Interaction of [Me3NH][7,8-CH2OCH2-7,8-C2B9H10] with M(NR2)4 gave the simple amine elimination
products [η5-(CH2OCH2)C2B9H9]M(NMe2)2(NHMe2) (M = Zr (2a), Hf (2b)) or the unexpected C−O
bond cleavage products [σ:η1:η5-(OCH2)(Me2NCH2)C2B9H9]Ti(NR2) (R = Me (3a), Et (3b)). The higher
oxophilicity of the Ti center provides the driving force for the latter reactions. It is suggested that the
C−O bond cleavage is prior to the amine elimination in the formation of 3a,b. This serves as a convenient
and practical method for the preparation of constrained-geometry half-sandwich metallacarboranes with
two different functional sidearms. Complex 3a can undergo a clean amine exchange reaction to produce
new constrained-geometry titanacarborane amides. Reactions of 3a with unsaturated molecules CyNCNCy, SCS, Xyl−NC, PhC⋮N, Bu
n
NCS, Ph2CCO, and PhNCO gave monoinsertion
products. They, except for [σ:η1:η5-(OCH2)(Me2NCH2)C2B9H9]Ti[η3-CyNC(NMe2)NCy] (7), do not react
with amines. In sharp contrast, 7 can react readily with Me2NH to regenerate 3a and release guanidine,
which leads to the discovery of new catalytic guanylation of amines. All new complexes were fully
characterized by various spectroscopic techniques and elemental analyses. Most of them were further
confirmed by single-crystal X-ray analyses.