Reactivity of the Inversely Polarized Arsaalkenes R-As=C(NMe2)2 {R = [(η5-C5Me5)(CO)2Fe], tBuC(O), 4-Et-C6H4C(O)} towards Phosphavinylidene Complexes [η5-(C5H5)(CO)2M=P=C(SiMe3)2] (M = Mo, W)

The reaction of the phosphavinylidene complexes [Cp(CO)2M=P=C(SiMe3)2] [Cp = C5H5, M = Mo (2), W (3)] with the ferrioaarsaalkene [Cp*(CO)2Fe–As=C(NMe2)2] (1a) (Cp* = C5Me5) afforded the novel η3‐2‐phospha‐1‐arsaallyl complexes [η3‐{[Fe]–As–P–C(SiMe3)2}M(CO)2Cp] {M = Mo, [Fe] = [Cp*(CO)2Fe] (4a);W (5a)}. Similarly, treatment of equimolar amounts of 3 with arsaalkene tBu–C(O)–As=C(NMe2)2 (1b) gave rise to the formation of [η3‐{tBuC(O)–As–P–C(SiMe3)2}W(CO)2Cp] (5b) by an arsinidene transfer process. In contrast to this, the more reactive arsaalkene 4‐Et–C6H4C(O)–As=C(NMe2)2 (1c) and complex 3 underwent reaction to give the cyclic phosphenium complex [Cp(CO)2W=P–O–Ca(4‐Et–C6H4)=As–Cb(SiMe3)2(P–Cb)] (6). The novel compounds 4a, 5a, 5b, and 6 were characterized by elemental analyses and by means of spectroscopy (IR, 1H, 13C, 31P NMR). Moreover, the molecular structures of 4a, 5b, and 6 were elucidated by X‐ray diffraction analyses.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)