Reactivity of bridged pentelidene complexes with isonitriles: a new way to pentel-containing heterocycles.
The reaction of [Cp*E{W(CO)5}2] (E=P (1a), As (1b); Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with isonitriles RNC (R=tBu, cyclohexyl (Cy), nBu) depends on the steric demand of the substituent at the isonitrile as well as on the stoichiometry of the starting materials. With tBuNC only the Lewis acid/base adducts [Cp*E{W(CO)5}2ACHTUNGTRENUNG(CNtBu)] (E=P (2a), As (2b)) are formed. The use of Cy and n-butylisonitrile leads first to the formation of the Lewis acid/base adduct, but only at low temperatures. At ambient temperatures, a rearrangement occurs and bicycloACHTUNGTRENUNG[3.2.0]heptane derivatives of the type [{C(Me)CACHTUNGTRENUNG( CH2)C(Me)C(Me)C(Me)}C(NR)-E{W(CO)5}2] (E=P, As; R=Cy, nBu) (3a-Cy, 3b-Cy, 3a-nBu and 3b-nBu) are obtained. The use of a further equivalent of isonitrile results in products revealing two new structural motifs, the four-membered ring derivatives [CACHTUNGTRENUNG(Cp*)N(R)C(NR)E{W(CO)5}2] (4: E=P, As; R=Cy, nBu) and the bicyclic complexes [[{C(Me)CACHTUNGTRENUNG( CH2)C(Me)C(Me)C(Me)}C(NR)2-E{W(CO)5}2] (5: E=As; R=Cy). The reaction pathway depends on the substituent at the isonitrile. By treatment of 1a with two equivalents of CyNC only a 2H-1,3-azaphosphet complex 4a-Cy (E=P; R=Cy) is formed. Treatment of 1b with two equivalents of CyNC exclusively leads to the complex 5b-Cy (E=As; R=Cy). Treatment of 1a with two equivalents of nBuNC results in a mixture of complexes, the 2H-1,3-azaphosphet 4a-nBu (E=P; R=nBu) and the bicyclic complex 5a-nBu (E=P; R=nBu). For the arsenidene complex 1b a mixture of the 2H-1,3-azarsete complex 4b-nBu (E=As; R=nBu) and the bicyclic complex 5b-nBu (E=P, As; R=Cy, nBu) is obtained. Complex 4b-nBu is the first example of a 2H-1,3-azarsete complex. All products have been characterized by using mass spectrometry, NMR spectroscopy, and X-ray diffraction analysis.
Michael
M
Seidl
Michael
M
Schiffer
Michael
M
Bodensteiner
Alexey Y
AY
Timoshkin
Manfred
M
Scheer