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.

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].

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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).

Radikal für Redoxstudien: Die Photolyse von [Cp*P{W(CO)5}2] mit einem Diphosphen verläuft über ein radikalisches Intermediat und liefert ein luftstabiles komplexiertes Triphosphaallylradikal, in dem das ungepaarte Elektron gleichmäßig über beide terminale P‐Atome verteilt ist. Die Oxidation des Radikals führt zu dem lediglich bei tiefen Temperaturen in Lösung stabilen Triphosphaallylkation, während bei der Reduktion das stabile Triphosphaallylanion gebildet wird. Mes*=2,4,6‐Tri‐tert‐butylphenyl.

The reaction of the phosphinidene complex [Cp*P{W(CO) 5 } 2 ] (1a) with secondary and tertiary phosphines, respectively, proceeds via W(CO) 5 elimination to form the phosphoranylidene complexes [{W(CO) 5 }(Cp*)-P-P(H) i Pr 2 ] (2), [{W(CO) 5 }(Cp*)P-PMe i Pr 2 ] (7), and [{W(CO) 5 }(Cp*)P-PEt 3 ] (9). Other novel types of products, the phosphine-coordinated bridged parent phosphinidene complexes [{W(CO) 5 } 2 (H)P-PMe i Pr 2 ] (6a) and [{W-(CO) 5 } 2 (H)P-PEt 3 ] (8a), are obtained by elimination of 1,2,3,4-tetramethylfulvene. The latter reaction path is predominantly found for the arsinidene complex [Cp*As{W(CO) 5 } 2 ] (1b) to yield [{W(CO) 5 } 2 (H)As-PH i Pr 2 ] (4) upon reaction with HP i Pr 2 and, with tertiary phosphines, the products [{W(CO) 5 } 2 (H)As-PMe i Pr 2 ] (6b) and [{W(CO) 5 } 2 (H)As-PEt 3 ] (8b). If a secondary phosphine coordinates to a bridged parent pentelidene complex, Cp*H elimination occurs to form either HP[P i Pr 2 {W(CO) 5 }] 2 (3) or the phosphine-substituted diarsene complex W(CO) 5 [AsP i Pr 2 {W(CO) 5 }] 2 (5). Each of the new products has been characterized by X-ray structure analysis, NMR, and mass spectroscopy. In each case as a first step the Lewis acid/base adducts are formed, which was monitored by 31 P NMR spectroscopy. The different reaction pathways of the electrophilic pentelidene complexes [Cp*E{W(CO) 5 } 2 ] (E = P, As) have been emphasized by extended DFT calculations.

Gar nicht so unschuldig. Der Phosphinidenkomplex 1 reagiert mit tBuCP über ein WP‐Intermediat zum Komplex 2 mit dem Diphosphabutenonyl‐Liganden. Die Reaktion mit MesCP (Mes=2,4,6‐Me3C6H2) führt dagegen über eine zuvor unbekannte Ringöffnung des „unschuldigen“ Cp*‐Liganden (Cp*=C5Me5) und Insertion des Phosphaalkins und des Phosphiniden‐P‐Atoms zum neuartigen Komplex 3 mit dem Diphosphacyclooctatetraen‐Liganden.

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