Versatile Reactivity of Bridged Pentelidene Complexes toward Secondary and Tertiary Phosphines
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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)iPr2] (2), [{W(CO)5}(Cp*)P-PMeiPr2] (7), and [{W(CO)5}(Cp*)P-PEt3] (9). Other novel types of products, the phosphine-coordinated bridged parent phosphinidene complexes [{W(CO)5}2(H)P-PMeiPr2] (6a) and [{W(CO)5}2(H)P-PEt3] (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-PHiPr2] (4) upon reaction with HPiPr2 and, with tertiary phosphines, the products [{W(CO)5}2(H)As-PMeiPr2] (6b) and [{W(CO)5}2(H)As-PEt3] (8b). If a secondary phosphine coordinates to a bridged parent pentelidene complex, Cp*H elimination occurs to form either HP[PiPr2{W(CO)5}]2 (3) or the phosphine-substituted diarsene complex W(CO)5[AsPiPr2{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 31P 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.
