SYNTHESIS, CHARACTERIZATION, AND REACTIVITY OF CHROMIUM-, MOLYBDENUM-, AND TUNGSTEN-ISOCYANIDE COMPLEXES CONTAINING LIGANDS WHICH POSSESS THE ALPHA-DIIMINE MOIETY, -NITROGEN = CARBON-CARBON = NITROGEN- (CARBONYL, 2,2'-BIPYRIDINE, 1,4-DIAZA-1,3-BUTADIENE)

ANDREW BELL, Purdue University

Abstract

The homoleptic complexes Mo(CNR)(,7) (PF(,6))(,2) (R = CH(,3), CHMe(,2), or C(,6)H(,11)) react with the aromatic amines bpy, Me(,2)bpy, and phen in l-propanol to form the species Mo(CNR)(,5)(N-N) (PF(,6))(,2). On the other hand, Mo(CNCMe(,3))(,7) -(PF(,6))(,2) reacts under the same conditions to give the cyanobridged dimolybdenum(II) species Mo(CNCMe(,3))(,4) (N-N) (,2) ((mu)-CN) (PF(,6))(,3), the identity of which has been confirmed by a crystal structure determination on the bpy derivative. The reaction of Me(,3)CCl with Mo(CNCMe(,3))(,4)(bpy) (,2)((mu)-CN) (PF(,6))(,3) yields Mo- (CNCMe(,3))(,4)(bpy)Cl PF(,6). Subsequent reaction of this chloro species with CNCMe(,3) gives rise to Mo-(CNCMe(,3))(,5)(bpy) (PF(,6))(,2). Dealkylation of Mo(CNCMe(,3))(,5)-(bpy) (PF(,6))(,2) occurs in refluxing l-propanol to regenerate Mo(CNCMe(,3))(,4)(bpy) (,2)((mu)-CN) (PF(,6))(,3). Reaction of the compounds Mo(,2)-Cl(,4)(bpy)(,2) and Mo(,2)Cl(,4)(py)(,4) with CNCMe(,3) results in the cleavage of the Mo-Mo bond and generation of Mo(CNCMe(,3))(,4)- (bpy)Cl PF(,6) and Mo(CNCMe(,3))(,6)(py) (PF(,6))(,2), respectively. A series of tungsten(II) salts W(CNR)(,5)(N-N (PF(,6))(,2) (R = CHMe(,2), CMe(,3), C(,6)H(,11), or CH(,2)Ph; N-N = bpy, Me(,2)bpy, or phen) have been prepared in high yield (>75%). The synthetic procedure involves the oxidation of W(CO)(,4)(N-N) with PhICl(,2) followed by displacement of CO and Cl('-) by RNC. These reactions work equally well for the conversion of Mo(CO)(,4)(N-N) to Mo(CNR)(,5)(N-N) (PF(,6))(,2). The dealkylation of W(CNCMe(,3))(,5)(N-N) (PF(,6))(,2) to give W(CNCMe(,3))(,4)(N-N) (,2)((mu)-CN) -(PF(,6))(,3) occurs in refluxing ethanol. The ('95)Mo spectra of a series of seven-coordinate molybdenum (II) isocyanide complexes of the types Mo(CNR)(,7-n)-L(,n) (PF(,6))(,2), Mo(CNCMe(,3))(,6)X PF(,6), and Mo(CNCMe(,3))(,4)(N-N) (,2)((mu)-CN) (PF(,6))(,3) have been studies. The ('95)Mo chemical shift range for this group of complexes is about 1100 ppm. The complexes M(CO)(,3)(NCR)(R'-DAB) and M(CO)(,4)(R'-DAB) (M = Cr, Mo, or W, R = Me or Et; R' = i-Pr, t-Bu, or Cy undergo single RCN and CO substitution, respectively, with RNC leading to M(CO)(,3)(CNR) (R'-DAB). Activation of the complexes M(CO)(,3)(CNR) (R'-DAB) (M = Cr or Mo) and Mo(CO)(,3)(NCR)(R'-DAB) via a one-electron oxidation enables further substitution chemistry to be developed. The ligand-based reduction of M(CO)(,3)(CNR) (R'-DAB) is readily accessible using either Na/Hg or LiEt(,3)BH to yield the radical anions M(CO)(,3)(CNR) (R'-DAB) ('- )(.). The oxidative-addition of SnCl(,4) o Mo(CO)(,4)(R'-DAB) gives M(CO)(,3)(R'-DAB)(SnCl(,3))Cl (M = Mo or W). The action of RNC on these complexes yields M(CNR)(,4)(R'-DAB)Cl PF(,6), M(CNR)(,5)(R'-DAB) (PF(,6))(,2), or M(CO)(,3)(CNR)(R'-DAB) depending on the R'-DAB ligand used.

Degree

Ph.D.

Subject Area

Chemistry

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