Synthesis of and Small Molecule Coordination to Highly Electrophilic Cationic Manganese(I) and Rhenium(I) Carbonyl Complexes with Tied-Back Phosphites

Formally 16e highly electrophilic fragments [Mn(CO)4(L)][BArF] with a tied-back phosphite
(L = P(OCH2)3CMe) coordinate Et2O (5b) or cis-cyclooctene (5c) and are prepared by reaction
of the neutral methyl complex Mn(Me)(CO)4(L) with [H(OEt2)2][BArF] or [Ph3C][BArF] in
the presence of cis-cyclooctene (cco), respectively. The solvent-bound rhenium complexes [Re(CO)4(L)(CH2Cl2)][BArF] (6a) and [Re(CO)3(L)2(CH2Cl2)][BArF] (7a) are prepared similarly
by reaction of the respective neutral precursors with [Ph3C][BArF] in CH2Cl2. The CH2Cl2
molecule binds tightly to the Re(I) center and could not be removed under high vacuum for
hours. However, the CH2Cl2 is readily displaced by Et2O, cco, and Et3SiH to afford ether-,
olefin-, and silane-coordinated complexes 6b−d and 7b−d, respectively. While the η2-(H−SiEt3)-coordinated 7d is stable in solution at room temperature and is a rare example of an
isolable cationic silane complex, the more electrophilic analogue 6d readily decomposes at
room temperature to give the hydride-bridged complex {[cis-Re(L)(CO)4]2(μ-H)}{BArF} (10).
Solid-state structures of 5c, 10, and 7b have been determined by single-crystal X-ray
structural analysis.