Treatment of either (i) Mg(PHPh)2(tmeda) with two equivalents of n-BuLi then with an excess of Me3SiCl or (ii) Li(PHPh)(tmeda) with Me3SiCl followed by n-BuLi yields [LiPPh(SiMe3)(tmeda)]2. Below ca. 0 and 5°C 31P and 7Li NMR spectroscopy shows that there is coupling of 7Li nuclei to two equivalent 31P nuclei, and vice versa. This is consistent with the dimeric structure found in the solid for the trans-isomer by an X-ray structure determination. The phosphido groups bridge two lithium centres to form Li2P2 rings; LiP (mean) 2.62 Å, LiN (mean) 2.16 Å, PLiP 94.5(6), 92.0(6)°, LiPLi 85.5(5), 88.0(5)°.