Quadruple bonds oxidation

The molecular structures of Mo2(hpp)4 and W2(hpp)4 studied by Cotton show M-M distances of 2.067(1) and 2.162(1) A, respectively [41]. These two complexes contain the shortest Mo2" or quadruple bonds known. The ready oxidation... 

Of considerable interest are reactions in which the metal-metal bond order changes. So far, there are no known examples in which a W—W triple bond is converted to a W—W quadruple bond, a reaction which is known for molybdenum.289 However, several reactions in which the W—W triple bond is oxidized are known. The preparation of alkoxo clusters of WIV have been mentioned (Section 37.5.4.1) and the reaction in which W=W reacts with RC CR or RC=N to give mononuclear complexes containing the W=CR and WssN units have been discussed (Section 37.3.3). 

The dimers have turned out to be a very interesting and useful class of metalloporphyrins which was extended to dimers containing two divalent metal ions with Rh-Rh single (see Sect. 3.3), Re-Re triple, and Mo-Mo or W-W quadruple bonds [49,222-224]. These species react with many donor and acceptor molecules (see the following Sects. 3.22 and 3.3). The reactions with typical neutral donor ligands may be seen in Scheme 1, the oxidation reactions in Scheme 2. 

Oxidation of molybdenum hexacarbonyl with acetic acid produces the carboxylate-bridged quadruple-bonded dimers, as shown inequation (35). This complex can undergo a number of substitution reactions that leave the metal metal bond intact. ... 

The dominant structural feature of complexes containing W2" + is the presence of a quadruple bond. However, the ditungsten core is extremely sensitive to oxidative addition and consequently the chemistry of species... 

Mo2(02CR)4]l3 Derivatives. The initial objective of work on the oxidation of Mo2(02CR)4 derivatives with halogens was to examine the possibility of achieving addition of halogen across the quadruple bond, as in the reaction ... 

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