Vor kurzem berichteten wir ilber einen neuen Zugang zu Metallacycloalkanen aus Metallkomplexen mit zwei nucleophilen Zenfren und a,wdisubstituierten Kohlenwasserstoffen I -5 ) . Von besonderer Bedeutung filr den Ablauf der Reakfionen ist die Natur der Abgangsgruppe in den Alkanen. Sie muD so beschaffen sein. daD die a,wstgndigen C-Aiome eine moglichst hohe 5( 2 ) Chem. Ber. 114(1981)

Activation of the CO ligands in the new six‐membered rhenacycle (1), R = Ph, by AlBr3 permitted the first insertion of CO into a RhC σ‐bond. The complex (2) takes up CO at 20°C at normal pressure.

Abstract The binuclear anions Na2[(OC)4MP(O)R2]2 (2a, a′, b, b′) [M = Mn: R = CH3 (a), C6H5 (a′); M = Re: R = CH3 (b), C6H5 (b′)] can be obtained quantitatively by reduction of the phosphinic acid complexes (OC)4BrMP(OH)R2 (1a, a′, b, b′) with sodium amalgam in ether. While the manganate anions 2 a, a′ can be transformed with excess sodium into the mononuclear salts Na2[(OC)4MnP(O)R2] (3a, a′), with two nucleophilic centres, the corresponding anions 2 b, b′ eliminate CO to give sparingly soluble species. From 3 a, a′ and dimethylsulphate the doubly methylated compounds CH3Mn(CO)4P(OCH3)R2 (4a, a′) are obtained. The rhenium derivatives CH3Re(CO)4P(OCH3)R2 (4b, b′) are formed only in very poor yields from 2 b, b′ and dimethylsulphate under reductive conditions. The IR, 1H NMR, and mass spectra are discussed.

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