| dc.description.abstract | Major objectives of this dissertation involve the synthesis of gyroscope like complexes based upon dibridgehead diphosphine and diarsine cages, complexes with neutral dipolar rotors, and reactivity and rotational behavior of such complexes.
Ring closing metathesis and hydrogenation reactions of trans-Fe(CO)3(P((CH2)mCH=CH2)3)2 (m = 4-8) yield trans-Fe(CO)3(P((CH2)n)3P) (n = 2m+2). Reactions with NO+ BF4– and [H(OEt2)2]^+ Barf^– (BArf = B(3,5-C6H3(CF3)2)4) give the cations trans-[Fe(CO)2(NO)(P((CH2)n)3P)]+ BF4^– and mer, trans-[Fe(CO)3(H)(P((CH2)n)3P)]+ BArf– (n = 10, 12, 14). The rotational dynamics of these complexes are probed by variable temperature NMR spectroscopy. As opposed to those with larger values of n, the rotators of trans-[Fe(CO)2(NO)(P((CH2)n)3P)]^+ BF4^– (n = 10, 12) and mer, trans-[Fe(CO)3(H)(P((CH2)n)3P)]^+ Barf^– (n = 10), show slow rotation on the NMR timescale at room temperature. VT-NMR data yield ΔH^‡/ΔS^‡ values (kcal/mol and eu) of 8.3/–28.4 and 9.5/–6.5 for Fe(CO)2(NO)^+ rotation (n = 10, 12), and 6.1/–23.5 for Fe(CO)3(H)+ rotation (n = 12).
Reaction of arsines As((CH2)mCH=CH2)3 (m = 4-6) with (BDA)Fe(CO)3 (BDA = benzylideneacetone) yield trans-Fe(CO)3(As((CH2)mCH=CH2)3)2. Metathesis and hydrogenation reactions afford trans-Fe(CO)3(As((CH2)n)3As) (n = 10, 12, 14). Previously discussed analogous reactions give trans-[Fe(CO)2(NO)(As((CH2)n)3As)]+ BF4– and mer,trans-[Fe(CO)3(H)(As((CH2)n)3As)]+ BArf–. VT-NMR data give ΔH‡/ΔS‡ values of 7.7/–22.1 and 5.4/–22.7 for Fe(CO)2(NO)^+ and Fe(CO)3(H)^+ rotation (n = 12) which are distinctly lower than those in diphosphine analogs.
Reactions of trans-Fe(CO)3(P((CH2)mCH=CH2)3)2 (m = 4-8) with NO^+ BF4^– afford trans-[Fe(CO)2(NO)(P((CH2)mCH=CH2)3)2]^+ BF4^–. Further substitution is effected with Bu4N^+ X^- (X = Cl, Br, I, CN) to give trans-Fe(CO)(NO)(X)(P((CH2)mCH=CH2)3)2.
Three synthetic routes to gyroscope-like complexes trans-Fe(CO)(NO)(X)(P((CH2)n)3P) (n/X = 4-8/Cl, Br, I, CN) are described. (1) Reaction of trans-[Fe(CO)2(NO)(P((CH2)14)3P)]+ BF4^– with Bu4N^+ X^- gives trans-Fe(CO)(NO)(X)(P((CH2)14)3P). (2) Treatment of the acyclic complexes trans-Fe(CO)(NO)(X)(P((CH2)mCH=CH2)3)2 with Grubbs' catalyst affords trans Fe(CO)(NO)(X)(P((CH2)mCH=CH(CH2)m)3P). (3) Similar reactions with trans [Fe(CO)2(NO)(P((CH2)mCH=CH2)3)2]^+ BF4^– can give trans-[Fe(CO)2(NO)(P((CH2)n)3P)]+ BF4^–. Consistent with NMR data, crystal structures of trans-Fe(CO)(NO)(X)(P((CH2)14)3P) (X = Cl, Br, CN) indicate that the void space within the diphosphine cages appears sufficient for Fe(CO)(NO)(X) rotation. | en |
