193 208 ley chem soc chem commun 1951 6 1979 i 4m

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Unformatted text preview: emistry of Inorganic Ring Sysrems, Elsevier, Amsterdam, 1992, pp. 193-208. LEY, .Chem. Soc., Chem. Commun., 1951-6 (1979). I . 4’M. H. CHISHOLM, K. FOLTING,J. C. H UFFMANand J. J. KOH,Pofyhedron 4 , 893-5 (1985). 48 H. SCHAFFER, . B D INDER and D. FENSKE, Angew. Chem. Int. Edn. Engl. 24, 522-4 (1985). 49 I Y. GOH,R. C. S . WONG . and T. C. W. MAK,J . Organometallic Chem. 364, 363-71 (1989) and 373,71-6 (1989). 486 Phosphorus Figure 12.6 Schematic representation of some of the coordination geometries of phosphorus. Ch. 12 S12.2.5 Chemical reactivity and stereochemistry 487 Figure 12.7 (a) (p,q2-Pz)4e-donor to 15e ML, vertices. (b) (p,q2-P2)4e-donorto 14e or 16e ML,. (c) Triply bridging ( /~3,q~-Pz),ormal 6e-donor. (d) Quadruply bridging (p4,q2-P2) af 8e-donor. Figure 12.8 (a) CycZo-P3 as an q 1 and q2 donor (see text). (b) CycZo-P3 as an q3 donor; addition of q 1 donation to I , 2 or 3 further metal centres is possible. (c) Bis-q3 ligation of cycZo-P3 to coordinated metal centres M(L,). (d) More open q2,q3 coordination of P3 to different metal centres, e.g. M = (Ni(triphos))+, (see M' = {pt(PPh3)2) text). The cyclo-P3 ligand can act in either the q ',q2 or q3 mode as shown schematically in Fig. 12.8(a)-(~).(~~,~') of the three P atoms Each in 8(b) can also have a further pendant ML, group attached thereby making the cyclo-P3 ligand p 2 , p 3 or p4. In addition, the more open structure 8(d) is known in the binuclear cation [(triphos)Ni(P3Pt(PPh3)2}]+, here w triphos is 1,1,1-tris(diphenylphosphinomethyl)ethane, {CH3C(CH2PPh2)3}.(42)The q 1 and q 2 modes in Fig. 12.8(a) have only recently been established (in [((qs-C,Me,)(C0)2Fe-P}3Cr(CO)4])(50) but the q3 mode in Fig. 12.8(b) has been known since 1976 when it was found that one of the main products of the reaction between P4 and [co2(co)8] was the reactive L. WEBER, U. SONNENBERG,H.-G. STAMMLER and B. NEUMANN,. anorg. allg. Chern. 605, 87-99 (1991). Z pale-yellow solid [ C O ( C O ) ~ ( ~ ~ - P ~ ) ] . ( ~ ~ ) Numerous other examples featuring Co, Rh and Ir, and the isoelectronic cationic metal centres with Ni, Pd and Pt are now known. Metals in earlier groups require more electron donation from pendant ligands to achieve the 15-electron vertex configuration isolobal with the subrogated P atom in P4, e.g. (Mo(q5-C5Mes)(CO),}. The binuclear q3,q3 mode of cyclo-P3 (Fig. 1 2 . 8 ~ ) and its As3 homologues were extensively studied by L. Sacconi and others in the early 1980s.(38,42,43) As a ligand, P4 can adopt various geor n e t r i e ~ , ( ~ ~ . ~ ~ ) the P4 tetrahedron, planar including cyclo-P4 (both square and trapezoidal), and a planar zig-zag chain. In principle, the tetrahedral cluster Pq could ligate in q 1,q2 and q 3 modes, A. VIZl-OROSZ J . Organornet. Chern. 111, 61-4 (1976). Ch. 12 Phosphorus 488 Figure 12.9 S chematic representation of v arious coordination modes: (a) q 1-P4; b) q2-P4;( c) q4-cyclo-P4;( d) ( p , ( q 2 - ~ 2 )(2 text). see though only the first two have so far been established (Fig. 12.9 (a), (b)). [Note, however, the face-coordinated q3 configuration in the Bi4 complex [(C0)4Fe(p4,q3-Bi4)(Fe(C0)3 }312The first example of what turned out to be a complex involving the q 1 mode was the unstable red-brown compound [(Fe(CO)4}3 (p3-P4)] which was made in 1977 by reacting P4 with Fez(C0)g in benzene at room temperature:(53)one vertex of the P4 tetrahedron was coordinated q' to one of the [Fe(CO)4] groups while opposite edges of the P4 cluster wer...
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