Synthesis, characterization and reactivity of organometallic Zr(IV) carboxylate and titanium aminotroponiminate complexes

Abstract

The synthesis and structure of several Zr(IV) carboxylate complexes are described in which the bridging carboxylate is the dianion of 111-xylylenediamine bis(Kemp's triacid imide) (H2XDK) or the more soluble propyl derivative (H2PXDK). Reaction of either H2XDK or H2PXDK with [Zr(CH2Ph)4] or [Zr(NMe2)4] afforded [Zr(CH2Ph)2(XDK)] or [Zr(NMe2)2(XDK)]. [Zr(CH2Ph)2(XDK)] is a rare example of an alkyl zirconium carboxylate complex. [Zr(CH2Ph)2(XDK)] reacts with various pyridine derivatives to yield the 7-coordinate pyridine adduct. An aryl isocyanide (2 equiv) reacts with [Zr(CH2Ph)2(XDK)] to afford the iminoacyl complex [Zr{11 2 -2,6- Me2PhNCCH2Ph}2(XDK)]. [Zr(CH2Ph)2(XDK)] is unreactive, however, towards weak sigma donors such as CO. The eight-coordinate complex [Zr(XDK)2] was formed by either treating [Zr(NMe2)4] with H2XDK (2 equiv) or [Zr(CH2Ph)2(XDK)] with H2XDK. Several of these complexes have been characterized by X-ray crystallography. [Zr(CH2Ph)2(XDK)] is electrophilic since the ipso carbon of one benzyl group is interacting with the Zr center as revealed by the acute Zr-C-C(ipso) angle in the X-ray structure of [Zr(CH2Ph)2(XDK)]. These studies have shown that 6-coordinate Zr carboxylate complexes are electrophilic. Complexes of this type are most stable when they possess high coordination numbers; this trend is exemplified by the stability of [Zr(XDK)2] and [Zr(eta)rt2-2,6-Me2PhNCCH2Phh(XDK)].