminal magnetic resonance imaging (MRI) on ex vivo gastric carcinomas. Twenty-eight consecutive patients referred to surgery with a clinically proven primary gastric malignancy were included. Surgical specimens were examined with a foldable and self-expanding loop coil (8-cm diameter) at 1.5 Tesla immediately after total gastrectomy. T1- and T2-weighted and opposed-phase sequences (axial, frontal sections; 3- to 4-mm slice thickness) were acquired. Investigators blinded to any patient information analyzed signal intensity of normal gastric wall, gastric tumor, and lymph nodes. Findings were compared with histopathological staging. On surgical specimens, 2-5 gastric wall layers could be visualized. All gastric tumors (26 carcinomas, two lymphomas) were identified on endoluminal MR data (100%). Overall accuracy for T staging was 75% (18/24); sensitivity to detect serosal involvement was 80% and specificity 89%. N staging correlated in 58% (14/24) with histopathology (N+ versus N-). The endoluminal coil concept is feasible and applicable for an ex vivo setting. Endoluminal MR data provided sufficient detail for gastric wall layer differentiation, and therefore, identification of T stages in gastric carcinoma is possible. Further investigations in in vivo settings should explore the potential of our coil concept for endoluminal MR imaging.

Prospective comparison of endoscopy, endosonography and computed tomography for staging of tumours of the oesophagus and gastric cardia.

BACKGROUND: Local and multimodal therapeutic strategies for tumours of the oesophagus and gastric cardia, require precise preoperative staging. Endosonography is considered the most accurate staging method, while computed tomography (CT) has limitations especially in the evaluation of local infiltration. Macroscopic endoscopic evaluation was reported to be accurate in selected series, but no study has yet compared all three staging modalities. METHODS: One hundred and seventeen unselected patients with tumours of the oesophagus and gastric cardia were prospectively staged first by the endoscopic macroscopic appearance and then by endosonography. All patients had preoperative CT scans, however, only the 36 patients receiving the scans at our institution were included in the study. The preoperative staging results were then compared to postoperative histology which was available as the gold standard in all included patients. Kappa statistics were used to exclude chance agreement of the clinical staging results with the pathohistological findings. Differences between the resulting kappa values for the different staging modalities were analysed with a jack-knife test. RESULTS: Endoscopic macroscopic staging and endosonography (accuracy 67 and 69%, weighted kappa 0.78 and 0.84) were significantly more accurate than CT (accuracy 33%, weighted kappa 0.44) for determination of the T category (p = 0.006 and p = 0.001). After exclusion of tumours of the cardia (n = 33), the accuracy of macroscopic and endosonographic staging (accuracy 72 and 75%, weighted kappa 0.86 and 0.88) increased and remained more accurate than CT (accuracy 50%, weighted kappa 0.62). The main pitfall in our series in staging the T category was the overestimation of T2 tumours in the cardia as T3 or even as T4 tumours due to the inability to visualise the serosa. The accuracy of predicting lymph node metastasis was 68% for macroscopic endoscopic, 79% for endosonographic, and 67% for CT staging. Only endosonographic staging was significantly different from chance agreement with histology (weighted kappa = 0.56). Endosonographic staging was significantly more accurate than endoscopic macroscopic and CT staging (p = 0.03). CONCLUSIONS: Endosonography is the most accurate staging modality for overall preoperative staging of oesophageal and cardial tumours. Endoscopic macroscopic staging allows a reasonably accurate assessment of the T category.