Compounds in which the Mo24+ unit is embraced by one, two or three formamidinate ligands together with acetonitrile ligands

The cationic complexes [Mo-2(DPhF)(MeCN)(6)](3+)[BF4-](3). MeCN 1a [throughout this paper the formamidinate anions, RNC(H)NR-, will be abbreviated as DRF-, with specific aryl groups represented by Ph for phenyl, and Ani for p-anisyl], [Mo-2(DAniF)(MeCN)(6)](3+)[BF4-](3). 1.59MeCN 1b, cis-[Mo-2(DPhF)(2)(MeCN)(4)](2+)[BF4-](2). MeCN 2a, cis-[Mo-2(DAniF)(2)(MeCN)(4)](2+)[BF4-](2). 2MeCN 2b, and [Mo-2(DPhF)(3)(MeCN)(2)](+)[BF4-] 3, have been prepared from the reactions between Mo-2(DArF)(4) and HBF4. Et2O or (Me3O)BF4 in an appropriate stoichiometry in acetonitrile or CH2Cl2-MeCN mixtures. A better procedure for the preparation of 3 involves the reaction between 2a and Li+(DPhF-) in acetonitrile. Compound 2a undergoes a reaction in pyridine to give the compound trans-[Mo-2(DPhF)(2)(py)(4)](2+)[BF4-](2) 4. The new compounds 1a, 1b, 2a, 2b and 4 have been structurally characterized and shown to contain Mo-Mo quadruple bonds.