Molybdenum compounds with quadruple bonds

Compounds 4-7 (Table 1) belong to this group. The physicochemical properties of the given binuclear clusters are close to those of the analogous rhenium and molybdenum compounds with the quadruple M-M bonds and are as a rule isostructural with them [1,89,90]. 

Dinuclear Species with Quadruple Bonds. Molybdenum carbonyl reacts readily with carboxylic acids to give yellow crystalline compounds Mo2(OOCR)4 which are thermally extremely stable. They have the copper... 

The existence of quadruple bonds was first recognized in 1964289 and since then a great many compounds of rhenium, technetium, chromium and molybdenum have been shown to contain them. Both bridged and unbridged compounds are known with a large variety of ligands. The bonding has been described in detail.289... 

The reaction of WCU with K2C8H8 in THF gives a reasonably air-stable material that was shown to be [W2(C8Hg)3]. The W—W bond length of 2.375 A, although long, is consistent with the presence of a quadruple bond.329 However, it is recognized that this compound (and the related chromium and molybdenum) is electronically different from other quadruply bonded species. 

The reaction of Mo(CO)6 and acetic acid is still the most convenient preparative route known for condensing two monomeric units into a compound containing a quadruple bond. In fact, facile conversion of Mo2(02CCH3)4 to chloro species occurs in concentrated hydrochloric acid to form the Mo2 Clj ion (36), which is isostructural with the Re2Clg ion. The eclipsed configuration of Mo2Clg" and the molybdenum atom separation of 2.14 A are entirely consistent with a quadruple bond in the anion as expected (33). 

The molybdenum and tunsten diphenylacetylene compounds have been chemically useful primarily as precursors to the quadruple metal-metal bonded dimers [M(Por)]2, formed by solid-state vacuum pyrolysis reactions. However. Mo(TTP)()/"-PhC CPh) is also a useful substrate in atom-transfer reactions, reacting with Sx or Cp2TiS i to form Mo(TTP)=S. The reaction can be reversed by treatment of Mo(TTP)=S with PPh (which removes sulfur as PhxP=S) and PhC CPh. The order of preference for ligand binding to molybdenum 11) has been established to be PPh < PhC CPh < 4-picoline. ... 

---