Dimeric phosphasilaboroles I (R = Me, CH2:CMe) react with transition metal complexes (MeCN)3M(CO)3 (M = Cr, Mo, W), Cr(CO)6, Fe(CO)5, Fe2(CO)9, Ru3(CO)12, (h5-C5H5)Co(C2H4)2, and (cyclodecatriene)nickel thermally or photochem. to form h1-P, h2-C2, and h4-C2PB complexes. The h4-ruthenium complexes exchange their Ph (on P) and Et (on B) substituents on further heating in mesitylene. Photochem. reaction of phosphasilaborin II with M(CO)6 gave h1-P complexes. The crystal structures of h1-P chromium and h4-C2PB nickel complexes were reported. The new transition metal complexes were compared by mass spectroscopy and by NMR (1H, 13C, 11B, 29Si, 31P) with the corresponding transition metal complexes of the C2SiXB heterocycles (X = NR, S, Se).