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The dimolybdenum complex cis -[Mo 2 Cp 2 (O)(μ-PPh 2 ) 2 (CO)] ( 1 ) reacted with either [H(OEt 2 ) 2 ](BAr′ 4 ), (Ar′ = 3,5-C 6 H 3 (CF 3 ) 2 ), or HBF 4 ·OEt 2 to give the corresponding hydroxo derivatives [Mo 2 Cp 2 (OH)(μ-PPh 2 ) 2 (CO)] + , which at room temperature rearrange to the oxohydride isomers [Mo 2 Cp 2 (μ-H)(O)(μ-PPh 2 ) 2 (CO)] + via a protonation/deprotonation sequence involving the hydride-hydroxo complex [Mo 2 Cp 2 (μ-H)(OH)(μ-PPh 2 ) 2 (CO)] 2+ (Cp = η 5 -C 5 H 5 ). All these cations were characterized spectroscopically in solution, but none of them could be isolated as a solid material. The reaction of 1 with 2 equiv of HBF 4 ·OEt 2 eventually led to the formation of the tetrafluoroborate complex [Mo 2 Cp 2 (κ 2 -F 2 BF 2 )(μ-PPh 2 ) 2 (CO)](BF 4 ) (Mo–Mo = 2.841(2) A). The BF 4 − ligand in the latter complex was easily displaced by nitriles at room temperature to give the corresponding tris(nitrile) derivatives [Mo 2 Cp 2 (μ-PPh 2 ) 2 (CO)(NCR) 3 ](BF 4 ) 2 (R = Me, Ph), and by acetylacetone (acac-H), to give the acetylacetonate complex [Mo 2 Cp 2 (κ 2 -acac)(μ-PPh 2 ) 2 (CO)](BF 4 ) (2.831(2) A). |
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