The reaction of the inversely polarized phosphaalkenes RP=C(NMe 2 ) 2 [R = tBu (1a), Cy (1b), 1-Ad (1c), Ph (1d), Mes (1e)] with an excess of diphenyl ketene in n-pentane affords the zwitterionic adduct (Me 2 N) 2 C-C(O)=CPh 2 (2) and the 3,5-dibenzhydrylidene-1,4,2-dioxaphospholanes 4a-e. The reaction of 1a with Ph 2 C=C=O in concentrated acetonitrile solution gives 4a and 5-benzhydrylidene-2-tert-butyl-4,4-diphenyl-1,2-oxaphospholan-3-one (6a) as a by-product. In contrast, treatment of Me 3 SiP=C(NMe 2 ) 2 (1i) with the ketene leads to the formation of 2-phospha-1,3-butadiene (5). The thermolabile phosphaalkene 8 decomposes into an imid-

Reaction of the inversely polarized phosphaalkene HP=C(NMe2)2 (1) with [AuCl(PPh3)] (2a) in a molar ratio of 2:1 in THF led to the formation of complex [Au{HP=C(NMe2)2}2]Cl (3) as a pale yellow solid. In contrast to this, treatment of 2a with two molar equivalents of tBuP=C(NMe2)2 (4) afforded a mixture of [Au{P(tBu)=C(NMe2)2}2]+Cl− (5) and [{(Me2N)2C=(tBu)PAu}2(μ‐Cl)]+Cl− (6). In CH2Cl2 solution this mixture was slowly converted into the novel decanuclear complex [Au8(AuCl)2{μ3‐P(tBu)}2{μ‐P(tBu)=C(NMe2)2}6]4+(Cl−)4 (7) featuring six edge‐bridging phosphaalkene ligands and two μ3‐tert‐butylphosphanediide ligands. In solution the cluster 7 shows a high order 31P{1H} NMR spectrum of the [AB2C]2 type. According to the X‐ray structural analysis the Au10 framework may be described as a slightly puckered ladder constructed of three quadrangles. The central Au4 parallelogram is capped on both faces by a pair of [tBuPAuCl] units. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Reaction of [(η5‐C5H5)(CO)2M=P=C(SiMe3)2] [where M = Mo (2), W (5)] with the phosphaalkene tBuP=C(NMe2)2 (1a) afforded the η3‐1,2‐diphosphaallyl complexes [(η5‐C5H5)(CO)2M{η3‐tBuPPC(SiMe3)2}], [where M = Mo (3a); M = W (6)]. Similarly, 2 and CyP=C(NMe2)2 (1b; where Cy = cyclohexyl) gave rise to the formation of [(η5‐C5H5)(CO)2Mo{CyPPC(SiMe3)2}] (3b) by a phosphinidene transfer process. Small amounts of [{η5‐C5H5)(CO)2Mo}2{η2:η2‐Cy3P5}] (4) were formed as a minor product. However, treatment of 2 and 5 with HP=C(NMe2)2 (1c) yielded the complexes [(η5‐C5H5)(CO)2M{η2‐(Me3Si)2CH–P=P–C(NMe2)2}] [where M = Mo (9), W (10)]. The novel compounds 3a, 3b, 9 and 10 were characterized by means of spectroscopy (IR, 1H, 13C{1H}, 31P{1H} NMR, MS). Moreover, the molecular structures of 3a, 3b, 4, 6 and 10 were determined by X‐ray diffraction analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)