Ditertiary phosphine complexes of (ν-allyl)dicarbonylmolybdenum(II) and -tungsten(II)

Compounds of the type [XM(CO)₂(ν-allyl)L₂] (where X = Cl and Br; M = Mo and W; L₂ = Ph₂PCH₂PPh₂ and Ph₂ PCH₂CH₂PPh₂) have been prepard from the corersponding MeCN complexes. The spectral properties of these compounds and the effects of chelate rign size on ³¹P coordination shifts and J(¹⁸³W—³¹P) have been investigated.     

A study of the protonation and alkylation oft-butyl isocyanide intrans-[M(CNBu-t 2(Ph2PCH2CH2PPh2)2] (M = Mo or W): Formation of carbyne-type complexes and theirtrans- tocis-isomerization

Summary Treatment of complexestrans-[M(CNBu-t)₂(dppe)₂][(1) M = Mo or W, dppe = Ph₂PCH₂CH₂PPh₂] with protic acid gives a mixture of the aminocarbyne complexestrans- pluscis-[M(CNHBu-t)(CNBu-t)(dppe)₂]⁺ (2) and the hydridocompounds [MH(CNBu-t)₂(dppe)₂]⁺ (3), whereas reaction with an alkylating agent (R⁺) appears to give the dialkylaminocarbyne compounds [M(CNRBu-t)(CNBu-t)(dppe)₂]⁺ (4) also as a mixture of thetrans andcis isomers.     

Synthesis and crystal structure of [MoH3(CCBut)(Ph2PCH2CH2PPh2)2], a trihydrido-alkynyl complex

Reaction of Bu^tCCH with trans-[Mo(N₂)₂(dppe)₂] (dppe = Ph₂PCH₂CH₂PPh₂) gives [MoH₃(CCBu^t)(dppe)₂], whose X-ray structure is reported.     

Reactions of (η-allyl)dicarbonylmolybdenum(II) complexes with phosphorus and arsenic donor ligands

Reaction of [MoX(CO)₂(η-C₃H₅)(MeCN)₂] with the arsines Ph₂AsCH₂CH₂AsPh₂ (dae) and Ph₂AsCH₂AsPh₂ (dam) yields complexes of stoichiometry [MoX(CO)₂(η-C₃H₅)dae] (where X = Cl, Br or I) and [MoX(CO)₂(η-C₃H₅)]₂dam (where X = Cl or Br). The former are isomorphous with the known Ph₂PCH₂CH₂PPH₂ complexes, whereas the latter probably contain halogen and dam bridges. Under forcing conditions the corresponding ditertiary phosphines form the molybdenum(0) derivatives $\text{cis}$-Mo(CO)₂(Ph₂P(CH₂)_nPPh₂]₂ (where n = 1 or 2).     

THE REACTIONS OF [MoCl(GeCl3)(CO)3(NCMe)2] WITH NEUTRAL BI- AND TERDENTATE DONOR LIGANDS

Abstract

The reaction of [MoCl(GeCl₃)(CO)₃(NCMe)₂] with an equimolar quantity of L?L {L?L = 2,2′-bipy, 1,10-phen, Ph₂P(CH₂)_nPPh₂ (n = 1 or 2)} in CH₂Cl₂ at room temperature gave either [MoCl(GeCl₃)(CO)₃(L?L)] (L?L = 2,2′-bipy or 1,10-phen) (1 and 2) or [MoCl(GeCl₃)(CO)₂ (NCMe)(L?L)]{L?L = Ph₂P(CH₂)_nPPh₂ (n = 1 or 2) (3 or 4), respectively. Equimolar quantities of [MoCl(GeCl₃)(CO)₂(NCMe){Ph₂P(CH₂)PPh₂}] (3) and L?L {L?L = 2,2′-bipy or Ph₂P(CH)₂PPh₂} react in CH₂Cl₂ at room temperature to afford the cationic complexes [Mo(GeCl₃)(CO)₂{Ph₂P(CH₂) PPh₂}(L?L)]Cl (5 and 6) in good yield. The cationic nature of 6 was established by chloride exchange by reacting Na[BPh₄] with 6 in acetonitrile to give the tetraphenylborate complex [Mo(GeCl₃)(CO)₂{Ph₂P(CH₂)PPh₂}₂][BPh₄] (7). Reaction of equimolar quantities of [MoCl(GeCl₃) (CO)₃(NCMe)₂] and PhP(CH₂CH₂PPh₂)₂ in CH₂Cl₂ at room temperature afforded the dicarbonyl complex [MoCl(GeCl₃)(CO)₂{PhP(CH₂CH₂PPh₂)₂}] (8) in good yield.     

Koordinativ ungesättigte Dieisenkomplexe: Synthese und Kristallstrukturen von [Fe2(CO)4(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [Fe2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diiron Complexes: Synthesis and Crystal Structures of [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] and [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] [Fe₂(μ‐CO)(CO)₆(μ‐H)(μ‐P^tBu₂)] ( 1 ) reacts spontaneously with dppm (dppm = Ph₂PCH₂PPh₂) to give [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 2 c ). By thermolysis or photolysis, 2 c loses very easily one carbonyl ligand and yields the corresponding electronically and coordinatively unsaturated complex [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ). 3 exhibits a Fe–Fe double bond which could be confirmed by the addition of methylene to the corresponding dimetallacyclopropane [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). The reaction of 1 with dppe (Ph₂PC₂H₄PPh₂) affords [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppe)] ( 5 ). In contrast to the thermolysis of 2 c , yielding 3 , the heating of 5 in toluene leads rapidly to complete decomposition. The reaction of 1 with PPh₃ yields [Fe₂(CO)₆(H)(μ‐P^tBu₂)(PPh₃)] ( 6 a ), while with ^tBu₂PH the compound [Fe₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 6 b ) is formed. The thermolysis of 6 b affords [Fe₂(CO)₅(μ‐P^tBu₂)₂] and the degradation products [Fe(CO)₃(^tBu₂PH)₂] and [Fe(CO)₄(^tBu₂PH)]. The molecular structures of 3 , 4 and 6 b were determined by X‐ray crystal structure analyses.     

Preparation and Properties of Molybdenum and Tungsten Dinitrogen Complexes. 30.1 Syntheses of Zero-Valent Molybdenum Complexes with the DMF Ligand: The Crystal Structure of Trans-[Mo(CO)(DMF)(Ph2PCH2CH2PPh2)2]

Abstract

Treatment of trans-[Mo(N₂)₂(dpe)(dpm)] (dpe = Ph₂PCH₂CH₂PPh₂, dpm = Ph₂PCH₂PPh₂) or trans-[Mo(N₂)₂(dpe)(dpp)] (dpp = Ph₂PCH₂CH₂CH₂PPh₂) with excess DMF in benzene at reflux under Ar resulted in the formation of trans-[Mo(CO)(DMF)(dpe)(dpm)] or trans-[Mo(CO)(DMF)(dpe)(dpp)]. X-ray structural analysis of trans-[Mo(CO)(DMF)(dpe)₂] was performed using single crystals isolated as the minor product from the reaction mixture of trans-[Mo(N₂)₂(dpe)(dpp)] and DMF. Crystal data: C₅₆H₅₅O₂NP₄Mo, monoclinic, space group P2₁, a = 11.145(4), b = 23.425(5), c = 10.516(3) Å, β = 117.17(2)° V = 2442.6(13) ų, D _calcd = 1.35 g/cm³ for Z = 2. This disclosed the relatively long C O bond distance of the carbonyl ligand and the significantly short C=O bond length in the DMF ligand. When recrystallized from benzene/hexane under N₂, trans-[Mo(CO)(DMF)(dpe)(dpm)] was converted into trans-[Mo(CO)(N₂)(dpe)(dpm)].     

Reactions of [Mo(N2)2(dppe)2] with organic isocyanates

The reactions of [Mo(N₂₂(dppe)₂], (dppe  Ph₂PCH₂CH₂PPh₂) with RC₆H₄NCO (R  H, p-CH₃, p-Cl) in benzene under irradiation produces [Mo(RC₆H₄NCO)₂(dppe)₂] in good yields. Comparison of the infrared data for these complexes, with those previously reported for metal complexes of CO₂-like molecules suggest a η²-C,O coordination to the metal.     

Synthesis of the cyanamide-derived bis(cyanoimido) complexes trans-[M(NCN)2(Ph2PCH2CH2PPh2)2] (M = Mo or W) and crystal structure of the molybdenum compound

Reaction of cyanamide (NCNH₂) with trans-[M(N₂)₂(dppe)₂] (M = Mo or W, dppe = PH₂PCH₂CH₂PPh₂) leads to the formation of the bis(cyanoimido) complexes trans-[M(NCN)₂(dppe)₂]. The crystal structure of trans-[Mo(NCN)₂(dppe)₂] has been determined by an X-ray diffraction study.     

Transition metal complexes with bidentate ligands spanning trans-positions. IV. Preparation and properties of some rhodium and iridium complexes of 2,11-bis(diphenylphosphinomethyl)benzo [c]phenanthrene

The bidentate phosphine 2,11-bis(diphenylphosphinomethyl)benzo [c]phenanthrene ( 1 ) has been used to prepare the mononuclear, square planar complexes trans-[MX(CO)( 1 )] and trans-[M(CO)(CH₃CN)( 1 )][BF₄] (M = Rh, Ir; X = Cl, Br, I, NCS). It is found that the tendency of these complexes to form adducts with CO, O₂ and SO₂ is significantly lower than that of the corresponding Ph₃P complexes. The oxidative-addition reactions of complexes trans-[IrX (CO) ( 1 )] with hydrogen halides give the six-coordinate species [IrHX₂(CO) ( 1 )]. The complexes [IrH₂I (CO) ( 1 )] and [IrH₂L (CO) ( 1 )] [BF₄] (L = CO and CH₃CN) have been obtained from hydrogen and the corresponding substrates. The model compounds trans-[MCl (CO) (Ph₂PCH₂Ph)₂] (M = Rh, Ir), trans-[Ir (CO) (CH₃CN) (Ph₂PCH₂Ph)₂] [BF₄], [IrHCl₂(CO)(Ph₂PCH₂Ph)₂] and [IrH₂(CO)₂(Ph₂PCH₂Ph)₂] [BF₄] have been prepared and their special parameters are compared with those of the corresponding complexes of ligand 1 . The influence of the static requirements of this ligand on the chemistry of its rhodium and iridium complexes is discussed.     

The cis-Re(Ph2PCH2CH2PPh2)2)+ metal centre. Synthesis and molecular structure of the dinitrile complex cis-[Re(NCC6H4Me-4 2(Ph 2 PCH 2 CH 2 PPh 2 2 ][BF4]

Reaction of NCC₆H₄X-4 (X  Me, OMe, or Cl) with trans-[ReCl(N₂)(dppe)₂] (dppe  Ph₂PCH₂CH₂PPh₂), at room temperature, in the presence of Tl[BF₄], gives the corresponding complexes cis-[Re(NCC₆H₄X-4)₂(dppe)₂][BF₄] (1); the crystal structure of 1 (X  Me) has been determined by single crystal X-ray diffraction analysis.     

Heterodinukleare Komplexe: Synthese und Kristallstrukturen von [RuRh(μ‐CO)(CO)4(μ‐PtBu2)(tBu2PH)], [RuRh(μ‐CO)(CO)3(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [CoRh(CO)4(μ‐H)(μ‐PtBu2)(tBu2PH)]

Heterobinuclear Complexes: Synthesis and X‐ray Crystal Structures of [RuRh(μ‐CO)(CO)₄(μ‐P^tBu₂)(^tBu₂PH)], [RuRh(μ‐CO)(CO)₃(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)], and [CoRh(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] [Ru₃Rh(CO)₇(μ₃‐H)(μ‐P^tBu₂)₂(^tBu₂PH)(μ‐Cl)₂] ( 2 ) yields by cluster degradation under CO pressure as main product the heterobinuclear complex [RuRh(μ‐CO)(CO)₄(μ‐P^tBu₂)(^tBu₂PH)] ( 4 ). The compound crystallizes in the orthorhombic space group Pcab with a = 15.6802(15), b = 28.953(3), c = 11.8419(19) Å and V = 5376.2(11) ų. The reaction of 4 with dppm (Ph₂PCH₂PPh₂) in THF at room temperature affords in good yields [RuRh(μ‐CO)(CO)₃(μ‐P^tBu₂)(μ‐dppm)] ( 7 ). 7 crystallizes in the triclinic space group P 1 with a = 9.7503(19), b = 13.399(3), c = 15.823(3) Å and V = 1854.6 ų. Moreover single crystals of [CoRh(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 9 ) could be obtained and the single‐crystal X‐ray structure analysis revealed that 9 crystallizes in the monoclinic space group P2₁/a with a = 11.611(2), b = 13.333(2), c = 18.186(3) Å and V = 2693.0(8) ų.     

Koordinativ ungesättigte Dirutheniumkomplexe: Synthese und Kristallstrukturen von [Ru2(CO)n(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] (n = 4; 5) und [Ru2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diruthenium Complexes: Synthesis and X‐ray Crystal Structures of [Ru₂(CO)_n(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] (n = 4; 5) and [Ru₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] The reaction of [Ru₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 2 ) with dppm yields the dinuclear species [Ru₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ) (dppm = Ph₂PCH₂PPh₂). Under thermal or photolytic conditions 3 loses very easily one carbonyl ligand and affords the corresponding electronically and coordinatively unsaturated complex [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). 4 is also obtainable by an one‐pot synthesis from [Ru₃(CO)₁₂], an excess of ^tBu₂PH and stoichiometric amounts of dppm via the formation of [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)₂] ( 1 ). 4 exhibits a Ru–Ru double bond which could be confirmed by addition of methylene to the dimetallacyclopropane [Ru₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 5 ). The molecular structures of 3 , 4 and 5 were determined by X‐ray crystal structure analyses.     

Preparation and crystallographic characterization of Pd(II) complexes containing imidobis(diphenylthiophosphinato) ligand

The reactions of PdCI₂(L-L) [L-L = Ph₂PCH₂PPh₂(dppm), Ph₂PCH₂CH₂PPh₂(dppe) and Ph₂PCH₂CH₂CH₂PPh₂(dppp)] with equivalent amount of (Ph₂P(S)NHP(S)Ph₂)(dppaS₂) gave the complexes [Pd(L-L)(dppaS₂-H)]ClO₄ [L-L = dppm (1), dppe (2), dppp (3)]. The different synthetic route was used for complex 2 by using of Pd(dppe)Cl₂ and K[N(PSPh₂)₂] as starting materials (2a). All of these complexes have been characterized ³¹P{¹H} NMR, IR and elemental analyses. The complexes 2, 2a and 3 were crystallographically characterized. The coordination geometry around the Pd atoms in these complexes distorted square planar. Six membered dppaS₂-H rings are twist boat conformations in three complexes.     

Synthesis of trans-[Re(NO)2-(Ph2PCH2CH2PPh2)2][BF4], a formal dinitrosyl complex of rhenium(-I) and its protic denitrosylation. X-Ray structure of trans-[ReF(NO)-(Ph2PCH2CH2PPh2)2][BF4]

Treatment of a THF solution of trans-[ReCl(N₂)(dppe)₂] (dppe = Ph₂PCH₂CH₂PPh₂) with NO, in the presence of Tl[BF₄], forms trans-[Re(NO)₂(dppe)₂][BF₄], a rare formal 20-electron d⁸-rhenium nitrosyl complex which, by reaction with HX (X = BF₄, Cl or HSO₄), gives trans-[ReF(NO)(dppe)₂][BF₄] (2) (the X-ray structure of which is reported) or trans-[ReX(NO)(dppe)₂]X (3, X = Cl or HSO₄), respectively, as well as nitrous oxide.     

Synthesis of bridged and linked ruthenium and osmium carbonyl clusters containing a [Au2(Ph2PCH2CH2PPh2)]2+ unit. The crystal and molecular structures of Ru5C(CO)14Au2(Ph2PCH2CH2PPh2) and {Os4H3(CO)12}2Au2(Ph2PCH2CH2PPh2)

Treatment of Au₂(Ph₂PCH₂CH₂PPh₂)Cl₂ with one equivalent of the [Ru₅C(CO)₁₄]²⁻ dianion in the presence of TlPF₆ gives Ru₅C(CO)₁₄Au₂(Ph₂PCH₂CH₂PPh₂) (1) in good yield and the [{Ru₅C(CO)₁₄}₂Au₂(Ph₂PCH₂CH₂PPh₂)]²⁻ (2) anion in low yield. Complex 2 becomes the major product if 2 equivalents of [Ru₅C(CO)₁₄]²⁻ are used. Reaction of [Au₂(Ph₂PCH₂CH₂PPh₂)Cl₂] with 3 equivalents of [H₃Os₄(CO)₁₂]⁻ anion in the presence of TlPF₆ affords {H₃Os₄(CO)₁₂}₂Au₂(Ph₂PCH₂CH₂PPh₂) (3) in reasonable yield. X-ray diffraction studies of 1 and 3 show that they contain the [Au₂(Ph₂PCH₂CH₂PPh₂)]²⁺ fragment in different coordination modes.     

On the Reaction of [(CO)3Fe(μ‐Me2NCO)2Fe(CO)2(NHMe2)] with Chelating Ligands — X‐Ray Structures of New Binuclear μ‐Carbamoyl Complexes

Reaction of the binuclear μ‐carbamoyl complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(HNMe₂)] ( 1 ) in toluene with the chelating ligands Ph₂PCH₂PPh₂ (dppm) and Ph₂PCH₂CH₂PPh₂ (dppe) gives different results. With dppm only the complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(dppm)] ( 3 ) with a dangling ligand is obtained under replacement of amine, whereas with dppe depending on the reaction conditions up to three compounds are found. A 1 : 1 mixture of the educts generates the related complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(dppe)] ( 4 ) together with the tetranuclear complex [{(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂}₂(dppe)] (5 ). 4 slowly converts into [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)(dppe)] ( 6 ) with dppe acting as a chelating ligand. 6 is the first compound in this series in which one of the five CO groups is replaced by another donor. A 2 : 1 molar ratio of 1 and dppe quantitatively produces 5 . Addition of CO to a solution of 6 proceeds under slow reversible conversion of the complex into 4 . The compounds were characterized by the usual spectroscopic methods; 3 , 5 and 6 were also studied by X‐ray diffraction analyses.     

Carbonyl complexes of manganese(I) with chelating phosphino-alkyl or -acyl ligands. Crystal and molecular structure of [Ph2PCH2CH2(O)CMn(CO)2(dppm)l

The phosphine Ph₂PCH₂CH₂Cl reacts with fac-[XMn(CO)₃(dppm)] (X = Cl or Br) in refluxing toluene to give the complexes cis,cis-[XMn(CO)₂(dppm)(Ph₂PCH₂CH₂Cl)] (I). Treatment of those species with Na amalgam in THF leads to the alkyl complex [Ph₂$\text{PCH}{}_2\text{CH}{}_2\text{M}$n(CO)₂(dppm)] (II), which does not react with CO under normal conditions but can be converted into cis,cis-[ClMn(CO)₂(dppm)(PPh₂Et)] by reacting with HCl (g) in ether. If the reduction of I with Na/Hg is carried out in the presence of CO the compound cis-[Ph₂$\text{PCH}{}_2\text{CH}{}_2\text{(O)CM}$n(CO)₂(dppm)] (III) is obtained. The latter has also been prepared directly from fac-[BrMn(CO)3(dppm)], Ph₂PCH₂CH₂Cl, and Na/Hg in THF, and characterized by X-ray crystallography. The crystals are monoclinic, space group P2₁/n; refinement gave R = 0.053 for 2593 reflections with I ? 2.5σ(I). The reaction of the complex fac-[O₃ClOMn(CO)₃(dppm)] with Ph₂PCH₂CH₂Cl in Cl₂CH₂ gives the salt fac-[Mn(CO)₃(dppm)(Ph₂PCH₂CH₂Cl)]ClO₄ which isomerizes to mer-[Mn(CO)₃(dppm)(Ph₂PCH₂CH₂Cl)]ClO₄ in boiling butanol. Both cationic carbonyl complexes give the acyl species III upon reduction with Na amalgam.     

A dinuclear hydride complex of platinum(I) containing both bidentate and monodentate bis(diphenylphosphino)methane ligands: the crystal structure of [Pt2H(Ph2PCH2PPh2)(μ-Ph2PCH2PPh2)2][PF6]

The crystal structure of the title compound has been determined from 6049 X-ray diffractometric intensities with I > 3σ(I), and refined by a least-squares procedure to R = 0.050. The crystals are monoclinic, space group P2₁/n, a = 13.702(2) b = 14.255(2), c = 39.556(6) Å, β = 94.75(1)°, Z = 4. The structure of the cation displays two different coordination modes of the Ph₂PCH₂PPh₂ ligands. Two of these are bidentate, bridging the Pt-Pt bond [2.769(1)Å] to form a Pt₂(μ-Ph₂PCH₂PPh₂)₂ nucleus, while the third acts as a monodentate two-electron donor. The hydrido ligand was not located, but its position is inferred from the coordination geometry of the platinum atom to which it is bonded. The metalligand distances are: Pt-P(trans to P) 2.248(3)–2.289(4) and Pt—P(trans to Pt) 2.347(4) Å.     

Reactions of cis-[dicarbonylbis(1,2-bis(dimethylphosphino)ethane)metal] compounds of chromium and molybdenum with organic electron acceptors; Tetracyanoethene, 1,2,4,5-tetracyanobenzene and 1,3,5-trinitrobenzene

Reaction between cis-[Mo(CO)₂(dmpe)₂] (dmpe =Me₂PCH₂CH₂PMe₂) and organic π-acids tetracyanoethene (TCNE), 1,2,4,5-tetracyanobenzene (TCNB) and 1,3,5-trinitrobenzene (TNB) proceeds via electron transfer from the metal complex, which is oxidised to the 17-electron trans-[Mo(CO)₂(dmpe)₂]⁺ ion, to the organic acceptor which is reduced to the radical anion. The final products of the reactions are characterised ascis-[Mo{C₂(CN)₃} (CO)₂(dmpe)₂] [CN], cis-[Mo{C₆H₂(CN)₄} (CO)₂(dmpe)₂] [C₆H₂(CN)₄]₈ and [Mo(CO)₂(dmpe)₂ · 2 C₆H₃(NO₂)₃] by analysis and spectroscopic (IR, NMR, ESR) measurements which are compared with those of cis-[MoX(CO)₂(dmpe)₂]X (X = Cl, Br, I) and fac, fac-[Mo₂Cl₄(CO)₄(dmpe)₃]. The reaction of cis-[Cr(CO)₂(dmpe)₂] with TCNE gives trans-[Cr(CO)₂(dmpe)₂]⁺ [TCNE]^? only.