Soluble Ring‐Unsubstituted Phthalocyanine Zirconium(IV) and Niobium(V) <i>cis</i>‐Alkoxides and Their Catalytic Activity Toward the Ring‐Opening Polymerization of <i>rac‐</i>Lactide

A series of soluble ring-unsubstituted early-transition metallophthalocyanine (PcM) alkoxides with zirconium(IV) and niobium(V) metal centers was prepared via salt metathesis with PcM chlorides and a range of lithium or sodium alkoxides (NaOMe, NaOEt, LiOⁱPr, and NaO^tBu); several examples were structurally characterized. Given their large ionic size, the metal centers protrude out of the Pc cavity, engendering cis-axial ligation of the alkoxides and thereby generating substantially improved solubility relative to the starting PcM chlorides. Seven-coordinate PcM(OR)₃-type coordination spheres were typically observed, with lithium- or sodium-balanced "ate" species PcZr(OⁱPr)₃Li(THF) and PcZr(O^tBu)₃Na(THF) isolated for PcZr(IV), compared to the neutral PcNb(OⁱPr)₃. With the highly steric R = ^tBu the neutral six-coordinate PcZr(O^tBu)₂ was also structurally characterized. The catalytic activity of the PcZr(IV) and PcNb(V) alkoxides was probed toward the ring-opening polymerization (ROP) of rac-lactide, with PcZr(OⁱPr)₃Li(THF) being the most active, while the PcNb(V) systems were either inactive or yielded oligomers.