Reaction of [Fe2Cp2(μ-CO)2(CO)(PRH2)] (Cp = η5-C5H5; R = Cy, Ph) with [FeCp2]BF4 gives the phosphide-bridged complexes [Fe2Cp2(μ-PRH)(μ-CO)(CO)2]BF4, which are deprotonated by M(OH) (M = Na, K) to give the phosphinidene derivatives [Fe2Cp2(μ-PR)(μ-CO)(CO)2] in high yield. The cyclohexylphosphinidene complex reacts at room temperature with MeI, O2, S8, or H2CCHR‘ (R‘ = CO2Me) to give selectively [Fe2Cp2(μ-PCyMe)(μ-CO)(CO)2]I or neutral derivatives of the types [Fe2Cp2{μ-P(E)Cy}(μ-CO)(CO)2] (E = O, S) and [Fe2Cp2{μ-κ1:κ1,η1-CyPCH2CHR‘C(O)}(μ-CO)(CO)].

The title complexes reacted readily with the methylating agents MeI and CF(3)SO(3)Me, chalcogens (O(2), S(8)) and borane adducts BH(3)·L (L = THF, N(t)Bu(3), PPh(3)) to initially give the corresponding neutral or cationic derivatives of the type [Fe(2)Cp(2){μ-P(E)R}(μ-CO)(CO)(2)](n) (Cp = η(5)-C(5)H(5); n = 0, E = O, S, BH(3); n = +1, E = Me), which could be further functionalized through additional reactions. Thus, the oxophosphinidene complex [Fe(2)Cp(2){μ-P(O)Cy}(μ-CO)(CO)(2)] could be protonated or alkylated with HBF(4)·OEt(2) or CF(3)SO(3)Me, to give the complexes [Fe(2)Cp(2){μ-P(OR')Cy}(μ-CO)(CO)(2)](+) (R' = H, Me) respectively, while the photochemical treatment of compounds [Fe(2)Cp(2){μ-P(BH(3))R}(μ-CO)(CO)(2)] gave the dicarbonyl derivatives [Fe(2)Cp(2){μ-κ(1):κ(1),η(2)-P(BH(3))R}(μ-CO)(CO)], with a phosphinidene-borane ligand displaying coordination of a B-H bond to one of the iron atoms in a side-on fashion (Fe-H = 1.78(4) Å, Fe-B = 2.351(5) Å for the PCy compound). The title complexes also reacted readily with 3,5-di-tert-butyl-o-benzoquinone or benzyl azide. The first reaction gave the phosphonite complex [Fe(2)Cp(2)(μ-CO)(2)(CO){P(O(2)C(6)H(2)(t)Bu(2))R}], while the second reaction yielded initially the corresponding 1 : 1 adducts [Fe(2)Cp(2){μ-P(N(3)CH(2)Ph)R}(μ-CO)(CO)(2)], with a P:P-bound phosphatriazadiene ligand. The PCy compound underwent clean denitrogenation in toluene at 368 K to give the iminophosphinidene complex [Fe(2)Cp(2){μ-P(NCH(2)Ph)Cy}(μ-CO)(CO)(2)], which in turn could be protonated selectively with [NH(4)]PF(6) at the P-bound nitrogen atom, to yield the aminophosphide derivative [Fe(2)Cp(2){μ-P(NHCH(2)Ph)Cy}(μ-CO)(CO)(2)]PF(6) (Fe-Fe = 2.6362(8) Å). Denitrogenation could be also induced photochemically on the phosphatriazadiene complex, but this also caused fragmentation and recombination of different bonds to give the trinuclear compound [Fe(3)Cp(3)(μ(3)-PCy){μ-κ(1):κ(1)-C(O)(NHCH(2)Ph)}(μ-CO)(2)], having phosphinidene and C:O-bound aminoacyl ligands bridging the metal atoms.

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The phosphinidene-bridged complex [Fe 2 Cp 2 (µ-PCy)(µ-CO)(CO) 2 ] (1) reacts with HCtCR (R ) p-tol, CO 2 Me) to giVe products incorporating one or two alkyne molecules and inVolVing further coupling with Cp or CO ligands, as shown by the formation of the complexes [Fe 2 Cp{µ-η 5 :κ 1 -C 5 H 4 PCyCHCH(p-tol)}(CO) 3 ], [Fe 2 Cp 2 {µ-κ 1 :κ 1 ,η 1 -CyPCHC(p-tol)C(O)}(µ-CO)(CO)],and[Fe 2 Cp 2 (µ-CO) 2 (CO){PCy(CHCHCO 2 Me)(C 2 CO 2 Me)}]. In contrast, the reactions of 1 with benzyl azide or (trimethylsilyl)diazomethane initially giVe the simple 1:1 adducts [Fe 2 Cp 2 (µ-CyPN 3 CH 2 Ph)(µ-CO)(CO) 2 ] and [Fe 2 Cp 2 {µ-CyPN 2 CH(SiMe 3 )}(µ-CO)(CO) 2 ], re-spectiVely, although the latter rearranges to yield [Fe 2 Cp 2 {µ-κ 1 : κ 1 ,η 1 -CyPN(SiMe 3 )NCH}(µ-CO)(CO)] under photolytic conditions.