This article reviews recent advances in late-transition-metal complexes with chelating Si and Ge ligands. Compounds with two Si−H bonds, such as bis(silyl)alkanes, bis(silyl)arenes, and tetramethyldisiloxanes, react with Re, Rh, Ir, Pd, and Pt complexes to form disilametallacycles with five- or six-membered chelate rings. Four- and five-membered disilacycloalkanes and disilanyldiylcarboranes undergo Si−Si bond cleavage promoted by Pd(0) and Pt(0) complexes to produce the corresponding disilametallacycles. High reactivity of the Si−Si bond toward oxidative addition facilitates the above ring enlargement, even for compounds with stable five-membered rings. Platinum complexes with a η2-silene ligand react with small molecules having electronegative atoms, such as O2 and NH3, to produce metallacycles formed via addition of the electronegative atom to the Si−Si bond. The above disilametallacycles undergo insertion of alkynes and carbonyl compounds into the M−Si bonds of the disilametallacycles. The persilyl metallacycle [Pt(SiPh2SiPh2SiPh2SiPh2)(PPh3)2] is obtained by the double oxidative addition of tetrakis(diphenylsilane) with two Si−H groups and via a metathesis reaction of its dilithio derivative with [PtCl2(PPh3)2]. Reactions of H2GeAr2 with Pd(II) and Pt(II) complexes having diphenylgermyl ligands yield the tetragerampalladacyclopentane and its Pt analogue. Trigermaplatinacyclobutane reacts with Ph2GeH2 to produce the tetragermaplatinacyclopentane via formal insertion of GePh2 into a Pt−Ge bond.
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