MULTIPLY-BONDED DIRHENIUM COMPLEXES CONTAINING BRIDGING BIDENTATE LIGANDS
Abstract
The use of benzoyl chloride as a reducing agent provides a convenient and high yield synthetic route to the key starting material for entry into multiply-bonded dirhenium chemistry: the Re(,2)Cl(,8) ('2-) anion. The reaction of this anion and Re(,2)Cl(,6)(PR(,3))(,2) with the ligand 2-(diphenylphosphino)pyridine (Ph(,2)Ppy) produces several new triply-bonded complexes, including the first example of an ortho-metallation reaction occurring at an M(,2)L(,8) core; Re(,2)Cl(,3) (Ph(,2)Ppy)(,2) (C(,6)H(,5))(C(,6)H(,4))Ppy , and a rare example of a dimetal complex having four neutral bridging ligands; (Re(,2)Cl(,2)(Ph(,2)Ppy)(,4)) (PF(,6))(,2). Extension of this chemistry to include the bridging ligands bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)amine (dppa) has generated a new class of doubly-bonded complexes Re(,2)((mu)-Cl)(,2)(dppm)(,2)(OR)Cl(,3) (R = n-alkyl) Re(,2)((mu)-Cl)(,2)(dppm)(,2)Cl(,4), Re(,2)((mu)-Cl(,2) (dppa)(,2)Cl(,4) and Re(,2)((mu)-Cl)(,2)(Ph(,2)Ppy)(,2)Cl(,4), thereby greatly expanding the chemistry of doubly-bonded complexes of the early transition metals. The substitution chemistry and electrochemistry of the triply-bonded complex Re(,2)Cl(,4)(dppm)(,2) has been explored, utilizing donor ligands such as pyridines, nitriles and isocyanides. This has produced a number of complexes unique to multiply-bonded dirhenium chemistry of which those of the types Re(,2)Cl(,3)(dppm)(,2)(NCR)(,2) PF(,6), Re(,2)Cl(,4)(dppm)(,2) (CNR) and Re(,2)Cl(,3)(dppm)(,2)(CNR)(,2)(CNHR) PR(,6) are especially noteworthy. This substitution chemistry shows some resemblances to that found for similar group VIII dimetal system which readily form A-frame type molecules. Full spectroscopic and electrochemical details on all the above complexes is reported along with the crystallographic details on a number of them to confirm the nature of the substitution products.
Degree
Ph.D.
Subject Area
Chemistry
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