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Reaction of M(N(SiMe3)2)2 (M = Ge, Sn, or Pb) with the sterically encumbered primary phosphine Ar'PH2 (2), Ar1 = C6H3-2.6-(C6H3-2,6-Pr'2), at ca. 200 °C afforded the highly colored phosphinidene dimers (M(μ-PAr'))2, M = Ge(3), Sn(4), or Pb(5), with disilylamine elimination. The compounds were characterized by single-crystal X-ray crystallography and heteronuclear NMR spectroscopy. The structures of 3.4, and 5 featured similar M2P2 ring cores, of which 4 and 5 have 50/50 P atom disorder, consistent with either a planar four-membered M2P2 arrangement with anti aryl groups or with an M2P2 ring folded along the M-M axis with syn aryl groups. A syn-folded structure was resolved for the Ge2P2 ring in compound 3. The M-P distances resembled those in M( II) phosphido complexes and are consistent with single bonding. The coordination geometries at the phosphorus atoms are pyramidal. DFT calculations on the gas phase models (M(μ-PMe))2 (M = Ge, Sn. Pb) agreed with the syn (M-M folded) structural interpretation of the X-ray data. The synthesis of the bulky phosphine Ar'PH2 2 with the use of the aryl transfer agent Ar'MgBr(THF)2 is also reported. This route afforded a significantly higher yield of product than that which was obtained using LiAr', which tends to result in aryl halide elimination and the observation of insoluble red phosphorus. [ABSTRACT FROM AUTHOR]