New metallocyclic Re(I) and Os(II) complexes with polyphosphane/polyyne spacers, including dimers [(Re(CO)3Cl(C2nP2))2] (n = 1, 1; 2, 2) and tetramers [(Re(CO)3Cl(C2nP2))4] (n = 1, 3; 2, 4, C2P2 = Ph2P-C...C-PPh2, C4P2 = Ph2P-C...C-C...C-PPh2), as well as the mixed-metal