Date of Award

Spring 1995

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

Edward H Wong

Abstract

The reactions of the dimolybdenum cage complex Mo(CO)$\sb4$-$\rm \lbrack\sp{i}Pr\sb2NPO\rbrack\sb4Mo(CO)\sb4\sp{*}$ with phosphorus and nitrogen nucleophiles were studied. This dimolybdenum cage complex reacted with tertiary phosphines of the type PPh$\sb2$R (R = Ph, Me, H) in refluxing toluene. In each case, incorporation of a single phosphine led to the loss of three carbonyls to form orange complexes of the type $\rm Mo(CO)\sb3\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4Mo(CO)\sb2PPh\sb2R$(2, 3, 4). The X-ray molecular structure of 2 has been determined. This revealed that a cage P-O-P bond has been cleaved near the substitution site with the resulting phosphinito oxygen replacing a second CO. Additionally, the phosphido group generated displaced a third CO at the other Mo center to bridge the two metals which are now within bonding distance of each other. Under milder conditions, reactions using phosphite yielded both mono- and disubstituted products $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack\sb4Mo(CO)\sb3P(OMe)\sb3$ or $\rm Mo(CO)\sb3P(OMe)\sb3$-$\rm \lbrack \sp{i}Pr\sb2NPO\rbrack \sb4Mo(CO)\sb3P(OMe)\sb3$ with the original core structure intact. Both products were mixtures of diastereomers and can be transformed to orange $\rm Mo(CO)\sb3\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4Mo(CO)\sb2P(OMe)\sb3$.

Treatment of the mixed-valent $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4Mo(CO)\sb2I\sb2$ cage complex with sodium dimethyldithiocarbamate selectively removed the divalent molybdenum vertex to give the metalla-ligand $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4$ (14) via an orange intermediate $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack\sb4$-$\rm Mo(CO)\sb2(S\sb2CNMe\sb2)\sb2$. The metalla-ligand has been characterized spectrally and by X-ray crystallography. It has been used as a precursor to assemble novel heterobimetallic cage complexes of the type $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4ML\sb{n}$ where ML$\sb{\rm n}$ can be $\rm Cr(CO)\sb4, Fe(CO)\sb3, Cu(MeCN)\sb2BF\sb4, AgNO\sb3, PtCl\sb2, NiBr\sb2$ and PdBr$\sb2$, or the type $\rm Mo(CO)\sb3\lbrack \sp{i}Pr\sb2NPO\rbrack \sb5ML\sb{n}$ where ML$\sb{\rm n}$ can be PdCl$\sb2$, PdBr$\sb2$. All these heterobimetallic cage complexes have been characterized by elemental analyses and spectral data. In addition, X-ray structures of the heterobimetallic cage complexes $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4MBr2$ (M = Ni(21), Pd(25)) have been determined. Comparison of the well-resolved Al carbonyl stretching frequency and the $\sp{13}$C NMR chemical shift of the cis-Mo(CO)$\sb4$ moiety in $\rm Mo(CO)\sb4\lbrack \sp{i}Pr\sb2NPO\rbrack \sb4ML\sb{n}$ and also the X-ray structures of 14, 21, 25 suggest a transmission of the increasing electron demand of the second cage metal to the molybdenum vertex. ftn*See Appendix A for the structure.

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