Lineare oligophosphaalkane XIII. Triphosphaalkane mit demPCPCP-donorskelett; liganden für den aufbau von mehrkernkomplexen

Abstract

The triphosphaalkane Cl 2PCH 2PClCH 2PCl 2 (III) is formed as a by-product in the synthesis of Cl 2PCH 2PCl 2 (II). On treating III with MeMgCl or EtOH (in the presence of a base), the methyl or ethoxy derivative (V or VI) may be obtained in satisfactory yields. With Ni(CO) 4 or Fe 2 (CO) 9, V forms trinuclear complexes [(CO) n M]PMe 2CH 2PMe[M(CO) n ]CH 2PMe 2 [M(CO) n ] (X, XIII; M  Fe, Ni; n = 4, 3) or binuclear stable six-membered chelate ring systems [M(CO) n ]- PMe(CH 2PMe 2) 2[M(CO) m ] (IX, XIV; M  Fe, Ni: n = 4, 3: m = 3, 2). An excess of Fe 2(CO) 9, (molar ratio V/Fe 2(CO) 9 1/5) yields XI with an FeFe bond or the cluster XII, respectively. In both cases V bridges the FeFe bond with a PCP donor set. X-ray structural analysis of X (triclinic, space group P 1 ) exhibits a staggered arrangement of the three metal carbonyl fragments bound to the “stretched” PCPCP skeleton of V (Fe(1)P(1) 2.236(1), Fe(2)P(2) 2.226(1), Fe(3)P(3) 2.231(1) Å, P(1)C(13)P(2) 126.7(1), P(2)C(14)P(3) 127.6(1)°). In XI (monoclinic, space group P2 1/ n) one PCP donor set together with the two iron atoms Fe(2) and Fe(3) form a stable five-membered Fe 2P 2C ring (Fe(2)Fe(3) 2.705(1), Fe(2)P(2) 2.251(1), Fe(3)P(3) 2.239(1) Å). The third phosphorus atom P(1) binds an Fe(CO) 4 group (Fe(1)P(1) 2.245(1) Å). The structure of cluster compound XII (monoclinic, space group P2 1/ n) is derived from that of Os 3(CO) 12. One PCP donor set of V replaced two CO groups in equatorial positions, forming a stable Fe 2P 2C five-membered ring. The remaining donor position of V coordinates with an Fe(CO) 4 group.