A paramagnetic W alkyne complex bearing free terminal diphenylphosphino groups at the side-on coordinated alkyne was synthesized using a stepwise template strategy. This moderately stable metal supported open shell diphosphine shows an unprecedented spontaneous splitting of nitric oxide providing a W-η-C{P(NH)Ph}{P(O)Ph} complex featuring an amino phosphonium and a phosphine oxide substituent.

We present the synthesis and coordination chemistry of a series of W alkyne complexes with symmetric and asymmetric acetylene diphosphines. Chelate-like P,P'-coordination of PtCl cause a drastic potential change of the W centered oxidation proving intermetallic cooperativity. The choice of peripheric P-substituents has a measurable influence on the potential itself as well on the respective potential change upon coordination. The enlarged deviation of the diphosphino alkyne from linearity in the dinuclear complexes unlock alkyne rotation making different isomers accessible.

The terminal phosphine groups at the tungsten bisphosphine alkyne complex [Tp*W­(CO)­(I)­(η2-C,C′-Ph2PC2PPh2)] (2) {Tp* = hydridotris­(3,4,5-trimethylpyrazolyl)­borate} were selectively oxidized by common methods to form the alkyne complexes 2EE (E = O, S) with either two phosphine oxide or two phosphine sulfide substituents. The respective mono-oxidized analogues 2E (E = O, S) were obtained by subjecting the already oxidized intermediates [Tp*W­(CO)­(I)­(η2-C,C′-Ph2P­(E)­C2H)] 1E (E = O, S) to a late-stage phosphine introduction at the complex template. These modulations of the peripheral alkyne moiety have a clear impact on the redox potential of the metal-based oxidation altering the W­(II/III) potential by +0.1 V on average per oxidized phosphine. In contrast to the comparable redox behavior of 2O and 2S, the coordination behavior of these complex ligands differs substantially. XRD studies show that complex 2 and the sulfide 2S act either as a P,P’- or P,S-chelate ligand leading to the dinuclear complexes [(2)­PdCl2], 3, and [(2S)PdCl2], 3S. In contrast, the corresponding PdCl2 complex of the monoxide 2O is connected by the free phosphine group and the W-bonded iodide as a μ2-bridging ligand leaving the phosphine oxide pending. A similar binding mode was found for the trinuclear gold complex [(2)2Au]­[PF6] (5-PF6). Furthermore, these findings explain the undesired outcome in the reaction of [Pd­(NCMe)4]­[BF4]2 with two equivalents of 2, which resulted in the iodide abstraction product [(2)­PdI2] (4).

The C/C coupling activity of the cationic Re­(III) species [(C5H5)­ReBr]+ with different heteroatom-substituted alkynes was investigated. By using the sulfide-substituted bis­(benzylsulfanyl)­acetylene an unprecedented rhenacyclopentatriene complex was obtained. An XRD structure determination of [(C5H5)­ReBr­(CSBn)4]+ uncovered the coordination of the remote ethylene moiety at Re leading to an η4-coordination mode of the C4(SBn)4 ligand and a folded five-membered metallacycle. In contrast, reaction of the monoalkyne complex [(C5H5)­ReBr­(CSBn)2]+ with diphenylacetylene as well as diiodoacetylene led to the mixed bis­(alkyne) complexes. The different behavior is attributed to kinetic reasons according to DFT calculations. XRD as well as IR studies with the cationic bis­(alkyne) complexes [(C5H5)­ReBr­(CSBn)2(C2Ph2)]+ and [(C5H5)­ReBr­(CSBn)2(C2I2)]+ revealed clear differences in the bond strengths of the coordinated alkynes at the same metal center. Further investigations on the coupling activity resulted in addition products with H2O and a trimerization of two diphenylacetylene molecules and one bis­(benzylsulfanyl)­acetylene, both as byproducts and involved in a sulfide bond cleavage.

The oxo tungsten(IV) alkyne complexes [Tp′W(O)(I)(η2‐C2Ph2)] (1), [Tp′W(O)(I){η2‐C2(SC2H4SiMe3)2}] (2), and [Tp′W(O)(I){η2‐C2(SBn)2}] (3) [Tp′ = hydridotris(3, 5‐dimethylpyrazolyl)borate, Bn = benzyl] were synthesized from [Tp′W(O)(CO)(I)]. All three compounds were fully characterized including structure determination by X‐ray diffraction analysis. Further elucidation of these reactions led to the isolation of several by‐products including an unexpected tungsten(IV) thioketene complex [Tp′W(O)(I){η2‐S = C=C(H)(SBn)}] (4), which is formed by removal of one Bn group from the alkyne, and dinuclear [Tp′W(O)(I)]2(μ‐O) (6). Both complexes were also fully characterized. X‐ray diffraction analysis reveals an η2‐S, C side‐on binding mode for 4 and a planar O–W–O–W–O moiety for 6. In addition, by changing the solvent from THF to dichloromethane formation of the chiral dihalogen complex [Tp′W(O)(Cl)(I)] (5) was proven.

The synthesis and reactivity of a W(ii) C2I2 complex towards various nucleophiles are described. Soft, aprotic nucleophiles like 4-dimethylaminopyridine (DMAP) lead to substitution of one CO at tungsten, whereas reaction with an excess of benzylamine results in a dual nucleophilic substitution at the alkyne moiety involving the rearrangement to a novel cationic amidinium carbyne complex.

A pair of diastereomeric dinuclear complexes, [Tp′(CO)BrW{μ‐η2‐C,C′‐κ2‐S,P‐C2(PPh2)S}Ru(η5‐C5H5)(PPh3)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side‐on carbon P,S‐chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like‐isomer is oxidized at W while the unlike‐isomer is oxidized at Ru, which is proven by IR, NIR and EPR‐spectroscopy supported by spectro‐electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp′(CO)(PhS)W{μ‐η2‐C,C′‐κ2‐S,P‐C2(PPh2)S}Ru(η5‐C5H5)‐(PPh3)], in which valence trapped WIII/RuII and WII/RuIII cationic species are at equilibrium.

Eleven complexes with the general formular [Tp*W(CO)L{η2-C2(PPh2)2}]n+ {Tp* = hydridotris(3,4,5-trimethylpyrazolyl)-borate, L = F‒, Cl‒, Br‒, I‒, MeS‒, PhS‒, pyCH2S‒, CN‒ and TfO‒: n = 0 and L = CH3CN, pyridine,...